Abstract

This is a strict subset of the HTML5 specification that omits user-agent (UA) implementation details. It is targeted toward Web authors and others who are not UA implementors and who want a view of the HTML specification that focuses more precisely on details relevant to using the HTML language to create Web documents and Web applications. Because this document does not provide implementation conformance criteria, UA implementors should not rely on it, but should instead refer to the full specification.

This specification defines the 5th major revision of the core language of the World Wide Web: the Hypertext Markup Language (HTML). In this version, new features are introduced to help Web application authors, new elements are introduced based on research into prevailing authoring practices, and special attention has been given to defining clear conformance criteria for user agents in an effort to improve interoperability.

Status of This document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the most recently formally published revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

If you wish to make comments regarding this document in a manner that is tracked by the W3C, please submit them via using our public bug database. If you do not have an account then you can enter feedback using this form:

Feedback Comments

Please don't use section numbers as these tend to change rapidly and make your feedback harder to understand.

(Note: Your IP address will be publicly recorded for spam prevention purposes.)

If you cannot do this then you can also e-mail feedback to public-html-comments@w3.org (subscribe, archives), and arrangements will be made to transpose the comments to our public bug database. Alternatively, you can e-mail feedback to whatwg@whatwg.org (subscribe, archives). The editor guarantees that all substantive feedback sent to this list will receive a reply. However, such feedback is not considered formal feedback for the W3C process. All feedback is welcome.

The working groups maintains a list of all bug reports that the editor has not yet tried to address and a list of issues for which the chairs have not yet declared a decision. The editor also maintains a list of all e-mails that he has not yet tried to address. These bugs, issues, and e-mails apply to multiple HTML-related specifications, not just this one.

Implementors should be aware that this specification is not stable. Implementors who are not taking part in the discussions are likely to find the specification changing out from under them in incompatible ways. Vendors interested in implementing this specification before it eventually reaches the Candidate Recommendation stage should join the aforementioned mailing lists and take part in the discussions.

The publication of this document by the W3C as a W3C Working Draft does not imply that all of the participants in the W3C HTML working group endorse the contents of the specification. Indeed, for any section of the specification, one can usually find many members of the working group or of the W3C as a whole who object strongly to the current text, the existence of the section at all, or the idea that the working group should even spend time discussing the concept of that section.

The latest stable version of the editor's draft of this specification is always available on the W3C CVS server and in the WHATWG Subversion repository. The latest editor's working copy (which may contain unfinished text in the process of being prepared) contains the latest draft text of this specification (amongst others). For more details, please see the WHATWG FAQ.

There are various ways to follow the change history for the HTML specifications:

E-mail notifications of changes
HTML-Diffs mailing list (diff-marked HTML versions for each change): http://lists.w3.org/Archives/Public/public-html-diffs/latest
Commit-Watchers mailing list (complete source diffs): http://lists.whatwg.org/listinfo.cgi/commit-watchers-whatwg.org
Real-time notifications of changes:
Generated diff-marked HTML versions for each change: http://twitter.com/HTML5
Browsable version-control record of all changes:
CVSWeb interface with side-by-side diffs: http://dev.w3.org/cvsweb/html5/
Annotated summary with unified diffs: http://html5.org/tools/web-apps-tracker
Raw Subversion interface: svn checkout http://svn.whatwg.org/webapps/

The W3C HTML Working Group is the W3C working group responsible for this specification's progress along the W3C Recommendation track. This specification is the 13 January 2011 Working Draft.

Work on this specification is also done at the WHATWG. The W3C HTML working group actively pursues convergence with the WHATWG, as required by the W3C HTML working group charter.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

Table of Contents

  1. 1 Introduction
    1. 1.1 Background
    2. 1.2 Audience
    3. 1.3 Scope
    4. 1.4 History
    5. 1.5 Design notes
      1. 1.5.1 Serializability of script execution
      2. 1.5.2 Compliance with other specifications
    6. 1.6 HTML vs XHTML
    7. 1.7 Structure of this specification
      1. 1.7.1 How to read this specification
      2. 1.7.2 Typographic conventions
    8. 1.8 A quick introduction to HTML
    9. 1.9 Conformance requirements for authors
      1. 1.9.1 Presentational markup
      2. 1.9.2 Syntax errors
      3. 1.9.3 Restrictions on content models and on attribute values
    10. 1.10 Recommended reading
  2. 2 Common infrastructure
    1. 2.1 Terminology
      1. 2.1.1 Resources
      2. 2.1.2 XML
      3. 2.1.3 DOM trees
      4. 2.1.4 Scripting
      5. 2.1.5 Plugins
      6. 2.1.6 Character encodings
    2. 2.2 Conformance requirements
      1. 2.2.1 Extensibility
    3. 2.3 Case-sensitivity and string comparison
    4. 2.4 Common microsyntaxes
      1. 2.4.1 Boolean attributes
      2. 2.4.2 Keywords and enumerated attributes
      3. 2.4.3 Numbers
        1. 2.4.3.1 Non-negative integers
        2. 2.4.3.2 Signed integers
        3. 2.4.3.3 Real numbers
        4. 2.4.3.4 Lists of integers
      4. 2.4.4 Dates and times
        1. 2.4.4.1 Months
        2. 2.4.4.2 Dates
        3. 2.4.4.3 Times
        4. 2.4.4.4 Local dates and times
        5. 2.4.4.5 Global dates and times
        6. 2.4.4.6 Weeks
        7. 2.4.4.7 Vaguer moments in time
      5. 2.4.5 Colors
      6. 2.4.6 Space-separated tokens
      7. 2.4.7 Comma-separated tokens
      8. 2.4.8 References
      9. 2.4.9 Media queries
    5. 2.5 URLs
      1. 2.5.1 Terminology
      2. 2.5.2 Interfaces for URL manipulation
    6. 2.6 Common DOM interfaces
      1. 2.6.1 Reflecting content attributes in IDL attributes
      2. 2.6.2 Collections
        1. 2.6.2.1 HTMLCollection
        2. 2.6.2.2 HTMLAllCollection
        3. 2.6.2.3 HTMLFormControlsCollection
        4. 2.6.2.4 HTMLOptionsCollection
      3. 2.6.3 DOMTokenList
      4. 2.6.4 DOMSettableTokenList
      5. 2.6.5 DOMStringMap
      6. 2.6.6 DOM feature strings
      7. 2.6.7 Exceptions
    7. 2.7 Namespaces
  3. 3 Semantics, structure, and APIs of HTML documents
    1. 3.1 Documents
      1. 3.1.1 Documents in the DOM
      2. 3.1.2 Security
      3. 3.1.3 Resource metadata management
      4. 3.1.4 DOM tree accessors
      5. 3.1.5 Creating documents
    2. 3.2 Elements
      1. 3.2.1 Semantics
      2. 3.2.2 Elements in the DOM
      3. 3.2.3 Global attributes
        1. 3.2.3.1 The id attribute
        2. 3.2.3.2 The title attribute
        3. 3.2.3.3 The lang and xml:lang attributes
        4. 3.2.3.4 The xml:base attribute (XML only)
        5. 3.2.3.5 The dir attribute
        6. 3.2.3.6 The class attribute
        7. 3.2.3.7 The style attribute
        8. 3.2.3.8 Embedding custom non-visible data with the data-* attributes
      4. 3.2.4 Element definitions
        1. 3.2.4.1 Attributes
      5. 3.2.5 Content models
        1. 3.2.5.1 Kinds of content
          1. 3.2.5.1.1 Metadata content
          2. 3.2.5.1.2 Flow content
          3. 3.2.5.1.3 Sectioning content
          4. 3.2.5.1.4 Heading content
          5. 3.2.5.1.5 Phrasing content
          6. 3.2.5.1.6 Embedded content
          7. 3.2.5.1.7 Interactive content
        2. 3.2.5.2 Transparent content models
        3. 3.2.5.3 Paragraphs
      6. 3.2.6 Requirements relating to bidirectional-algorithm formatting characters
      7. 3.2.7 Annotations for assistive technology products (ARIA)
    3. 3.3 APIs in HTML documents
    4. 3.4 Dynamic markup insertion
      1. 3.4.1 Opening the input stream
      2. 3.4.2 Closing the input stream
      3. 3.4.3 document.write()
      4. 3.4.4 document.writeln()
      5. 3.4.5 innerHTML
      6. 3.4.6 outerHTML
      7. 3.4.7 insertAdjacentHTML()
  4. 4 The elements of HTML
    1. 4.1 The root element
      1. 4.1.1 The html element
    2. 4.2 Document metadata
      1. 4.2.1 The head element
      2. 4.2.2 The title element
      3. 4.2.3 The base element
      4. 4.2.4 The link element
      5. 4.2.5 The meta element
        1. 4.2.5.1 Standard metadata names
        2. 4.2.5.2 Other metadata names
        3. 4.2.5.3 Pragma directives
        4. 4.2.5.4 Other pragma directives
        5. 4.2.5.5 Specifying the document's character encoding
      6. 4.2.6 The style element
      7. 4.2.7 Styling
    3. 4.3 Scripting
      1. 4.3.1 The script element
        1. 4.3.1.1 Scripting languages
        2. 4.3.1.2 Restrictions for contents of script elements
        3. 4.3.1.3 Inline documentation for external scripts
      2. 4.3.2 The noscript element
    4. 4.4 Sections
      1. 4.4.1 The body element
      2. 4.4.2 The section element
      3. 4.4.3 The nav element
      4. 4.4.4 The article element
      5. 4.4.5 The aside element
      6. 4.4.6 The h1, h2, h3, h4, h5, and h6 elements
      7. 4.4.7 The hgroup element
      8. 4.4.8 The header element
      9. 4.4.9 The footer element
      10. 4.4.10 The address element
      11. 4.4.11 Headings and sections
        1. 4.4.11.1 Creating an outline
    5. 4.5 Grouping content
      1. 4.5.1 The p element
      2. 4.5.2 The hr element
      3. 4.5.3 The pre element
      4. 4.5.4 The blockquote element
      5. 4.5.5 The ol element
      6. 4.5.6 The ul element
      7. 4.5.7 The li element
      8. 4.5.8 The dl element
      9. 4.5.9 The dt element
      10. 4.5.10 The dd element
      11. 4.5.11 The figure element
      12. 4.5.12 The figcaption element
      13. 4.5.13 The div element
    6. 4.6 Text-level semantics
      1. 4.6.1 The a element
      2. 4.6.2 The em element
      3. 4.6.3 The strong element
      4. 4.6.4 The small element
      5. 4.6.5 The s element
      6. 4.6.6 The cite element
      7. 4.6.7 The q element
      8. 4.6.8 The dfn element
      9. 4.6.9 The abbr element
      10. 4.6.10 The time element
      11. 4.6.11 The code element
      12. 4.6.12 The var element
      13. 4.6.13 The samp element
      14. 4.6.14 The kbd element
      15. 4.6.15 The sub and sup elements
      16. 4.6.16 The i element
      17. 4.6.17 The b element
      18. 4.6.18 The mark element
      19. 4.6.19 The ruby element
      20. 4.6.20 The rt element
      21. 4.6.21 The rp element
      22. 4.6.22 The bdi element
      23. 4.6.23 The bdo element
      24. 4.6.24 The span element
      25. 4.6.25 The br element
      26. 4.6.26 The wbr element
      27. 4.6.27 Usage summary
    7. 4.7 Edits
      1. 4.7.1 The ins element
      2. 4.7.2 The del element
      3. 4.7.3 Attributes common to ins and del elements
      4. 4.7.4 Edits and paragraphs
      5. 4.7.5 Edits and lists
    8. 4.8 Embedded content
      1. 4.8.1 The img element
        1. 4.8.1.1 Requirements for providing text to act as an alternative for images
          1. 4.8.1.1.1 General guidelines
          2. 4.8.1.1.2 A link or button containing nothing but the image
          3. 4.8.1.1.3 A phrase or paragraph with an alternative graphical representation: charts, diagrams, graphs, maps, illustrations
          4. 4.8.1.1.4 A short phrase or label with an alternative graphical representation: icons, logos
          5. 4.8.1.1.5 Text that has been rendered to a graphic for typographical effect
          6. 4.8.1.1.6 A graphical representation of some of the surrounding text
          7. 4.8.1.1.7 A purely decorative image that doesn't add any information
          8. 4.8.1.1.8 A group of images that form a single larger picture with no links
          9. 4.8.1.1.9 A group of images that form a single larger picture with links
          10. 4.8.1.1.10 A key part of the content
          11. 4.8.1.1.11 An image not intended for the user
          12. 4.8.1.1.12 An image in an e-mail or private document intended for a specific person who is known to be able to view images
      2. 4.8.2 The iframe element
      3. 4.8.3 The embed element
      4. 4.8.4 The object element
      5. 4.8.5 The param element
      6. 4.8.6 The video element
      7. 4.8.7 The audio element
      8. 4.8.8 The source element
      9. 4.8.9 The track element
      10. 4.8.10 Media elements
        1. 4.8.10.1 Error codes
        2. 4.8.10.2 Location of the media resource
        3. 4.8.10.3 MIME types
        4. 4.8.10.4 Network states
        5. 4.8.10.5 Loading the media resource
        6. 4.8.10.6 Offsets into the media resource
        7. 4.8.10.7 The ready states
        8. 4.8.10.8 Playing the media resource
        9. 4.8.10.9 Seeking
        10. 4.8.10.10 Timed text tracks
          1. 4.8.10.10.1 Text track model
          2. 4.8.10.10.2 Sourcing in-band text tracks
          3. 4.8.10.10.3 Text track API
        11. 4.8.10.11 User interface
        12. 4.8.10.12 Time ranges
        13. 4.8.10.13 Event summary
        14. 4.8.10.14 Best practices for authors using media elements
      11. 4.8.11 The canvas element
      12. 4.8.12 The map element
      13. 4.8.13 The area element
      14. 4.8.14 Image maps
      15. 4.8.15 MathML
      16. 4.8.16 SVG
      17. 4.8.17 Dimension attributes
    9. 4.9 Tabular data
      1. 4.9.1 The table element
      2. 4.9.2 The caption element
      3. 4.9.3 The colgroup element
      4. 4.9.4 The col element
      5. 4.9.5 The tbody element
      6. 4.9.6 The thead element
      7. 4.9.7 The tfoot element
      8. 4.9.8 The tr element
      9. 4.9.9 The td element
      10. 4.9.10 The th element
      11. 4.9.11 Attributes common to td and th elements
      12. 4.9.12 Examples
    10. 4.10 Forms
      1. 4.10.1 Introduction
        1. 4.10.1.1 Writing a form's user interface
        2. 4.10.1.2 Implementing the server-side processing for a form
        3. 4.10.1.3 Configuring a form to communicate with a server
        4. 4.10.1.4 Client-side form validation
      2. 4.10.2 Categories
      3. 4.10.3 The form element
      4. 4.10.4 The fieldset element
      5. 4.10.5 The legend element
      6. 4.10.6 The label element
      7. 4.10.7 The input element
        1. 4.10.7.1 States of the type attribute
          1. 4.10.7.1.1 Hidden state
          2. 4.10.7.1.2 Text state and Search state
          3. 4.10.7.1.3 Telephone state
          4. 4.10.7.1.4 URL state
          5. 4.10.7.1.5 E-mail state
          6. 4.10.7.1.6 Password state
          7. 4.10.7.1.7 Date and Time state
          8. 4.10.7.1.8 Date state
          9. 4.10.7.1.9 Month state
          10. 4.10.7.1.10 Week state
          11. 4.10.7.1.11 Time state
          12. 4.10.7.1.12 Local Date and Time state
          13. 4.10.7.1.13 Number state
          14. 4.10.7.1.14 Range state
          15. 4.10.7.1.15 Color state
          16. 4.10.7.1.16 Checkbox state
          17. 4.10.7.1.17 Radio Button state
          18. 4.10.7.1.18 File Upload state
          19. 4.10.7.1.19 Submit Button state
          20. 4.10.7.1.20 Image Button state
          21. 4.10.7.1.21 Reset Button state
          22. 4.10.7.1.22 Button state
        2. 4.10.7.2 Common input element attributes
          1. 4.10.7.2.1 The autocomplete attribute
          2. 4.10.7.2.2 The dirname attribute
          3. 4.10.7.2.3 The list attribute
          4. 4.10.7.2.4 The readonly attribute
          5. 4.10.7.2.5 The size attribute
          6. 4.10.7.2.6 The required attribute
          7. 4.10.7.2.7 The multiple attribute
          8. 4.10.7.2.8 The maxlength attribute
          9. 4.10.7.2.9 The pattern attribute
          10. 4.10.7.2.10 The min and max attributes
          11. 4.10.7.2.11 The step attribute
          12. 4.10.7.2.12 The placeholder attribute
        3. 4.10.7.3 Common input element APIs
      8. 4.10.8 The button element
      9. 4.10.9 The select element
      10. 4.10.10 The datalist element
      11. 4.10.11 The optgroup element
      12. 4.10.12 The option element
      13. 4.10.13 The textarea element
      14. 4.10.14 The keygen element
      15. 4.10.15 The output element
      16. 4.10.16 The progress element
      17. 4.10.17 The meter element
      18. 4.10.18 Association of controls and forms
      19. 4.10.19 Attributes common to form controls
        1. 4.10.19.1 Naming form controls
        2. 4.10.19.2 Enabling and disabling form controls
        3. 4.10.19.3 Autofocusing a form control
        4. 4.10.19.4 Limiting user input length
        5. 4.10.19.5 Form submission
        6. 4.10.19.6 Submitting element directionality
      20. 4.10.20 APIs for the text field selections
      21. 4.10.21 Constraints
        1. 4.10.21.1 Definitions
        2. 4.10.21.2 The constraint validation API
        3. 4.10.21.3 Security
      22. 4.10.22 Form submission
    11. 4.11 Interactive elements
      1. 4.11.1 The details element
      2. 4.11.2 The summary element
      3. 4.11.3 The command element
      4. 4.11.4 The menu element
        1. 4.11.4.1 Introduction
        2. 4.11.4.2 Context menus
      5. 4.11.5 Commands
    12. 4.12 Links
      1. 4.12.1 Introduction
      2. 4.12.2 Links created by a and area elements
      3. 4.12.3 Link types
        1. 4.12.3.1 Link type "alternate"
        2. 4.12.3.2 Link type "archives"
        3. 4.12.3.3 Link type "author"
        4. 4.12.3.4 Link type "bookmark"
        5. 4.12.3.5 Link type "external"
        6. 4.12.3.6 Link type "help"
        7. 4.12.3.7 Link type "icon"
        8. 4.12.3.8 Link type "license"
        9. 4.12.3.9 Link type "nofollow"
        10. 4.12.3.10 Link type "noreferrer"
        11. 4.12.3.11 Link type "pingback"
        12. 4.12.3.12 Link type "prefetch"
        13. 4.12.3.13 Link type "search"
        14. 4.12.3.14 Link type "stylesheet"
        15. 4.12.3.15 Link type "sidebar"
        16. 4.12.3.16 Link type "tag"
        17. 4.12.3.17 Hierarchical link types
          1. 4.12.3.17.1 Link type "index"
          2. 4.12.3.17.2 Link type "up"
        18. 4.12.3.18 Sequential link types
          1. 4.12.3.18.1 Link type "first"
          2. 4.12.3.18.2 Link type "last"
          3. 4.12.3.18.3 Link type "next"
          4. 4.12.3.18.4 Link type "prev"
        19. 4.12.3.19 Other link types
    13. 4.13 Common idioms without dedicated elements
      1. 4.13.1 The main part of the content
      2. 4.13.2 Tag clouds
      3. 4.13.3 Conversations
      4. 4.13.4 Footnotes
  5. 5 Loading Web pages
    1. 5.1 Browsing contexts
      1. 5.1.1 Nested browsing contexts
        1. 5.1.1.1 Navigating nested browsing contexts in the DOM
      2. 5.1.2 Auxiliary browsing contexts
        1. 5.1.2.1 Navigating auxiliary browsing contexts in the DOM
      3. 5.1.3 Secondary browsing contexts
      4. 5.1.4 Browsing context names
    2. 5.2 The Window object
      1. 5.2.1 APIs for creating and navigating browsing contexts by name
      2. 5.2.2 Accessing other browsing contexts
      3. 5.2.3 Named access on the Window object
      4. 5.2.4 Browser interface elements
    3. 5.3 Origin
      1. 5.3.1 Relaxing the same-origin restriction
    4. 5.4 Session history and navigation
      1. 5.4.1 The session history of browsing contexts
      2. 5.4.2 The History interface
      3. 5.4.3 The Location interface
    5. 5.5 Browsing the Web
      1. 5.5.1 History traversal
      2. 5.5.2 Unloading documents
    6. 5.6 Offline Web applications
      1. 5.6.1 Introduction
        1. 5.6.1.1 Event summary
      2. 5.6.2 The cache manifest syntax
        1. 5.6.2.1 Some sample manifests
        2. 5.6.2.2 Writing cache manifests
      3. 5.6.3 Application cache API
      4. 5.6.4 Browser state
  6. 6 Web application APIs
    1. 6.1 Scripting
      1. 6.1.1 Introduction
      2. 6.1.2 Events
    2. 6.2 Timers
    3. 6.3 User prompts
      1. 6.3.1 Simple dialogs
      2. 6.3.2 Printing
      3. 6.3.3 Dialogs implemented using separate documents
    4. 6.4 System state and capabilities: the Navigator object
      1. 6.4.1 Client identification
      2. 6.4.2 Custom scheme and content handlers
      3. 6.4.3 Manually releasing the storage mutex
  7. 7 User interaction
    1. 7.1 The hidden attribute
    2. 7.2 Activation
    3. 7.3 Focus
      1. 7.3.1 Sequential focus navigation and the tabindex attribute
      2. 7.3.2 Document-level focus APIs
      3. 7.3.3 Element-level focus APIs
    4. 7.4 Assigning keyboard shortcuts
      1. 7.4.1 Introduction
      2. 7.4.2 The accesskey attribute
    5. 7.5 The contenteditable attribute
      1. 7.5.1 Making entire documents editable
    6. 7.6 Spelling and grammar checking
    7. 7.7 Drag and drop
      1. 7.7.1 Introduction
      2. 7.7.2 The drag data store
      3. 7.7.3 The DataTransfer interface
        1. 7.7.3.1 The DataTransferItems interface
        2. 7.7.3.2 The DataTransferItem interface
      4. 7.7.4 The DragEvent interface
      5. 7.7.5 Events summary
      6. 7.7.6 The draggable attribute
      7. 7.7.7 The dropzone attribute
    8. 7.8 Editing APIs
  8. 8 The HTML syntax
    1. 8.1 Writing HTML documents
      1. 8.1.1 The DOCTYPE
      2. 8.1.2 Elements
        1. 8.1.2.1 Start tags
        2. 8.1.2.2 End tags
        3. 8.1.2.3 Attributes
        4. 8.1.2.4 Optional tags
        5. 8.1.2.5 Restrictions on content models
        6. 8.1.2.6 Restrictions on the contents of raw text and RCDATA elements
      3. 8.1.3 Text
        1. 8.1.3.1 Newlines
      4. 8.1.4 Character references
      5. 8.1.5 CDATA sections
      6. 8.1.6 Comments
    2. 8.2 Named character references
  9. 9 The XHTML syntax
  10. 10 Obsolete features
    1. 10.1 Obsolete but conforming features
    2. 10.2 Non-conforming features
  11. 11 IANA considerations
    1. 11.1 text/html
    2. 11.2 text/html-sandboxed
    3. 11.3 application/xhtml+xml
    4. 11.4 text/cache-manifest
  12. Index
    1. Elements
    2. Element content categories
    3. Attributes
    4. Interfaces
    5. Events
  13. References
  14. Acknowledgements

1 Introduction

1.1 Background

This section is non-normative.

The World Wide Web's markup language has always been HTML. HTML was primarily designed as a language for semantically describing scientific documents, although its general design and adaptations over the years have enabled it to be used to describe a number of other types of documents.

The main area that has not been adequately addressed by HTML is a vague subject referred to as Web Applications. This specification attempts to rectify this, while at the same time updating the HTML specifications to address issues raised in the past few years.

1.2 Audience

This section is non-normative.

This specification is intended for authors of documents and scripts that use the features defined in this specification.

This document is probably not suited to readers who do not already have at least a passing familiarity with Web technologies, as in places it sacrifices clarity for precision, and brevity for completeness. More approachable tutorials and authoring guides can provide a gentler introduction to the topic.

In particular, familiarity with the basics of DOM Core and DOM Events is necessary for a complete understanding of some of the more technical parts of this specification. An understanding of Web IDL, HTTP, XML, Unicode, character encodings, JavaScript, and CSS will also be helpful in places but is not essential.

1.3 Scope

This section is non-normative.

This specification is limited to providing a semantic-level markup language and associated semantic-level scripting APIs for authoring accessible pages on the Web ranging from static documents to dynamic applications.

The scope of this specification does not include providing mechanisms for media-specific customization of presentation (although default rendering rules for Web browsers are included at the end of this specification, and several mechanisms for hooking into CSS are provided as part of the language).

The scope of this specification is not to describe an entire operating system. In particular, hardware configuration software, image manipulation tools, and applications that users would be expected to use with high-end workstations on a daily basis are out of scope. In terms of applications, this specification is targeted specifically at applications that would be expected to be used by users on an occasional basis, or regularly but from disparate locations, with low CPU requirements. For instance online purchasing systems, searching systems, games (especially multiplayer online games), public telephone books or address books, communications software (e-mail clients, instant messaging clients, discussion software), document editing software, etc.

1.4 History

This section is non-normative.

For its first five years (1990-1995), HTML went through a number of revisions and experienced a number of extensions, primarily hosted first at CERN, and then at the IETF.

With the creation of the W3C, HTML's development changed venue again. A first abortive attempt at extending HTML in 1995 known as HTML 3.0 then made way to a more pragmatic approach known as HTML 3.2, which was completed in 1997. HTML4 followed, reaching completion in 1998.

At this time, the W3C membership decided to stop evolving HTML and instead begin work on an XML-based equivalent, called XHTML. This effort started with a reformulation of HTML4 in XML, known as XHTML 1.0, which added no new features except the new serialization, and which was completed in 2000. After XHTML 1.0, the W3C's focus turned to making it easier for other working groups to extend XHTML, under the banner of XHTML Modularization. In parallel with this, the W3C also worked on a new language that was not compatible with the earlier HTML and XHTML languages, calling it XHTML2.

Around the time that HTML's evolution was stopped in 1998, parts of the API for HTML developed by browser vendors were specified and published under the name DOM Level 1 (in 1998) and DOM Level 2 Core and DOM Level 2 HTML (starting in 2000 and culminating in 2003). These efforts then petered out, with some DOM Level 3 specifications published in 2004 but the working group being closed before all the Level 3 drafts were completed.

In 2003, the publication of XForms, a technology which was positioned as the next generation of Web forms, sparked a renewed interest in evolving HTML itself, rather than finding replacements for it. This interest was borne from the realization that XML's deployment as a Web technology was limited to entirely new technologies (like RSS and later Atom), rather than as a replacement for existing deployed technologies (like HTML).

A proof of concept to show that it was possible to extend HTML4's forms to provide many of the features that XForms 1.0 introduced, without requiring browsers to implement rendering engines that were incompatible with existing HTML Web pages, was the first result of this renewed interest. At this early stage, while the draft was already publicly available, and input was already being solicited from all sources, the specification was only under Opera Software's copyright.

The idea that HTML's evolution should be reopened was tested at a W3C workshop in 2004, where some of the principles that underlie the HTML5 work (described below), as well as the aforementioned early draft proposal covering just forms-related features, were presented to the W3C jointly by Mozilla and Opera. The proposal was rejected on the grounds that the proposal conflicted with the previously chosen direction for the Web's evolution; the W3C staff and membership voted to continue developing XML-based replacements instead.

Shortly thereafter, Apple, Mozilla, and Opera jointly announced their intent to continue working on the effort under the umbrella of a new venue called the WHATWG. A public mailing list was created, and the draft was moved to the WHATWG site. The copyright was subsequently amended to be jointly owned by all three vendors, and to allow reuse of the specification.

The WHATWG was based on several core principles, in particular that technologies need to be backwards compatible, that specifications and implementations need to match even if this means changing the specification rather than the implementations, and that specifications need to be detailed enough that implementations can achieve complete interoperability without reverse-engineering each other.

The latter requirement in particular required that the scope of the HTML5 specification include what had previously been specified in three separate documents: HTML4, XHTML1, and DOM2 HTML. It also meant including significantly more detail than had previously been considered the norm.

In 2006, the W3C indicated an interest to participate in the development of HTML5 after all, and in 2007 formed a working group chartered to work with the WHATWG on the development of the HTML5 specification. Apple, Mozilla, and Opera allowed the W3C to publish the specification under the W3C copyright, while keeping a version with the less restrictive license on the WHATWG site.

Since then, both groups have been working together.

The HTML specification published by the WHATWG is not identical to this specification. At the time of this publication, the main differences were that the WHATWG version included features not included in this W3C version: some features have been omitted, but may be considered for future revisions of HTML beyond HTML5; and other features were omitted because at the W3C they are published as separate specifications.

A separate document has been published by the W3C HTML working group to document the differences between this specification and the language described in the HTML4 specification. [HTMLDIFF]

1.5 Design notes

This section is non-normative.

It must be admitted that many aspects of HTML appear at first glance to be nonsensical and inconsistent.

HTML, its supporting DOM APIs, as well as many of its supporting technologies, have been developed over a period of several decades by a wide array of people with different priorities who, in many cases, did not know of each other's existence.

Features have thus arisen from many sources, and have not always been designed in especially consistent ways. Furthermore, because of the unique characteristics of the Web, implementation bugs have often become de-facto, and now de-jure, standards, as content is often unintentionally written in ways that rely on them before they can be fixed.

Despite all this, efforts have been made to adhere to certain design goals. These are described in the next few subsections.

1.5.1 Serializability of script execution

This section is non-normative.

To avoid exposing Web authors to the complexities of multithreading, the HTML and DOM APIs are designed such that no script can ever detect the simultaneous execution of other scripts. Even with workers, the intent is that the behavior of implementations can be thought of as completely serializing the execution of all scripts in all browsing contexts.

The navigator.yieldForStorageUpdates() method, in this model, is equivalent to allowing other scripts to run while the calling script is blocked.

1.5.2 Compliance with other specifications

This section is non-normative.

This specification interacts with and relies on a wide variety of other specifications. In certain circumstances, unfortunately, conflicting needs have led to this specification violating the requirements of these other specifications. Whenever this has occurred, the transgressions have each been noted as a "willful violation", and the reason for the violation has been noted.

1.6 HTML vs XHTML

This section is non-normative.

This specification defines an abstract language for describing documents and applications, and some APIs for interacting with in-memory representations of resources that use this language.

The in-memory representation is known as "DOM HTML", or "the DOM" for short. This specification defines version 5 of DOM HTML, known as "DOM5 HTML".

There are various concrete syntaxes that can be used to transmit resources that use this abstract language, two of which are defined in this specification.

The first such concrete syntax is the HTML syntax. This is the format suggested for most authors. It is compatible with most legacy Web browsers. If a document is transmitted with an HTML MIME type, such as text/html, then it will be processed as an HTML document by Web browsers. This specification defines version 5 of the HTML syntax, known as "HTML5".

The second concrete syntax is the XHTML syntax, which is an application of XML. When a document is transmitted with an XML MIME type, such as application/xhtml+xml, then it is treated as an XML document by Web browsers, to be parsed by an XML processor. Authors are reminded that the processing for XML and HTML differs; in particular, even minor syntax errors will prevent a document labeled as XML from being rendered fully, whereas they would be ignored in the HTML syntax. This specification defines version 5 of the XHTML syntax, known as "XHTML5".

The DOM, the HTML syntax, and XML cannot all represent the same content. For example, namespaces cannot be represented using the HTML syntax, but they are supported in the DOM and in XML. Similarly, documents that use the noscript feature can be represented using the HTML syntax, but cannot be represented with the DOM or in XML. Comments that contain the string "-->" can only be represented in the DOM, not in the HTML and XML syntaxes.

1.7 Structure of this specification

This section is non-normative.

This specification is divided into the following major sections:

Common infrastructure
The conformance classes, algorithms, definitions, and the common underpinnings of the rest of the specification.
Semantics, structure, and APIs of HTML documents
Documents are built from elements. These elements form a tree using the DOM. This section defines the features of this DOM, as well as introducing the features common to all elements, and the concepts used in defining elements.
The elements of HTML
Each element has a predefined meaning, which is explained in this section. Rules for authors on how to use the element are also given.
Loading Web pages
HTML documents do not exist in a vacuum — this section defines many of the features that affect environments that deal with multiple pages.
Web application APIs
This section introduces basic features for scripting of applications in HTML.
User interaction
HTML documents can provide a number of mechanisms for users to interact with and modify content, which are described in this section.
The HTML syntax
The XHTML syntax
All of these features would be for naught if they couldn't be represented in a serialized form and sent to other people, and so these sections define the syntaxes of HTML, along with rules for how to parse content using those syntaxes.

There are also some appendices, defining rendering rules for Web browsers and listing obsolete features and IANA considerations.

1.7.1 How to read this specification

This specification should be read like all other specifications. First, it should be read cover-to-cover, multiple times. Then, it should be read backwards at least once. Then it should be read by picking random sections from the contents list and following all the cross-references.

1.7.2 Typographic conventions

This is a definition, requirement, or explanation.

This is a note.

This is an example.

This is an open issue.

This is a warning.

interface Example {
  // this is an IDL definition
};
variable = object . method( [ optionalArgument ] )

This is a note to authors describing the usage of an interface.

/* this is a CSS fragment */

The defining instance of a term is marked up like this. Uses of that term are marked up like this or like this.

The defining instance of an element, attribute, or API is marked up like this. References to that element, attribute, or API are marked up like this.

Other code fragments are marked up like this.

Variables are marked up like this.

1.8 A quick introduction to HTML

This section is non-normative.

A basic HTML document looks like this:

<!DOCTYPE html>
<html>
 <head>
  <title>Sample page</title>
 </head>
 <body>
  <h1>Sample page</h1>
  <p>This is a <a href="demo.html">simple</a> sample.</p>
  <!-- this is a comment -->
 </body>
</html>

HTML documents consist of a tree of elements and text. Each element is denoted in the source by a start tag, such as "<body>", and an end tag, such as "</body>". (Certain start tags and end tags can in certain cases be omitted and are implied by other tags.)

Tags have to be nested such that elements are all completely within each other, without overlapping:

<p>This is <em>very <strong>wrong</em>!</strong></p>
<p>This <em>is <strong>correct</strong>.</em></p>

This specification defines a set of elements that can be used in HTML, along with rules about the ways in which the elements can be nested.

Elements can have attributes, which control how the elements work. In the example below, there is a hyperlink, formed using the a element and its href attribute:

<a href="demo.html">simple</a>

Attributes are placed inside the start tag, and consist of a name and a value, separated by an "=" character. The attribute value can remain unquoted if it doesn't contain spaces or any of " ' ` = < or >. Otherwise, it has to be quoted using either single or double quotes. The value, along with the "=" character, can be omitted altogether if the value is the empty string.

<!-- empty attributes -->
<input name=address disabled>
<input name=address disabled="">

<!-- attributes with a value -->
<input name=address maxlength=200>
<input name=address maxlength='200'>
<input name=address maxlength="200">

HTML user agents (e.g. Web browsers) then parse this markup, turning it into a DOM (Document Object Model) tree. A DOM tree is an in-memory representation of a document.

DOM trees contain several kinds of nodes, in particular a DOCTYPE node, elements, text nodes, and comment nodes.

The markup snippet at the top of this section would be turned into the following DOM tree:

The root element of this tree is the html element, which is the element always found at the root of HTML documents. It contains two elements, head and body, as well as a text node between them.

There are many more text nodes in the DOM tree than one would initially expect, because the source contains a number of spaces (represented here by "␣") and line breaks ("⏎") that all end up as text nodes in the DOM. However, for historical reasons not all of the spaces and line breaks in the original markup appear in the DOM. In particular, all the whitespace before head start tag ends up being dropped silently, and all the whitespace after the body end tag ends up placed at the end of the body.

The head element contains a title element, which itself contains a text node with the text "Sample page". Similarly, the body element contains an h1 element, a p element, and a comment.


This DOM tree can be manipulated from scripts in the page. Scripts (typically in JavaScript) are small programs that can be embedded using the script element or using event handler content attributes. For example, here is a form with a script that sets the value of the form's output element to say "Hello World":

<form name="main">
 Result: <output name="result"></output>
 <script>
  document.forms.main.elements.result.value = 'Hello World';
 </script>
</form>

Each element in the DOM tree is represented by an object, and these objects have APIs so that they can be manipulated. For instance, a link (e.g. the a element in the tree above) can have its "href" attribute changed in several ways:

var a = document.links[0]; // obtain the first link in the document
a.href = 'sample.html'; // change the destination URL of the link
a.protocol = 'https'; // change just the scheme part of the URL
a.setAttribute('href', 'http://example.com/'); // change the content attribute directly

Since DOM trees are used as the way to represent HTML documents when they are processed and presented by implementations (especially interactive implementations like Web browsers), this specification is mostly phrased in terms of DOM trees, instead of the markup described above.


HTML documents represent a media-independent description of interactive content. HTML documents might be rendered to a screen, or through a speech synthesizer, or on a braille display. To influence exactly how such rendering takes place, authors can use a styling language such as CSS.

In the following example, the page has been made yellow-on-blue using CSS.

<!DOCTYPE html>
<html>
 <head>
  <title>Sample styled page</title>
  <style>
   body { background: navy; color: yellow; }
  </style>
 </head>
 <body>
  <h1>Sample styled page</h1>
  <p>This page is just a demo.</p>
 </body>
</html>

For more details on how to use HTML, authors are encouraged to consult tutorials and guides. Some of the examples included in this specification might also be of use, but the novice author is cautioned that this specification, by necessity, defines the language with a level of detail that might be difficult to understand at first.

1.9 Conformance requirements for authors

This section is non-normative.

Unlike previous versions of the HTML specification, this specification defines in some detail the required processing for invalid documents as well as valid documents.

However, even though the processing of invalid content is in most cases well-defined, conformance requirements for documents are still important: in practice, interoperability (the situation in which all implementations process particular content in a reliable and identical or equivalent way) is not the only goal of document conformance requirements. This section details some of the more common reasons for still distinguishing between a conforming document and one with errors.

1.9.1 Presentational markup

This section is non-normative.

The majority of presentational features from previous versions of HTML are no longer allowed. Presentational markup in general has been found to have a number of problems:

The use of presentational elements leads to poorer accessibility

While it is possible to use presentational markup in a way that provides users of assistive technologies (ATs) with an acceptable experience (e.g. using ARIA), doing so is significantly more difficult than doing so when using semantically-appropriate markup. Furthermore, even using such techniques doesn't help make pages accessible for non-AT non-graphical users, such as users of text-mode browsers.

Using media-independent markup, on the other hand, provides an easy way for documents to be authored in such a way that they work for more users (e.g. text browsers).

Higher cost of maintenance

It is significantly easier to maintain a site written in such a way that the markup is style-independent. For example, changing the color of a site that uses <font color=""> throughout requires changes across the entire site, whereas a similar change to a site based on CSS can be done by changing a single file.

Higher document sizes

Presentational markup tends to be much more redundant, and thus results in larger document sizes.

For those reasons, presentational markup has been removed from HTML in this version. This change should not come as a surprise; HTML4 deprecated presentational markup many years ago and provided a mode (HTML4 Transitional) to help authors move away from presentational markup; later, XHTML 1.1 went further and obsoleted those features altogether.

The only remaining presentational markup features in HTML are the style attribute and the style element. Use of the style attribute is somewhat discouraged in production environments, but it can be useful for rapid prototyping (where its rules can be directly moved into a separate style sheet later) and for providing specific styles in unusual cases where a separate style sheet would be inconvenient. Similarly, the style element can be useful in syndication or for page-specific styles, but in general an external style sheet is likely to be more convenient when the styles apply to multiple pages.

It is also worth noting that some elements that were previously presentational have been redefined in this specification to be media-independent: b, i, hr, s, and small.

1.9.2 Syntax errors

This section is non-normative.

The syntax of HTML is constrained to avoid a wide variety of problems.

Unintuitive error-handling behavior

Certain invalid syntax constructs, when parsed, result in DOM trees that are highly unintuitive.

For example, the following markup fragment results in a DOM with an hr element that is an earlier sibling of the corresponding table element:

<table><hr>...
Errors with optional error recovery

To allow user agents to be used in controlled environments without having to implement the more bizarre and convoluted error handling rules, user agents are permitted to fail whenever encountering a parse error.

Errors where the error-handling behavior is not compatible with streaming user agents

Some error-handling behavior, such as the behavior for the <table><hr>... example mentioned above, are incompatible with streaming user agents (user agents that process HTML files in one pass, without storing state). To avoid interoperability problems with such user agents, any syntax resulting in such behavior is considered invalid.

Errors that can result in infoset coercion

When a user agent based on XML is connected to an HTML parser, it is possible that certain invariants that XML enforces, such as comments never containing two consecutive hyphens, will be violated by an HTML file. Handling this can require that the parser coerce the HTML DOM into an XML-compatible infoset. Most syntax constructs that require such handling are considered invalid.

Errors that result in disproportionally poor performance

Certain syntax constructs can result in disproportionally poor performance. To discourage the use of such constructs, they are typically made non-conforming.

For example, the following markup results in poor performance, since all the unclosed i elements have to be reconstructed in each paragraph, resulting in progressively more elements in each paragraph:

<p><i>He dreamt.
<p><i>He dreamt that he ate breakfast.
<p><i>Then lunch.
<p><i>And finally dinner.

The resulting DOM for this fragment would be:

  • p
    • i
      • #text: He dreamt.
  • p
    • i
      • i
        • #text: He dreamt that he ate breakfast.
  • p
    • i
      • i
        • i
          • #text: Then lunch.
  • p
    • i
      • i
        • i
          • i
            • #text: And finally dinner.
Errors involving fragile syntax constructs

There are syntax constructs that, for historical reasons, are relatively fragile. To help reduce the number of users who accidentally run into such problems, they are made non-conforming.

For example, the parsing of certain named character references in attributes happens even with the closing semicolon being omitted. It is safe to include an ampersand followed by letters that do not form a named character reference, but if the letters are changed to a string that does form a named character reference, they will be interpreted as that character instead.

In this fragment, the attribute's value is "?bill&ted":

<a href="?bill&ted">Bill and Ted</a>

In the following fragment, however, the attribute's value is actually "?art©", not the intended "?art&copy":

<a href="?art&copy">Art and Copy</a>

To avoid this problem, all named character references are required to end with a semicolon, and uses of named character references without a semicolon are flagged as errors.

Thus, the correct way to express the above cases is as follows:

<a href="?bill&ted">Bill and Ted</a> <!-- &ted is ok, since it's not a named character reference -->
<a href="?art&amp;copy">Art and Copy</a> <!-- the & has to be escaped, since &copy is a named character reference -->
Errors involving known interoperability problems in legacy user agents

Certain syntax constructs are known to cause especially subtle or serious problems in legacy user agents, and are therefore marked as non-conforming to help authors avoid them.

For example, this is why the U+0060 GRAVE ACCENT character (`) is not allowed in unquoted attributes. In certain legacy user agents, it is sometimes treated as a quote character.

Another example of this is the DOCTYPE, which is required to trigger no-quirks mode, because the behavior of legacy user agents in quirks mode is often largely undocumented.

Errors that risk exposing authors to security attacks

Certain restrictions exist purely to avoid known security problems.

For example, the restriction on using UTF-7 exists purely to avoid authors falling prey to a known cross-site-scripting attack using UTF-7.

Cases where the author's intent is unclear

Markup where the author's intent is very unclear is often made non-conforming. Correcting these errors early makes later maintenance easier.

For example, it is unclear whether the author intended the following to be an h1 heading or an h2 heading:

<h1>Contact details</h2>
Cases that are likely to be typos

When a user makes a simple typo, it is helpful if the error can be caught early, as this can save the author a lot of debugging time. This specification therefore usually considers it an error to use element names, attribute names, and so forth, that do not match the names defined in this specification.

For example, if the author typed <capton> instead of <caption>, this would be flagged as an error and the author could correct the typo immediately.

Errors that could interfere with new syntax in the future

In order to allow the language syntax to be extended in the future, certain otherwise harmless features are disallowed.

For example, "attributes" in end tags are ignored currently, but they are invalid, in case a future change to the language makes use of that syntax feature without conflicting with already-deployed (and valid!) content.

Some authors find it helpful to be in the practice of always quoting all attributes and always including all optional tags, preferring the consistency derived from such custom over the minor benefits of terseness afforded by making use of the flexibility of the HTML syntax. To aid such authors, conformance checkers can provide modes of operation wherein such conventions are enforced.

1.9.3 Restrictions on content models and on attribute values

This section is non-normative.

Beyond the syntax of the language, this specification also places restrictions on how elements and attributes can be specified. These restrictions are present for similar reasons:

Errors involving content with dubious semantics

To avoid misuse of elements with defined meanings, content models are defined that restrict how elements can be nested when such nestings would be of dubious value.

For example, this specification disallows nesting a section element inside a kbd element, since it is highly unlikely for an author to indicate that an entire section should be keyed in.

Errors that involve a conflict in expressed semantics

Similarly, to draw the author's attention to mistakes in the use of elements, clear contradictions in the semantics expressed are also considered conformance errors.

In the fragments below, for example, the semantics are nonsensical: a row cannot simultaneously be a cell, nor can a radio button be a progress bar.

<tr role="cell">
<input type=radio role=progressbar>

Another example is the restrictions on the content models of the ul element, which only allows li element children. Lists by definition consist just of zero or more list items, so if a ul element contains something other than an li element, it's not clear what was meant.

Cases where the default styles are likely to lead to confusion

Certain elements have default styles or behaviors that make certain combinations likely to lead to confusion. Where these have equivalent alternatives without this problem, the confusing combinations are disallowed.

For example, div elements are rendered as block boxes, and span elements as inline boxes. Putting a block box in an inline box is unnecessarily confusing; since either nesting just div elements, or nesting just span elements, or nesting span elements inside div elements all serve the same purpose as nesting a div element in a span element, but only the latter involves a block box in an inline box, the latter combination is disallowed.

Another example would be the way interactive content cannot be nested. For example, a button element cannot contain a textarea element. This is because the default behavior of such nesting interactive elements would be highly confusing to users. Instead of nesting these elements, they can be placed side by side.

Errors that indicate a likely misunderstanding of the specification

Sometimes, something is disallowed because allowing it would likely cause author confusion.

For example, setting the disabled attribute to the value "false" is disallowed, because despite the appearance of meaning that the element is enabled, it in fact means that the element is disabled (what matters for implementations is the presence of the attribute, not its value).

Errors involving limits that have been imposed merely to simplify the language

Some conformance errors simplify the language that authors need to learn.

For example, the area element's shape attribute, despite accepting both circ and circle values in practice as synonyms, disallows the use of the circ value, so as to simplify tutorials and other learning aids. There would be no benefit to allowing both, but it would cause extra confusion when teaching the language.

Errors that involve peculiarities of the parser

Certain elements are parsed in somewhat eccentric ways (typically for historical reasons), and their content model restrictions are intended to avoid exposing the author to these issues.

For example, a form element isn't allowed inside phrasing content, because when parsed as HTML, a form element's start tag will imply a p element's end tag. Thus, the following markup results in two paragraphs, not one:

<p>Welcome. <form><label>Name:</label> <input></form>

It is parsed exactly like the following:

<p>Welcome. </p><form><label>Name:</label> <input></form>
Errors that would likely result in scripts failing in hard-to-debug ways

Some errors are intended to help prevent script problems that would be hard to debug.

This is why, for instance, it is non-conforming to have two id attributes with the same value. Duplicate IDs lead to the wrong element being selected, with sometimes disastrous effects whose cause is hard to determine.

Errors that waste authoring time

Some constructs are disallowed because historically they have been the cause of a lot of wasted authoring time, and by encouraging authors to avoid making them, authors can save time in future efforts.

For example, a script element's src attribute causes the element's contents to be ignored. However, this isn't obvious, especially if the element's contents appear to be executable script — which can lead to authors spending a lot of time trying to debug the inline script without realizing that it is not executing. To reduce this problem, this specification makes it non-conforming to have executable script in a script element when the src attribute is present. This means that authors who are validating their documents are less likely to waste time with this kind of mistake.

Errors that involve areas that affect authors migrating to and from XHTML

Some authors like to write files that can be interpreted as both XML and HTML with similar results. Though this practice is discouraged in general due to the myriad of subtle complications involved (especially when involving scripting, styling, or any kind of automated serialization), this specification has a few restrictions intended to at least somewhat mitigate the difficulties. This makes it easier for authors to use this as a transitionary step when migrating between HTML and XHTML.

For example, there are somewhat complicated rules surrounding the lang and xml:lang attributes intended to keep the two synchronized.

Another example would be the restrictions on the values of xmlns attributes in the HTML serialization, which are intended to ensure that elements in conforming documents end up in the same namespaces whether processed as HTML or XML.

Errors that involve areas reserved for future expansion

As with the restrictions on the syntax intended to allow for new syntax in future revisions of the language, some restrictions on the content models of elements and values of attributes are intended to allow for future expansion of the HTML vocabulary.

For example, limiting the values of the target attribute that start with an U+005F LOW LINE character (_) to only specific predefined values allows new predefined values to be introduced at a future time without conflicting with author-defined values.

Errors that indicate a mis-use of other specifications

Certain restrictions are intended to support the restrictions made by other specifications.

For example, requiring that attributes that take media queries use only valid media queries reinforces the importance of following the conformance rules of that specification.

This section is non-normative.

The following documents might be of interest to readers of this specification.

Character Model for the World Wide Web 1.0: Fundamentals [CHARMOD]

This Architectural Specification provides authors of specifications, software developers, and content developers with a common reference for interoperable text manipulation on the World Wide Web, building on the Universal Character Set, defined jointly by the Unicode Standard and ISO/IEC 10646. Topics addressed include use of the terms 'character', 'encoding' and 'string', a reference processing model, choice and identification of character encodings, character escaping, and string indexing.

Unicode Security Considerations [UTR36]

Because Unicode contains such a large number of characters and incorporates the varied writing systems of the world, incorrect usage can expose programs or systems to possible security attacks. This is especially important as more and more products are internationalized. This document describes some of the security considerations that programmers, system analysts, standards developers, and users should take into account, and provides specific recommendations to reduce the risk of problems.

Web Content Accessibility Guidelines (WCAG) 2.0 [WCAG]

Web Content Accessibility Guidelines (WCAG) 2.0 covers a wide range of recommendations for making Web content more accessible. Following these guidelines will make content accessible to a wider range of people with disabilities, including blindness and low vision, deafness and hearing loss, learning disabilities, cognitive limitations, limited movement, speech disabilities, photosensitivity and combinations of these. Following these guidelines will also often make your Web content more usable to users in general.

Polyglot Markup: HTML-Compatible XHTML Documents [POLYGLOT]

A document that uses polyglot markup is document that is a stream of bytes that parses into identical document trees (with the exception of the xmlns attribute on the root element) when processed as HTML and when processed as XML. Polyglot markup that meets a well defined set of constraints is interpreted as compatible, regardless of whether they are processed as HTML or as XHTML, per the HTML5 specification. Polyglot markup uses a specific DOCTYPE, namespace declarations, and a specific case — normally lower case but occasionally camel case — for element and attribute names. Polyglot markup uses lower case for certain attribute values. Further constraints include those on empty elements, named entity references, and the use of scripts and style.

2 Common infrastructure

2.1 Terminology

This specification refers to both HTML and XML attributes and IDL attributes, often in the same context. When it is not clear which is being referred to, they are referred to as content attributes for HTML and XML attributes, and IDL attributes for those defined on IDL interfaces. Similarly, the term "properties" is used for both JavaScript object properties and CSS properties. When these are ambiguous they are qualified as object properties and CSS properties respectively.

Generally, when the specification states that a feature applies to the HTML syntax or the XHTML syntax, it also includes the other. When a feature specifically only applies to one of the two languages, it is called out by explicitly stating that it does not apply to the other format, as in "for HTML, ... (this does not apply to XHTML)".

This specification uses the term document to refer to any use of HTML, ranging from short static documents to long essays or reports with rich multimedia, as well as to fully-fledged interactive applications.

For simplicity, terms such as shown, displayed, and visible might sometimes be used when referring to the way a document is rendered to the user. These terms are not meant to imply a visual medium; they must be considered to apply to other media in equivalent ways.

2.1.1 Resources

The specification uses the term supported when referring to whether a user agent has an implementation capable of decoding the semantics of an external resource. A format or type is said to be supported if the implementation can process an external resource of that format or type without critical aspects of the resource being ignored. Whether a specific resource is supported can depend on what features of the resource's format are in use.

For example, a PNG image would be considered to be in a supported format if its pixel data could be decoded and rendered, even if, unbeknownst to the implementation, the image also contained animation data.

A MPEG4 video file would not be considered to be in a supported format if the compression format used was not supported, even if the implementation could determine the dimensions of the movie from the file's metadata.

What some specifications, in particular the HTTP and URI specifications, refer to as a representation is referred to in this specification as a resource. [HTTP] [RFC3986]

The term MIME type is used to refer to what is sometimes called an Internet media type in protocol literature. The term media type in this specification is used to refer to the type of media intended for presentation, as used by the CSS specifications. [RFC2046] [MQ]

A string is a valid MIME type if it matches the media-type rule defined in section 3.7 "Media Types" of RFC 2616. In particular, a valid MIME type may include MIME type parameters. [HTTP]

A string is a valid MIME type with no parameters if it matches the media-type rule defined in section 3.7 "Media Types" of RFC 2616, but does not contain any U+003B SEMICOLON characters (;). In other words, if it consists only of a type and subtype, with no MIME Type parameters. [HTTP]

The term HTML MIME type is used to refer to the MIME types text/html and text/html-sandboxed.

A resource's critical subresources are those that the resource needs to have available to be correctly processed. Which resources are considered critical or not is defined by the specification that defines the resource's format. For CSS resources, only @import rules introduce critical subresources; other resources, e.g. fonts or backgrounds, are not.

The term data: URL refers to URLs that use the data: scheme. [RFC2397]

2.1.2 XML

To ease migration from HTML to XHTML, UAs conforming to this specification will place elements in HTML in the http://www.w3.org/1999/xhtml namespace, at least for the purposes of the DOM and CSS. The term "HTML elements", when used in this specification, refers to any element in that namespace, and thus refers to both HTML and XHTML elements.

Except where otherwise stated, all elements defined or mentioned in this specification are in the http://www.w3.org/1999/xhtml namespace, and all attributes defined or mentioned in this specification have no namespace.

Attribute names are said to be XML-compatible if they match the Name production defined in XML, they contain no U+003A COLON characters (:), and their first three characters are not an ASCII case-insensitive match for the string "xml". [XML]

The term XML MIME type is used to refer to the MIME types text/xml, application/xml, and any MIME type whose subtype ends with the four characters "+xml". [RFC3023]

2.1.3 DOM trees

The term root element, when not explicitly qualified as referring to the document's root element, means the furthest ancestor element node of whatever node is being discussed, or the node itself if it has no ancestors. When the node is a part of the document, then the node's root element is indeed the document's root element; however, if the node is not currently part of the document tree, the root element will be an orphaned node.

When an element's root element is the root element of a Document, it is said to be in a Document. An element is said to have been inserted into a document when its root element changes and is now the document's root element. Analogously, an element is said to have been removed from a document when its root element changes from being the document's root element to being another element.

A node's home subtree is the subtree rooted at that node's root element. When a node is in a Document, its home subtree is that Document's tree.

The Document of a Node (such as an element) is the Document that the Node's ownerDocument IDL attribute returns. When a Node is in a Document then that Document is always the Node's Document, and the Node's ownerDocument IDL attribute thus always returns that Document.

The term tree order means a pre-order, depth-first traversal of DOM nodes involved (through the parentNode/childNodes relationship).

When it is stated that some element or attribute is ignored, or treated as some other value, or handled as if it was something else, this refers only to the processing of the node after it is in the DOM.

The term text node refers to any Text node, including CDATASection nodes; specifically, any Node with node type TEXT_NODE (3) or CDATA_SECTION_NODE (4). [DOMCORE]

A content attribute is said to change value only if its new value is different than its previous value; setting an attribute to a value it already has does not change it.

The term empty, when used of an attribute value, text node, or string, means that the length of the text is zero (i.e. not even containing spaces or control characters).

2.1.4 Scripting

The construction "a Foo object", where Foo is actually an interface, is sometimes used instead of the more accurate "an object implementing the interface Foo".

An IDL attribute is said to be getting when its value is being retrieved (e.g. by author script), and is said to be setting when a new value is assigned to it.

If a DOM object is said to be live, then the attributes and methods on that object operate on the actual underlying data, not a snapshot of the data.

The terms fire and dispatch are used interchangeably in the context of events, as in the DOM Events specifications. The term trusted event is used as defined by the DOM Events specification. [DOMEVENTS]

2.1.5 Plugins

The term plugin refers to a user-agent defined set of content handlers used by the user agent that can take part in the user agent's rendering of a Document object, but that neither act as child browsing contexts of the Document nor introduce any Node objects to the Document's DOM.

Typically such content handlers are provided by third parties, though a user agent can also designate built-in content handlers as plugins.

One example of a plugin would be a PDF viewer that is instantiated in a browsing context when the user navigates to a PDF file. This would count as a plugin regardless of whether the party that implemented the PDF viewer component was the same as that which implemented the user agent itself. However, a PDF viewer application that launches separate from the user agent (as opposed to using the same interface) is not a plugin by this definition.

This specification does not define a mechanism for interacting with plugins, as it is expected to be user-agent- and platform-specific. Some UAs might opt to support a plugin mechanism such as the Netscape Plugin API; others might use remote content converters or have built-in support for certain types. [NPAPI]

2.1.6 Character encodings

ISSUE-101 (us-ascii-ref) blocks progress to Last Call

The preferred MIME name of a character encoding is the name or alias labeled as "preferred MIME name" in the IANA Character Sets registry, if there is one, or the encoding's name, if none of the aliases are so labeled. [IANACHARSET]

An ASCII-compatible character encoding is a single-byte or variable-length encoding in which the bytes 0x09, 0x0A, 0x0C, 0x0D, 0x20 - 0x22, 0x26, 0x27, 0x2C - 0x3F, 0x41 - 0x5A, and 0x61 - 0x7A, ignoring bytes that are the second and later bytes of multibyte sequences, all correspond to single-byte sequences that map to the same Unicode characters as those bytes in ANSI_X3.4-1968 (US-ASCII). [RFC1345]

This includes such encodings as Shift_JIS, HZ-GB-2312, and variants of ISO-2022, even though it is possible in these encodings for bytes like 0x70 to be part of longer sequences that are unrelated to their interpretation as ASCII. It excludes such encodings as UTF-7, UTF-16, GSM03.38, and EBCDIC variants.

The term Unicode character is used to mean a Unicode scalar value (i.e. any Unicode code point that is not a surrogate code point). [UNICODE]

2.2 Conformance requirements

All diagrams, examples, and notes in this specification are non-normative, as are all sections explicitly marked non-normative. Everything else in this specification is normative.

The key words "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in the normative parts of this document are to be interpreted as described in RFC2119. For readability, these words do not appear in all uppercase letters in this specification. [RFC2119]

This specification describes the conformance criteria for documents.

Conforming documents are those that comply with all the conformance criteria for documents. For readability, some of these conformance requirements are phrased as conformance requirements on authors; such requirements are implicitly requirements on documents: by definition, all documents are assumed to have had an author. (In some cases, that author may itself be a user agent — such user agents are subject to additional rules, as explained below.)

For example, if a requirement states that "authors must not use the foobar element", it would imply that documents are not allowed to contain elements named foobar.

For compatibility with existing content and prior specifications, this specification describes two authoring formats: one based on XML (referred to as the XHTML syntax), and one using a custom format inspired by SGML (referred to as the HTML syntax).

2.2.1 Extensibility

ISSUE-41 (Decentralized-extensibility) blocks progress to Last Call

HTML has a wide number of extensibility mechanisms that can be used for adding semantics in a safe manner:

2.3 Case-sensitivity and string comparison

Comparing two strings in a case-sensitive manner means comparing them exactly, code point for code point.

Comparing two strings in an ASCII case-insensitive manner means comparing them exactly, code point for code point, except that the characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) and the corresponding characters in the range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z) are considered to also match.

Comparing two strings in a compatibility caseless manner means using the Unicode compatibility caseless match operation to compare the two strings. [UNICODE]

Except where otherwise stated, string comparisons must be performed in a case-sensitive manner.

A string pattern is a prefix match for a string s when pattern is not longer than s and truncating s to pattern's length leaves the two strings as matches of each other.

2.4 Common microsyntaxes

There are various places in HTML that accept particular data types, such as dates or numbers. This section describes what the conformance criteria for content in those formats is, and how to parse them.

2.4.1 Boolean attributes

A number of attributes are boolean attributes. The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.

If the attribute is present, its value must either be the empty string or a value that is an ASCII case-insensitive match for the attribute's canonical name, with no leading or trailing whitespace.

The values "true" and "false" are not allowed on boolean attributes. To represent a false value, the attribute has to be omitted altogether.

Here is an example of a checkbox that is checked and disabled. The checked and disabled attributes are the boolean attributes.

<label><input type=checkbox checked name=cheese disabled> Cheese</label>

This could be equivalently written as this:

<label><input type=checkbox checked=checked name=cheese disabled=disabled> Cheese</label>

You can also mix styles; the following is still equivalent:

<label><input type='checkbox' checked name=cheese disabled=""> Cheese</label>

2.4.2 Keywords and enumerated attributes

Some attributes are defined as taking one of a finite set of keywords. Such attributes are called enumerated attributes. The keywords are each defined to map to a particular state (several keywords might map to the same state, in which case some of the keywords are synonyms of each other; additionally, some of the keywords can be said to be non-conforming, and are only in the specification for historical reasons). In addition, two default states can be given. The first is the invalid value default, the second is the missing value default.

If an enumerated attribute is specified, the attribute's value must be an ASCII case-insensitive match for one of the given keywords that are not said to be non-conforming, with no leading or trailing whitespace.

When the attribute is specified, if its value is an ASCII case-insensitive match for one of the given keywords then that keyword's state is the state that the attribute represents. If the attribute value matches none of the given keywords, but the attribute has an invalid value default, then the attribute represents that state. Otherwise, if the attribute value matches none of the keywords but there is a missing value default state defined, then that is the state represented by the attribute. Otherwise, there is no default, and invalid values must be ignored.

When the attribute is not specified, if there is a missing value default state defined, then that is the state represented by the (missing) attribute. Otherwise, the absence of the attribute means that there is no state represented.

The empty string can be a valid keyword.

2.4.3 Numbers

2.4.3.1 Non-negative integers

A string is a valid non-negative integer if it consists of one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9).

A valid non-negative integer represents the number that is represented in base ten by that string of digits.

2.4.3.2 Signed integers

A string is a valid integer if it consists of one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), optionally prefixed with a U+002D HYPHEN-MINUS character (-).

A valid integer without a U+002D HYPHEN-MINUS (-) prefix represents the number that is represented in base ten by that string of digits. A valid integer with a U+002D HYPHEN-MINUS (-) prefix represents the number represented in base ten by the string of digits that follows the U+002D HYPHEN-MINUS, subtracted from zero.

2.4.3.3 Real numbers

A string is a valid floating point number if it consists of:

  1. Optionally, a U+002D HYPHEN-MINUS character (-).
  2. A series of one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9).
  3. Optionally:
    1. A single U+002E FULL STOP character (.).
    2. A series of one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9).
  4. Optionally:
    1. Either a U+0065 LATIN SMALL LETTER E character (e) or a U+0045 LATIN CAPITAL LETTER E character (E).
    2. Optionally, a U+002D HYPHEN-MINUS character (-) or U+002B PLUS SIGN character (+).
    3. A series of one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9).

A valid floating point number represents the number obtained by multiplying the significand by ten raised to the power of the exponent, where the significand is the first number, interpreted as base ten (including the decimal point and the number after the decimal point, if any, and interpreting the significand as a negative number if the whole string starts with a U+002D HYPHEN-MINUS character (-) and the number is not zero), and where the exponent is the number after the E, if any (interpreted as a negative number if there is a U+002D HYPHEN-MINUS character (-) between the E and the number and the number is not zero, or else ignoring a U+002B PLUS SIGN character (+) between the E and the number if there is one). If there is no E, then the exponent is treated as zero.

The Infinity and Not-a-Number (NaN) values are not valid floating point numbers.

2.4.3.4 Lists of integers

A valid list of integers is a number of valid integers separated by U+002C COMMA characters, with no other characters (e.g. no space characters). In addition, there might be restrictions on the number of integers that can be given, or on the range of values allowed.

2.4.4 Dates and times

In the algorithms below, the number of days in month month of year year is: 31 if month is 1, 3, 5, 7, 8, 10, or 12; 30 if month is 4, 6, 9, or 11; 29 if month is 2 and year is a number divisible by 400, or if year is a number divisible by 4 but not by 100; and 28 otherwise. This takes into account leap years in the Gregorian calendar. [GREGORIAN]

The digits in the date and time syntaxes defined in this section must be characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), used to express numbers in base ten.

2.4.4.1 Months

A month consists of a specific proleptic Gregorian date with no time-zone information and no date information beyond a year and a month. [GREGORIAN]

A string is a valid month string representing a year year and month month if it consists of the following components in the given order:

  1. Four or more digits, representing year, where year > 0
  2. A U+002D HYPHEN-MINUS character (-)
  3. Two digits, representing the month month, in the range 1 ≤ month ≤ 12
2.4.4.2 Dates

A date consists of a specific proleptic Gregorian date with no time-zone information, consisting of a year, a month, and a day. [GREGORIAN]

A string is a valid date string representing a year year, month month, and day day if it consists of the following components in the given order:

  1. A valid month string, representing year and month
  2. A U+002D HYPHEN-MINUS character (-)
  3. Two digits, representing day, in the range 1 ≤ day ≤ maxday where maxday is the number of days in the month month and year year
2.4.4.3 Times

A time consists of a specific time with no time-zone information, consisting of an hour, a minute, a second, and a fraction of a second.

A string is a valid time string representing an hour hour, a minute minute, and a second second if it consists of the following components in the given order:

  1. Two digits, representing hour, in the range 0 ≤ hour ≤ 23
  2. A U+003A COLON character (:)
  3. Two digits, representing minute, in the range 0 ≤ minute ≤ 59
  4. Optionally (required if second is non-zero):
    1. A U+003A COLON character (:)
    2. Two digits, representing the integer part of second, in the range 0 ≤ s ≤ 59
    3. Optionally (required if second is not an integer):
      1. A 002E FULL STOP character (.)
      2. One or more digits, representing the fractional part of second

The second component cannot be 60 or 61; leap seconds cannot be represented.

2.4.4.4 Local dates and times

A local date and time consists of a specific proleptic Gregorian date, consisting of a year, a month, and a day, and a time, consisting of an hour, a minute, a second, and a fraction of a second, but expressed without a time zone. [GREGORIAN]

A string is a valid local date and time string representing a date and time if it consists of the following components in the given order:

  1. A valid date string representing the date.
  2. A U+0054 LATIN CAPITAL LETTER T character (T).
  3. A valid time string representing the time.
2.4.4.5 Global dates and times

A global date and time consists of a specific proleptic Gregorian date, consisting of a year, a month, and a day, and a time, consisting of an hour, a minute, a second, and a fraction of a second, expressed with a time-zone offset, consisting of a signed number of hours and minutes. [GREGORIAN]

A string is a valid global date and time string representing a date, time, and a time-zone offset if it consists of the following components in the given order:

  1. A valid date string representing the date
  2. A U+0054 LATIN CAPITAL LETTER T character (T)
  3. A valid time string representing the time
  4. Either:

This format allows for time-zone offsets from -23:59 to +23:59. In practice, however, the range of offsets of actual time zones is -12:00 to +14:00, and the minutes component of offsets of actual time zones is always either 00, 30, or 45.

The following are some examples of dates written as valid global date and time strings.

"0037-12-13T00:00Z"
Midnight UTC on the birthday of Nero (the Roman Emperor). See below for further discussion on which date this actually corresponds to.
"1979-10-14T12:00:00.001-04:00"
One millisecond after noon on October 14th 1979, in the time zone in use on the east coast of the USA during daylight saving time.
"8592-01-01T02:09+02:09"
Midnight UTC on the 1st of January, 8592. The time zone associated with that time is two hours and nine minutes ahead of UTC, which is not currently a real time zone, but is nonetheless allowed.

Several things are notable about these dates:

2.4.4.6 Weeks

A week consists of a week-year number and a week number representing a seven-day period starting on a Monday. Each week-year in this calendaring system has either 52 or 53 such seven-day periods, as defined below. The seven-day period starting on the Gregorian date Monday December 29th 1969 (1969-12-29) is defined as week number 1 in week-year 1970. Consecutive weeks are numbered sequentially. The week before the number 1 week in a week-year is the last week in the previous week-year, and vice versa. [GREGORIAN]

A week-year with a number year has 53 weeks if it corresponds to either a year year in the proleptic Gregorian calendar that has a Thursday as its first day (January 1st), or a year year in the proleptic Gregorian calendar that has a Wednesday as its first day (January 1st) and where year is a number divisible by 400, or a number divisible by 4 but not by 100. All other week-years have 52 weeks.

The week number of the last day of a week-year with 53 weeks is 53; the week number of the last day of a week-year with 52 weeks is 52.

The week-year number of a particular day can be different than the number of the year that contains that day in the proleptic Gregorian calendar. The first week in a week-year y is the week that contains the first Thursday of the Gregorian year y.

A string is a valid week string representing a week-year year and week week if it consists of the following components in the given order:

  1. Four or more digits, representing year, where year > 0
  2. A U+002D HYPHEN-MINUS character (-)
  3. A U+0057 LATIN CAPITAL LETTER W character (W)
  4. Two digits, representing the week week, in the range 1 ≤ week ≤ maxweek, where maxweek is the week number of the last day of week-year year
2.4.4.7 Vaguer moments in time

A string is a valid date or time string if it is also one of the following:

A string is a valid date or time string in content if it consists of zero or more White_Space characters, followed by a valid date or time string, followed by zero or more further White_Space characters.


A string is a valid date string with optional time if it is also one of the following:

A string is a valid date string in content with optional time if it consists of zero or more White_Space characters, followed by a valid date string with optional time, followed by zero or more further White_Space characters.

2.4.5 Colors

A simple color consists of three 8-bit numbers in the range 0..255, representing the red, green, and blue components of the color respectively, in the sRGB color space. [SRGB]

A string is a valid simple color if it is exactly seven characters long, and the first character is a U+0023 NUMBER SIGN character (#), and the remaining six characters are all in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), U+0041 LATIN CAPITAL LETTER A to U+0046 LATIN CAPITAL LETTER F, U+0061 LATIN SMALL LETTER A to U+0066 LATIN SMALL LETTER F, with the first two digits representing the red component, the middle two digits representing the green component, and the last two digits representing the blue component, in hexadecimal.

A string is a valid lowercase simple color if it is a valid simple color and doesn't use any characters in the range U+0041 LATIN CAPITAL LETTER A to U+0046 LATIN CAPITAL LETTER F.


2.4.6 Space-separated tokens

A set of space-separated tokens is a string containing zero or more words (known as tokens) separated by one or more space characters, where words consist of any string of one or more characters, none of which are space characters.

A string containing a set of space-separated tokens may have leading or trailing space characters.

An unordered set of unique space-separated tokens is a set of space-separated tokens where none of the tokens are duplicated.

An ordered set of unique space-separated tokens is a set of space-separated tokens where none of the tokens are duplicated but where the order of the tokens is meaningful.

Sets of space-separated tokens sometimes have a defined set of allowed values. When a set of allowed values is defined, the tokens must all be from that list of allowed values; other values are non-conforming. If no such set of allowed values is provided, then all values are conforming.

How tokens in a set of space-separated tokens are to be compared (e.g. case-sensitively or not) is defined on a per-set basis.

2.4.7 Comma-separated tokens

A set of comma-separated tokens is a string containing zero or more tokens each separated from the next by a single U+002C COMMA character (,), where tokens consist of any string of zero or more characters, neither beginning nor ending with space characters, nor containing any U+002C COMMA characters (,), and optionally surrounded by space characters.

For instance, the string " a ,b,,d d " consists of four tokens: "a", "b", the empty string, and "d d". Leading and trailing whitespace around each token doesn't count as part of the token, and the empty string can be a token.

Sets of comma-separated tokens sometimes have further restrictions on what consists a valid token. When such restrictions are defined, the tokens must all fit within those restrictions; other values are non-conforming. If no such restrictions are specified, then all values are conforming.

2.4.8 References

A valid hash-name reference to an element of type type is a string consisting of a U+0023 NUMBER SIGN character (#) followed by a string which exactly matches the value of the name attribute of an element with type type in the document.

2.4.9 Media queries

A string is a valid media query if it matches the media_query_list production of the Media Queries specification. [MQ]

A string matches the environment of the user if it is the empty string, a string consisting of only space characters, or is a media query that matches the user's environment according to the definitions given in the Media Queries specification. [MQ]

2.5 URLs

ISSUE-56 (urls-webarch) blocks progress to Last Call

2.5.1 Terminology

A URL is a string used to identify a resource.

A URL is a valid URL if at least one of the following conditions holds:

A string is a valid non-empty URL if it is a valid URL but it is not the empty string.

A string is a valid URL potentially surrounded by spaces if, after stripping leading and trailing whitespace from it, it is a valid URL.

A string is a valid non-empty URL potentially surrounded by spaces if, after stripping leading and trailing whitespace from it, it is a valid non-empty URL.

A URL is an absolute URL if resolving it results in the same output regardless of what it is resolved relative to, and that output is not a failure.

An absolute URL is a hierarchical URL if, when resolved and then parsed, there is a character immediately after the <scheme> component and it is a U+002F SOLIDUS character (/).

An absolute URL is an authority-based URL if, when resolved and then parsed, there are two characters immediately after the <scheme> component and they are both U+002F SOLIDUS characters (//).


This specification defines the URL about:legacy-compat as a reserved, though unresolvable, about: URI, for use in DOCTYPEs in HTML documents when needed for compatibility with XML tools. [ABOUT]

This specification defines the URL about:srcdoc as a reserved, though unresolvable, about: URI, that is used as the document's address of iframe srcdoc documents. [ABOUT]

The term "URL" in this specification is used in a manner distinct from the precise technical meaning it is given in RFC 3986. Readers familiar with that RFC will find it easier to read this specification if they pretend the term "URL" as used herein is really called something else altogether. This is a willful violation of RFC 3986. [RFC3986]

2.5.2 Interfaces for URL manipulation

An interface that has a complement of URL decomposition IDL attributes will have seven attributes with the following definitions:

           attribute DOMString protocol;
           attribute DOMString host;
           attribute DOMString hostname;
           attribute DOMString port;
           attribute DOMString pathname;
           attribute DOMString search;
           attribute DOMString hash;
o . protocol [ = value ]

Returns the current scheme of the underlying URL.

Can be set, to change the underlying URL's scheme.

o . host [ = value ]

Returns the current host and port (if it's not the default port) in the underlying URL.

Can be set, to change the underlying URL's host and port.

The host and the port are separated by a colon. The port part, if omitted, will be assumed to be the current scheme's default port.

o . hostname [ = value ]

Returns the current host in the underlying URL.

Can be set, to change the underlying URL's host.

o . port [ = value ]

Returns the current port in the underlying URL.

Can be set, to change the underlying URL's port.

o . pathname [ = value ]

Returns the current path in the underlying URL.

Can be set, to change the underlying URL's path.

o . search [ = value ]

Returns the current query component in the underlying URL.

Can be set, to change the underlying URL's query component.

o . hash [ = value ]

Returns the current fragment identifier in the underlying URL.

Can be set, to change the underlying URL's fragment identifier.

The table below demonstrates how the getter for search results in different results depending on the exact original syntax of the URL:

Input URL search value Explanation
http://example.com/ empty string No <query> component in input URL.
http://example.com/? ? There is a <query> component, but it is empty.
http://example.com/?test ?test The <query> component has the value "test".
http://example.com/?test# ?test The (empty) <fragment> component is not part of the <query> component.

The following table is similar; it provides a list of what each of the URL decomposition IDL attributes returns for a given input URL.

Input protocol host hostname port pathname search hash
http://example.com/carrot#question%3f http: example.com example.com (empty string) /carrot (empty string) #question%3f
https://www.example.com:4443? https: www.example.com:4443 www.example.com 4443 / ? (empty string)

2.6 Common DOM interfaces

2.6.1 Reflecting content attributes in IDL attributes

Some IDL attributes are defined to reflect a particular content attribute. This means that on getting, the IDL attribute returns the current value of the content attribute, and on setting, the IDL attribute changes the value of the content attribute to the given value.

2.6.2 Collections

The HTMLCollection, HTMLAllCollection, HTMLFormControlsCollection, HTMLOptionsCollection, interfaces represent various lists of DOM nodes. Collectively, objects implementing these interfaces are called collections.

When a collection is created, a filter and a root are associated with the collection.

For example, when the HTMLCollection object for the document.images attribute is created, it is associated with a filter that selects only img elements, and rooted at the root of the document.

The collection then represents a live view of the subtree rooted at the collection's root, containing only nodes that match the given filter. The view is linear.

2.6.2.1 HTMLCollection

The HTMLCollection interface represents a generic collection of elements.

interface HTMLCollection {
  readonly attribute unsigned long length;
  caller getter Element item(in unsigned long index);
  caller getter object namedItem(in DOMString name); // only returns Element
};
collection . length

Returns the number of elements in the collection.

element = collection . item(index)
collection[index]
collection(index)

Returns the item with index index from the collection. The items are sorted in tree order.

Returns null if index is out of range.

element = collection . namedItem(name)
collection[name]
collection(name)

Returns the first item with ID or name name from the collection.

Returns null if no element with that ID or name could be found.

Only a, applet, area, embed, form, frame, frameset, iframe, img, and object elements can have a name for the purpose of this method; their name is given by the value of their name attribute.

2.6.2.2 HTMLAllCollection

The HTMLAllCollection interface represents a generic collection of elements just like HTMLCollection, with the exception that its namedItem() method returns an HTMLAllCollection object when there are multiple matching elements.

interface HTMLAllCollection : HTMLCollection {
  // inherits length and item()
  caller getter object namedItem(in DOMString name); // overrides inherited namedItem()
  HTMLAllCollection tags(in DOMString tagName);
};
collection . length

Returns the number of elements in the collection.

element = collection . item(index)
collection[index]
collection(index)

Returns the item with index index from the collection. The items are sorted in tree order.

Returns null if index is out of range.

element = collection . namedItem(name)
collection = collection . namedItem(name)
collection[name]
collection(name)

Returns the item with ID or name name from the collection.

If there are multiple matching items, then an HTMLAllCollection object containing all those elements is returned.

Returns null if no element with that ID or name could be found.

Only a, applet, area, embed, form, frame, frameset, iframe, img, and object elements can have a name for the purpose of this method; their name is given by the value of their name attribute.

collection = collection . tags(tagName)

Returns a collection that is a filtered view of the current collection, containing only elements with the given tag name.

2.6.2.3 HTMLFormControlsCollection

The HTMLFormControlsCollection interface represents a collection of listed elements in form and fieldset elements.

interface HTMLFormControlsCollection : HTMLCollection {
  // inherits length and item()
  caller getter object namedItem(in DOMString name); // overrides inherited namedItem()
};

interface RadioNodeList : NodeList {
          attribute DOMString value;
};
collection . length

Returns the number of elements in the collection.

element = collection . item(index)
collection[index]
collection(index)

Returns the item with index index from the collection. The items are sorted in tree order.

Returns null if index is out of range.

element = collection . namedItem(name)
radioNodeList = collection . namedItem(name)
collection[name]
collection(name)

Returns the item with ID or name name from the collection.

If there are multiple matching items, then a RadioNodeList object containing all those elements is returned.

Returns null if no element with that ID or name could be found.

radioNodeList . value [ = value ]

Returns the value of the first checked radio button represented by the object.

Can be set, to check the first radio button with the given value represented by the object.

2.6.2.4 HTMLOptionsCollection

The HTMLOptionsCollection interface represents a list of option elements. It is always rooted on a select element and has attributes and methods that manipulate that element's descendants.

interface HTMLOptionsCollection : HTMLCollection {
  // inherits item()
           attribute unsigned long length; // overrides inherited length
  caller getter object namedItem(in DOMString name); // overrides inherited namedItem()
  void add(in HTMLElement element, in optional HTMLElement before);
  void add(in HTMLElement element, in long before);
  void remove(in long index);
           attribute long selectedIndex;
};
collection . length [ = value ]

Returns the number of elements in the collection.

When set to a smaller number, truncates the number of option elements in the corresponding container.

When set to a greater number, adds new blank option elements to that container.

element = collection . item(index)
collection[index]
collection(index)

Returns the item with index index from the collection. The items are sorted in tree order.

Returns null if index is out of range.

element = collection . namedItem(name)
nodeList = collection . namedItem(name)
collection[name]
collection(name)

Returns the item with ID or name name from the collection.

If there are multiple matching items, then a NodeList object containing all those elements is returned.

Returns null if no element with that ID could be found.

collection . add(element [, before ] )

Inserts element before the node given by before.

The before argument can be a number, in which case element is inserted before the item with that number, or an element from the collection, in which case element is inserted before that element.

If before is omitted, null, or a number out of range, then element will be added at the end of the list.

This method will throw a HIERARCHY_REQUEST_ERR exception if element is an ancestor of the element into which it is to be inserted. If element is not an option or optgroup element, then the method does nothing.

collection . selectedIndex [ = value ]

Returns the index of the first selected item, if any, or −1 if there is no selected item.

Can be set, to change the selection.

2.6.3 DOMTokenList

The DOMTokenList interface represents an interface to an underlying string that consists of a set of space-separated tokens.

DOMTokenList objects are always case-sensitive, even when the underlying string might ordinarily be treated in a case-insensitive manner.

interface DOMTokenList {
  readonly attribute unsigned long length;
  getter DOMString item(in unsigned long index);
  boolean contains(in DOMString token);
  void add(in DOMString token);
  void remove(in DOMString token);
  boolean toggle(in DOMString token);
  stringifier DOMString ();
};
tokenlist . length

Returns the number of tokens in the string.

element = tokenlist . item(index)
tokenlist[index]

Returns the token with index index. The tokens are returned in the order they are found in the underlying string.

Returns null if index is out of range.

hastoken = tokenlist . contains(token)

Returns true if the token is present; false otherwise.

Throws a SYNTAX_ERR exception if token is empty.

Throws an INVALID_CHARACTER_ERR exception if token contains any spaces.

tokenlist . add(token)

Adds token, unless it is already present.

Throws a SYNTAX_ERR exception if token is empty.

Throws an INVALID_CHARACTER_ERR exception if token contains any spaces.

tokenlist . remove(token)

Removes token if it is present.

Throws a SYNTAX_ERR exception if token is empty.

Throws an INVALID_CHARACTER_ERR exception if token contains any spaces.

hastoken = tokenlist . toggle(token)

Adds token if it is not present, or removes it if it is. Returns true if token is now present (it was added); returns false if it is not (it was removed).

Throws a SYNTAX_ERR exception if token is empty.

Throws an INVALID_CHARACTER_ERR exception if token contains any spaces.

2.6.4 DOMSettableTokenList

The DOMSettableTokenList interface is the same as the DOMTokenList interface, except that it allows the underlying string to be directly changed.

interface DOMSettableTokenList : DOMTokenList {
            attribute DOMString value;
};
tokenlist . value

Returns the underlying string.

Can be set, to change the underlying string.

2.6.5 DOMStringMap

The DOMStringMap interface represents a set of name-value pairs. It exposes these using the scripting language's native mechanisms for property access.

The dataset attribute on elements exposes the data-* attributes on the element.

Given the following fragment and elements with similar constructions:

<img class="tower" id="tower5" data-x="12" data-y="5"
     data-ai="robotarget" data-hp="46" data-ability="flames"
     src="towers/rocket.png alt="Rocket Tower">

...one could imagine a function splashDamage() that takes some arguments, the first of which is the element to process:

function splashDamage(node, x, y, damage) {
  if (node.classList.contains('tower') && // checking the 'class' attribute
      node.dataset.x == x && // reading the 'data-x' attribute
      node.dataset.y == y) { // reading the 'data-y' attribute
    var hp = parseInt(node.dataset.hp); // reading the 'data-hp' attribute
    hp = hp - damage;
    if (hp < 0) {
      hp = 0;
      node.dataset.ai = 'dead'; // setting the 'data-ai' attribute
      delete node.dataset.ability; // removing the 'data-ability' attribute
    }
    node.dataset.hp = hp; // setting the 'data-hp' attribute
  }
}

2.6.6 DOM feature strings

DOM3 Core defines mechanisms for checking for interface support, and for obtaining implementations of interfaces, using feature strings. [DOMCORE]

Authors are strongly discouraged from using these, as they are notoriously unreliable and imprecise. Authors are encouraged to rely on explicit feature testing or the graceful degradation behavior intrinsic to some of the features in this specification.

2.6.7 Exceptions

The following are DOMException codes. [DOMCORE]

  1. INDEX_SIZE_ERR
  2. DOMSTRING_SIZE_ERR
  3. HIERARCHY_REQUEST_ERR
  4. WRONG_DOCUMENT_ERR
  5. INVALID_CHARACTER_ERR
  6. NO_DATA_ALLOWED_ERR
  7. NO_MODIFICATION_ALLOWED_ERR
  8. NOT_FOUND_ERR
  9. NOT_SUPPORTED_ERR
  10. INUSE_ATTRIBUTE_ERR
  11. INVALID_STATE_ERR
  12. SYNTAX_ERR
  13. INVALID_MODIFICATION_ERR
  14. NAMESPACE_ERR
  15. INVALID_ACCESS_ERR
  16. VALIDATION_ERR
  17. TYPE_MISMATCH_ERR
  18. SECURITY_ERR
  19. NETWORK_ERR
  20. ABORT_ERR
  21. URL_MISMATCH_ERR
  22. QUOTA_EXCEEDED_ERR
  23. TIMEOUT_ERR
  24. NOT_READABLE_ERR
  25. DATA_CLONE_ERR
  26. ENCODING_ERR

2.7 Namespaces

The HTML namespace is: http://www.w3.org/1999/xhtml

The MathML namespace is: http://www.w3.org/1998/Math/MathML

The SVG namespace is: http://www.w3.org/2000/svg

The XLink namespace is: http://www.w3.org/1999/xlink

The XML namespace is: http://www.w3.org/XML/1998/namespace

The XMLNS namespace is: http://www.w3.org/2000/xmlns/


Data mining tools and other user agents that perform operations on content without running scripts, evaluating CSS or XPath expressions, or otherwise exposing the resulting DOM to arbitrary content, may "support namespaces" by just asserting that their DOM node analogues are in certain namespaces, without actually exposing the above strings.

3 Semantics, structure, and APIs of HTML documents

3.1 Documents

Every XML and HTML document in an HTML UA is represented by a Document object. [DOMCORE]

The document's address is an absolute URL that is set when the Document is created. The document's current address is an absolute URL that can change during the lifetime of the Document, for example when the user navigates to a fragment identifier on the page or when the pushState() method is called with a new URL.

Interactive user agents typically expose the document's current address in their user interface.

When a Document is created by a script using the createDocument() or createHTMLDocument() APIs, the document's address is the same as the document's address of the script's document.

Document objects are assumed to be XML documents unless they are flagged as being HTML documents when they are created. Whether a document is an HTML document or an XML document affects the behavior of certain APIs and the case-sensitivity of some selectors.

Each Document object has a reload override flag that is originally unset. The flag is set by the document.open() and document.write() methods in certain situations. When the flag is set, the Document also has a reload override buffer which is a Unicode string that is used as the source of the document when it is reloaded.

When the user agent is to perform an overridden reload, it must act as follows:

  1. Let source be the value of the browsing context's active document's reload override buffer.

  2. Navigate the browsing context to a resource whose source is source. When the navigate algorithm creates a Document object for this purpose, set that Document's reload override flag and set its reload override buffer to source.

3.1.1 Documents in the DOM

All Document objects (in user agents implementing this specification) also implement the HTMLDocument interface, available using binding-specific methods. (This is the case whether or not the document in question is an HTML document or indeed whether it contains any HTML elements at all.) Document objects also implement the document-level interface of any other namespaces that the UA supports.

For example, if an HTML implementation also supports SVG, then the Document object implements both HTMLDocument and SVGDocument.

Because the HTMLDocument interface is now obtained using binding-specific casting methods instead of simply being the primary interface of the document object, it is no longer defined as inheriting from Document.

[OverrideBuiltins]
interface HTMLDocument {
  // resource metadata management
  [PutForwards=href] readonly attribute Location location;
  readonly attribute DOMString URL;
           attribute DOMString domain;
  readonly attribute DOMString referrer;
           attribute DOMString cookie;
  readonly attribute DOMString lastModified;
  readonly attribute DOMString compatMode;
           attribute DOMString charset;
  readonly attribute DOMString characterSet;
  readonly attribute DOMString defaultCharset;
  readonly attribute DOMString readyState;

  // DOM tree accessors
  getter any (in DOMString name);
           attribute DOMString title;
           attribute DOMString dir;
           attribute HTMLElement body;
  readonly attribute HTMLHeadElement head;
  readonly attribute HTMLCollection images;
  readonly attribute HTMLCollection embeds;
  readonly attribute HTMLCollection plugins;
  readonly attribute HTMLCollection links;
  readonly attribute HTMLCollection forms;
  readonly attribute HTMLCollection scripts;
  NodeList getElementsByName(in DOMString elementName);
  NodeList getElementsByClassName(in DOMString classNames);

  // dynamic markup insertion
           attribute DOMString innerHTML;
  HTMLDocument open(in optional DOMString type, in optional DOMString replace);
  WindowProxy open(in DOMString url, in DOMString name, in DOMString features, in optional boolean replace);
  void close();
  void write(in DOMString... text);
  void writeln(in DOMString... text);

  // user interaction
  readonly attribute WindowProxy defaultView;
  readonly attribute Element activeElement;
  boolean hasFocus();
           attribute DOMString designMode;
  boolean execCommand(in DOMString commandId);
  boolean execCommand(in DOMString commandId, in boolean showUI);
  boolean execCommand(in DOMString commandId, in boolean showUI, in DOMString value);
  boolean queryCommandEnabled(in DOMString commandId);
  boolean queryCommandIndeterm(in DOMString commandId);
  boolean queryCommandState(in DOMString commandId);
  boolean queryCommandSupported(in DOMString commandId);
  DOMString queryCommandValue(in DOMString commandId);
  readonly attribute HTMLCollection commands;

  // event handler IDL attributes
           attribute Function onabort;
           attribute Function onblur;
           attribute Function oncanplay;
           attribute Function oncanplaythrough;
           attribute Function onchange;
           attribute Function onclick;
           attribute Function oncontextmenu;

           attribute Function oncuechange;

           attribute Function ondblclick;
           attribute Function ondrag;
           attribute Function ondragend;
           attribute Function ondragenter;
           attribute Function ondragleave;
           attribute Function ondragover;
           attribute Function ondragstart;
           attribute Function ondrop;
           attribute Function ondurationchange;
           attribute Function onemptied;
           attribute Function onended;
           attribute Function onerror;
           attribute Function onfocus;
           attribute Function onformchange;
           attribute Function onforminput;
           attribute Function oninput;
           attribute Function oninvalid;
           attribute Function onkeydown;
           attribute Function onkeypress;
           attribute Function onkeyup;
           attribute Function onload;
           attribute Function onloadeddata;
           attribute Function onloadedmetadata;
           attribute Function onloadstart;
           attribute Function onmousedown;
           attribute Function onmousemove;
           attribute Function onmouseout;
           attribute Function onmouseover;
           attribute Function onmouseup;
           attribute Function onmousewheel;
           attribute Function onpause;
           attribute Function onplay;
           attribute Function onplaying;
           attribute Function onprogress;
           attribute Function onratechange;
           attribute Function onreadystatechange;
           attribute Function onreset;
           attribute Function onscroll;
           attribute Function onseeked;
           attribute Function onseeking;
           attribute Function onselect;
           attribute Function onshow;
           attribute Function onstalled;
           attribute Function onsubmit;
           attribute Function onsuspend;
           attribute Function ontimeupdate;
           attribute Function onvolumechange;
           attribute Function onwaiting;
};
Document implements HTMLDocument;

Since the HTMLDocument interface holds methods and attributes related to a number of disparate features, the members of this interface are described in various different sections.

3.1.2 Security

User agents raise a SECURITY_ERR exception whenever any of the members of an HTMLDocument object are accessed by scripts whose effective script origin is not the same as the Document's effective script origin.

3.1.3 Resource metadata management

document . URL

Returns the document's address.

document . referrer

Returns the address of the Document from which the user navigated to this one, unless it was blocked or there was no such document, in which case it returns the empty string.

The noreferrer link type can be used to block the referrer.

In the case of HTTP, the referrer IDL attribute will match the Referer (sic) header that was sent when fetching the current page.

Typically user agents are configured to not report referrers in the case where the referrer uses an encrypted protocol and the current page does not (e.g. when navigating from an https: page to an http: page).


document . cookie [ = value ]

Returns the HTTP cookies that apply to the Document. If there are no cookies or cookies can't be applied to this resource, the empty string will be returned.

Can be set, to add a new cookie to the element's set of HTTP cookies.

If the contents are sandboxed into a unique origin (in an iframe with the sandbox attribute) or the resource was labeled as text/html-sandboxed, a SECURITY_ERR exception will be thrown on getting and setting.

document . lastModified

Returns the date of the last modification to the document, as reported by the server, in the form "MM/DD/YYYY hh:mm:ss", in the user's local time zone.

If the last modification date is not known, the current time is returned instead.

document . compatMode

In a conforming document, returns the string "CSS1Compat". (In quirks mode documents, returns the string "BackCompat", but a conforming document can never trigger quirks mode.)

document . charset [ = value ]

Returns the document's character encoding.

Can be set, to dynamically change the document's character encoding.

New values that are not IANA-registered aliases supported by the user agent are ignored.

document . characterSet

Returns the document's character encoding.

document . defaultCharset

Returns what might be the user agent's default character encoding. (The user agent might return another character encoding altogether, e.g. to protect the user's privacy, or if the user agent doesn't use a single default encoding.)

document . readyState

Returns "loading" while the Document is loading, "interactive" once it is finished parsing but still loading sub-resources, and "complete" once it has loaded.

The readystatechange event fires on the Document object when this value changes.

3.1.4 DOM tree accessors

The html element of a document is the document's root element, if there is one and it's an html element, or null otherwise.


document . head

Returns the head element.

The head element of a document is the first head element that is a child of the html element, if there is one, or null otherwise.


document . title [ = value ]

Returns the document's title, as given by the title element.

Can be set, to update the document's title. If there is no head element, the new value is ignored.

In SVG documents, the SVGDocument interface's title attribute takes precedence.

The title element of a document is the first title element in the document (in tree order), if there is one, or null otherwise.


document . body [ = value ]

Returns the body element.

Can be set, to replace the body element.

If the new value is not a body or frameset element, this will throw a HIERARCHY_REQUEST_ERR exception.

The body element of a document is the first child of the html element that is either a body element or a frameset element. If there is no such element, it is null.


document . images

Returns an HTMLCollection of the img elements in the Document.

document . embeds
document . plugins

Return an HTMLCollection of the embed elements in the Document.

document . links

Returns an HTMLCollection of the a and area elements in the Document that have href attributes.

document . forms

Return an HTMLCollection of the form elements in the Document.

document . scripts

Return an HTMLCollection of the script elements in the Document.

collection = document . getElementsByName(name)

Returns a NodeList of elements in the Document that have a name attribute with the value name.

collection = document . getElementsByClassName(classes)
collection = element . getElementsByClassName(classes)

Returns a NodeList of the elements in the object on which the method was invoked (a Document or an Element) that have all the classes given by classes.

The classes argument is interpreted as a space-separated list of classes.

HTML, SVG, and MathML elements define which classes they are in by having an attribute with no namespace with the name class containing a space-separated list of classes to which the element belongs. Other specifications may also allow elements in their namespaces to be labeled as being in specific classes.

Given the following XHTML fragment:

<div id="example">
 <p id="p1" class="aaa bbb"/>
 <p id="p2" class="aaa ccc"/>
 <p id="p3" class="bbb ccc"/>
</div>

A call to document.getElementById('example').getElementsByClassName('aaa') would return a NodeList with the two paragraphs p1 and p2 in it.

A call to getElementsByClassName('ccc bbb') would only return one node, however, namely p3. A call to document.getElementById('example').getElementsByClassName('bbb  ccc ') would return the same thing.

A call to getElementsByClassName('aaa,bbb') would return no nodes; none of the elements above are in the "aaa,bbb" class.


The dir attribute on the HTMLDocument interface is defined along with the dir content attribute.

3.1.5 Creating documents

XML documents can be created from script using the createDocument() method on the DOMImplementation interface.

HTML documents can be created using the createHTMLDocument() method:

[Supplemental, NoInterfaceObject]
interface DOMHTMLImplementation {
  Document createHTMLDocument(in DOMString title);
};
DOMImplementation implements DOMHTMLImplementation;
document = document . implementation . createHTMLDocument( title )

Returns a new Document, with a basic DOM already constructed with an appropriate title element.

3.2 Elements

3.2.1 Semantics

ISSUE-41 (Decentralized-extensibility) blocks progress to Last Call

Elements, attributes, and attribute values in HTML are defined (by this specification) to have certain meanings (semantics). For example, the ol element represents an ordered list, and the lang attribute represents the language of the content.

Authors must not use elements, attributes, or attribute values for purposes other than their appropriate intended semantic purpose. Authors must not use elements, attributes, or attribute values that are not permitted by this specification or other applicable specifications.

For example, the following document is non-conforming, despite being syntactically correct:

<!DOCTYPE HTML>
<html lang="en-GB">
 <head> <title> Demonstration </title> </head>
 <body>
  <table>
   <tr> <td> My favourite animal is the cat. </td> </tr>
   <tr>
    <td>
     —<a href="http://example.org/~ernest/"><cite>Ernest</cite></a>,
     in an essay from 1992
    </td>
   </tr>
  </table>
 </body>
</html>

...because the data placed in the cells is clearly not tabular data (and the cite element mis-used). A corrected version of this document might be:

<!DOCTYPE HTML>
<html lang="en-GB">
 <head> <title> Demonstration </title> </head>
 <body>
  <blockquote>
   <p> My favourite animal is the cat. </p>
  </blockquote>
  <p>
   —<a href="http://example.org/~ernest/">Ernest</a>,
   in an essay from 1992
  </p>
 </body>
</html>

This next document fragment, intended to represent the heading of a corporate site, is similarly non-conforming because the second line is not intended to be a heading of a subsection, but merely a subheading or subtitle (a subordinate heading for the same section).

<body>
 <h1>ABC Company</h1>
 <h2>Leading the way in widget design since 1432</h2>
 ...

The hgroup element is intended for these kinds of situations:

<body>
 <hgroup>
  <h1>ABC Company</h1>
  <h2>Leading the way in widget design since 1432</h2>
 </hgroup>
 ...

In the next example, there is a non-conforming attribute value ("carpet") and a non-conforming attribute ("texture"), which is not permitted by this specification:

<label>Carpet: <input type="carpet" name="c" texture="deep pile"></label>

Here would be an alternative and correct way to mark this up:

<label>Carpet: <input type="text" class="carpet" name="c" data-texture="deep pile"></label>

Through scripting and using other mechanisms, the values of attributes, text, and indeed the entire structure of the document may change dynamically while a user agent is processing it. The semantics of a document at an instant in time are those represented by the state of the document at that instant in time, and the semantics of a document can therefore change over time. User agents update their presentation of the document as this occurs.

HTML has a progress element that describes a progress bar. If its "value" attribute is dynamically updated by a script, the UA would update the rendering to show the progress changing.

3.2.2 Elements in the DOM

The nodes representing HTML elements in the DOM implement, and expose to scripts, the interfaces listed for them in the relevant sections of this specification. This includes HTML elements in XML documents, even when those documents are in another context (e.g. inside an XSLT transform).

Elements in the DOM represent things; that is, they have intrinsic meaning, also known as semantics.

For example, an ol element represents an ordered list.

The basic interface, from which all the HTML elements' interfaces inherit, is the HTMLElement interface.

interface HTMLElement : Element {
  // DOM tree accessors
  NodeList getElementsByClassName(in DOMString classNames);

  // dynamic markup insertion
           attribute DOMString innerHTML;
           attribute DOMString outerHTML;
  void insertAdjacentHTML(in DOMString position, in DOMString text);

  // metadata attributes
           attribute DOMString id;
           attribute DOMString title;
           attribute DOMString lang;
           attribute DOMString dir;
           attribute DOMString className;
  readonly attribute DOMTokenList classList;
  readonly attribute DOMStringMap dataset;

  // user interaction
           attribute boolean hidden;
  void click();
           attribute long tabIndex;
  void focus();
  void blur();
           attribute DOMString accessKey;
  readonly attribute DOMString accessKeyLabel;
           attribute boolean draggable;
  [PutForwards=value] attribute DOMSettableTokenList dropzone;
           attribute DOMString contentEditable;
  readonly attribute boolean isContentEditable;
           attribute HTMLMenuElement contextMenu;
           attribute boolean spellcheck;

  // command API
  readonly attribute DOMString commandType;
  readonly attribute DOMString label;
  readonly attribute DOMString icon;
  readonly attribute boolean disabled;
  readonly attribute boolean checked;

  // styling
  readonly attribute CSSStyleDeclaration style;

  // event handler IDL attributes
           attribute Function onabort;
           attribute Function onblur;
           attribute Function oncanplay;
           attribute Function oncanplaythrough;
           attribute Function onchange;
           attribute Function onclick;
           attribute Function oncontextmenu;

           attribute Function oncuechange;

           attribute Function ondblclick;
           attribute Function ondrag;
           attribute Function ondragend;
           attribute Function ondragenter;
           attribute Function ondragleave;
           attribute Function ondragover;
           attribute Function ondragstart;
           attribute Function ondrop;
           attribute Function ondurationchange;
           attribute Function onemptied;
           attribute Function onended;
           attribute Function onerror;
           attribute Function onfocus;
           attribute Function onformchange;
           attribute Function onforminput;
           attribute Function oninput;
           attribute Function oninvalid;
           attribute Function onkeydown;
           attribute Function onkeypress;
           attribute Function onkeyup;
           attribute Function onload;
           attribute Function onloadeddata;
           attribute Function onloadedmetadata;
           attribute Function onloadstart;
           attribute Function onmousedown;
           attribute Function onmousemove;
           attribute Function onmouseout;
           attribute Function onmouseover;
           attribute Function onmouseup;
           attribute Function onmousewheel;
           attribute Function onpause;
           attribute Function onplay;
           attribute Function onplaying;
           attribute Function onprogress;
           attribute Function onratechange;
           attribute Function onreadystatechange;
           attribute Function onreset;
           attribute Function onscroll;
           attribute Function onseeked;
           attribute Function onseeking;
           attribute Function onselect;
           attribute Function onshow;
           attribute Function onstalled;
           attribute Function onsubmit;
           attribute Function onsuspend;
           attribute Function ontimeupdate;
           attribute Function onvolumechange;
           attribute Function onwaiting;
};

interface HTMLUnknownElement : HTMLElement { };

The HTMLElement interface holds methods and attributes related to a number of disparate features, and the members of this interface are therefore described in various different sections of this specification.

3.2.3 Global attributes

The following attributes are common to and may be specified on all HTML elements:


The following event handler content attributes may be specified on any HTML element:

The attributes marked with an asterisk have a different meaning when specified on body elements as those elements expose event handlers of the Window object with the same names.

While these attributes apply to all elements, they are not useful on all elements. For example, only media elements will ever receive a volumechange event fired by the user agent.


Custom data attributes (e.g. data-foldername or data-msgid) can be specified on any HTML element, to store custom data specific to the page.


In HTML documents, elements in the HTML namespace may have an xmlns attribute specified, if, and only if, it has the exact value "http://www.w3.org/1999/xhtml". This does not apply to XML documents.

In HTML, the xmlns attribute has absolutely no effect. It is basically a talisman. It is allowed merely to make migration to and from XHTML mildly easier. When parsed by an HTML parser, the attribute ends up in no namespace, not the "http://www.w3.org/2000/xmlns/" namespace like namespace declaration attributes in XML do.

In XML, an xmlns attribute is part of the namespace declaration mechanism, and an element cannot actually have an xmlns attribute in no namespace specified.


The XML specification also allows the use of the xml:space attribute in the XML namespace on any element in an XML document. This attribute has no effect on HTML elements, as the default behavior in HTML is to preserve whitespace. [XML]

There is no way to serialize the xml:space attribute on HTML elements in the text/html syntax.


To enable assistive technology products to expose a more fine-grained interface than is otherwise possible with HTML elements and attributes, a set of annotations for assistive technology products can be specified (the ARIA role and aria-* attributes).

3.2.3.1 The id attribute

The id attribute specifies its element's unique identifier (ID). The value must be unique amongst all the IDs in the element's home subtree and must contain at least one character. The value must not contain any space characters.

An element's unique identifier can be used for a variety of purposes, most notably as a way to link to specific parts of a document using fragment identifiers, as a way to target an element when scripting, and as a way to style a specific element from CSS.

3.2.3.2 The title attribute

The title attribute represents advisory information for the element, such as would be appropriate for a tooltip. On a link, this could be the title or a description of the target resource; on an image, it could be the image credit or a description of the image; on a paragraph, it could be a footnote or commentary on the text; on a citation, it could be further information about the source; and so forth. The value is text.

If this attribute is omitted from an element, then it implies that the title attribute of the nearest ancestor HTML element with a title attribute set is also relevant to this element. Setting the attribute overrides this, explicitly stating that the advisory information of any ancestors is not relevant to this element. Setting the attribute to the empty string indicates that the element has no advisory information.

If the title attribute's value contains U+000A LINE FEED (LF) characters, the content is split into multiple lines. Each U+000A LINE FEED (LF) character represents a line break.

Caution is advised with respect to the use of newlines in title attributes.

For instance, the following snippet actually defines an abbreviation's expansion with a line break in it:

<p>My logs show that there was some interest in <abbr title="Hypertext
Transport Protocol">HTTP</abbr> today.</p>

Some elements, such as link, abbr, and input, define additional semantics for the title attribute beyond the semantics described above.

3.2.3.3 The lang and xml:lang attributes

The lang attribute (in no namespace) specifies the primary language for the element's contents and for any of the element's attributes that contain text. Its value must be a valid BCP 47 language tag, or the empty string. Setting the attribute to the empty string indicates that the primary language is unknown. [BCP47]

The lang attribute in the XML namespace is defined in XML. [XML]

If these attributes are omitted from an element, then the language of this element is the same as the language of its parent element, if any.

The lang attribute in no namespace may be used on any HTML element.

The lang attribute in the XML namespace may be used on HTML elements in XML documents, as well as elements in other namespaces if the relevant specifications allow it (in particular, MathML and SVG allow lang attributes in the XML namespace to be specified on their elements). If both the lang attribute in no namespace and the lang attribute in the XML namespace are specified on the same element, they must have exactly the same value when compared in an ASCII case-insensitive manner.

Authors must not use the lang attribute in the XML namespace on HTML elements in HTML documents. To ease migration to and from XHTML, authors may specify an attribute in no namespace with no prefix and with the literal localname "xml:lang" on HTML elements in HTML documents, but such attributes must only be specified if a lang attribute in no namespace is also specified, and both attributes must have the same value when compared in an ASCII case-insensitive manner.

The attribute in no namespace with no prefix and with the literal localname "xml:lang" has no effect on language processing.

3.2.3.4 The xml:base attribute (XML only)

The xml:base attribute is defined in XML Base. [XMLBASE]

The xml:base attribute may be used on elements of XML documents. Authors must not use the xml:base attribute in HTML documents.

3.2.3.5 The dir attribute

The dir attribute specifies the element's text directionality. The attribute is an enumerated attribute with the following keywords and states:

The ltr keyword, which maps to the ltr state

Indicates that the contents of the element are explicitly directionally embedded left-to-right text.

The rtl keyword, which maps to the rtl state

Indicates that the contents of the element are explicitly directionally embedded right-to-left text.

The auto keyword, which maps to the auto state

Indicates that the contents of the element are explicitly embedded text, but that the direction is to be determined programmatically using the contents of the element (as described below).

The heuristic used by this state is very crude (it just looks at the first character with a strong directionality, in a manner analogous to the Paragraph Level determination in the bidirectional algorithm). Authors are urged to only use this value as a last resort when the direction of the text is truly unknown and no better server-side heuristic can be applied.

The attribute has no invalid value default and no missing value default.

The directionality of an element is either 'ltr' or 'rtl', and is determined as per the first appropriate set of steps from the following list:

If the element's dir attribute is in the ltr state

The directionality of the element is 'ltr'.

If the element's dir attribute is in the rtl state

The directionality of the element is 'rtl'.

If the element's dir attribute is in the auto state
If the element is a bdi element and the dir attribute is not in a defined state (i.e. it is not present or has an invalid value)

Find the first character in tree order that matches the following criteria:

If such a character is found and it is of bidirectional character type AL or R, the directionality of the element is 'rtl'.

Otherwise, the directionality of the element is 'ltr'.

If the element is a root element and the dir attribute is not in a defined state (i.e. it is not present or has an invalid value)

The directionality of the element is 'ltr'.

If the element has a parent element and the dir attribute is not in a defined state (i.e. it is not present or has an invalid value)

The directionality of the element is the same as the element's parent element's directionality.

The effect of this attribute is primarily on the presentation layer. For example, the rendering section in this specification defines a mapping from this attribute to the CSS 'direction' and 'unicode-bidi' properties, and CSS defines rendering in terms of those properties.


document . dir [ = value ]

Returns the html element's dir attribute's value, if any.

Can be set, to either "ltr", "rtl", or "auto" to replace the html element's dir attribute's value.

If there is no html element, returns the empty string and ignores new values.

Authors are strongly encouraged to use the dir attribute to indicate text direction rather than using CSS, since that way their documents will continue to render correctly even in the absence of CSS (e.g. as interpreted by search engines).

This markup fragment is of an IM conversation.

<p dir=auto class="u1"><b><bdi>Student</bdi>:</b> How do you write "What's your name?" in Arabic?</p>
<p dir=auto class="u2"><b><bdi>Teacher</bdi>:</b> ما اسمك؟</p>
<p dir=auto class="u1"><b><bdi>Student</bdi>:</b> Thanks.</p>
<p dir=auto class="u2"><b><bdi>Teacher</bdi>:</b> That's written "شكرًا".</p>
<p dir=auto class="u2"><b><bdi>Teacher</bdi>:</b> Do you know how to write "Please"?</p>
<p dir=auto class="u1"><b><bdi>Student</bdi>:</b> "من فضلك", right?</p>

Given a suitable style sheet and the default alignment styles for the p element, namely to align the text to the start edge of the paragraph, the resulting rendering could be as follows:

Each paragraph rendered as a separate block, with the paragraphs left-aligned except the second paragraph and the last one, which would  be right aligned, with the usernames ('Student' and 'Teacher' in this example) flush right, with a colon to their left, and the text first to the left of that.

As noted earlier, the auto value is not a panacea. The final paragraph in this example is misinterpreted as being right-to-left text, since it begins with an Arabic character, which causes the "right?" to be to the left of the Arabic text.

3.2.3.6 The class attribute

Every HTML element may have a class attribute specified.

The attribute, if specified, must have a value that is a set of space-separated tokens representing the various classes that the element belongs to.

Assigning classes to an element affects class matching in selectors in CSS, the getElementsByClassName() method in the DOM, and other such features.

There are no additional restrictions on the tokens authors can use in the class attribute, but authors are encouraged to use values that describe the nature of the content, rather than values that describe the desired presentation of the content.

3.2.3.7 The style attribute

All HTML elements may have the style content attribute set. This is a CSS styling attribute as defined by the CSS Styling Attribute Syntax specification. [CSSATTR]

Documents that use style attributes on any of their elements must still be comprehensible and usable if those attributes were removed.

In particular, using the style attribute to hide and show content, or to convey meaning that is otherwise not included in the document, is non-conforming. (To hide and show content, use the hidden attribute.)


element . style

Returns a CSSStyleDeclaration object for the element's style attribute.

In the following example, the words that refer to colors are marked up using the span element and the style attribute to make those words show up in the relevant colors in visual media.

<p>My sweat suit is <span style="color: green; background:
transparent">green</span> and my eyes are <span style="color: blue;
background: transparent">blue</span>.</p>
3.2.3.8 Embedding custom non-visible data with the data-* attributes

A custom data attribute is an attribute in no namespace whose name starts with the string "data-", has at least one character after the hyphen, is XML-compatible, and contains no characters in the range U+0041 to U+005A (LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z).

All attributes on HTML elements in HTML documents get ASCII-lowercased automatically, so the restriction on ASCII uppercase letters doesn't affect such documents.

Custom data attributes are intended to store custom data private to the page or application, for which there are no more appropriate attributes or elements.

These attributes are not intended for use by software that is independent of the site that uses the attributes.

For instance, a site about music could annotate list items representing tracks in an album with custom data attributes containing the length of each track. This information could then be used by the site itself to allow the user to sort the list by track length, or to filter the list for tracks of certain lengths.

<ol>
 <li data-length="2m11s">Beyond The Sea</li>
 ...
</ol>

It would be inappropriate, however, for the user to use generic software not associated with that music site to search for tracks of a certain length by looking at this data.

This is because these attributes are intended for use by the site's own scripts, and are not a generic extension mechanism for publicly-usable metadata.

Every HTML element may have any number of custom data attributes specified, with any value.


element . dataset

Returns a DOMStringMap object for the element's data-* attributes.

Hyphenated names become camel-cased. For example, data-foo-bar="" becomes element.dataset.fooBar.

If a Web page wanted an element to represent a space ship, e.g. as part of a game, it would have to use the class attribute along with data-* attributes:

<div class="spaceship" data-ship-id="92432"
     data-weapons="laser 2" data-shields="50%"
     data-x="30" data-y="10" data-z="90">
 <button class="fire"
         onclick="spaceships[this.parentNode.dataset.shipId].fire()">
  Fire
 </button>
</div>

Notice how the hyphenated attribute name becomes camel-cased in the API.

Authors should carefully design such extensions so that when the attributes are ignored and any associated CSS dropped, the page is still usable.

JavaScript libraries may use the custom data attributes, as they are considered to be part of the page on which they are used. Authors of libraries that are reused by many authors are encouraged to include their name in the attribute names, to reduce the risk of clashes. Where it makes sense, library authors are also encouraged to make the exact name used in the attribute names customizable, so that libraries whose authors unknowingly picked the same name can be used on the same page, and so that multiple versions of a particular library can be used on the same page even when those versions are not mutually compatible.

For example, a library called "DoQuery" could use attribute names like data-doquery-range, and a library called "jJo" could use attributes names like data-jjo-range. The jJo library could also provide an API to set which prefix to use (e.g. J.setDataPrefix('j2'), making the attributes have names like data-j2-range).

3.2.4 Element definitions

Each element in this specification has a definition that includes the following information:

Categories

A list of categories to which the element belongs. These are used when defining the content models for each element.

Contexts in which this element can be used

A non-normative description of where the element can be used. This information is redundant with the content models of elements that allow this one as a child, and is provided only as a convenience.

For simplicity, only the most specific expectations are listed. For example, an element that is both flow content and phrasing content can be used anywhere that either flow content or phrasing content is expected, but since anywhere that flow content is expected, phrasing content is also expected (since all phrasing content is flow content), only "where phrasing content is expected" will be listed.

Content model

A normative description of what content must be included as children and descendants of the element.

Content attributes

A normative list of attributes that may be specified on the element (except where otherwise disallowed).

DOM interface

A normative definition of a DOM interface that such elements must implement.

This is then followed by a description of what the element represents, along with any additional normative conformance criteria that may apply to authors. Examples are sometimes also included.

3.2.4.1 Attributes

Except where otherwise specified, attributes on HTML elements may have any string value, including the empty string. Except where explicitly stated, there is no restriction on what text can be specified in such attributes.

3.2.5 Content models

Each element defined in this specification has a content model: a description of the element's expected contents. An HTML element must have contents that match the requirements described in the element's content model.

As noted in the conformance and terminology sections, for the purposes of determining if an element matches its content model or not, CDATASection nodes in the DOM are treated as equivalent to Text nodes, and entity reference nodes are treated as if they were expanded in place.

The space characters are always allowed between elements. User agents represent these characters between elements in the source markup as text nodes in the DOM. Empty text nodes and text nodes consisting of just sequences of those characters are considered inter-element whitespace.

Inter-element whitespace, comment nodes, and processing instruction nodes must be ignored when establishing whether an element's contents match the element's content model or not, and must be ignored when following algorithms that define document and element semantics.

Thus, an element A is said to be preceded or followed by a second element B if A and B have the same parent node and there are no other element nodes or text nodes (other than inter-element whitespace) between them. Similarly, a node is the only child of an element if that element contains no other nodes other than inter-element whitespace, comment nodes, and processing instruction nodes.

Authors must not use HTML elements anywhere except where they are explicitly allowed, as defined for each element, or as explicitly required by other specifications. For XML compound documents, these contexts could be inside elements from other namespaces, if those elements are defined as providing the relevant contexts.

For example, the Atom specification defines a content element. When its type attribute has the value xhtml, the Atom specification requires that it contain a single HTML div element. Thus, a div element is allowed in that context, even though this is not explicitly normatively stated by this specification. [ATOM]

In addition, HTML elements may be orphan nodes (i.e. without a parent node).

For example, creating a td element and storing it in a global variable in a script is conforming, even though td elements are otherwise only supposed to be used inside tr elements.

var data = {
  name: "Banana",
  cell: document.createElement('td'),
};
3.2.5.1 Kinds of content

Each element in HTML falls into zero or more categories that group elements with similar characteristics together. The following broad categories are used in this specification:

Some elements also fall into other categories, which are defined in other parts of this specification.

These categories are related as follows:

Sectioning content, heading content, phrasing content, and
  embedded content are all types of flow content. Embedded content is
  also a type of phrasing content.

In addition, certain elements are categorized as form-associated elements and further subcategorized to define their role in various form-related processing models.

Some elements have unique requirements and do not fit into any particular category.

3.2.5.1.1 Metadata content

Metadata content is content that sets up the presentation or behavior of the rest of the content, or that sets up the relationship of the document with other documents, or that conveys other "out of band" information.

Elements from other namespaces whose semantics are primarily metadata-related (e.g. RDF) are also metadata content.

Thus, in the XML serialization, one can use RDF, like this:

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:r="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
 <head>
  <title>Hedral's Home Page</title>
  <r:RDF>
   <Person xmlns="http://www.w3.org/2000/10/swap/pim/contact#"
           r:about="http://hedral.example.com/#">
    <fullName>Cat Hedral</fullName>
    <mailbox r:resource="mailto:hedral@damowmow.com"/>
    <personalTitle>Sir</personalTitle>
   </Person>
  </r:RDF>
 </head>
 <body>
  <h1>My home page</h1>
  <p>I like playing with string, I guess. Sister says squirrels are fun
  too so sometimes I follow her to play with them.</p>
 </body>
</html>

This isn't possible in the HTML serialization, however.

3.2.5.1.2 Flow content

Most elements that are used in the body of documents and applications are categorized as flow content.

As a general rule, elements whose content model allows any flow content should have either at least one descendant text node that is not inter-element whitespace, or at least one descendant element node that is embedded content. For the purposes of this requirement, del elements and their descendants must not be counted as contributing to the ancestors of the del element.

This requirement is not a hard requirement, however, as there are many cases where an element can be empty legitimately, for example when it is used as a placeholder which will later be filled in by a script, or when the element is part of a template and would on most pages be filled in but on some pages is not relevant.

3.2.5.1.3 Sectioning content

Sectioning content is content that defines the scope of headings and footers.

Each sectioning content element potentially has a heading and an outline. See the section on headings and sections for further details.

There are also certain elements that are sectioning roots. These are distinct from sectioning content, but they can also have an outline.

3.2.5.1.4 Heading content

Heading content defines the header of a section (whether explicitly marked up using sectioning content elements, or implied by the heading content itself).

3.2.5.1.5 Phrasing content

Phrasing content is the text of the document, as well as elements that mark up that text at the intra-paragraph level. Runs of phrasing content form paragraphs.

As a general rule, elements whose content model allows any phrasing content should have either at least one descendant text node that is not inter-element whitespace, or at least one descendant element node that is embedded content. For the purposes of this requirement, nodes that are descendants of del elements must not be counted as contributing to the ancestors of the del element.

Most elements that are categorized as phrasing content can only contain elements that are themselves categorized as phrasing content, not any flow content.

Text, in the context of content models, means text nodes. Text is sometimes used as a content model on its own, but is also phrasing content, and can be inter-element whitespace (if the text nodes are empty or contain just space characters).

3.2.5.1.6 Embedded content

Embedded content is content that imports another resource into the document, or content from another vocabulary that is inserted into the document.

Elements that are from namespaces other than the HTML namespace and that convey content but not metadata, are embedded content for the purposes of the content models defined in this specification. (For example, MathML, or SVG.)

Some embedded content elements can have fallback content: content that is to be used when the external resource cannot be used (e.g. because it is of an unsupported format). The element definitions state what the fallback is, if any.

3.2.5.1.7 Interactive content

Interactive content is content that is specifically intended for user interaction.

Certain elements in HTML have an activation behavior, which means that the user can activate them. This triggers a sequence of events dependent on the activation mechanism, and normally culminating in a click event.

3.2.5.2 Transparent content models

Some elements are described as transparent; they have "transparent" in the description of their content model. The content model of a transparent element is derived from the content model of its parent element: the elements required in the part of the content model that is "transparent" are the same elements as required in the part of the content model of the parent of the transparent element in which the transparent element finds itself.

For instance, an ins element inside a ruby element cannot contain an rt element, because the part of the ruby element's content model that allows ins elements is the part that allows phrasing content, and the rt element is not phrasing content.

In some cases, where transparent elements are nested in each other, the process has to be applied iteratively.

Consider the following markup fragment:

<p><object><param><ins><map><a href="/">Apples</a></map></ins></object></p>

To check whether "Apples" is allowed inside the a element, the content models are examined. The a element's content model is transparent, as is the map element's, as is the ins element's, as is the part of the object element's in which the ins element is found. The object element is found in the p element, whose content model is phrasing content. Thus, "Apples" is allowed, as text is phrasing content.

When a transparent element has no parent, then the part of its content model that is "transparent" must instead be treated as accepting any flow content.

3.2.5.3 Paragraphs

The term paragraph as defined in this section is distinct from (though related to) the p element defined later. The paragraph concept defined here is used to describe how to interpret documents.

A paragraph is typically a run of phrasing content that forms a block of text with one or more sentences that discuss a particular topic, as in typography, but can also be used for more general thematic grouping. For instance, an address is also a paragraph, as is a part of a form, a byline, or a stanza in a poem.

In the following example, there are two paragraphs in a section. There is also a heading, which contains phrasing content that is not a paragraph. Note how the comments and inter-element whitespace do not form paragraphs.

<section>
  <h1>Example of paragraphs</h1>
  This is the <em>first</em> paragraph in this example.
  <p>This is the second.</p>
  <!-- This is not a paragraph. -->
</section>

Paragraphs in flow content are defined relative to what the document looks like without the a, ins, del, and map elements complicating matters, since those elements, with their hybrid content models, can straddle paragraph boundaries, as shown in the first two examples below.

Generally, having elements straddle paragraph boundaries is best avoided. Maintaining such markup can be difficult.

The following example takes the markup from the earlier example and puts ins and del elements around some of the markup to show that the text was changed (though in this case, the changes admittedly don't make much sense). Notice how this example has exactly the same paragraphs as the previous one, despite the ins and del elements — the ins element straddles the heading and the first paragraph, and the del element straddles the boundary between the two paragraphs.

<section>
  <ins><h1>Example of paragraphs</h1>
  This is the <em>first</em> paragraph in</ins> this example<del>.
  <p>This is the second.</p></del>
  <!-- This is not a paragraph. -->
</section>

A paragraph is also formed explicitly by p elements.

The p element can be used to wrap individual paragraphs when there would otherwise not be any content other than phrasing content to separate the paragraphs from each other.

In the following example, the link spans half of the first paragraph, all of the heading separating the two paragraphs, and half of the second paragraph. It straddles the paragraphs and the heading.

<aside>
 Welcome!
 <a href="about.html">
  This is home of...
  <h1>The Falcons!</h1>
  The Lockheed Martin multirole jet fighter aircraft!
 </a>
 This page discusses the F-16 Fighting Falcon's innermost secrets.
</aside>

Here is another way of marking this up, this time showing the paragraphs explicitly, and splitting the one link element into three:

<aside>
 <p>Welcome! <a href="about.html">This is home of...</a></p>
 <h1><a href="about.html">The Falcons!</a></h1>
 <p><a href="about.html">The Lockheed Martin multirole jet
 fighter aircraft!</a> This page discusses the F-16 Fighting
 Falcon's innermost secrets.</p>
</aside>

It is possible for paragraphs to overlap when using certain elements that define fallback content. For example, in the following section:

<section>
 <h1>My Cats</h1>
 You can play with my cat simulator.
 <object data="cats.sim">
  To see the cat simulator, use one of the following links:
  <ul>
   <li><a href="cats.sim">Download simulator file</a>
   <li><a href="http://sims.example.com/watch?v=LYds5xY4INU">Use online simulator</a>
  </ul>
  Alternatively, upgrade to the Mellblom Browser.
 </object>
 I'm quite proud of it.
</section>

There are five paragraphs:

  1. The paragraph that says "You can play with my cat simulator. object I'm quite proud of it.", where object is the object element.
  2. The paragraph that says "To see the cat simulator, use one of the following links:".
  3. The paragraph that says "Download simulator file".
  4. The paragraph that says "Use online simulator".
  5. The paragraph that says "Alternatively, upgrade to the Mellblom Browser.".

The first paragraph is overlapped by the other four. A user agent that supports the "cats.sim" resource will only show the first one, but a user agent that shows the fallback will confusingly show the first sentence of the first paragraph as if it was in the same paragraph as the second one, and will show the last paragraph as if it was at the start of the second sentence of the first paragraph.

To avoid this confusion, explicit p elements can be used.

3.2.6 Requirements relating to bidirectional-algorithm formatting characters

Text content in HTML elements with child text nodes, and text in attributes of HTML elements that allow free-form text, may contain characters in the range U+202A to U+202E (the bidirectional-algorithm formatting characters). However, the use of these characters is restricted so that any embedding or overrides generated by these characters do not start and end with different parent elements, and so that all such embeddings and overrides are explicitly terminated by a U+202C POP DIRECTIONAL FORMATTING character. This helps reduces incidences of text being reused in a manner that has unforseen effects on the bidirectional algorithm.

The aforementioned restrictions are defined by specifying that certain parts of documents form bidirectional-algorithm formatting character ranges, and then imposing a requirement on such ranges.

The string resulting from the concatenation of the data of all of an HTML element's text nodes, if any, is a bidirectional-algorithm formatting character range.

The value of a namespace-less attribute of an HTML element is a bidirectional-algorithm formatting character range.

Any strings that, as described above, are bidirectional-algorithm formatting character ranges must match the string production in the following ABNF, the character set for which is Unicode. [ABNF]

string        = *( plaintext ( embedding / override ) ) plaintext
embedding     = ( lre / rle ) string pdf
override      = ( lro / rlo ) string pdf
lre           = %x202A ; U+202A LEFT-TO-RIGHT EMBEDDING
rle           = %x202B ; U+202B RIGHT-TO-LEFT EMBEDDING
lro           = %x202D ; U+202D LEFT-TO-RIGHT OVERRIDE
rlo           = %x202E ; U+202E RIGHT-TO-LEFT OVERRIDE
pdf           = %x202C ; U+202C POP DIRECTIONAL FORMATTING
plaintext     = *( %x0000-2029 / %x202F-10FFFF )
                ; any string with no bidirectional-algorithm formatting characters

For convenience, where possible authors will likely prefer to use the dir attribute, the bdo element, and the bdi element, rather than maintaining the bidirectional-algorithm formatting characters manually.

3.2.7 Annotations for assistive technology products (ARIA)

Authors may use the ARIA role and aria-* attributes on HTML elements, in accordance with the requirements described in the ARIA specifications, except where these conflict with the strong native semantics described below. These exceptions are intended to prevent authors from making assistive technology products report nonsensical states that do not represent the actual state of the document. [ARIA]

The following table defines the strong native semantics that apply to HTML elements. Each language feature (element or attribute) in a cell in the first column implies the ARIA semantics (role, states, and/or properties) given in the cell in the second column of the same row. Authors must not set the ARIA role and aria-* attributes in a manner that conflicts with the semantics described in the following table, except that the presentation role may always be used.

Language feature Strong native semantics
base element No role
a element that creates a hyperlink link role
area element that creates a hyperlink link role
button element button role
datalist element listbox role, with the aria-multiselectable property set to "false"
details element aria-expanded state set to "true" if the element's open attribute is present, and set to "false" otherwise
h1 element that does not have an hgroup ancestor heading role, with the aria-level property set to the element's outline depth
h2 element that does not have an hgroup ancestor heading role, with the aria-level property set to the element's outline depth
h3 element that does not have an hgroup ancestor heading role, with the aria-level property set to the element's outline depth
h4 element that does not have an hgroup ancestor heading role, with the aria-level property set to the element's outline depth
h5 element that does not have an hgroup ancestor heading role, with the aria-level property set to the element's outline depth
h6 element that does not have an hgroup ancestor heading role, with the aria-level property set to the element's outline depth
head element No role
hgroup element heading role, with the aria-level property set to the element's outline depth
hr element separator role
html element No role
img element whose alt attribute's value is empty presentation role
input element with a type attribute in the Button state button role
input element with a type attribute in the Checkbox state aria-checked state set to "mixed" if the element's indeterminate IDL attribute is true, or "true" if the element's checkedness is true, or "false" otherwise
input element with a type attribute in the Color state No role
input element with a type attribute in the Date state No role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the Date and Time state No role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the Local Date and Time state No role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the E-mail state with no suggestions source element textbox role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the File Upload state No role
input element with a type attribute in the Hidden state No role
input element with a type attribute in the Image Button state button role
input element with a type attribute in the Month state No role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the Number state spinbutton role, with the aria-readonly state set to "true" if the element has a readonly attribute, the aria-valuemax property set to the element's maximum, the aria-valuemin property set to the element's minimum, and, if the result of applying the rules for parsing floating point number values to the element's value is a number, with the aria-valuenow property set to that number
input element with a type attribute in the Password state textbox role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the Radio Button state aria-checked state set to "true" if the element's checkedness is true, or "false" otherwise
input element with a type attribute in the Range state slider role, with the aria-valuemax property set to the element's maximum, the aria-valuemin property set to the element's minimum, and the aria-valuenow property set to the result of applying the rules for parsing floating point number values to the element's value, if that results in a number, or the default value otherwise
input element with a type attribute in the Reset Button state button role
input element with a type attribute in the Search state with no suggestions source element textbox role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the Submit Button state button role
input element with a type attribute in the Telephone state with no suggestions source element textbox role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the Text state with no suggestions source element textbox role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the Text, Search, Telephone, URL, or E-mail states with a suggestions source element combobox role, with the aria-owns property set to the same value as the list attribute, and the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the Time state No role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the URL state with no suggestions source element textbox role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element with a type attribute in the Week state No role, with the aria-readonly state set to "true" if the element has a readonly attribute
input element that is required The aria-required state set to "true"
keygen element No role
label element No role
link element that creates a hyperlink link role
menu element with a type attribute in the context menu state No role
menu element with a type attribute in the list state menu role
menu element with a type attribute in the toolbar state toolbar role
meta element No role
meter element No role
nav element navigation role
noscript element No role
optgroup element No role
option element that is in a list of options or that represents a suggestion in a datalist element option role, with the aria-selected state set to "true" if the element's selectedness is true, or "false" otherwise.
param element No role
progress element progressbar role, with, if the progress bar is determinate, the aria-valuemax property set to the maximum value of the progress bar, the aria-valuemin property set to zero, and the aria-valuenow property set to the current value of the progress bar
script element No role
select element with a multiple attribute listbox role, with the aria-multiselectable property set to "true"
select element with no multiple attribute listbox role, with the aria-multiselectable property set to "false"
select element with a required attribute The aria-required state set to "true"
source element No role
style element No role
summary element heading role
textarea element textbox role, with the aria-multiline property set to "true", and the aria-readonly state set to "true" if the element has a readonly attribute
textarea element with a required attribute The aria-required state set to "true"
title element No role
An element that defines a command, whose Type facet is "checkbox", and that is a descendant of a menu element whose type attribute in the list state menuitemcheckbox role, with the aria-checked state set to "true" if the command's Checked State facet is true, and "false" otherwise
An element that defines a command, whose Type facet is "command", and that is a descendant of a menu element whose type attribute in the list state menuitem role
An element that defines a command, whose Type facet is "radio", and that is a descendant of a menu element whose type attribute in the list state menuitemradio role, with the aria-checked state set to "true" if the command's Checked State facet is true, and "false" otherwise
Element that is disabled The aria-disabled state set to "true"
Element with a hidden attribute The aria-hidden state set to "true"
Element that is a candidate for constraint validation but that does not satisfy its constraints The aria-invalid state set to "true"

Some HTML elements have native semantics that can be overridden. The following table lists these elements, along with the restrictions that apply to those elements. Each language feature (element or attribute) in a cell in the first column implies, unless otherwise overridden, the ARIA semantic (role, state, or property) given in the cell in the second column of the same row, but this semantic may be overridden under the conditions listed in the cell in the third column of that row. In addition, any element may be given the presentation role, regardless of the restrictions below.

Language feature Default implied ARIA semantic Restrictions
address element No role If specified, role must be contentinfo
article element article role Role must be either article, document, application, or main
aside element note role Role must be either note, complementary, or search
audio element No role If specified, role must be application
details element group role Role must be a role that supports aria-expanded
embed element No role If specified, role must be either application, document, or img
footer element No role If specified, role must be contentinfo
header element No role If specified, role must be banner
iframe element No role If specified, role must be either application, document, or img
img element whose alt attribute's value is absent img role No restrictions
input element with a type attribute in the Checkbox state checkbox role Role must be either checkbox or menuitemcheckbox
input element with a type attribute in the Radio Button state radio role Role must be either radio or menuitemradio
li element whose parent is an ol or ul element listitem role Role must be either listitem, menuitemcheckbox, menuitemradio, option, tab, or treeitem
object element No role If specified, role must be either application, document, or image
ol element list role Role must be either directory, list, listbox, menu, menubar, tablist, toolbar, tree
output element status role No restrictions
section element region role Role must be either alert, alertdialog, application, contentinfo, dialog, document, log, main, marquee, region, search, or status
ul element list role Role must be either directory, list, listbox, menu, menubar, tablist, toolbar, tree
video element No role If specified, role must be application
The body element document role Role must be either document or application

These features can be used to make accessibility tools render content to their users in more useful ways. For example, ASCII art, which is really an image, appears to be text, and in the absence of appropriate annotations would end up being rendered by screen readers as a very painful reading of lots of punctuation. Using the features described in this section, one can instead make the ATs skip the ASCII art and just read the caption:

<figure role="img" aria-labelledby="fish-caption"> 
 <pre>
 o           .'`/
     '      /  (
   O    .-'` ` `'-._      .')
      _/ (o)        '.  .' /
      )       )))     ><  <
      `\  |_\      _.'  '. \
        '-._  _ .-'       '.)
    jgs     `\__\
 </pre>
 <figcaption id="fish-caption">
  Joan G. Stark, "<cite>fish</cite>".
  October 1997. ASCII on electrons. 28×8.
 </figcaption> 
</figure> 
   

3.3 APIs in HTML documents

For HTML documents, and for HTML elements in HTML documents, certain APIs defined in DOM Core become case-insensitive or case-changing, as sometimes defined in DOM Core, and as summarized below. [DOMCORE]

This does not apply to XML documents or to elements that are not in the HTML namespace despite being in HTML documents.

Element.tagName and Node.nodeName

These attributes return element names converted to ASCII uppercase, regardless of the case with which they were created.

Document.createElement()

The canonical form of HTML markup is all-lowercase; thus, this method will lowercase the argument before creating the requisite element. .

This doesn't apply to Document.createElementNS(). Thus, it is possible, by passing this last method a tag name in the wrong case, to create an element that appears to have the same tag name as that of an element defined in this specification when its tagName attribute is examined, but that doesn't support the corresponding interfaces. The "real" element name (unaffected by case conversions) can be obtained from the localName attribute.

Element.setAttribute()
Element.setAttributeNode()

Attribute names are converted to ASCII lowercase.

This doesn't apply to Element.setAttributeNS() and Element.setAttributeNodeNS().

Element.getAttribute()
Element.getAttributeNode()

Attribute names are converted to ASCII lowercase.

This doesn't apply to Element.getAttributeNS() and Element.getAttributeNodeNS().

Document.getElementsByTagName()
Element.getElementsByTagName()

HTML elements match by lower-casing the argument before comparison, elements from other namespaces are treated as in XML (case-sensitively).

Thus, in an HTML document with nodes in multiple namespaces, these methods will effectively be both case-sensitive and case-insensitive at the same time.

3.4 Dynamic markup insertion

APIs for dynamically inserting markup into the document interact with the parser, and thus their behavior varies depending on whether they are used with HTML documents (and the HTML parser) or XHTML in XML documents (and the XML parser).

3.4.1 Opening the input stream

The open() method comes in several variants with different numbers of arguments.

document = document . open( [ type [, replace ] ] )

Causes the Document to be replaced in-place, as if it was a new Document object, but reusing the previous object, which is then returned.

If the type argument is omitted or has the value "text/html", then the resulting Document has an HTML parser associated with it, which can be given data to parse using document.write(). Otherwise, all content passed to document.write() will be parsed as plain text.

If the replace argument is present and has the value "replace", the existing entries in the session history for the Document object are removed.

The method has no effect if the Document is still being parsed.

Throws an INVALID_STATE_ERR exception if the Document is an XML document.

window = document . open( url, name, features [, replace ] )

Works like the window.open() method.

3.4.2 Closing the input stream

document . close()

Closes the input stream that was opened by the document.open() method.

Throws an INVALID_STATE_ERR exception if the Document is an XML document.

3.4.3 document.write()

document . write(text...)

In general, adds the given string(s) to the Document's input stream.

This method has very idiosyncratic behavior. In some cases, this method can affect the state of the HTML parser while the parser is running, resulting in a DOM that does not correspond to the source of the document. In other cases, the call can clear the current page first, as if document.open() had been called. In yet more cases, the method is simply ignored, or throws an exception. To make matters worse, the exact behavior of this method can in some cases be dependent on network latency, which can lead to failures that are very hard to debug. For all these reasons, use of this method is strongly discouraged.

This method throws an INVALID_STATE_ERR exception when invoked on XML documents.

3.4.4 document.writeln()

document . writeln(text...)

Adds the given string(s) to the Document's input stream, followed by a newline character. If necessary, calls the open() method implicitly first.

This method throws an INVALID_STATE_ERR exception when invoked on XML documents.

3.4.5 innerHTML

The innerHTML IDL attribute represents the markup of the node's contents.

document . innerHTML [ = value ]

Returns a fragment of HTML or XML that represents the Document.

Can be set, to replace the Document's contents with the result of parsing the given string.

In the case of XML documents, will throw an INVALID_STATE_ERR if the Document cannot be serialized to XML, and a SYNTAX_ERR if the given string is not well-formed.

element . innerHTML [ = value ]

Returns a fragment of HTML or XML that represents the element's contents.

Can be set, to replace the contents of the element with nodes parsed from the given string.

In the case of XML documents, will throw an INVALID_STATE_ERR if the element cannot be serialized to XML, and a SYNTAX_ERR if the given string is not well-formed.

3.4.6 outerHTML

The outerHTML IDL attribute represents the markup of the element and its contents.

element . outerHTML [ = value ]

Returns a fragment of HTML or XML that represents the element and its contents.

Can be set, to replace the element with nodes parsed from the given string.

In the case of XML documents, will throw an INVALID_STATE_ERR if the element cannot be serialized to XML, and a SYNTAX_ERR if the given string is not well-formed.

Throws a NO_MODIFICATION_ALLOWED_ERR exception if the parent of the element is the Document node.

3.4.7 insertAdjacentHTML()

element . insertAdjacentHTML(position, text)

Parses the given string text as HTML or XML and inserts the resulting nodes into the tree in the position given by the position argument, as follows:

"beforebegin"
Before the element itself.
"afterbegin"
Just inside the element, before its first child.
"beforeend"
Just inside the element, after its last child.
"afterend"
After the element itself.

Throws a SYNTAX_ERR exception if the arguments have invalid values (e.g., in the case of XML documents, if the given string is not well-formed).

Throws a NO_MODIFICATION_ALLOWED_ERR exception if the given position isn't possible (e.g. inserting elements after the root element of a Document).

4 The elements of HTML

4.1 The root element

4.1.1 The html element

Categories
None.
Contexts in which this element can be used:
As the root element of a document.
Wherever a subdocument fragment is allowed in a compound document.
Content model:
A head element followed by a body element.
Content attributes:
Global attributes
manifest
DOM interface:
interface HTMLHtmlElement : HTMLElement {};

The html element represents the root of an HTML document.

The manifest attribute gives the address of the document's application cache manifest, if there is one. If the attribute is present, the attribute's value must be a valid non-empty URL potentially surrounded by spaces.

The manifest attribute only has an effect during the early stages of document load. Changing the attribute dynamically thus has no effect (and thus, no DOM API is provided for this attribute).

For the purposes of application cache selection, later base elements cannot affect the resolving of relative URLs in manifest attributes, as the attributes are processed before those elements are seen.

The window.applicationCache IDL attribute provides scripted access to the offline application cache mechanism.

The html element in the following example declares that the document's language is English.

<!DOCTYPE html>
<html lang="en">
<head>
<title>Swapping Songs</title>
</head>
<body>
<h1>Swapping Songs</h1>
<p>Tonight I swapped some of the songs I wrote with some friends, who
gave me some of the songs they wrote. I love sharing my music.</p>
</body>
</html>

4.2 Document metadata

4.2.1 The head element

Categories
None.
Contexts in which this element can be used:
As the first element in an html element.
Content model:
If the document is an iframe srcdoc document or if title information is available from a higher-level protocol: Zero or more elements of metadata content.
Otherwise: One or more elements of metadata content, of which exactly one is a title element.
Content attributes:
Global attributes
DOM interface:
interface HTMLHeadElement : HTMLElement {};

The head element represents a collection of metadata for the Document.

The collection of metadata in a head element can be large or small. Here is an example of a very short one:

<!doctype html>
<html>
 <head>
  <title>A document with a short head</title>
 </head>
 <body>
 ...

Here is an example of a longer one:

<!DOCTYPE HTML>
<HTML>
 <HEAD>
  <META CHARSET="UTF-8">
  <BASE HREF="http://www.example.com/">
  <TITLE>An application with a long head</TITLE>
  <LINK REL="STYLESHEET" HREF="default.css">
  <LINK REL="STYLESHEET ALTERNATE" HREF="big.css" TITLE="Big Text">
  <SCRIPT SRC="support.js"></SCRIPT>
  <META NAME="APPLICATION-NAME" CONTENT="Long headed application">
 </HEAD>
 <BODY>
 ...

The title element is a required child in most situations, but when a higher-level protocol provides title information, e.g. in the Subject line of an e-mail when HTML is used as an e-mail authoring format, the title element can be omitted.

4.2.2 The title element

Categories
Metadata content.
Contexts in which this element can be used:
In a head element containing no other title elements.
Content model:
Text.
Content attributes:
Global attributes
DOM interface:
interface HTMLTitleElement : HTMLElement {
           attribute DOMString text;
};

The title element represents the document's title or name. Authors should use titles that identify their documents even when they are used out of context, for example in a user's history or bookmarks, or in search results. The document's title is often different from its first heading, since the first heading does not have to stand alone when taken out of context.

There must be no more than one title element per document.

title . text [ = value ]

Returns the contents of the element, ignoring child nodes that aren't text nodes.

Can be set, to replace the element's children with the given value.

Here are some examples of appropriate titles, contrasted with the top-level headings that might be used on those same pages.

  <title>Introduction to The Mating Rituals of Bees</title>
    ...
  <h1>Introduction</h1>
  <p>This companion guide to the highly successful
  <cite>Introduction to Medieval Bee-Keeping</cite> book is...

The next page might be a part of the same site. Note how the title describes the subject matter unambiguously, while the first heading assumes the reader knows what the context is and therefore won't wonder if the dances are Salsa or Waltz:

  <title>Dances used during bee mating rituals</title>
    ...
  <h1>The Dances</h1>

The string to use as the document's title is given by the document.title IDL attribute.

4.2.3 The base element

Categories
Metadata content.
Contexts in which this element can be used:
In a head element containing no other base elements.
Content model:
Empty.
Content attributes:
Global attributes
href
target
DOM interface:
interface HTMLBaseElement : HTMLElement {
           attribute DOMString href;
           attribute DOMString target;
};

The base element allows authors to specify the document base URL for the purposes of resolving relative URLs, and the name of the default browsing context for the purposes of following hyperlinks. The element does not represent any content beyond this information.

There must be no more than one base element per document.

A base element must have either an href attribute, a target attribute, or both.

The href content attribute, if specified, must contain a valid URL potentially surrounded by spaces.

A base element, if it has an href attribute, must come before any other elements in the tree that have attributes defined as taking URLs, except the html element (its manifest attribute isn't affected by base elements).

The target attribute, if specified, must contain a valid browsing context name or keyword, which specifies which browsing context is to be used as the default when hyperlinks and forms in the Document cause navigation.

A base element, if it has a target attribute, must come before any elements in the tree that represent hyperlinks.

In this example, a base element is used to set the document base URL:

<!DOCTYPE html>
<html>
    <head>
        <title>This is an example for the &lt;base&gt; element</title>
        <base href="http://www.example.com/news/index.html">
    </head>
    <body>
        <p>Visit the <a href="archives.html">archives</a>.</p>
    </body>
</html>

The link in the above example would be a link to "http://www.example.com/news/archives.html".

Categories
Metadata content.
Contexts in which this element can be used:
Where metadata content is expected.
In a noscript element that is a child of a head element.
Content model:
Empty.
Content attributes:
Global attributes
href
rel
media
hreflang
type
sizes
Also, the title attribute has special semantics on this element.
DOM interface:
interface HTMLLinkElement : HTMLElement {
           attribute boolean disabled;
           attribute DOMString href;
           attribute DOMString rel;
  readonly attribute DOMTokenList relList;
           attribute DOMString media;
           attribute DOMString hreflang;
           attribute DOMString type;
  [PutForwards=value] readonly attribute DOMSettableTokenList sizes;
};
HTMLLinkElement implements LinkStyle;

The link element allows authors to link their document to other resources.

The destination of the link(s) is given by the href attribute, which must be present and must contain a valid non-empty URL potentially surrounded by spaces.

A link element must have rel attribute.

The types of link indicated (the relationships) are given by the value of the rel attribute, which, if present, must have a value that is a set of space-separated tokens. The allowed keywords and their meanings are defined in a later section.

Two categories of links can be created using the link element: Links to external resources and hyperlinks. The link types section defines whether a particular link type is an external resource or a hyperlink. One link element can create multiple links (of which some might be external resource links and some might be hyperlinks); exactly which and how many links are created depends on the keywords given in the rel attribute. User agents must process the links on a per-link basis, not a per-element basis.

Each link created for a link element is handled separately. For instance, if there are two link elements with rel="stylesheet", they each count as a separate external resource, and each is affected by its own attributes independently. Similarly, if a single link element has a rel attribute with the value next stylesheet, it creates both a hyperlink (for the keyword) and an external resource link (for the stylesheet keyword), and they are affected by other attributes (such as media or title) differently.

The exact behavior for links to external resources depends on the exact relationship, as defined for the relevant link type. Some of the attributes control whether or not the external resource is to be applied (as defined below).

Hyperlinks created with the link element and its rel attribute apply to the whole page. This contrasts with the rel attribute of a and area elements, which indicates the type of a link whose context is given by the link's location within the document.

The media attribute says which media the resource applies to. The value must be a valid media query.

The default, if the media attribute is omitted, is "all", meaning that by default links apply to all media.

The hreflang attribute on the link element has the same semantics as the hreflang attribute on a and area elements.

The type attribute gives the MIME type of the linked resource. It is purely advisory. The value must be a valid MIME type.

For external resource links, the type attribute is used as a hint to user agents so that they can avoid fetching resources they do not support.

The title attribute gives the title of the link. With one exception, it is purely advisory. The value is text. The exception is for style sheet links, where the title attribute defines alternative style sheet sets.

The title attribute on link elements differs from the global title attribute of most other elements in that a link without a title does not inherit the title of the parent element: it merely has no title.

The sizes attribute is used with the icon link type. The attribute must not be specified on link elements that do not have a rel attribute that specifies the icon keyword.

The IDL attribute disabled only applies to style sheet links. When the link element defines a style sheet link, then the disabled attribute behaves as defined for the alternative style sheets DOM. For all other link elements it always return false and does nothing on setting.

The LinkStyle interface is also implemented by this element; the styling processing model defines how. [CSSOM]

Here, a set of link elements provide some style sheets:

<!-- a persistent style sheet -->
<link rel="stylesheet" href="default.css">

<!-- the preferred alternate style sheet -->
<link rel="stylesheet" href="green.css" title="Green styles">

<!-- some alternate style sheets -->
<link rel="alternate stylesheet" href="contrast.css" title="High contrast">
<link rel="alternate stylesheet" href="big.css" title="Big fonts">
<link rel="alternate stylesheet" href="wide.css" title="Wide screen">

The following example shows how you can specify versions of the page that use alternative formats, are aimed at other languages, and that are intended for other media:

<link rel=alternate href="/en/html" hreflang=en type=text/html title="English HTML">
<link rel=alternate href="/fr/html" hreflang=fr type=text/html title="French HTML">
<link rel=alternate href="/en/html/print" hreflang=en type=text/html media=print title="English HTML (for printing)">
<link rel=alternate href="/fr/html/print" hreflang=fr type=text/html media=print title="French HTML (for printing)">
<link rel=alternate href="/en/pdf" hreflang=en type=application/pdf title="English PDF">
<link rel=alternate href="/fr/pdf" hreflang=fr type=application/pdf title="French PDF">

4.2.5 The meta element

Categories
Metadata content.
Contexts in which this element can be used:
If the charset attribute is present, or if the element's http-equiv attribute is in the Encoding declaration state: in a head element.
If the http-equiv attribute is present but not in the Encoding declaration state: in a head element.
If the http-equiv attribute is present but not in the Encoding declaration state: in a noscript element that is a child of a head element.
If the name attribute is present: where metadata content is expected.
Content model:
Empty.
Content attributes:
Global attributes
name
http-equiv
content
charset
DOM interface:
interface HTMLMetaElement : HTMLElement {
           attribute DOMString name;
           attribute DOMString httpEquiv;
           attribute DOMString content;
};

The meta element represents various kinds of metadata that cannot be expressed using the title, base, link, style, and script elements.

The meta element can represent document-level metadata with the name attribute, pragma directives with the http-equiv attribute, and the file's character encoding declaration when an HTML document is serialized to string form (e.g. for transmission over the network or for disk storage) with the charset attribute.

Exactly one of the name, http-equiv, and charset attributes must be specified.

If either name or http-equiv is specified, then the content attribute must also be specified. Otherwise, it must be omitted.

The charset attribute specifies the character encoding used by the document. This is a character encoding declaration. If the attribute is present in an XML document, its value must be an ASCII case-insensitive match for the string "UTF-8" (and the document is therefore forced to use UTF-8 as its encoding).

The charset attribute on the meta element has no effect in XML documents, and is only allowed in order to facilitate migration to and from XHTML.

There must not be more than one meta element with a charset attribute per document.

The content attribute gives the value of the document metadata or pragma directive when the element is used for those purposes. The allowed values depend on the exact context, as described in subsequent sections of this specification.

If a meta element has a name attribute, it sets document metadata. Document metadata is expressed in terms of name/value pairs, the name attribute on the meta element giving the name, and the content attribute on the same element giving the value. The name specifies what aspect of metadata is being set; valid names and the meaning of their values are described in the following sections. If a meta element has no content attribute, then the value part of the metadata name/value pair is the empty string.

4.2.5.1 Standard metadata names

This specification defines a few names for the name attribute of the meta element.

Names are case-insensitive.

application-name

The value must be a short free-form string giving the name of the Web application that the page represents. If the page is not a Web application, the application-name metadata name must not be used. There must not be more than one meta element with its name attribute set to the value application-name per document.

author

The value must be a free-form string giving the name of one of the page's authors.

description

The value must be a free-form string that describes the page. The value must be appropriate for use in a directory of pages, e.g. in a search engine. There must not be more than one meta element with its name attribute set to the value description per document.

generator

The value must be a free-form string that identifies one of the software packages used to generate the document. This value must not be used on hand-authored pages.

Here is what a tool called "Frontweaver" could include in its output, in the page's head element, to identify itself as the tool used to generate the page:

<meta name=generator content="Frontweaver 8.2">
keywords

The value must be a set of comma-separated tokens, each of which is a keyword relevant to the page.

This page about typefaces on British motorways uses a meta element to specify some keywords that users might use to look for the page:

<!DOCTYPE HTML>
<html>
 <head>
  <title>Typefaces on UK motorways</title>
  <meta name="keywords" content="british,type face,font,fonts,highway,highways">
 </head>
 <body>
  ...

Many search engines do not consider such keywords, because this feature has historically been used unreliably and even misleadingly as a way to spam search engine results in a way that is not helpful for users.

4.2.5.2 Other metadata names

ISSUE-27 (rel-ownership) blocks progress to Last Call

Extensions to the predefined set of metadata names may be registered in the WHATWG Wiki MetaExtensions page. [WHATWGWIKI]

Anyone is free to edit the WHATWG Wiki MetaExtensions page at any time to add a type. These new names must be specified with the following information:

Keyword

The actual name being defined. The name should not be confusingly similar to any other defined name (e.g. differing only in case).

Brief description

A short non-normative description of what the metadata name's meaning is, including the format the value is required to be in.

Specification
A link to a more detailed description of the metadata name's semantics and requirements. It could be another page on the Wiki, or a link to an external page.
Synonyms

A list of other names that have exactly the same processing requirements. Authors should not use the names defined to be synonyms, they are only intended to allow user agents to support legacy content. Anyone may remove synonyms that are not used in practice; only names that need to be processed as synonyms for compatibility with legacy content are to be registered in this way.

Status

One of the following:

Proposed
The name has not received wide peer review and approval. Someone has proposed it and is, or soon will be, using it.
Ratified
The name has received wide peer review and approval. It has a specification that unambiguously defines how to handle pages that use the name, including when they use it in incorrect ways.
Discontinued
The metadata name has received wide peer review and it has been found wanting. Existing pages are using this metadata name, but new pages should avoid it. The "brief description" and "specification" entries will give details of what authors should use instead, if anything.

If a metadata name is found to be redundant with existing values, it should be removed and listed as a synonym for the existing value.

If a metadata name is registered in the "proposed" state for a period of a month or more without being used or specified, then it may be removed from the registry.

If a metadata name is added with the "proposed" status and found to be redundant with existing values, it should be removed and listed as a synonym for the existing value. If a metadata name is added with the "proposed" status and found to be harmful, then it should be changed to "discontinued" status.

Anyone can change the status at any time, but should only do so in accordance with the definitions above.

Metadata names whose values are to be URLs must not be proposed or accepted. Links must be represented using the link element, not the meta element.

4.2.5.3 Pragma directives

When the http-equiv attribute is specified on a meta element, the element is a pragma directive.

The http-equiv attribute is an enumerated attribute. The following table lists the keywords defined for this attribute. The states given in the first cell of the rows with keywords give the states to which those keywords map.

State Keyword Notes
Content Language content-language Conformance checkers will include a warning
Encoding declaration content-type
Default style default-style
Refresh refresh
Content language state (http-equiv="content-language")

This pragma sets the pragma-set default language. Until the pragma is successfully processed, there is no pragma-set default language.

Conformance checkers will include a warning if this pragma is used. Authors are encouraged to use the lang attribute instead.

For meta elements with an http-equiv attribute in the Content Language state, the content attribute must have a value consisting of a valid BCP 47 language tag. [BCP47]

This pragma is not exactly equivalent to the HTTP Content-Language header, for instance it only supports one language. [HTTP]

Encoding declaration state (http-equiv="content-type")

The Encoding declaration state is just an alternative form of setting the charset attribute: it is a character encoding declaration.

For meta elements with an http-equiv attribute in the Encoding declaration state, the content attribute must have a value that is an ASCII case-insensitive match for a string that consists of: the literal string "text/html;", optionally followed by any number of space characters, followed by the literal string "charset=", followed by the character encoding name of the character encoding declaration.

If the document contains a meta element with an http-equiv attribute in the Encoding declaration state, then the document must not contain a meta element with the charset attribute present.

The Encoding declaration state may be used in HTML documents, but elements with an http-equiv attribute in that state must not be used in XML documents.

Default style state (http-equiv="default-style")

This pragma sets the name of the default alternative style sheet set.

Refresh state (http-equiv="refresh")

This pragma acts as timed redirect.

For meta elements with an http-equiv attribute in the Refresh state, the content attribute must have a value consisting either of:

In the former case, the integer represents a number of seconds before the page is to be reloaded; in the latter case the integer represents a number of seconds before the page is to be replaced by the page at the given URL.

A news organization's front page could include the following markup in the page's head element, to ensure that the page automatically reloads from the server every five minutes:

<meta http-equiv="Refresh" content="300">

A sequence of pages could be used as an automated slide show by making each page refresh to the next page in the sequence, using markup such as the following:

<meta http-equiv="Refresh" content="20; URL=page4.html">

There must not be more than one meta element with any particular state in the document at a time.

4.2.5.4 Other pragma directives

Extensions to the predefined set of pragma directives may, under certain conditions, be registered in the WHATWG Wiki PragmaExtensions page. [WHATWGWIKI]

Such extensions must use a name that is identical to an HTTP header registered in the Permanent Message Header Field Registry, and must have behavior identical to that described for the HTTP header. [IANAPERMHEADERS]

Pragma directives corresponding to headers describing metadata, or not requiring specific user agent processing, must not be registered; instead, use metadata names. Pragma directives corresponding to headers that affect the HTTP processing model (e.g. caching) must not be registered, as they would result in HTTP-level behavior being different for user agents that implement HTML than for user agents that do not.

Anyone is free to edit the WHATWG Wiki PragmaExtensions page at any time to add a pragma directive satisfying these conditions. Such registrations must specify the following information:

Keyword

The actual name being defined. The name must match a previously-registered HTTP name with the same requirements.

Brief description

A short non-normative description of the purpose of the pragma directive.

Specification
A link to the specification defining the corresponding HTTP header.
4.2.5.5 Specifying the document's character encoding

A character encoding declaration is a mechanism by which the character encoding used to store or transmit a document is specified.

The following restrictions apply to character encoding declarations:

If an HTML document does not start with a BOM, and if its encoding is not explicitly given by Content-Type metadata, and the document is not an iframe srcdoc document, then the character encoding used must be an ASCII-compatible character encoding, and, in addition, if that encoding isn't US-ASCII itself, then the encoding must be specified using a meta element with a charset attribute or a meta element with an http-equiv attribute in the Encoding declaration state.

If the document is an iframe srcdoc document, the document must not have a character encoding declaration. (In this case, the source is already decoded, since it is part of the document that contained the iframe.)

If an HTML document contains a meta element with a charset attribute or a meta element with an http-equiv attribute in the Encoding declaration state, then the character encoding used must be an ASCII-compatible character encoding.

Authors are encouraged to use UTF-8. Conformance checkers may advise authors against using legacy encodings. [RFC3629]

Encodings in which a series of bytes in the range 0x20 to 0x7E can encode characters other than the corresponding characters in the range U+0020 to U+007E represent a potential security vulnerability: a user agent that does not support the encoding (or does not support the label used to declare the encoding, or does not use the same mechanism to detect the encoding of unlabelled content as another user agent) might end up interpreting technically benign plain text content as HTML tags and JavaScript. For example, this applies to encodings in which the bytes corresponding to "<script>" in ASCII can encode a different string. Authors should not use such encodings, which are known to include JIS_C6226-1983, JIS_X0212-1990, HZ-GB-2312, JOHAB (Windows code page 1361), encodings based on ISO-2022, and encodings based on EBCDIC. Furthermore, authors must not use the CESU-8, UTF-7, BOCU-1 and SCSU encodings, which also fall into this category, because these encodings were never intended for use for Web content. [RFC1345] [RFC1842] [RFC1468] [RFC2237] [RFC1554] [RFC1922] [RFC1557] [CESU8] [UTF7] [BOCU1] [SCSU]

Authors should not use UTF-32, as the encoding detection algorithms described in this specification intentionally do not distinguish it from UTF-16. [UNICODE]

Using non-UTF-8 encodings can have unexpected results on form submission and URL encodings, which use the document's character encoding by default.

In XHTML, the XML declaration should be used for inline character encoding information, if necessary.

In HTML, to declare that the character encoding is UTF-8, the author could include the following markup near the top of the document (in the head element):

<meta charset="utf-8">

In XML, the XML declaration would be used instead, at the very top of the markup:

<?xml version="1.0" encoding="utf-8"?>

4.2.6 The style element

Categories
Metadata content.
If the scoped attribute is present: flow content.
Contexts in which this element can be used:
If the scoped attribute is absent: where metadata content is expected.
If the scoped attribute is absent: in a noscript element that is a child of a head element.
If the scoped attribute is present: where flow content is expected, but before any other flow content other than other style elements and inter-element whitespace.
Content model:
Depends on the value of the type attribute, but must match requirements described in prose below.
Content attributes:
Global attributes
media
type
scoped
Also, the title attribute has special semantics on this element.
DOM interface:
interface HTMLStyleElement : HTMLElement {
           attribute boolean disabled;
           attribute DOMString media;
           attribute DOMString type;
           attribute boolean scoped;
};
HTMLStyleElement implements LinkStyle;

The style element allows authors to embed style information in their documents. The style element is one of several inputs to the styling processing model. The element does not represent content for the user.

The type attribute gives the styling language. If the attribute is present, its value must be a valid MIME type that designates a styling language. The charset parameter must not be specified. The default value for the type attribute, which is used if the attribute is absent, is "text/css". [RFC2318]

The media attribute says which media the styles apply to. The value must be a valid media query.

The default, if the media attribute is omitted, is "all", meaning that by default styles apply to all media.

The scoped attribute is a boolean attribute. If set, it indicates that the styles are intended just for the subtree rooted at the style element's parent element, as opposed to the whole Document.

The title attribute on style elements defines alternative style sheet sets. If the style element has no title attribute, then it has no title; the title attribute of ancestors does not apply to the style element. [CSSOM]

The title attribute on style elements, like the title attribute on link elements, differs from the global title attribute in that a style block without a title does not inherit the title of the parent element: it merely has no title.

The textContent of a style element must match the style production in the following ABNF, the character set for which is Unicode. [ABNF]

style         = no-c-start *( c-start no-c-end c-end no-c-start )
no-c-start    = <any string that doesn't contain a substring that matches c-start >
c-start       = "<!--"
no-c-end      = <any string that doesn't contain a substring that matches c-end >
c-end         = "-->"

This specification does not specify a style system, but CSS is expected to be supported by most Web browsers. [CSS]

The disabled IDL attribute behaves as defined for the alternative style sheets DOM.

The LinkStyle interface is also implemented by this element; the styling processing model defines how. [CSSOM]

The following document has its emphasis styled as bright red text rather than italics text, while leaving titles of works and Latin words in their default italics. It shows how using appropriate elements enables easier restyling of documents.

<!DOCTYPE html>
<html lang="en-US">
 <head>
  <title>My favorite book</title>
  <style>
   body { color: black; background: white; }
   em { font-style: normal; color: red; }
  </style>
 </head>
 <body>
  <p>My <em>favorite</em> book of all time has <em>got</em> to be
  <cite>A Cat's Life</cite>. It is a book by P. Rahmel that talks
  about the <i lang="la">Felis Catus</i> in modern human society.</p>
 </body>
</html>

4.2.7 Styling

The link and style elements can provide styling information for the user agent to use when rendering the document. The DOM Styling specification specifies what styling information is to be used by the user agent and how it is to be used. [CSSOM]

The style and link elements implement the LinkStyle interface. [CSSOM]

4.3 Scripting

Scripts allow authors to add interactivity to their documents.

Authors are encouraged to use declarative alternatives to scripting where possible, as declarative mechanisms are often more maintainable, and many users disable scripting.

For example, instead of using script to show or hide a section to show more details, the details element could be used.

Authors are also encouraged to make their applications degrade gracefully in the absence of scripting support.

For example, if an author provides a link in a table header to dynamically resort the table, the link could also be made to function without scripts by requesting the sorted table from the server.

4.3.1 The script element

Categories
Metadata content.
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where metadata content is expected.
Where phrasing content is expected.
Content model:
If there is no src attribute, depends on the value of the type attribute, but must match script content restrictions.
If there is a src attribute, the element must be either empty or contain only script documentation that also matches script content restrictions.
Content attributes:
Global attributes
src
async
defer
type
charset
DOM interface:
interface HTMLScriptElement : HTMLElement {
           attribute DOMString src;
           attribute boolean async;
           attribute boolean defer;
           attribute DOMString type;
           attribute DOMString charset;
           attribute DOMString text;
};

The script element allows authors to include dynamic script and data blocks in their documents. The element does not represent content for the user.

When used to include dynamic scripts, the scripts may either be embedded inline or may be imported from an external file using the src attribute. If the language is not that described by "text/javascript", then the type attribute must be present, as described below.

When used to include data blocks (as opposed to scripts), the data must be embedded inline, the format of the data must be given using the type attribute, and the src attribute must not be specified.

The type attribute gives the language of the script or format of the data. If the attribute is present, its value must be a valid MIME type. The charset parameter must not be specified. The default, which is used if the attribute is absent, is "text/javascript".

The src attribute, if specified, gives the address of the external script resource to use. The value of the attribute must be a valid non-empty URL potentially surrounded by spaces identifying a script resource of the type given by the type attribute, if the attribute is present, or of the type "text/javascript", if the attribute is absent. A resource is a script resource of a given type if that type identifies a scripting language and the resource conforms with the requirements of that language's specification.

The charset attribute gives the character encoding of the external script resource. The attribute must not be specified if the src attribute is not present. If the attribute is set, its value must be a valid character encoding name, must be an ASCII case-insensitive match for the preferred MIME name for that encoding, and must match the encoding given in the charset parameter of the Content-Type metadata of the external file, if any. [IANACHARSET]

The async and defer attributes are boolean attributes that indicate how the script should be executed. The defer and async attributes must not be specified if the src attribute is not present.

There are three possible modes that can be selected using these attributes. If the async attribute is present, then the script will be executed asynchronously, as soon as it is available. If the async attribute is not present but the defer attribute is present, then the script is executed when the page has finished parsing. If neither attribute is present, then the script is fetched and executed immediately, before the user agent continues parsing the page.

The exact processing details for these attributes are, for mostly historical reasons, somewhat non-trivial, involving a number of aspects of HTML. The implementation requirements are therefore by necessity scattered throughout the specification. The algorithms below (in this section) describe the core of this processing, but these algorithms reference and are referenced by the parsing rules for script start and end tags in HTML, in foreign content, and in XML, the rules for the document.write() method, the handling of scripting, etc.

The defer attribute may be specified even if the async attribute is specified, to cause legacy Web browsers that only support defer (and not async) to fall back to the defer behavior instead of the synchronous blocking behavior that is the default.

Changing the src, type, charset, async, and defer attributes dynamically has no direct effect; these attribute are only used at specific times described below.

script . text [ = value ]

Returns the contents of the element, ignoring child nodes that aren't text nodes.

Can be set, to replace the element's children with the given value.

When inserted using the document.write() method, script elements execute (typically synchronously), but when inserted using innerHTML and outerHTML attributes, they do not execute at all.

In this example, two script elements are used. One embeds an external script, and the other includes some data.

<script src="game-engine.js"></script>
<script type="text/x-game-map">
........U.........e
o............A....e
.....A.....AAA....e
.A..AAA...AAAAA...e
</script>

The data in this case might be used by the script to generate the map of a video game. The data doesn't have to be used that way, though; maybe the map data is actually embedded in other parts of the page's markup, and the data block here is just used by the site's search engine to help users who are looking for particular features in their game maps.

The following sample shows how a script element can be used to define a function that is then used by other parts of the document. It also shows how a script element can be used to invoke script while the document is being parsed, in this case to initialize the form's output.

<script>
 function calculate(form) {
   var price = 52000;
   if (form.elements.brakes.checked)
     price += 1000;
   if (form.elements.radio.checked)
     price += 2500;
   if (form.elements.turbo.checked)
     price += 5000;
   if (form.elements.sticker.checked)
     price += 250;
   form.elements.result.value = price;
 }
</script>
<form name="pricecalc" onsubmit="return false">
 <fieldset>
  <legend>Work out the price of your car</legend>
  <p>Base cost: £52000.</p>
  <p>Select additional options:</p>
  <ul>
   <li><label><input type=checkbox name=brakes> Ceramic brakes (£1000)</label></li>
   <li><label><input type=checkbox name=radio> Satellite radio (£2500)</label></li>
   <li><label><input type=checkbox name=turbo> Turbo charger (£5000)</label></li>
   <li><label><input type=checkbox name=sticker> "XZ" sticker (£250)</label></li>
  </ul>
  <p>Total: £<output name=result onformchange="calculate(form)"></output></p>
 </fieldset>
 <script>
  document.forms.pricecalc.dispatchFormChange();
 </script>
</form>
4.3.1.1 Scripting languages

The following lists some MIME type strings and the languages to which they refer:

"application/ecmascript"
"application/javascript"
"application/x-ecmascript"
"application/x-javascript"
"text/ecmascript"
"text/javascript"
"text/javascript1.0"
"text/javascript1.1"
"text/javascript1.2"
"text/javascript1.3"
"text/javascript1.4"
"text/javascript1.5"
"text/jscript"
"text/livescript"
"text/x-ecmascript"
"text/x-javascript"
JavaScript. [ECMA262]
"text/javascript;e4x=1"
JavaScript with ECMAScript for XML. [ECMA357]
4.3.1.2 Restrictions for contents of script elements

The textContent of a script element must match the script production in the following ABNF, the character set for which is Unicode. [ABNF]

script        = data1 *( escape [ script-start data3 ] "-->" data1 ) [ escape ]
escape        = "<!--" data2 *( script-start data3 script-end data2 )

data1         = <any string that doesn't contain a substring that matches not-data1>
not-data1     = "<!--"             

data2         = <any string that doesn't contain a substring that matches not-data2>
not-data2     = script-start / "-->"  

data3         = <any string that doesn't contain a substring that matches not-data3>
not-data3     = script-end / "-->"

script-start  = lt       s c r i p t tag-end
script-end    = lt slash s c r i p t tag-end

lt            =  %x003C ; U+003C LESS-THAN SIGN character (<)
slash         =  %x002F ; U+002F SOLIDUS character (/)

s             =  %x0053 ; U+0053 LATIN CAPITAL LETTER S
s             =/ %x0073 ; U+0073 LATIN SMALL LETTER S
c             =  %x0043 ; U+0043 LATIN CAPITAL LETTER C
c             =/ %x0063 ; U+0063 LATIN SMALL LETTER C
r             =  %x0052 ; U+0052 LATIN CAPITAL LETTER R
r             =/ %x0072 ; U+0072 LATIN SMALL LETTER R
i             =  %x0049 ; U+0049 LATIN CAPITAL LETTER I
i             =/ %x0069 ; U+0069 LATIN SMALL LETTER I
p             =  %x0050 ; U+0050 LATIN CAPITAL LETTER P
p             =/ %x0070 ; U+0070 LATIN SMALL LETTER P
t             =  %x0054 ; U+0054 LATIN CAPITAL LETTER T
t             =/ %x0074 ; U+0074 LATIN SMALL LETTER T

tag-end       =  %x0009 ; U+0009 CHARACTER TABULATION
tag-end       =/ %x000A ; U+000A LINE FEED (LF)
tag-end       =/ %x000C ; U+000C FORM FEED (FF)
tag-end       =/ %x0020 ; U+0020 SPACE
tag-end       =/ %x002F ; U+002F SOLIDUS (/)
tag-end       =/ %x003E ; U+003E GREATER-THAN SIGN (>)

When a script element contains script documentation, there are further restrictions on the contents of the element, as described in the section below.

4.3.1.3 Inline documentation for external scripts

If a script element's src attribute is specified, then the contents of the script element, if any, must be such that the value of the text IDL attribute, which is derived from the element's contents, matches the documentation production in the following ABNF, the character set for which is Unicode. [ABNF]

documentation = *( *( space / tab / comment ) [ line-comment ] newline )
comment       = slash star *( not-star / star not-slash ) 1*star slash
line-comment  = slash slash *not-newline

; characters
tab           = %x0009 ; U+0009 TAB
newline       = %x000A ; U+000A LINE FEED (LF)
space         = %x0020 ; U+0020 SPACE
star          = %x002A ; U+002A ASTERISK (*)
slash         = %x002F ; U+002F SOLIDUS (/)
not-newline   = %x0000-0009 / %x000B-10FFFF
                ; a Unicode character other than U+000A LINE FEED (LF)
not-star      = %x0000-0029 / %x002B-10FFFF
                ; a Unicode character other than U+002A ASTERISK (*)
not-slash     = %x0000-002E / %x0030-10FFFF
                ; a Unicode character other than U+002F SOLIDUS (/)

This corresponds to putting the contents of the element in JavaScript comments.

This requirement is in addition to the earlier restrictions on the syntax of contents of script elements.

This allows authors to include documentation, such as license information or API information, inside their documents while still referring to external script files. The syntax is constrained so that authors don't accidentally include what looks like valid script while also providing a src attribute.

<script src="cool-effects.js">
 // create new instances using:
 //    var e = new Effect();
 // start the effect using .play, stop using .stop:
 //    e.play();
 //    e.stop();
</script>

4.3.2 The noscript element

Categories
Metadata content.
Flow content.
Phrasing content.
Contexts in which this element can be used:
In a head element of an HTML document, if there are no ancestor noscript elements.
Where phrasing content is expected in HTML documents, if there are no ancestor noscript elements.
Content model:
When scripting is disabled, in a head element: in any order, zero or more link elements, zero or more style elements, and zero or more meta elements.
When scripting is disabled, not in a head element: transparent, but there must be no noscript element descendants.
Otherwise: text that conforms to the requirements given in the prose.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The noscript element represents nothing if scripting is enabled, and represents its children if scripting is disabled. It is used to present different markup to user agents that support scripting and those that don't support scripting, by affecting how the document is parsed.

When used in HTML documents, the allowed content model is as follows:

In a head element, if scripting is disabled for the noscript element

The noscript element must contain only link, style, and meta elements.

In a head element, if scripting is enabled for the noscript element

The noscript element must contain only text, except that invoking the HTML fragment parsing algorithm with the noscript element as the context element and the text contents as the input must result in a list of nodes that consists only of link, style, and meta elements that would be conforming if they were children of the noscript element, and no parse errors.

Outside of head elements, if scripting is disabled for the noscript element

The noscript element's content model is transparent, with the additional restriction that a noscript element must not have a noscript element as an ancestor (that is, noscript can't be nested).

Outside of head elements, if scripting is enabled for the noscript element

The noscript element must contain only text, except that the text must be such that running the following algorithm results in a conforming document with no noscript elements and no script elements, and such that no step in the algorithm causes an HTML parser to flag a parse error:

  1. Remove every script element from the document.
  2. Make a list of every noscript element in the document. For every noscript element in that list, perform the following steps:
    1. Let the parent element be the parent element of the noscript element.
    2. Take all the children of the parent element that come before the noscript element, and call these elements the before children.
    3. Take all the children of the parent element that come after the noscript element, and call these elements the after children.
    4. Let s be the concatenation of all the text node children of the noscript element.
    5. Set the innerHTML attribute of the parent element to the value of s. (This, as a side-effect, causes the noscript element to be removed from the document.)
    6. Insert the before children at the start of the parent element, preserving their original relative order.
    7. Insert the after children at the end of the parent element, preserving their original relative order.

All these contortions are required because, for historical reasons, the noscript element is handled differently by the HTML parser based on whether scripting was enabled or not when the parser was invoked.

The noscript element must not be used in XML documents.

The noscript element is only effective in the HTML syntax, it has no effect in the XHTML syntax.

In the following example, a noscript element is used to provide fallback for a script.

<form action="calcSquare.php">
 <p>
  <label for=x>Number</label>:
  <input id="x" name="x" type="number">
 </p>
 <script>
  var x = document.getElementById('x');
  var output = document.createElement('p');
  output.textContent = 'Type a number; it will be squared right then!';
  x.form.appendChild(output);
  x.form.onsubmit = function () { return false; }
  x.oninput = function () {
    var v = x.valueAsNumber;
    output.textContent = v + ' squared is ' + v * v;
  };
 </script>
 <noscript>
  <input type=submit value="Calculate Square">
 </noscript>
</form>

When script is disabled, a button appears to do the calculation on the server side. When script is enabled, the value is computed on-the-fly instead.

The noscript element is a blunt instrument. Sometimes, scripts might be enabled, but for some reason the page's script might fail. For this reason, it's generally better to avoid using noscript, and to instead design the script to change the page from being a scriptless page to a scripted page on the fly, as in the next example:

<form action="calcSquare.php">
 <p>
  <label for=x>Number</label>:
  <input id="x" name="x" type="number">
 </p>
 <input id="submit" type=submit value="Calculate Square">
 <script>
  var x = document.getElementById('x');
  var output = document.createElement('p');
  output.textContent = 'Type a number; it will be squared right then!';
  x.form.appendChild(output);
  x.form.onsubmit = function () { return false; }
  x.oninput = function () {
    var v = x.valueAsNumber;
    output.textContent = v + ' squared is ' + v * v;
  };
  var submit = document.getElementById('submit');
  submit.parentNode.removeChild(submit);
 </script>
</form>

The above technique is also useful in XHTML, since noscript is not supported in the XHTML syntax.

4.4 Sections

4.4.1 The body element

Categories
Sectioning root.
Contexts in which this element can be used:
As the second element in an html element.
Content model:
Flow content.
Content attributes:
Global attributes
onafterprint
onbeforeprint
onbeforeunload
onblur
onerror
onfocus
onhashchange
onload
onmessage
onoffline
ononline
onpagehide
onpageshow
onpopstate
onredo
onresize
onscroll
onstorage
onundo
onunload
DOM interface:
interface HTMLBodyElement : HTMLElement {
           attribute Function onafterprint;
           attribute Function onbeforeprint;
           attribute Function onbeforeunload;
           attribute Function onblur;
           attribute Function onerror;
           attribute Function onfocus;
           attribute Function onhashchange;
           attribute Function onload;
           attribute Function onmessage;
           attribute Function onoffline;
           attribute Function ononline;
           attribute Function onpopstate;
           attribute Function onpagehide;
           attribute Function onpageshow;
           attribute Function onredo;
           attribute Function onresize;
           attribute Function onscroll;
           attribute Function onstorage;
           attribute Function onundo;
           attribute Function onunload;
};

The body element represents the main content of the document.

In conforming documents, there is only one body element. The document.body IDL attribute provides scripts with easy access to a document's body element.

The body element exposes as event handler content attributes a number of the event handlers of the Window object. It also mirrors their event handler IDL attributes.

The onblur, onerror, onfocus, onload, and onscroll event handlers of the Window object, exposed on the body element, shadow the generic event handlers with the same names normally supported by HTML elements.

Thus, for example, a bubbling error event fired on a child of the body element of a Document would first trigger the onerror event handler content attributes of that element, then that of the root html element, and only then would it trigger the onerror event handler content attribute on the body element. This is because the event would bubble from the target, to the body, to the html, to the Document, to the Window, and the event handler on the body is watching the Window not the body. A regular event listener attached to the body using addEventListener(), however, would fire when the event bubbled through the body and not when it reaches the Window object.

This page updates an indicator to show whether or not the user is online:

<!DOCTYPE HTML>
<html>
 <head>
  <title>Online or offline?</title>
  <script>
   function update(online) {
     document.getElementById('status').textContent =
       online ? 'Online' : 'Offline';
   }
  </script>
 </head>
 <body ononline="update(true)"
       onoffline="update(false)"
       onload="update(navigator.onLine)">
  <p>You are: <span id="status">(Unknown)</span></p>
 </body>
</html>

4.4.2 The section element

Categories
Flow content.
Sectioning content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The section element represents a generic section of a document or application. A section, in this context, is a thematic grouping of content, typically with a heading.

Examples of sections would be chapters, the various tabbed pages in a tabbed dialog box, or the numbered sections of a thesis. A Web site's home page could be split into sections for an introduction, news items, and contact information.

Authors are encouraged to use the article element instead of the section element when it would make sense to syndicate the contents of the element.

The section element is not a generic container element. When an element is needed for styling purposes or as a convenience for scripting, authors are encouraged to use the div element instead. A general rule is that the section element is appropriate only if the element's contents would be listed explicitly in the document's outline.

In the following example, we see an article (part of a larger Web page) about apples, containing two short sections.

<article>
 <hgroup>
  <h1>Apples</h1>
  <h2>Tasty, delicious fruit!</h2>
 </hgroup>
 <p>The apple is the pomaceous fruit of the apple tree.</p>
 <section>
  <h1>Red Delicious</h1>
  <p>These bright red apples are the most common found in many
  supermarkets.</p>
 </section>
 <section>
  <h1>Granny Smith</h1>
  <p>These juicy, green apples make a great filling for
  apple pies.</p>
 </section>
</article>

Notice how the use of section means that the author can use h1 elements throughout, without having to worry about whether a particular section is at the top level, the second level, the third level, and so on.

Here is a graduation programme with two sections, one for the list of people graduating, and one for the description of the ceremony.

<!DOCTYPE Html>
<Html
 ><Head
   ><Title
     >Graduation Ceremony Summer 2022</Title
   ></Head
 ><Body
   ><H1
     >Graduation</H1
   ><Section
     ><H1
       >Ceremony</H1
     ><P
       >Opening Procession</P
     ><P
       >Speech by Validactorian</P
     ><P
       >Speech by Class President</P
     ><P
       >Presentation of Diplomas</P
     ><P
       >Closing Speech by Headmaster</P
   ></Section
   ><Section
     ><H1
       >Graduates</H1
     ><Ul
       ><Li
         >Molly Carpenter</Li
       ><Li
         >Anastasia Luccio</Li
       ><Li
         >Ebenezar McCoy</Li
       ><Li
         >Karrin Murphy</Li
       ><Li
         >Thomas Raith</Li
       ><Li
         >Susan Rodriguez</Li
     ></Ul
   ></Section
 ></Body
></Html>

4.4.3 The nav element

Categories
Flow content.
Sectioning content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The nav element represents a section of a page that links to other pages or to parts within the page: a section with navigation links.

Not all groups of links on a page need to be in a nav element — only sections that consist of major navigation blocks are appropriate for the nav element. In particular, it is common for footers to have a short list of links to various pages of a site, such as the terms of service, the home page, and a copyright page. The footer element alone is sufficient for such cases, without a nav element.

User agents (such as screen readers) that are targeted at users who can benefit from navigation information being omitted in the initial rendering, or who can benefit from navigation information being immediately available, can use this element as a way to determine what content on the page to initially skip and/or provide on request.

In the following example, the page has several places where links are present, but only one of those places is considered a navigation section.

<body>
 <header>
  <h1>Wake up sheeple!</h1>
  <p><a href="news.html">News</a> -
     <a href="blog.html">Blog</a> -
     <a href="forums.html">Forums</a></p>
  <p>Last Modified: <time>2009-04-01</time></p>
  <nav>
   <h1>Navigation</h1>
   <ul>
    <li><a href="articles.html">Index of all articles</a></li>
    <li><a href="today.html">Things sheeple need to wake up for today</a></li>
    <li><a href="successes.html">Sheeple we have managed to wake</a></li>
   </ul>
  </nav>
 </header>
 <div>
  <article>
   <header>
    <h1>My Day at the Beach</h1>
   </header>
   <div>
    <p>Today I went to the beach and had a lot of fun.</p>
    ...more content...
   </div>
   <footer>
    <p>Posted <time pubdate="" datetime="2009-10-10T14:36-08:00">Thursday</time>.</p>
   </footer>
  </article>
  ...more blog posts...
 </div>
 <footer>
  <p>Copyright © 2006 The Example Company</p>
  <p><a href="about.html">About</a> -
     <a href="policy.html">Privacy Policy</a> -
     <a href="contact.html">Contact Us</a></p>
 </footer>
</body>

Notice the div elements being used to wrap all the contents of the page other than the header and footer, and all the contents of the blog entry other than its header and footer.

In the following example, there are two nav elements, one for primary navigation around the site, and one for secondary navigation around the page itself.

<body>
 <h1>The Wiki Center Of Exampland</h1>
 <nav>
  <ul>
   <li><a href="/">Home</a></li>
   <li><a href="/events">Current Events</a></li>
   ...more...
  </ul>
 </nav>
 <article>
  <header>
   <h1>Demos in Exampland</h1>
   <p>Written by A. N. Other.</p>
  </header>
  <nav>
   <ul>
    <li><a href="#public">Public demonstrations</a></li>
    <li><a href="#destroy">Demolitions</a></li>
    ...more...
   </ul>
  </nav>
  <div>
   <section id="public">
    <h1>Public demonstrations</h1>
    <p>...more...</p>
   </section>
   <section id="destroy">
    <h1>Demolitions</h1>
    <p>...more...</p>
   </section>
   ...more...
  </div>
  <footer>
   <p><a href="?edit">Edit</a> | <a href="?delete">Delete</a> | <a href="?Rename">Rename</a></p>
  </footer>
 </article>
 <footer>
  <p><small>© copyright 1998 Exampland Emperor</small></p>
 </footer>
</body>

4.4.4 The article element

Categories
Flow content.
Sectioning content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The article element represents a self-contained composition in a document, page, application, or site and that is, in principle, independently distributable or reusable, e.g. in syndication. This could be a forum post, a magazine or newspaper article, a blog entry, a user-submitted comment, an interactive widget or gadget, or any other independent item of content.

When article elements are nested, the inner article elements represent articles that are in principle related to the contents of the outer article. For instance, a blog entry on a site that accepts user-submitted comments could represent the comments as article elements nested within the article element for the blog entry.

Author information associated with an article element (q.v. the address element) does not apply to nested article elements.

When used specifically with content to be redistributed in syndication, the article element is similar in purpose to the entry element in Atom. [ATOM]

The time element's pubdate attribute can be used to provide the publication date for an article element.

This example shows a blog post using the article element:

<article>
 <header>
  <h1>The Very First Rule of Life</h1>
  <p><time pubdate datetime="2009-10-09T14:28-08:00"></time></p>
 </header>
 <p>If there's a microphone anywhere near you, assume it's hot and
 sending whatever you're saying to the world. Seriously.</p>
 <p>...</p>
 <footer>
  <a href="?comments=1">Show comments...</a>
 </footer>
</article>

Here is that same blog post, but showing some of the comments:

<article>
 <header>
  <h1>The Very First Rule of Life</h1>
  <p><time pubdate datetime="2009-10-09T14:28-08:00"></time></p>
 </header>
 <p>If there's a microphone anywhere near you, assume it's hot and
 sending whatever you're saying to the world. Seriously.</p>
 <p>...</p>
 <section>
  <h1>Comments</h1>
  <article>
   <footer>
    <p>Posted by: George Washington</p>
    <p><time pubdate datetime="2009-10-10T19:10-08:00"></time></p>
   </footer>
   <p>Yeah! Especially when talking about your lobbyist friends!</p>
  </article>
  <article>
   <footer>
    <p>Posted by: George Hammond</p>
    <p><time pubdate datetime="2009-10-10T19:15-08:00"></time></p>
   </footer>
   <p>Hey, you have the same first name as me.</p>
  </article>
 </section>
</article>

Notice the use of footer to give the information for each comment (such as who wrote it and when): the footer element can appear at the start of its section when appropriate, such as in this case. (Using header in this case wouldn't be wrong either; it's mostly a matter of authoring preference.)

4.4.5 The aside element

Categories
Flow content.
Sectioning content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The aside element represents a section of a page that consists of content that is tangentially related to the content around the aside element, and which could be considered separate from that content. Such sections are often represented as sidebars in printed typography.

The element can be used for typographical effects like pull quotes or sidebars, for advertising, for groups of nav elements, and for other content that is considered separate from the main content of the page.

It's not appropriate to use the aside element just for parentheticals, since those are part of the main flow of the document.

The following example shows how an aside is used to mark up background material on Switzerland in a much longer news story on Europe.

<aside>
 <h1>Switzerland</h1>
 <p>Switzerland, a land-locked country in the middle of geographic
 Europe, has not joined the geopolitical European Union, though it is
 a signatory to a number of European treaties.</p>
</aside>

The following example shows how an aside is used to mark up a pull quote in a longer article.

...

<p>He later joined a large company, continuing on the same work.
<q>I love my job. People ask me what I do for fun when I'm not at
work. But I'm paid to do my hobby, so I never know what to
answer. Some people wonder what they would do if they didn't have to
work... but I know what I would do, because I was unemployed for a
year, and I filled that time doing exactly what I do now.</q></p>

<aside>
 <q> People ask me what I do for fun when I'm not at work. But I'm
 paid to do my hobby, so I never know what to answer. </q>
</aside>

<p>Of course his work — or should that be hobby? —
isn't his only passion. He also enjoys other pleasures.</p>

...

The following extract shows how aside can be used for blogrolls and other side content on a blog:

<body>
 <header>
  <h1>My wonderful blog</h1>
  <p>My tagline</p>
 </header>
 <aside>
  <!-- this aside contains two sections that are tangentially related
  to the page, namely, links to other blogs, and links to blog posts
  from this blog -->
  <nav>
   <h1>My blogroll</h1>
   <ul>
    <li><a href="http://blog.example.com/">Example Blog</a>
   </ul>
  </nav>
  <nav>
   <h1>Archives</h1>
   <ol reversed>
    <li><a href="/last-post">My last post</a>
    <li><a href="/first-post">My first post</a>
   </ol>
  </nav>
 </aside>
 <aside>
  <!-- this aside is tangentially related to the page also, it
  contains twitter messages from the blog author -->
  <h1>Twitter Feed</h1>
  <blockquote cite="http://twitter.example.net/t31351234">
   I'm on vacation, writing my blog.
  </blockquote>
  <blockquote cite="http://twitter.example.net/t31219752">
   I'm going to go on vacation soon.
  </blockquote>
 </aside>
 <article>
  <!-- this is a blog post -->
  <h1>My last post</h1>
  <p>This is my last post.</p>
  <footer>
   <p><a href="/last-post" rel=bookmark>Permalink</a>
  </footer>
 </article>
 <article>
  <!-- this is also a blog post -->
  <h1>My first post</h1>
  <p>This is my first post.</p>
  <aside>
   <!-- this aside is about the blog post, since it's inside the
   <article> element; it would be wrong, for instance, to put the
   blogroll here, since the blogroll isn't really related to this post
   specifically, only to the page as a whole -->
   <h1>Posting</h1>
   <p>While I'm thinking about it, I wanted to say something about
   posting. Posting is fun!</p>
  </aside>
  <footer>
   <p><a href="/first-post" rel=bookmark>Permalink</a>
  </footer>
 </article>
 <footer>
  <nav>
   <a href="/archives">Archives</a> —
   <a href="/about">About me</a> —
   <a href="/copyright">Copyright</a>
  </nav>
 </footer>
</body>

4.4.6 The h1, h2, h3, h4, h5, and h6 elements

Categories
Flow content.
Heading content.
formatBlock candidate.
Contexts in which this element can be used:
As a child of an hgroup element.
Where flow content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
interface HTMLHeadingElement : HTMLElement {};

These elements represent headings for their sections.

The semantics and meaning of these elements are defined in the section on headings and sections.

These elements have a rank given by the number in their name. The h1 element is said to have the highest rank, the h6 element has the lowest rank, and two elements with the same name have equal rank.

These two snippets are equivalent:

<body>
<h1>Let's call it a draw(ing surface)</h1>
<h2>Diving in</h2>
<h2>Simple shapes</h2>
<h2>Canvas coordinates</h2>
<h3>Canvas coordinates diagram</h3>
<h2>Paths</h2>
</body>
<body>
 <h1>Let's call it a draw(ing surface)</h1>
 <section>
  <h1>Diving in</h1>
 </section>
 <section>
  <h1>Simple shapes</h1>
 </section>
 <section>
  <h1>Canvas coordinates</h1>
  <section>
   <h1>Canvas coordinates diagram</h1>
  </section>
 </section>
 <section>
  <h1>Paths</h1>
 </section>
</body>

4.4.7 The hgroup element

Categories
Flow content.
Heading content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
One or more h1, h2, h3, h4, h5, and/or h6 elements.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The hgroup element represents the heading of a section. The element is used to group a set of h1h6 elements when the heading has multiple levels, such as subheadings, alternative titles, or taglines.

For the purposes of document summaries, outlines, and the like, the text of hgroup elements is defined to be the text of the highest ranked h1h6 element descendant of the hgroup element, if there are any such elements, and the first such element if there are multiple elements with that rank. If there are no such elements, then the text of the hgroup element is the empty string.

Other elements of heading content in the hgroup element indicate subheadings or subtitles.

The rank of an hgroup element is the rank of the highest-ranked h1h6 element descendant of the hgroup element, if there are any such elements, or otherwise the same as for an h1 element (the highest rank).

The section on headings and sections defines how hgroup elements are assigned to individual sections.

Here are some examples of valid headings. In each case, the emphasized text represents the text that would be used as the heading in an application extracting heading data and ignoring subheadings.

<hgroup>
 <h1>The reality dysfunction</h1>
 <h2>Space is not the only void</h2>
</hgroup>
<hgroup>
 <h1>Dr. Strangelove</h1>
 <h2>Or: How I Learned to Stop Worrying and Love the Bomb</h2>
</hgroup>

The point of using hgroup in these examples is to mask the h2 element (which acts as a secondary title) from the outline algorithm.

4.4.8 The header element

Categories
Flow content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content, but with no header or footer element descendants.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The header element represents a group of introductory or navigational aids.

A header element is intended to usually contain the section's heading (an h1h6 element or an hgroup element), but this is not required. The header element can also be used to wrap a section's table of contents, a search form, or any relevant logos.

Here are some sample headers. This first one is for a game:

<header>
 <p>Welcome to...</p>
 <h1>Voidwars!</h1>
</header>

The following snippet shows how the element can be used to mark up a specification's header:

<header>
 <hgroup>
  <h1>Scalable Vector Graphics (SVG) 1.2</h1>
  <h2>W3C Working Draft 27 October 2004</h2>
 </hgroup>
 <dl>
  <dt>This version:</dt>
  <dd><a href="http://www.w3.org/TR/2004/WD-SVG12-20041027/">http://www.w3.org/TR/2004/WD-SVG12-20041027/</a></dd>
  <dt>Previous version:</dt>
  <dd><a href="http://www.w3.org/TR/2004/WD-SVG12-20040510/">http://www.w3.org/TR/2004/WD-SVG12-20040510/</a></dd>
  <dt>Latest version of SVG 1.2:</dt>
  <dd><a href="http://www.w3.org/TR/SVG12/">http://www.w3.org/TR/SVG12/</a></dd>
  <dt>Latest SVG Recommendation:</dt>
  <dd><a href="http://www.w3.org/TR/SVG/">http://www.w3.org/TR/SVG/</a></dd>
  <dt>Editor:</dt>
  <dd>Dean Jackson, W3C, <a href="mailto:dean@w3.org">dean@w3.org</a></dd>
  <dt>Authors:</dt>
  <dd>See <a href="#authors">Author List</a></dd>
 </dl>
 <p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notic ...
</header>

The header element is not sectioning content; it doesn't introduce a new section.

In this example, the page has a page heading given by the h1 element, and two subsections whose headings are given by h2 elements. The content after the header element is still part of the last subsection started in the header element, because the header element doesn't take part in the outline algorithm.

<body>
 <header>
  <h1>Little Green Guys With Guns</h1>
  <nav>
   <ul>
    <li><a href="/games">Games</a>
    <li><a href="/forum">Forum</a>
    <li><a href="/download">Download</a>
   </ul>
  </nav>
  <h2>Important News</h2> <!-- this starts a second subsection -->
  <!-- this is part of the subsection entitled "Important News" -->
  <p>To play today's games you will need to update your client.</p>
  <h2>Games</h2> <!-- this starts a third subsection -->
 </header>
 <p>You have three active games:</p>
 <!-- this is still part of the subsection entitled "Games" -->
 ...
Categories
Flow content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content, but with no header or footer element descendants.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The footer element represents a footer for its nearest ancestor sectioning content or sectioning root element. A footer typically contains information about its section such as who wrote it, links to related documents, copyright data, and the like.

Contact information for the author or editor of a section belongs in an address element, possibly itself inside a footer.

Footers don't necessarily have to appear at the end of a section, though they usually do.

When the footer element contains entire sections, they represent appendices, indexes, long colophons, verbose license agreements, and other such content.

The footer element is not sectioning content; it doesn't introduce a new section.

When the nearest ancestor sectioning content or sectioning root element is the body element, then it applies to the whole page.

Here is a page with two footers, one at the top and one at the bottom, with the same content:

<body>
 <footer><a href="../">Back to index...</a></footer>
 <hgroup>
  <h1>Lorem ipsum</h1>
  <h2>The ipsum of all lorems</h2>
 </hgroup>
 <p>A dolor sit amet, consectetur adipisicing elit, sed do eiusmod
 tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim
 veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex
 ea commodo consequat. Duis aute irure dolor in reprehenderit in
 voluptate velit esse cillum dolore eu fugiat nulla
 pariatur. Excepteur sint occaecat cupidatat non proident, sunt in
 culpa qui officia deserunt mollit anim id est laborum.</p>
 <footer><a href="../">Back to index...</a></footer>
</body>

Here is an example which shows the footer element being used both for a site-wide footer and for a section footer.

<!DOCTYPE HTML>
<HTML><HEAD>
<TITLE>The Ramblings of a Scientist</TITLE>
<BODY>
<H1>The Ramblings of a Scientist</H1>
<ARTICLE>
 <H1>Episode 15</H1>
 <VIDEO SRC="/fm/015.ogv" CONTROLS PRELOAD>
  <P><A HREF="/fm/015.ogv">Download video</A>.</P>
 </VIDEO>
 <FOOTER> <!-- footer for article -->
  <P>Published <TIME PUBDATE DATETIME="2009-10-21T18:26-07:00"></TIME></P>
 </FOOTER>
</ARTICLE>
<ARTICLE>
 <H1>My Favorite Trains</H1>
 <P>I love my trains. My favorite train of all time is a Köf.</P>
 <P>It is fun to see them pull some coal cars because they look so
 dwarfed in comparison.</P>
 <FOOTER> <!-- footer for article -->
  <P>Published <TIME PUBDATE DATETIME="2009-09-15T14:54-07:00"></TIME></P>
 </FOOTER>
</ARTICLE>
<FOOTER> <!-- site wide footer -->
 <NAV>
  <P><A HREF="/credits.html">Credits</A> —
     <A HREF="/tos.html">Terms of Service</A> —
     <A HREF="/index.html">Blog Index</A></P>
 </NAV>
 <P>Copyright © 2009 Gordon Freeman</P>
</FOOTER>
</BODY>
</HTML>

4.4.10 The address element

Categories
Flow content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content, but with no heading content descendants, no sectioning content descendants, and no header, footer, or address element descendants.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The address element represents the contact information for its nearest article or body element ancestor. If that is the body element, then the contact information applies to the document as a whole.

For example, a page at the W3C Web site related to HTML might include the following contact information:

<ADDRESS>
 <A href="../People/Raggett/">Dave Raggett</A>,
 <A href="../People/Arnaud/">Arnaud Le Hors</A>,
 contact persons for the <A href="Activity">W3C HTML Activity</A>
</ADDRESS>

The address element must not be used to represent arbitrary addresses (e.g. postal addresses), unless those addresses are in fact the relevant contact information. (The p element is the appropriate element for marking up postal addresses in general.)

The address element must not contain information other than contact information.

For example, the following is non-conforming use of the address element:

<ADDRESS>Last Modified: 1999/12/24 23:37:50</ADDRESS>

Typically, the address element would be included along with other information in a footer element.

4.4.11 Headings and sections

The h1h6 elements and the hgroup element are headings.

The first element of heading content in an element of sectioning content represents the heading for that section. Subsequent headings of equal or higher rank start new (implied) sections, headings of lower rank start implied subsections that are part of the previous one. In both cases, the element represents the heading of the implied section.

Certain elements are said to be sectioning roots, including blockquote and td elements. These elements can have their own outlines, but the sections and headings inside these elements do not contribute to the outlines of their ancestors.

Sectioning content elements are always considered subsections of their nearest ancestor sectioning root or their nearest ancestor element of sectioning content, whichever is nearest, regardless of what implied sections other headings may have created.

For the following fragment:

<body>
 <h1>Foo</h1>
 <h2>Bar</h2>
 <blockquote>
  <h3>Bla</h3>
 </blockquote>
 <p>Baz</p>
 <h2>Quux</h2>
 <section>
  <h3>Thud</h3>
 </section>
 <p>Grunt</p>
</body>

...the structure would be:

  1. Foo (heading of explicit body section, containing the "Grunt" paragraph)
    1. Bar (heading starting implied section, containing a block quote and the "Baz" paragraph)
    2. Quux (heading starting implied section with no content other than the heading itself)
    3. Thud (heading of explicit section section)

Notice how the section ends the earlier implicit section so that a later paragraph ("Grunt") is back at the top level.

Sections may contain headings of any rank, but authors are strongly encouraged to either use only h1 elements, or to use elements of the appropriate rank for the section's nesting level.

Authors are also encouraged to explicitly wrap sections in elements of sectioning content, instead of relying on the implicit sections generated by having multiple headings in one element of sectioning content.

For example, the following is correct:

<body>
 <h4>Apples</h4>
 <p>Apples are fruit.</p>
 <section>
  <h2>Taste</h2>
  <p>They taste lovely.</p>
  <h6>Sweet</h6>
  <p>Red apples are sweeter than green ones.</p>
  <h1>Color</h1>
  <p>Apples come in various colors.</p>
 </section>
</body>

However, the same document would be more clearly expressed as:

<body>
 <h1>Apples</h1>
 <p>Apples are fruit.</p>
 <section>
  <h2>Taste</h2>
  <p>They taste lovely.</p>
  <section>
   <h3>Sweet</h3>
   <p>Red apples are sweeter than green ones.</p>
  </section>
 </section>
 <section>
  <h2>Color</h2>
  <p>Apples come in various colors.</p>
 </section>
</body>

Both of the documents above are semantically identical and would produce the same outline in compliant user agents.

This third example is also semantically identical, and might be easier to maintain (e.g. if sections are often moved around in editing):

<body>
 <h1>Apples</h1>
 <p>Apples are fruit.</p>
 <section>
  <h1>Taste</h1>
  <p>They taste lovely.</p>
  <section>
   <h1>Sweet</h1>
   <p>Red apples are sweeter than green ones.</p>
  </section>
 </section>
 <section>
  <h1>Color</h1>
  <p>Apples come in various colors.</p>
 </section>
</body>
4.4.11.1 Creating an outline

The outline for a sectioning content element or a sectioning root element consists of a list of one or more potentially nested sections. A section is a container that corresponds to some nodes in the original DOM tree. Each section can have one heading associated with it, and can contain any number of further nested sections. (The sections in the outline aren't section elements, though some may correspond to such elements — they are merely conceptual sections.)

The following markup fragment:

<body>
 <h1>A</h1>
 <p>B</p>
 <h2>C</h2>
 <p>D</p>
 <h2>E</h2>
 <p>F</p>
</body>

...results in the following outline being created for the body node (and thus the entire document):

  1. Section created for body node.

    Associated with heading "A".

    Also associated with paragraph "B".

    Nested sections:

    1. Section implied for first h2 element.

      Associated with heading "C".

      Also associated with paragraph "D".

      No nested sections.

    2. Section implied for second h2 element.

      Associated with heading "E".

      Also associated with paragraph "F".

      No nested sections.

4.5 Grouping content

4.5.1 The p element

Categories
Flow content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
interface HTMLParagraphElement : HTMLElement {};

The p element represents a paragraph.

While paragraphs are usually represented in visual media by blocks of text that are physically separated from adjacent blocks through blank lines, a style sheet or user agent would be equally justified in presenting paragraph breaks in a different manner, for instance using inline pilcrows (¶).

The following examples are conforming HTML fragments:

<p>The little kitten gently seated himself on a piece of
carpet. Later in his life, this would be referred to as the time the
cat sat on the mat.</p>
<fieldset>
 <legend>Personal information</legend>
 <p>
   <label>Name: <input name="n"></label>
   <label><input name="anon" type="checkbox"> Hide from other users</label>
 </p>
 <p><label>Address: <textarea name="a"></textarea></label></p>
</fieldset>
<p>There was once an example from Femley,<br>
Whose markup was of dubious quality.<br>
The validator complained,<br>
So the author was pained,<br>
To move the error from the markup to the rhyming.</p>

The p element should not be used when a more specific element is more appropriate.

The following example is technically correct:

<section>
 <!-- ... -->
 <p>Last modified: 2001-04-23</p>
 <p>Author: fred@example.com</p>
</section>

However, it would be better marked-up as:

<section>
 <!-- ... -->
 <footer>Last modified: 2001-04-23</footer>
 <address>Author: fred@example.com</address>
</section>

Or:

<section>
 <!-- ... -->
 <footer>
  <p>Last modified: 2001-04-23</p>
  <address>Author: fred@example.com</address>
 </footer>
</section>

4.5.2 The hr element

Categories
Flow content.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Empty.
Content attributes:
Global attributes
DOM interface:
interface HTMLHRElement : HTMLElement {};

The hr element represents a paragraph-level thematic break, e.g. a scene change in a story, or a transition to another topic within a section of a reference book.

The following fictional extract from a project manual shows two sections that use the hr element to separate topics within the section.

<section>
 <h1>Communication</h1>
 <p>There are various methods of communication. This section
 covers a few of the important ones used by the project.</p>
 <hr>
 <p>Communication stones seem to come in pairs and have mysterious
 properties:</p>
 <ul>
  <li>They can transfer thoughts in two directions once activated
  if used alone.</li>
  <li>If used with another device, they can transfer one's
  consciousness to another body.</li>
  <li>If both stones are used with another device, the
  consciousnesses switch bodies.</li>
 </ul>
 <hr>
 <p>Radios use the electromagnetic spectrum in the meter range and
 longer.</p>
 <hr>
 <p>Signal flares use the electromagnetic spectrum in the
 nanometer range.</p>
</section>
<section>
 <h1>Food</h1>
 <p>All food at the project is rationed:</p>
 <dl>
  <dt>Potatoes</dt>
  <dd>Two per day</dd>
  <dt>Soup</dt>
  <dd>One bowl per day</dd>
 </dl>
 <hr>
 <p>Cooking is done by the chefs on a set rotation.</p>
</section>

There is no need for an hr element between the sections themselves, since the section elements and the h1 elements imply thematic changes themselves.

The following extract from Pandora's Star by Peter F. Hamilton shows two paragraphs that precede a scene change and the paragraph that follows it. The scene change, represented in the printed book by a gap containing a solitary centered star between the second and third paragraphs, is here represented using the hr element.

<p>Dudley was ninety-two, in his second life, and fast approaching
time for another rejuvenation. Despite his body having the physical
age of a standard fifty-year-old, the prospect of a long degrading
campaign within academia was one he regarded with dread. For a
supposedly advanced civilization, the Intersolar Commonwearth could be
appallingly backward at times, not to mention cruel.</p>
<p><i>Maybe it won't be that bad</i>, he told himself. The lie was
comforting enough to get him through the rest of the night's
shift.</p>
<hr>
<p>The Carlton AllLander drove Dudley home just after dawn. Like the
astronomer, the vehicle was old and worn, but perfectly capable of
doing its job. It had a cheap diesel engine, common enough on a
semi-frontier world like Gralmond, although its drive array was a
thoroughly modern photoneural processor. With its high suspension and
deep-tread tyres it could plough along the dirt track to the
observatory in all weather and seasons, including the metre-deep snow
of Gralmond's winters.</p>

The hr element does not affect the document's outline.

4.5.3 The pre element

Categories
Flow content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
interface HTMLPreElement : HTMLElement {};

The pre element represents a block of preformatted text, in which structure is represented by typographic conventions rather than by elements.

In the HTML syntax, a leading newline character immediately following the pre element start tag is stripped.

Some examples of cases where the pre element could be used:

Authors are encouraged to consider how preformatted text will be experienced when the formatting is lost, as will be the case for users of speech synthesizers, braille displays, and the like. For cases like ASCII art, it is likely that an alternative presentation, such as a textual description, would be more universally accessible to the readers of the document.

To represent a block of computer code, the pre element can be used with a code element; to represent a block of computer output the pre element can be used with a samp element. Similarly, the kbd element can be used within a pre element to indicate text that the user is to enter.

A newline in a pre element separates paragraphs for the purposes of the Unicode bidirectional algorithm. [BIDI]

In the following snippet, a sample of computer code is presented.

<p>This is the <code>Panel</code> constructor:</p>
<pre><code>function Panel(element, canClose, closeHandler) {
  this.element = element;
  this.canClose = canClose;
  this.closeHandler = function () { if (closeHandler) closeHandler() };
}</code></pre>

In the following snippet, samp and kbd elements are mixed in the contents of a pre element to show a session of Zork I.

<pre><samp>You are in an open field west of a big white house with a boarded
front door.
There is a small mailbox here.

></samp> <kbd>open mailbox</kbd>

<samp>Opening the mailbox reveals:
A leaflet.

></samp></pre>

The following shows a contemporary poem that uses the pre element to preserve its unusual formatting, which forms an intrinsic part of the poem itself.

<pre>                maxling

it is with a          heart
               heavy

that i admit loss of a feline
        so           loved

a friend lost to the
        unknown
                                (night)

~cdr 11dec07</pre>

4.5.4 The blockquote element

Categories
Flow content.
Sectioning root.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content.
Content attributes:
Global attributes
cite
DOM interface:
interface HTMLQuoteElement : HTMLElement {
           attribute DOMString cite;
};

The HTMLQuoteElement interface is also used by the q element.

The blockquote element represents a section that is quoted from another source.

Content inside a blockquote must be quoted from another source, whose address, if it has one, may be cited in the cite attribute.

If the cite attribute is present, it must be a valid URL potentially surrounded by spaces.

This next example shows the use of cite alongside blockquote:

<p>His next piece was the aptly named <cite>Sonnet 130</cite>:</p>
<blockquote cite="http://quotes.example.org/s/sonnet130.html">
  <p>My mistress' eyes are nothing like the sun,<br>
  Coral is far more red, than her lips red,<br>
  ...

This example shows how a forum post could use blockquote to show what post a user is replying to. The article element is used for each post, to mark up the threading.

<article>
 <h1><a href="http://bacon.example.com/?blog=109431">Bacon on a crowbar</a></h1>
 <article>
  <header><strong>t3yw</strong> 12 points 1 hour ago</header>
  <p>I bet a narwhal would love that.</p>
  <footer><a href="?pid=29578">permalink</a></footer>
  <article>
   <header><strong>greg</strong> 8 points 1 hour ago</header>
   <blockquote><p>I bet a narwhal would love that.</p></blockquote>
   <p>Dude narwhals don't eat bacon.</p>
   <footer><a href="?pid=29579">permalink</a></footer>
   <article>
    <header><strong>t3yw</strong> 15 points 1 hour ago</header>
    <blockquote>
     <blockquote><p>I bet a narwhal would love that.</p></blockquote>
     <p>Dude narwhals don't eat bacon.</p>
    </blockquote>
    <p>Next thing you'll be saying they don't get capes and wizard
    hats either!</p>
    <footer><a href="?pid=29580">permalink</a></footer>
    <article>
     <article>
      <header><strong>boing</strong> -5 points 1 hour ago</header>
      <p>narwhals are worse than ceiling cat</p>
      <footer><a href="?pid=29581">permalink</a></footer>
     </article>
    </article>
   </article>
  </article>
  <article>
   <header><strong>fred</strong> 1 points 23 minutes ago</header>
   <blockquote><p>I bet a narwhal would love that.</p></blockquote>
   <p>I bet they'd love to peel a banana too.</p>
   <footer><a href="?pid=29582">permalink</a></footer>
  </article>
 </article>
</article>

Examples of how to represent a conversation are shown in a later section; it is not appropriate to use the cite and blockquote elements for this purpose.

4.5.5 The ol element

Categories
Flow content.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Zero or more li elements.
Content attributes:
Global attributes
reversed
start
type
DOM interface:
interface HTMLOListElement : HTMLElement {
           attribute boolean reversed;
           attribute long start;
           attribute DOMString type;
};

The ol element represents a list of items, where the items have been intentionally ordered, such that changing the order would change the meaning of the document.

The items of the list are the li element child nodes of the ol element, in tree order.

The reversed attribute is a boolean attribute. If present, it indicates that the list is a descending list (..., 3, 2, 1). If the attribute is omitted, the list is an ascending list (1, 2, 3, ...).

The start attribute, if present, must be a valid integer giving the ordinal value of the first list item.

The type attribute can be used to specify the kind of marker to use in the list, in the cases where that matters (e.g. because items are to be referened by their number/letter). The attribute, if specified, must have a value that is a case-sensitive match for one of the characters given in the first cell of one of the rows of the following table.

Keyword State Description Examples for values 1-3 and 3999-4001
1 (U+0031) decimal Decimal numbers 1. 2. 3. ... 3999. 4000. 4001. ...
a (U+0061) lower-alpha Lowercase latin alphabet a. b. c. ... ewu. ewv. eww. ...
A (U+0041) upper-alpha Uppercase latin alphabet A. B. C. ... EWU. EWV. EWW. ...
i (U+0069) lower-roman Lowercase roman numerals i. ii. iii. ... mmmcmxcix. i̅v̅. i̅v̅i. ...
I (U+0049) upper-roman Uppercase roman numerals I. II. III. ... MMMCMXCIX. I̅V̅. I̅V̅I. ...

The following markup shows a list where the order matters, and where the ol element is therefore appropriate. Compare this list to the equivalent list in the ul section to see an example of the same items using the ul element.

<p>I have lived in the following countries (given in the order of when
I first lived there):</p>
<ol>
 <li>Switzerland
 <li>United Kingdom
 <li>United States
 <li>Norway
</ol>

Note how changing the order of the list changes the meaning of the document. In the following example, changing the relative order of the first two items has changed the birthplace of the author:

<p>I have lived in the following countries (given in the order of when
I first lived there):</p>
<ol>
 <li>United Kingdom
 <li>Switzerland
 <li>United States
 <li>Norway
</ol>

4.5.6 The ul element

Categories
Flow content.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Zero or more li elements.
Content attributes:
Global attributes
DOM interface:
interface HTMLUListElement : HTMLElement {};

The ul element represents a list of items, where the order of the items is not important — that is, where changing the order would not materially change the meaning of the document.

The items of the list are the li element child nodes of the ul element.

The following markup shows a list where the order does not matter, and where the ul element is therefore appropriate. Compare this list to the equivalent list in the ol section to see an example of the same items using the ol element.

<p>I have lived in the following countries:</p>
<ul>
 <li>Norway
 <li>Switzerland
 <li>United Kingdom
 <li>United States
</ul>

Note that changing the order of the list does not change the meaning of the document. The items in the snippet above are given in alphabetical order, but in the snippet below they are given in order of the size of their current account balance in 2007, without changing the meaning of the document whatsoever:

<p>I have lived in the following countries:</p>
<ul>
 <li>Switzerland
 <li>Norway
 <li>United Kingdom
 <li>United States
</ul>

4.5.7 The li element

Categories
None.
Contexts in which this element can be used:
Inside ol elements.
Inside ul elements.
Inside menu elements.
Content model:
Flow content.
Content attributes:
Global attributes
If the element is a child of an ol element: value
DOM interface:
interface HTMLLIElement : HTMLElement {
           attribute long value;
};

The li element represents a list item. If its parent element is an ol, ul, or menu element, then the element is an item of the parent element's list, as defined for those elements. Otherwise, the list item has no defined list-related relationship to any other li element.

If the parent element is an ol element, then the li element has an ordinal value.

The value attribute, if present, must be a valid integer giving the ordinal value of the list item.

The following example, the top ten movies are listed (in reverse order). Note the way the list is given a title by using a figure element and its figcaption element.

<figure>
 <figcaption>The top 10 movies of all time</figcaption>
 <ol>
  <li value="10"><cite>Josie and the Pussycats</cite>, 2001</li>
  <li value="9"><cite lang="sh">Црна мачка, бели мачор</cite>, 1998</li>
  <li value="8"><cite>A Bug's Life</cite>, 1998</li>
  <li value="7"><cite>Toy Story</cite>, 1995</li>
  <li value="6"><cite>Monsters, Inc</cite>, 2001</li>
  <li value="5"><cite>Cars</cite>, 2006</li>
  <li value="4"><cite>Toy Story 2</cite>, 1999</li>
  <li value="3"><cite>Finding Nemo</cite>, 2003</li>
  <li value="2"><cite>The Incredibles</cite>, 2004</li>
  <li value="1"><cite>Ratatouille</cite>, 2007</li>
 </ol>
</figure>

The markup could also be written as follows, using the reversed attribute on the ol element:

<figure>
 <figcaption>The top 10 movies of all time</figcaption>
 <ol reversed>
  <li><cite>Josie and the Pussycats</cite>, 2001</li>
  <li><cite lang="sh">Црна мачка, бели мачор</cite>, 1998</li>
  <li><cite>A Bug's Life</cite>, 1998</li>
  <li><cite>Toy Story</cite>, 1995</li>
  <li><cite>Monsters, Inc</cite>, 2001</li>
  <li><cite>Cars</cite>, 2006</li>
  <li><cite>Toy Story 2</cite>, 1999</li>
  <li><cite>Finding Nemo</cite>, 2003</li>
  <li><cite>The Incredibles</cite>, 2004</li>
  <li><cite>Ratatouille</cite>, 2007</li>
 </ol>
</figure>

If the li element is the child of a menu element and itself has a child that defines a command, then the li element will match the :enabled and :disabled pseudo-classes in the same way as the first such child element does.

4.5.8 The dl element

Categories
Flow content.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Zero or more groups each consisting of one or more dt elements followed by one or more dd elements.
Content attributes:
Global attributes
DOM interface:
interface HTMLDListElement : HTMLElement {};

The dl element represents an association list consisting of zero or more name-value groups (a description list). Each group must consist of one or more names (dt elements) followed by one or more values (dd elements). Within a single dl element, there should not be more than one dt element for each name.

Name-value groups may be terms and definitions, metadata topics and values, questions and answers, or any other groups of name-value data.

The values within a group are alternatives; multiple paragraphs forming part of the same value must all be given within the same dd element.

The order of the list of groups, and of the names and values within each group, may be significant.

In the following example, one entry ("Authors") is linked to two values ("John" and "Luke").

<dl>
 <dt> Authors
 <dd> John
 <dd> Luke
 <dt> Editor
 <dd> Frank
</dl>

In the following example, one definition is linked to two terms.

<dl>
 <dt lang="en-US"> <dfn>color</dfn> </dt>
 <dt lang="en-GB"> <dfn>colour</dfn> </dt>
 <dd> A sensation which (in humans) derives from the ability of
 the fine structure of the eye to distinguish three differently
 filtered analyses of a view. </dd>
</dl>

The following example illustrates the use of the dl element to mark up metadata of sorts. At the end of the example, one group has two metadata labels ("Authors" and "Editors") and two values ("Robert Rothman" and "Daniel Jackson").

<dl>
 <dt> Last modified time </dt>
 <dd> 2004-12-23T23:33Z </dd>
 <dt> Recommended update interval </dt>
 <dd> 60s </dd>
 <dt> Authors </dt>
 <dt> Editors </dt>
 <dd> Robert Rothman </dd>
 <dd> Daniel Jackson </dd>
</dl>

The following example shows the dl element used to give a set of instructions. The order of the instructions here is important (in the other examples, the order of the blocks was not important).

<p>Determine the victory points as follows (use the
first matching case):</p>
<dl>
 <dt> If you have exactly five gold coins </dt>
 <dd> You get five victory points </dd>
 <dt> If you have one or more gold coins, and you have one or more silver coins </dt>
 <dd> You get two victory points </dd>
 <dt> If you have one or more silver coins </dt>
 <dd> You get one victory point </dd>
 <dt> Otherwise </dt>
 <dd> You get no victory points </dd>
</dl>

The following snippet shows a dl element being used as a glossary. Note the use of dfn to indicate the word being defined.

<dl>
 <dt><dfn>Apartment</dfn>, n.</dt>
 <dd>An execution context grouping one or more threads with one or
 more COM objects.</dd>
 <dt><dfn>Flat</dfn>, n.</dt>
 <dd>A deflated tire.</dd>
 <dt><dfn>Home</dfn>, n.</dt>
 <dd>The user's login directory.</dd>
</dl>

The dl element is inappropriate for marking up dialogue. Examples of how to mark up dialogue are shown below.

4.5.9 The dt element

Categories
None.
Contexts in which this element can be used:
Before dd or dt elements inside dl elements.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The dt element represents the term, or name, part of a term-description group in a description list (dl element).

The dt element itself, when used in a dl element, does not indicate that its contents are a term being defined, but this can be indicated using the dfn element.

This example shows a list of frequently asked questions (a FAQ) marked up using the dt element for questions and the dd element for answers.

<article>
 <h1>FAQ</h1>
 <dl>
  <dt>What do we want?</dt>
  <dd>Our data.</dd>
  <dt>When do we want it?</dt>
  <dd>Now.</dd>
  <dt>Where is it?</dt>
  <dd>We are not sure.</dd>
 </dl>
</article>

4.5.10 The dd element

Categories
None.
Contexts in which this element can be used:
After dt or dd elements inside dl elements.
Content model:
Flow content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The dd element represents the description, definition, or value, part of a term-description group in a description list (dl element).

A dl can be used to define a vocabulary list, like in a dictionary. In the following example, each entry, given by a dt with a dfn, has several dds, showing the various parts of the definition.

<dl>
 <dt><dfn>happiness</dfn></dt>
 <dd class="pronunciation">/'hæ p. nes/</dd>
 <dd class="part-of-speech"><i><abbr>n.</abbr></i></dd>
 <dd>The state of being happy.</dd>
 <dd>Good fortune; success. <q>Oh <b>happiness</b>! It worked!</q></dd>
 <dt><dfn>rejoice</dfn></dt>
 <dd class="pronunciation">/ri jois'/</dd>
 <dd><i class="part-of-speech"><abbr>v.intr.</abbr></i> To be delighted oneself.</dd>
 <dd><i class="part-of-speech"><abbr>v.tr.</abbr></i> To cause one to be delighted.</dd>
</dl>

4.5.11 The figure element

Categories
Flow content.
Sectioning root.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Either: One figcaption element followed by flow content.
Or: Flow content followed by one figcaption element.
Or: Flow content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The figure element represents some flow content, optionally with a caption, that is self-contained and is typically referenced as a single unit from the main flow of the document.

The element can thus be used to annotate illustrations, diagrams, photos, code listings, etc, that are referred to from the main content of the document, but that could, without affecting the flow of the document, be moved away from that primary content, e.g. to the side of the page, to dedicated pages, or to an appendix.

The figcaption element child of the element, if any, represents the caption of the figure element's contents. If there is no child figcaption element, then there is no caption.

This example shows the figure element to mark up a code listing.

<p>In <a href="#l4">listing 4</a> we see the primary core interface
API declaration.</p>
<figure id="l4">
 <figcaption>Listing 4. The primary core interface API declaration.</figcaption>
 <pre><code>interface PrimaryCore {
 boolean verifyDataLine();
 void sendData(in sequence&lt;byte> data);
 void initSelfDestruct();
}</code></pre>
</figure>
<p>The API is designed to use UTF-8.</p>

Here we see a figure element to mark up a photo.

<figure>
 <img src="bubbles-work.jpeg"
      alt="Bubbles, sitting in his office chair, works on his
           latest project intently.">
 <figcaption>Bubbles at work</figcaption>
</figure>

In this example, we see an image that is not a figure, as well as an image and a video that are.

<h2>Malinko's comics</h2>

<p>This case centered on some sort of "intellectual property"
infringement related to a comic (see Exhibit A). The suit started
after a trailer ending with these words:

<blockquote>
 <img src="promblem-packed-action.png" alt="ROUGH COPY! Promblem-Packed Action!">
</blockquote>

<p>...was aired. A lawyer, armed with a Bigger Notebook, launched a
preemptive strike using snowballs. A complete copy of the trailer is
included with Exhibit B.

<figure>
 <img src="ex-a.png" alt="Two squiggles on a dirty piece of paper.">
 <figcaption>Exhibit A. The alleged <cite>rough copy</cite> comic.</figcaption>
</figure>

<figure>
 <video src="ex-b.mov"></video>
 <figcaption>Exhibit B. The <cite>Rough Copy</cite> trailer.</figcaption>
</figure>

<p>The case was resolved out of court.

Here, a part of a poem is marked up using figure.

<figure>
 <p>'Twas brillig, and the slithy toves<br>
 Did gyre and gimble in the wabe;<br>
 All mimsy were the borogoves,<br>
 And the mome raths outgrabe.</p>
 <figcaption><cite>Jabberwocky</cite> (first verse). Lewis Carroll, 1832-98</figcaption>
</figure>

In this example, which could be part of a much larger work discussing a castle, the figure has three images in it.

<figure>
 <img src="castle1423.jpeg" title="Etching. Anonymous, ca. 1423."
      alt="The castle has one tower, and a tall wall around it.">
 <img src="castle1858.jpeg" title="Oil-based paint on canvas. Maria Towle, 1858."
      alt="The castle now has two towers and two walls.">
 <img src="castle1999.jpeg" title="Film photograph. Peter Jankle, 1999."
      alt="The castle lies in ruins, the original tower all that remains in one piece.">
 <figcaption>The castle through the ages: 1423, 1858, and 1999 respectively.</figcaption>
</figure>

4.5.12 The figcaption element

Categories
None.
Contexts in which this element can be used:
As the first or last child of a figure element.
Content model:
Flow content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The figcaption element represents a caption or legend for the rest of the contents of the figcaption element's parent figure element.

4.5.13 The div element

Categories
Flow content.
formatBlock candidate.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content.
Content attributes:
Global attributes
DOM interface:
interface HTMLDivElement : HTMLElement {};

The div element has no special meaning at all. It represents its children. It can be used with the class, lang, and title attributes to mark up semantics common to a group of consecutive elements.

Authors are strongly encouraged to view the div element as an element of last resort, for when no other element is suitable. Use of the div element instead of more appropriate elements leads to poor accessibility for readers and poor maintainability for authors.

For example, a blog post would be marked up using article, a chapter using section, a page's navigation aids using nav, and a group of form controls using fieldset.

On the other hand, div elements can be useful for stylistic purposes or to wrap multiple paragraphs within a section that are all to be annotated in a similar way. In the following example, we see div elements used as a way to set the language of two paragraphs at once, instead of setting the language on the two paragraph elements separately:

<article lang="en-US">
 <h1>My use of language and my cats</h1>
 <p>My cat's behavior hasn't changed much since her absence, except
 that she plays her new physique to the neighbors regularly, in an
 attempt to get pets.</p>
 <div lang="en-GB">
  <p>My other cat, coloured black and white, is a sweetie. He followed
  us to the pool today, walking down the pavement with us. Yesterday
  he apparently visited our neighbours. I wonder if he recognises that
  their flat is a mirror image of ours.</p>
  <p>Hm, I just noticed that in the last paragraph I used British
  English. But I'm supposed to write in American English. So I
  shouldn't say "pavement" or "flat" or "colour"...</p>
 </div>
 <p>I should say "sidewalk" and "apartment" and "color"!</p>
</article>

4.6 Text-level semantics

4.6.1 The a element

Categories
Flow content.
When the element only contains phrasing content: phrasing content.
Interactive content.
Contexts in which this element can be used:
When the element only contains phrasing content: where phrasing content is expected.
Otherwise: where flow content is expected.
Content model:
Transparent, but there must be no interactive content descendant.
Content attributes:
Global attributes
href
target
rel
media
hreflang
type
DOM interface:
interface HTMLAnchorElement : HTMLElement {
  stringifier attribute DOMString href;
           attribute DOMString target;
           attribute DOMString rel;
  readonly attribute DOMTokenList relList;
           attribute DOMString media;
           attribute DOMString hreflang;
           attribute DOMString type;

           attribute DOMString text;

  // URL decomposition IDL attributes
           attribute DOMString protocol;
           attribute DOMString host;
           attribute DOMString hostname;
           attribute DOMString port;
           attribute DOMString pathname;
           attribute DOMString search;
           attribute DOMString hash;
};

If the a element has an href attribute, then it represents a hyperlink (a hypertext anchor).

If the a element has no href attribute, then the element represents a placeholder for where a link might otherwise have been placed, if it had been relevant.

The target, rel, media, hreflang, and type attributes must be omitted if the href attribute is not present.

If a site uses a consistent navigation toolbar on every page, then the link that would normally link to the page itself could be marked up using an a element:

<nav>
 <ul>
  <li> <a href="/">Home</a> </li>
  <li> <a href="/news">News</a> </li>
  <li> <a>Examples</a> </li>
  <li> <a href="/legal">Legal</a> </li>
 </ul>
</nav>
a . text

Same as textContent.

The a element may be wrapped around entire paragraphs, lists, tables, and so forth, even entire sections, so long as there is no interactive content within (e.g. buttons or other links). This example shows how this can be used to make an entire advertising block into a link:

<aside class="advertising">
 <h1>Advertising</h1>
 <a href="http://ad.example.com/?adid=1929&amp;pubid=1422">
  <section>
   <h1>Mellblomatic 9000!</h1>
   <p>Turn all your widgets into mellbloms!</p>
   <p>Only $9.99 plus shipping and handling.</p>
  </section>
 </a>
 <a href="http://ad.example.com/?adid=375&amp;pubid=1422">
  <section>
   <h1>The Mellblom Browser</h1>
   <p>Web browsing at the speed of light.</p>
   <p>No other browser goes faster!</p>
  </section>
 </a>
</aside>

4.6.2 The em element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The em element represents stress emphasis of its contents.

The level of emphasis that a particular piece of content has is given by its number of ancestor em elements.

The placement of emphasis changes the meaning of the sentence. The element thus forms an integral part of the content. The precise way in which emphasis is used in this way depends on the language.

These examples show how changing the emphasis changes the meaning. First, a general statement of fact, with no emphasis:

<p>Cats are cute animals.</p>

By emphasizing the first word, the statement implies that the kind of animal under discussion is in question (maybe someone is asserting that dogs are cute):

<p><em>Cats</em> are cute animals.</p>

Moving the emphasis to the verb, one highlights that the truth of the entire sentence is in question (maybe someone is saying cats are not cute):

<p>Cats <em>are</em> cute animals.</p>

By moving it to the adjective, the exact nature of the cats is reasserted (maybe someone suggested cats were mean animals):

<p>Cats are <em>cute</em> animals.</p>

Similarly, if someone asserted that cats were vegetables, someone correcting this might emphasize the last word:

<p>Cats are cute <em>animals</em>.</p>

By emphasizing the entire sentence, it becomes clear that the speaker is fighting hard to get the point across. This kind of emphasis also typically affects the punctuation, hence the exclamation mark here.

<p><em>Cats are cute animals!</em></p>

Anger mixed with emphasizing the cuteness could lead to markup such as:

<p><em>Cats are <em>cute</em> animals!</em></p>

The em element isn't a generic "italics" element. Sometimes, text is intended to stand out from the rest of the paragraph, as if it was in a different mood or voice. For this, the i element is more appropriate.

The em element also isn't intended to convey importance; for that purpose, the strong element is more appropriate.

4.6.3 The strong element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The strong element represents strong importance for its contents.

The relative level of importance of a piece of content is given by its number of ancestor strong elements; each strong element increases the importance of its contents.

Changing the importance of a piece of text with the strong element does not change the meaning of the sentence.

Here is an example of a warning notice in a game, with the various parts marked up according to how important they are:

<p><strong>Warning.</strong> This dungeon is dangerous.
<strong>Avoid the ducks.</strong> Take any gold you find.
<strong><strong>Do not take any of the diamonds</strong>,
they are explosive and <strong>will destroy anything within
ten meters.</strong></strong> You have been warned.</p>

4.6.4 The small element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The small element represents side comments such as small print.

Small print typically features disclaimers, caveats, legal restrictions, or copyrights. Small print is also sometimes used for attribution, or for satisfying licensing requirements.

The small element does not "de-emphasize" or lower the importance of text emphasized by the em element or marked as important with the strong element. To mark text as not emphasized or important, simply do not mark it up with the em or strong elements respectively.

The small element should not be used for extended spans of text, such as multiple paragraphs, lists, or sections of text. It is only intended for short runs of text. The text of a page listing terms of use, for instance, would not be a suitable candidate for the small element: in such a case, the text is not a side comment, it is the main content of the page.

In this example the footer contains contact information and a copyright notice.

<footer>
 <address>
  For more details, contact
  <a href="mailto:js@example.com">John Smith</a>.
 </address>
 <p><small>© copyright 2038 Example Corp.</small></p>
</footer>

In this second example, the small element is used for a side comment in an article.

<p>Example Corp today announced record profits for the
second quarter <small>(Full Disclosure: Foo News is a subsidiary of
Example Corp)</small>, leading to speculation about a third quarter
merger with Demo Group.</p>

This is distinct from a sidebar, which might be multiple paragraphs long and is removed from the main flow of text. In the following example, we see a sidebar from the same article. This sidebar also has small print, indicating the source of the information in the sidebar.

<aside>
 <h1>Example Corp</h1>
 <p>This company mostly creates small software and Web
 sites.</p>
 <p>The Example Corp company mission is "To provide entertainment
 and news on a sample basis".</p>
 <p><small>Information obtained from <a
 href="http://example.com/about.html">example.com</a> home
 page.</small></p>
</aside>

In this last example, the small element is marked as being important small print.

<p><strong><small>Continued use of this service will result in a kiss.</small></strong></p>

4.6.5 The s element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The s element represents contents that are no longer accurate or no longer relevant.

The s element is not appropriate when indicating document edits; to mark a span of text as having been removed from a document, use the del element.

In this example a recommended retail price has been marked as no longer relevant as the product in question has a new sale price.

<p>Buy our Iced Tea and Lemonade!</p>
<p><s>Recommended retail price: $3.99 per bottle</s></p>
<p><strong>Now selling for just $2.99 a bottle!</strong></p>

4.6.6 The cite element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The cite element represents the title of a work (e.g. a book, a paper, an essay, a poem, a score, a song, a script, a film, a TV show, a game, a sculpture, a painting, a theatre production, a play, an opera, a musical, an exhibition, a legal case report, etc). This can be a work that is being quoted or referenced in detail (i.e. a citation), or it can just be a work that is mentioned in passing.

A person's name is not the title of a work — even if people call that person a piece of work — and the element must therefore not be used to mark up people's names. (In some cases, the b element might be appropriate for names; e.g. in a gossip article where the names of famous people are keywords rendered with a different style to draw attention to them. In other cases, if an element is really needed, the span element can be used.)

This next example shows a typical use of the cite element:

<p>My favorite book is <cite>The Reality Dysfunction</cite> by
Peter F. Hamilton. My favorite comic is <cite>Pearls Before
Swine</cite> by Stephan Pastis. My favorite track is <cite>Jive
Samba</cite> by the Cannonball Adderley Sextet.</p>

This is correct usage:

<p>According to the Wikipedia article <cite>HTML</cite>, as it
stood in mid-February 2008, leaving attribute values unquoted is
unsafe. This is obviously an over-simplification.</p>

The following, however, is incorrect usage, as the cite element here is containing far more than the title of the work:

<!-- do not copy this example, it is an example of bad usage! -->
<p>According to <cite>the Wikipedia article on HTML</cite>, as it
stood in mid-February 2008, leaving attribute values unquoted is
unsafe. This is obviously an over-simplification.</p>

The cite element is obviously a key part of any citation in a bibliography, but it is only used to mark the title:

<p><cite>Universal Declaration of Human Rights</cite>, United Nations,
December 1948. Adopted by General Assembly resolution 217 A (III).</p>

A citation is not a quote (for which the q element is appropriate).

This is incorrect usage, because cite is not for quotes:

<p><cite>This is wrong!</cite>, said Ian.</p>

This is also incorrect usage, because a person is not a work:

<p><q>This is still wrong!</q>, said <cite>Ian</cite>.</p>

The correct usage does not use a cite element:

<p><q>This is correct</q>, said Ian.</p>

As mentioned above, the b element might be relevant for marking names as being keywords in certain kinds of documents:

<p>And then <b>Ian</b> said <q>this might be right, in a
gossip column, maybe!</q>.</p>

4.6.7 The q element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
cite
DOM interface:
Uses HTMLQuoteElement.

The q element represents some phrasing content quoted from another source.

Quotation punctuation (such as quotation marks) that is quoting the contents of the element must not appear immediately before, after, or inside q elements; they will be inserted into the rendering by the user agent.

Content inside a q element must be quoted from another source, whose address, if it has one, may be cited in the cite attribute. The source may be fictional, as when quoting characters in a novel or screenplay.

If the cite attribute is present, it must be a valid URL potentially surrounded by spaces.

The q element must not be used in place of quotation marks that do not represent quotes; for example, it is inappropriate to use the q element for marking up sarcastic statements.

The use of q elements to mark up quotations is entirely optional; using explicit quotation punctuation without q elements is just as correct.

Here is a simple example of the use of the q element:

<p>The man said <q>Things that are impossible just take
longer</q>. I disagreed with him.</p>

Here is an example with both an explicit citation link in the q element, and an explicit citation outside:

<p>The W3C page <cite>About W3C</cite> says the W3C's
mission is <q cite="http://www.w3.org/Consortium/">To lead the
World Wide Web to its full potential by developing protocols and
guidelines that ensure long-term growth for the Web</q>. I
disagree with this mission.</p>

In the following example, the quotation itself contains a quotation:

<p>In <cite>Example One</cite>, he writes <q>The man
said <q>Things that are impossible just take longer</q>. I
disagreed with him</q>. Well, I disagree even more!</p>

In the following example, quotation marks are used instead of the q element:

<p>His best argument was ❝I disagree❞, which
I thought was laughable.</p>

In the following example, there is no quote — the quotation marks are used to name a word. Use of the q element in this case would be inappropriate.

<p>The word "ineffable" could have been used to describe the disaster
resulting from the campaign's mismanagement.</p>

4.6.8 The dfn element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content, but there must be no dfn element descendants.
Content attributes:
Global attributes
Also, the title attribute has special semantics on this element.
DOM interface:
Uses HTMLElement.

The dfn element represents the defining instance of a term. The paragraph, description list group, or section that is the nearest ancestor of the dfn element must also contain the definition(s) for the term given by the dfn element.

Defining term: If the dfn element has a title attribute, then the exact value of that attribute is the term being defined. Otherwise, if it contains exactly one element child node and no child text nodes, and that child element is an abbr element with a title attribute, then the exact value of that attribute is the term being defined. Otherwise, it is the exact textContent of the dfn element that gives the term being defined.

If the title attribute of the dfn element is present, then it must contain only the term being defined.

The title attribute of ancestor elements does not affect dfn elements.

An a element that links to a dfn element represents an instance of the term defined by the dfn element.

In the following fragment, the term "GDO" is first defined in the first paragraph, then used in the second.

<p>The <dfn><abbr title="Garage Door Opener">GDO</abbr></dfn>
is a device that allows off-world teams to open the iris.</p>
<!-- ... later in the document: -->
<p>Teal'c activated his <abbr title="Garage Door Opener">GDO</abbr>
and so Hammond ordered the iris to be opened.</p>

With the addition of an a element, the reference can be made explicit:

<p>The <dfn id=gdo><abbr title="Garage Door Opener">GDO</abbr></dfn>
is a device that allows off-world teams to open the iris.</p>
<!-- ... later in the document: -->
<p>Teal'c activated his <a href=#gdo><abbr title="Garage Door Opener">GDO</abbr></a>
and so Hammond ordered the iris to be opened.</p>

4.6.9 The abbr element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
Also, the title attribute has special semantics on this element.
DOM interface:
Uses HTMLElement.

The abbr element represents an abbreviation or acronym, optionally with its expansion. The title attribute may be used to provide an expansion of the abbreviation. The attribute, if specified, must contain an expansion of the abbreviation, and nothing else.

The paragraph below contains an abbreviation marked up with the abbr element. This paragraph defines the term "Web Hypertext Application Technology Working Group".

<p>The <dfn id=whatwg><abbr
title="Web Hypertext Application Technology Working Group">WHATWG</abbr></dfn>
is a loose unofficial collaboration of Web browser manufacturers and
interested parties who wish to develop new technologies designed to
allow authors to write and deploy Applications over the World Wide
Web.</p>

An alternative way to write this would be:

<p>The <dfn id=whatwg>Web Hypertext Application Technology
Working Group</dfn> (<abbr
title="Web Hypertext Application Technology Working Group">WHATWG</abbr>)
is a loose unofficial collaboration of Web browser manufacturers and
interested parties who wish to develop new technologies designed to
allow authors to write and deploy Applications over the World Wide
Web.</p>

This paragraph has two abbreviations. Notice how only one is defined; the other, with no expansion associated with it, does not use the abbr element.

<p>The
<abbr title="Web Hypertext Application Technology Working Group">WHATWG</abbr>
started working on HTML5 in 2004.</p>

This paragraph links an abbreviation to its definition.

<p>The <a href="#whatwg"><abbr
title="Web Hypertext Application Technology Working Group">WHATWG</abbr></a>
community does not have much representation from Asia.</p>

This paragraph marks up an abbreviation without giving an expansion, possibly as a hook to apply styles for abbreviations (e.g. smallcaps).

<p>Philip` and Dashiva both denied that they were going to
get the issue counts from past revisions of the specification to
backfill the <abbr>WHATWG</abbr> issue graph.</p>

If an abbreviation is pluralized, the expansion's grammatical number (plural vs singular) must match the grammatical number of the contents of the element.

Here the plural is outside the element, so the expansion is in the singular:

<p>Two <abbr title="Working Group">WG</abbr>s worked on
this specification: the <abbr>WHATWG</abbr> and the
<abbr>HTMLWG</abbr>.</p>

Here the plural is inside the element, so the expansion is in the plural:

<p>Two <abbr title="Working Groups">WGs</abbr> worked on
this specification: the <abbr>WHATWG</abbr> and the
<abbr>HTMLWG</abbr>.</p>

Abbreviations do not have to be marked up using this element. It is expected to be useful in the following cases:

Providing an expansion in a title attribute once will not necessarily cause other abbr elements in the same document with the same contents but without a title attribute to behave as if they had the same expansion. Every abbr element is independent.

4.6.10 The time element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content, but there must be no time element descendants.
Content attributes:
Global attributes
datetime
pubdate
DOM interface:
interface HTMLTimeElement : HTMLElement {
           attribute DOMString dateTime;
           attribute boolean pubDate;
  readonly attribute Date valueAsDate;
};

The time element represents either a time on a 24 hour clock, or a precise date in the proleptic Gregorian calendar, optionally with a time and a time-zone offset. [GREGORIAN]

This element is intended as a way to encode modern dates and times in a machine-readable way so that, for example, user agents can offer to add birthday reminders or scheduled events to the user's calendar.

The time element is not intended for encoding times for which a precise date or time cannot be established. For example, it would be inappropriate for encoding times like "one millisecond after the big bang", "the early part of the Jurassic period", or "a winter around 250 BCE".

For dates before the introduction of the Gregorian calendar, authors are encouraged to not use the time element, or else to be very careful about converting dates and times from the period to the Gregorian calendar. This is complicated by the manner in which the Gregorian calendar was phased in, which occurred at different times in different countries, ranging from partway through the 16th century all the way to early in the 20th.

The pubdate attribute is a boolean attribute. If specified, it indicates that the date and time given by the element is the publication date and time of the nearest ancestor article element, or, if the element has no ancestor article element, of the document as a whole. If the element has a pubdate attribute specified, then the element needs a date. For each article element, there must be no more than one time element with a pubdate attribute whose nearest ancestor is that article element. Furthermore, for each Document, there must be no more than one time element with a pubdate attribute that does not have an ancestor article element.

The datetime attribute, if present, gives the date or time being specified. Otherwise, the date or time is given by the element's contents.

If the element needs a date, and the datetime attribute is present, then the attribute's value must be a valid date string with optional time.

If the element needs a date, but the datetime attribute is not present, then the element's textContent must be a valid date string in content with optional time.

If the element does not need a date, and the datetime attribute is present, then the attribute's value must be a valid date or time string.

If the element does not need a date, but the datetime attribute is not present, then the element's textContent must be a valid date or time string in content.

The date, if any, must be expressed using the Gregorian calendar.

The time element can be used to encode dates, for example in Microformats. The following shows a hypothetical way of encoding an event using a variant on hCalendar that uses the time element:

<div class="vevent">
 <a class="url" href="http://www.web2con.com/">http://www.web2con.com/</a>
  <span class="summary">Web 2.0 Conference</span>:
  <time class="dtstart" datetime="2007-10-05">October 5</time> -
  <time class="dtend" datetime="2007-10-20">19</time>,
  at the <span class="location">Argent Hotel, San Francisco, CA</span>
 </div>

(The end date is encoded as one day after the last date of the event because in the iCalendar format, end dates are exclusive, not inclusive.)

The time element is not necessary for encoding dates or times. In the following snippet, the time is encoded using time, so that it can be restyled (e.g. using XBL2) to match local conventions, while the year is not marked up at all, since marking it up would not be particularly useful.

<p>I usually have a snack at <time>16:00</time>.</p>
<p>I've liked model trains since at least 1983.</p>

Using a styling technology that supports restyling times, the first paragraph from the above snippet could be rendered as follows:

I usually have a snack at 4pm.

Or it could be rendered as follows:

I usually have a snack at 16h00.

time . valueAsDate

Returns a Date object representing the specified date and time.

In the following snippet:

<p>Our first date was <time datetime="2006-09-23">a Saturday</time>.</p>

...the time element's valueAsDate attribute would have the value 1,158,969,600,000ms.

In the following snippet:

<p>Many people get up at <time>08:00</time>.</p>

...the time element's valueAsDate attribute would have the value 28,800,000ms.

In this example, an article's publication date is marked up using time:

<article>
 <h1>Small tasks</h1>
 <footer>Published <time pubdate>2009-08-30</time>.</footer>
 <p>I put a bike bell on his bike.</p>
</article>

Here is another way that could be marked up. In this example, legacy user agents would say "today", while newer user agents would render the time in a locale-specific manner based on the value of the attribute.

<article>
 <h1>Small tasks</h1>
 <footer>Published <time pubdate datetime="2009-08-30">today</time>.</footer>
 <p>I put a bike bell on his bike.</p>
</article>

Here is the same thing but with the time included only. Because the element is empty, legacy user agents will not show anything useful; user agents that implement this specification, on the other hand, would show the date and time in a locale-specific manner.

<article>
 <h1>Small tasks</h1>
 <footer>Published <time pubdate datetime="2009-08-30T07:13Z"></time>.</footer>
 <p>I put a bike bell on his bike.</p>
</article>

4.6.11 The code element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The code element represents a fragment of computer code. This could be an XML element name, a filename, a computer program, or any other string that a computer would recognize.

Although there is no formal way to indicate the language of computer code being marked up, authors who wish to mark code elements with the language used, e.g. so that syntax highlighting scripts can use the right rules, may do so by adding a class prefixed with "language-" to the element.

The following example shows how the element can be used in a paragraph to mark up element names and computer code, including punctuation.

<p>The <code>code</code> element represents a fragment of computer
code.</p>

<p>When you call the <code>activate()</code> method on the
<code>robotSnowman</code> object, the eyes glow.</p>

<p>The example below uses the <code>begin</code> keyword to indicate
the start of a statement block. It is paired with an <code>end</code>
keyword, which is followed by the <code>.</code> punctuation character
(full stop) to indicate the end of the program.</p>

The following example shows how a block of code could be marked up using the pre and code elements.

<pre><code class="language-pascal">var i: Integer;
begin
   i := 1;
end.</code></pre>

A class is used in that example to indicate the language used.

See the pre element for more details.

4.6.12 The var element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The var element represents a variable. This could be an actual variable in a mathematical expression or programming context, or it could just be a term used as a placeholder in prose.

In the paragraph below, the letter "n" is being used as a variable in prose:

<p>If there are <var>n</var> pipes leading to the ice
cream factory then I expect at <em>least</em> <var>n</var>
flavors of ice cream to be available for purchase!</p>

For mathematics, in particular for anything beyond the simplest of expressions, MathML is more appropriate. However, the var element can still be used to refer to specific variables that are then mentioned in MathML expressions.

In this example, an equation is shown, with a legend that references the variables in the equation. The expression itself is marked up with MathML, but the variables are mentioned in the figure's legend using var.

<figure>
 <math>
  <mi>a</mi>
  <mo>=</mo>
  <msqrt>
   <msup><mi>b</mi><mn>2</mn></msup>
   <mi>+</mi>
   <msup><mi>c</mi><mn>2</mn></msup>
  </msqrt>
 </math>
 <figcaption>
  Using Pythagoras' theorem to solve for the hypotenuse <var>a</var> of
  a triangle with sides <var>b</var> and <var>c</var>
 </figcaption>
</figure>

4.6.13 The samp element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The samp element represents (sample) output from a program or computing system.

See the pre and kbd elements for more details.

This example shows the samp element being used inline:

<p>The computer said <samp>Too much cheese in tray
two</samp> but I didn't know what that meant.</p>

This second example shows a block of sample output. Nested samp and kbd elements allow for the styling of specific elements of the sample output using a style sheet.

<pre><samp><span class="prompt">jdoe@mowmow:~$</span> <kbd>ssh demo.example.com</kbd>
Last login: Tue Apr 12 09:10:17 2005 from mowmow.example.com on pts/1
Linux demo 2.6.10-grsec+gg3+e+fhs6b+nfs+gr0501+++p3+c4a+gr2b-reslog-v6.189 #1 SMP Tue Feb 1 11:22:36 PST 2005 i686 unknown

<span class="prompt">jdoe@demo:~$</span> <span class="cursor">_</span></samp></pre>

4.6.14 The kbd element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The kbd element represents user input (typically keyboard input, although it may also be used to represent other input, such as voice commands).

When the kbd element is nested inside a samp element, it represents the input as it was echoed by the system.

When the kbd element contains a samp element, it represents input based on system output, for example invoking a menu item.

When the kbd element is nested inside another kbd element, it represents an actual key or other single unit of input as appropriate for the input mechanism.

Here the kbd element is used to indicate keys to press:

<p>To make George eat an apple, press <kbd><kbd>Shift</kbd>+<kbd>F3</kbd></kbd></p>

In this second example, the user is told to pick a particular menu item. The outer kbd element marks up a block of input, with the inner kbd elements representing each individual step of the input, and the samp elements inside them indicating that the steps are input based on something being displayed by the system, in this case menu labels:

<p>To make George eat an apple, select
    <kbd><kbd><samp>File</samp></kbd>|<kbd><samp>Eat Apple...</samp></kbd></kbd>
</p>

Such precision isn't necessary; the following is equally fine:

<p>To make George eat an apple, select <kbd>File | Eat Apple...</kbd></p>

4.6.15 The sub and sup elements

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Use HTMLElement.

The sup element represents a superscript and the sub element represents a subscript.

These elements must be used only to mark up typographical conventions with specific meanings, not for typographical presentation for presentation's sake. For example, it would be inappropriate for the sub and sup elements to be used in the name of the LaTeX document preparation system. In general, authors should use these elements only if the absence of those elements would change the meaning of the content.

In certain languages, superscripts are part of the typographical conventions for some abbreviations.

<p>The most beautiful women are
<span lang="fr"><abbr>M<sup>lle</sup></abbr> Gwendoline</span> and
<span lang="fr"><abbr>M<sup>me</sup></abbr> Denise</span>.</p>

The sub element can be used inside a var element, for variables that have subscripts.

Here, the sub element is used to represents the subscript that identifies the variable in a family of variables:

<p>The coordinate of the <var>i</var>th point is
(<var>x<sub><var>i</var></sub></var>, <var>y<sub><var>i</var></sub></var>).
For example, the 10th point has coordinate
(<var>x<sub>10</sub></var>, <var>y<sub>10</sub></var>).</p>

Mathematical expressions often use subscripts and superscripts. Authors are encouraged to use MathML for marking up mathematics, but authors may opt to use sub and sup if detailed mathematical markup is not desired. [MATHML]

<var>E</var>=<var>m</var><var>c</var><sup>2</sup>
f(<var>x</var>, <var>n</var>) = log<sub>4</sub><var>x</var><sup><var>n</var></sup>

4.6.16 The i element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The i element represents a span of text in an alternate voice or mood, or otherwise offset from the normal prose, such as a taxonomic designation, a technical term, an idiomatic phrase from another language, a thought, a ship name, or some other prose whose typical typographic presentation is italicized.

Terms in languages different from the main text should be annotated with lang attributes (or, in XML, lang attributes in the XML namespace).

The examples below show uses of the i element:

<p>The <i class="taxonomy">Felis silvestris catus</i> is cute.</p>
<p>The term <i>prose content</i> is defined above.</p>
<p>There is a certain <i lang="fr">je ne sais quoi</i> in the air.</p>

In the following example, a dream sequence is marked up using i elements.

<p>Raymond tried to sleep.</p>
<p><i>The ship sailed away on Thursday</i>, he
dreamt. <i>The ship had many people aboard, including a beautiful
princess called Carey. He watched her, day-in, day-out, hoping she
would notice him, but she never did.</i></p>
<p><i>Finally one night he picked up the courage to speak with
her—</i></p>
<p>Raymond woke with a start as the fire alarm rang out.</p>

Authors can use the class attribute on the i element to identify why the element is being used, so that if the style of a particular use (e.g. dream sequences as opposed to taxonomic terms) is to be changed at a later date, the author doesn't have to go through the entire document (or series of related documents) annotating each use.

Authors are encouraged to consider whether other elements might be more applicable than the i element, for instance the em element for marking up stress emphasis, or the dfn element to mark up the defining instance of a term.

Style sheets can be used to format i elements, just like any other element can be restyled. Thus, it is not the case that content in i elements will necessarily be italicized.

4.6.17 The b element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The b element represents a span of text to be stylistically offset from the normal prose without conveying any extra importance, such as key words in a document abstract, product names in a review, or other spans of text whose typical typographic presentation is boldened.

The following example shows a use of the b element to highlight key words without marking them up as important:

<p>The <b>frobonitor</b> and <b>barbinator</b> components are fried.</p>

In the following example, objects in a text adventure are highlighted as being special by use of the b element.

<p>You enter a small room. Your <b>sword</b> glows
brighter. A <b>rat</b> scurries past the corner wall.</p>

Another case where the b element is appropriate is in marking up the lede (or lead) sentence or paragraph. The following example shows how a BBC article about kittens adopting a rabbit as their own could be marked up:

<article>
 <h2>Kittens 'adopted' by pet rabbit</h2>
 <p><b class="lede">Six abandoned kittens have found an
 unexpected new mother figure — a pet rabbit.</b></p>
 <p>Veterinary nurse Melanie Humble took the three-week-old
 kittens to her Aberdeen home.</p>
[...]

As with the i element, authors can use the class attribute on the b element to identify why the element is being used, so that if the style of a particular use is to be changed at a later date, the author doesn't have to go through annotating each use.

The b element should be used as a last resort when no other element is more appropriate. In particular, headings should use the h1 to h6 elements, stress emphasis should use the em element, importance should be denoted with the strong element, and text marked or highlighted should use the mark element.

The following would be incorrect usage:

<p><b>WARNING!</b> Do not frob the barbinator!</p>

In the previous example, the correct element to use would have been strong, not b.

Style sheets can be used to format b elements, just like any other element can be restyled. Thus, it is not the case that content in b elements will necessarily be boldened.

4.6.18 The mark element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The mark element represents a run of text in one document marked or highlighted for reference purposes, due to its relevance in another context. When used in a quotation or other block of text referred to from the prose, it indicates a highlight that was not originally present but which has been added to bring the reader's attention to a part of the text that might not have been considered important by the original author when the block was originally written, but which is now under previously unexpected scrutiny. When used in the main prose of a document, it indicates a part of the document that has been highlighted due to its likely relevance to the user's current activity.

This example shows how the mark element can be used to bring attention to a particular part of a quotation:

<p lang="en-US">Consider the following quote:</p>
<blockquote lang="en-GB">
 <p>Look around and you will find, no-one's really
 <mark>colour</mark> blind.</p>
</blockquote>
<p lang="en-US">As we can tell from the <em>spelling</em> of the word,
the person writing this quote is clearly not American.</p>

Another example of the mark element is highlighting parts of a document that are matching some search string. If someone looked at a document, and the server knew that the user was searching for the word "kitten", then the server might return the document with one paragraph modified as follows:

<p>I also have some <mark>kitten</mark>s who are visiting me
these days. They're really cute. I think they like my garden! Maybe I
should adopt a <mark>kitten</mark>.</p>

In the following snippet, a paragraph of text refers to a specific part of a code fragment.

<p>The highlighted part below is where the error lies:</p>
<pre><code>var i: Integer;
begin
   i := <mark>1.1</mark>;
end.</code></pre>

This is separate from syntax highlighting, for which span is more appropriate. Combining both, one would get:

<p>The highlighted part below is where the error lies:</p>
<pre><code><span class=keyword>var</span> <span class=ident>i</span>: <span class=type>Integer</span>;
<span class=keyword>begin</span>
   <span class=ident>i</span> := <span class=literal><mark>1.1</mark></span>;
<span class=keyword>end</span>.</code></pre>

This is another example showing the use of mark to highlight a part of quoted text that was originally not emphasized. In this example, common typographic conventions have led the author to explicitly style mark elements in quotes to render in italics.

<article>
 <style scoped>
  blockquote mark, q mark {
    font: inherit; font-style: italic;
    text-decoration: none;
    background: transparent; color: inherit;
  }
  .bubble em {
    font: inherit; font-size: larger;
    text-decoration: underline;
  }
 </style>
 <h1>She knew</h1>
 <p>Did you notice the subtle joke in the joke on panel 4?</p>
 <blockquote>
  <p class="bubble">I didn't <em>want</em> to believe. <mark>Of course
  on some level I realized it was a known-plaintext attack.</mark> But I
  couldn't admit it until I saw for myself.</p>
 </blockquote>
 <p>(Emphasis mine.) I thought that was great. It's so pedantic, yet it
 explains everything neatly.</p>
</article>

Note, incidentally, the distinction between the em element in this example, which is part of the original text being quoted, and the mark element, which is highlighting a part for comment.

The following example shows the difference between denoting the importance of a span of text (strong) as opposed to denoting the relevance of a span of text (mark). It is an extract from a textbook, where the extract has had the parts relevant to the exam highlighted. The safety warnings, important though they may be, are apparently not relevant to the exam.

<h3>Wormhole Physics Introduction</h3>

<p><mark>A wormhole in normal conditions can be held open for a
maximum of just under 39 minutes.</mark> Conditions that can increase
the time include a powerful energy source coupled to one or both of
the gates connecting the wormhole, and a large gravity well (such as a
black hole).</p>

<p><mark>Momentum is preserved across the wormhole. Electromagnetic
radiation can travel in both directions through a wormhole,
but matter cannot.</mark></p>

<p>When a wormhole is created, a vortex normally forms.
<strong>Warning: The vortex caused by the wormhole opening will
annihilate anything in its path.</strong> Vortexes can be avoided when
using sufficiently advanced dialing technology.</p>

<p><mark>An obstruction in a gate will prevent it from accepting a
wormhole connection.</mark></p>

4.6.19 The ruby element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
One or more groups of: phrasing content followed either by a single rt element, or an rp element, an rt element, and another rp element.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The ruby element allows one or more spans of phrasing content to be marked with ruby annotations. Ruby annotations are short runs of text presented alongside base text, primarily used in East Asian typography as a guide for pronunciation or to include other annotations. In Japanese, this form of typography is also known as furigana.

A ruby element represents the spans of phrasing content it contains, ignoring all the child rt and rp elements and their descendants. Those spans of phrasing content have associated annotations created using the rt element.

In this example, each ideograph in the Japanese text 漢字 is annotated with its reading in hiragana.

...
<ruby>漢<rt>かん</rt>字<rt>じ </rt></ruby>
...

This might be rendered as:

The two main ideographs, each with its annotation in hiragana rendered in a smaller font above it.

In this example, each ideograph in the traditional Chinese text 漢字 is annotated with its bopomofo reading.

<ruby>漢<rt>ㄏㄢˋ</rt>字<rt>ㄗˋ </rt></ruby>

This might be rendered as:

The two main ideographs, each with its bopomofo annotation rendered in a smaller font next to it.

In this example, each ideograph in the simplified Chinese text 汉字 is annotated with its pinyin reading.

...<ruby>汉<rt>hàn</rt>字<rt>zì </rt></ruby>...

This might be rendered as:

The two main ideographs, each with its pinyin annotation rendered in a smaller font above it.

4.6.20 The rt element

Categories
None.
Contexts in which this element can be used:
As a child of a ruby element.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The rt element marks the ruby text component of a ruby annotation.

An rt element represents an annotation (given by its children) for the zero or more nodes of phrasing content that immediately precedes it in the ruby element, ignoring rp elements.

4.6.21 The rp element

Categories
None.
Contexts in which this element can be used:
As a child of a ruby element, either immediately before or immediately after an rt element.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The rp element can be used to provide parentheses around a ruby text component of a ruby annotation, to be shown by user agents that don't support ruby annotations.

An rp element represents nothing.

The example above, in which each ideograph in the text 漢字 is annotated with its phonetic reading, could be expanded to use rp so that in legacy user agents the readings are in parentheses:

...
<ruby>
 漢 <rp>(</rp><rt>かん</rt><rp>)</rp>
 字 <rp>(</rp><rt>じ</rt><rp>)</rp>
</ruby>
...

In conforming user agents the rendering would be as above, but in user agents that do not support ruby, the rendering would be:

... 漢 (かん) 字 (じ) ...

4.6.22 The bdi element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
Also, the dir global attribute has special semantics on this element.
DOM interface:
Uses HTMLElement.

The bdi element represents a span of text that is to be isolated from its surroundings for the purposes of bidirectional text formatting. [BIDI]

The dir global attribute defaults to auto on this element (it never inherits from the parent element like with other elements).

This element is especially useful when embedding user-generated content with an unknown directionality.

In this example, usernames are shown along with the number of posts that the user has submitted. If the bdi element were not used, the username of the Arabic user would end up confusing the text (the bidirectional algorithm would put the colon and the number "3" next to the word "User" rather than next to the word "posts").

<ul>
 <li>User <bdi>jcranmer</bdi>: 12 posts.
 <li>User <bdi>hober</bdi>: 5 posts.
 <li>User <bdi>إيان</bdi>: 3 posts.
</ul>

4.6.23 The bdo element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
Also, the dir global attribute has special semantics on this element.
DOM interface:
Uses HTMLElement.

The bdo element represents explicit text directionality formatting control for its children. It allows authors to override the Unicode bidirectional algorithm by explicitly specifying a direction override. [BIDI]

Authors must specify the dir attribute on this element, with the value ltr to specify a left-to-right override and with the value rtl to specify a right-to-left override.

4.6.24 The span element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
interface HTMLSpanElement : HTMLElement {};

The span element doesn't mean anything on its own, but can be useful when used together with the global attributes, e.g. class, lang, or dir. It represents its children.

In this example, a code fragment is marked up using span elements and class attributes so that its keywords and identifiers can be color-coded from CSS:

<pre><code class="lang-c"><span class="keyword">for</span> (<span class="ident">j</span> = 0; <span class="ident">j</span> &lt; 256; <span class="ident">j</span>++) {
  <span class="ident">i_t3</span> = (<span class="ident">i_t3</span> & 0x1ffff) | (<span class="ident">j</span> &lt;&lt; 17);
  <span class="ident">i_t6</span> = (((((((<span class="ident">i_t3</span> >> 3) ^ <span class="ident">i_t3</span>) >> 1) ^ <span class="ident">i_t3</span>) >> 8) ^ <span class="ident">i_t3</span>) >> 5) & 0xff;
  <span class="keyword">if</span> (<span class="ident">i_t6</span> == <span class="ident">i_t1</span>)
    <span class="keyword">break</span>;
}</code></pre>

4.6.25 The br element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Empty.
Content attributes:
Global attributes
DOM interface:
interface HTMLBRElement : HTMLElement {};

The br element represents a line break.

While line breaks are usually represented in visual media by physically moving subsequent text to a new line, a style sheet or user agent would be equally justified in causing line breaks to be rendered in a different manner, for instance as green dots, or as extra spacing.

br elements must be used only for line breaks that are actually part of the content, as in poems or addresses.

The following example is correct usage of the br element:

<p>P. Sherman<br>
42 Wallaby Way<br>
Sydney</p>

br elements must not be used for separating thematic groups in a paragraph.

The following examples are non-conforming, as they abuse the br element:

<p><a ...>34 comments.</a><br>
<a ...>Add a comment.</a></p>
<p><label>Name: <input name="name"></label><br>
<label>Address: <input name="address"></label></p>

Here are alternatives to the above, which are correct:

<p><a ...>34 comments.</a></p>
<p><a ...>Add a comment.</a></p>
<p><label>Name: <input name="name"></label></p>
<p><label>Address: <input name="address"></label></p>

If a paragraph consists of nothing but a single br element, it represents a placeholder blank line (e.g. as in a template). Such blank lines must not be used for presentation purposes.

4.6.26 The wbr element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Empty.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The wbr element represents a line break opportunity.

In the following example, someone is quoted as saying something which, for effect, is written as one long word. However, to ensure that the text can be wrapped in a readable fashion, the individual words in the quote are separated using a wbr element.

<p>So then he pointed at the tiger and screamed
"there<wbr>is<wbr>no<wbr>way<wbr>you<wbr>are<wbr>ever<wbr>going<wbr>to<wbr>catch<wbr>me"!</p>

4.6.27 Usage summary

This section is non-normative.

Element Purpose Example
a Hyperlinks
Visit my <a href="drinks.html">drinks</a> page.
em Stress emphasis
I must say I <em>adore</em> lemonade.
strong Importance
This tea is <strong>very hot</strong>.
small Side comments
These grapes are made into wine. <small>Alcohol is addictive.</small>
s Inaccurate text
Price: <s>£4.50</s> £2.00!
cite Titles of works
The case <cite>Hugo v. Danielle</cite> is relevant here.
q Quotations
The judge said <q>You can drink water from the fish tank</q> but advised against it.
dfn Defining instance
The term <dfn>organic food</dfn> refers to food produced without synthetic chemicals.
abbr Abbreviations
Organic food in Ireland is certified by the <abbr title="Irish Organic Farmers and Growers Association">IOFGA</abbr>.
time Date and/or time
Published <time>2009-10-21</time>.
code Computer code
The <code>fruitdb</code> program can be used for tracking fruit production.
var Variables
If there are <var>n</var> fruit in the bowl, at least <var>n</var>÷2 will be ripe.
samp Computer output
The computer said <samp>Unknown error -3</samp>.
kbd User input
Hit <kbd>F1</kbd> to continue.
sub Subscripts
Water is H<sub>2</sub>O.
sup Superscripts
The Hydrogen in heavy water is usually <sup>2</sup>H.
i Alternative voice
Lemonade consists primarily of <i>Citrus limon</i>.
b Keywords
Take a <b>lemon</b> and squeeze it with a <b>juicer</b>.
mark Highlight
Elderflower cordial, with one <mark>part</mark> cordial to ten <mark>part</mark>s water, stands a<mark>part</mark> from the rest.
ruby, rt, rp Ruby annotations
<ruby> OJ <rp>(<rt>Orange Juice<rp>)</ruby>
bdi Text directionality isolation
The recommended restaurant is <bdi lang="">My Juice Café (At The Beach)</bdi>.
bdo Text directionality formatting
The proposal is to write English, but in reverse order. "Juice" would become "<bdo dir=rtl>Juice</bdo>"
span Other
In French we call it <span lang="fr">sirop de sureau</span>.
br Line break
Simply Orange Juice Company<br>Apopka, FL 32703<br>U.S.A.
wbr Line breaking opportunity
www.simply<wbr>orange<wbr>juice.com

4.7 Edits

The ins and del elements represent edits to the document.

4.7.1 The ins element

Categories
Flow content.
When the element only contains phrasing content: phrasing content.
Contexts in which this element can be used:
When the element only contains phrasing content: where phrasing content is expected.
Otherwise: where flow content is expected.
Content model:
Transparent.
Content attributes:
Global attributes
cite
datetime
DOM interface:
Uses the HTMLModElement interface.

The ins element represents an addition to the document.

The following represents the addition of a single paragraph:

<aside>
 <ins>
  <p> I like fruit. </p>
 </ins>
</aside>

As does this, because everything in the aside element here counts as phrasing content and therefore there is just one paragraph:

<aside>
 <ins>
  Apples are <em>tasty</em>.
 </ins>
 <ins>
  So are pears.
 </ins>
</aside>

ins elements should not cross implied paragraph boundaries.

The following example represents the addition of two paragraphs, the second of which was inserted in two parts. The first ins element in this example thus crosses a paragraph boundary, which is considered poor form.

<aside>
 <!-- don't do this -->
 <ins datetime="2005-03-16T00:00Z">
  <p> I like fruit. </p>
  Apples are <em>tasty</em>.
 </ins>
 <ins datetime="2007-12-19T00:00Z">
  So are pears.
 </ins>
</aside>

Here is a better way of marking this up. It uses more elements, but none of the elements cross implied paragraph boundaries.

<aside>
 <ins datetime="2005-03-16T00:00Z">
  <p> I like fruit. </p>
 </ins>
 <ins datetime="2005-03-16T00:00Z">
  Apples are <em>tasty</em>.
 </ins>
 <ins datetime="2007-12-19T00:00Z">
  So are pears.
 </ins>
</aside>

4.7.2 The del element

Categories
Flow content.
When the element only contains phrasing content: phrasing content.
Contexts in which this element can be used:
When the element only contains phrasing content: where phrasing content is expected.
Otherwise: where flow content is expected.
Content model:
Transparent.
Content attributes:
Global attributes
cite
datetime
DOM interface:
Uses the HTMLModElement interface.

The del element represents a removal from the document.

del elements should not cross implied paragraph boundaries.

The following shows a "to do" list where items that have been done are crossed-off with the date and time of their completion.

<h1>To Do</h1>
<ul>
 <li>Empty the dishwasher</li>
 <li><del datetime="2009-10-11T01:25-07:00">Watch Walter Lewin's lectures</del></li>
 <li><del datetime="2009-10-10T23:38-07:00">Download more tracks</del></li>
 <li>Buy a printer</li>
</ul>

4.7.3 Attributes common to ins and del elements

The cite attribute may be used to specify the address of a document that explains the change. When that document is long, for instance the minutes of a meeting, authors are encouraged to include a fragment identifier pointing to the specific part of that document that discusses the change.

If the cite attribute is present, it must be a valid URL potentially surrounded by spaces that explains the change.

The datetime attribute may be used to specify the time and date of the change.

If present, the datetime attribute's value must be a valid date string with optional time.

The ins and del elements implement the HTMLModElement interface:

interface HTMLModElement : HTMLElement {
           attribute DOMString cite;
           attribute DOMString dateTime;
};

4.7.4 Edits and paragraphs

This section is non-normative.

Since the ins and del elements do not affect paragraphing, it is possible, in some cases where paragraphs are implied (without explicit p elements), for an ins or del element to span both an entire paragraph or other non-phrasing content elements and part of another paragraph. For example:

<section>
 <ins>
  <p>
   This is a paragraph that was inserted.
  </p>
  This is another paragraph whose first sentence was inserted
  at the same time as the paragraph above.
 </ins>
 This is a second sentence, which was there all along.
</section>

By only wrapping some paragraphs in p elements, one can even get the end of one paragraph, a whole second paragraph, and the start of a third paragraph to be covered by the same ins or del element (though this is very confusing, and not considered good practice):

<section>
 This is the first paragraph. <ins>This sentence was
 inserted.
 <p>This second paragraph was inserted.</p>
 This sentence was inserted too.</ins> This is the
 third paragraph in this example.
 <!-- (don't do this) -->
</section>

However, due to the way implied paragraphs are defined, it is not possible to mark up the end of one paragraph and the start of the very next one using the same ins or del element. You instead have to use one (or two) p element(s) and two ins or del elements, as for example:

<section>
 <p>This is the first paragraph. <del>This sentence was
 deleted.</del></p>
 <p><del>This sentence was deleted too.</del> That
 sentence needed a separate &lt;del&gt; element.</p>
</section>

Partly because of the confusion described above, authors are strongly encouraged to always mark up all paragraphs with the p element, instead of having ins or del elements that cross implied paragraphs boundaries.

4.7.5 Edits and lists

This section is non-normative.

The content models of the ol and ul elements do not allow ins and del elements as children. Lists always represent all their items, including items that would otherwise have been marked as deleted.

To indicate that an item is inserted or deleted, an ins or del element can be wrapped around the contents of the li element. To indicate that an item has been replaced by another, a single li element can have one or more del elements followed by one or more ins elements.

In the following example, a list that started empty had items added and removed from it over time. The bits in the example that have been emphasized show the parts that are the "current" state of the list. The list item numbers don't take into account the edits, though.

<h1>Stop-ship bugs</h1>
<ol>
 <li><ins datetime="2008-02-12T15:20Z">Bug 225:
 Rain detector doesn't work in snow</ins></li>
 <li><del datetime="2008-03-01T20:22Z"><ins datetime="2008-02-14T12:02Z">Bug 228:
 Water buffer overflows in April</ins></del></li>
 <li><ins datetime="2008-02-16T13:50Z">Bug 230:
 Water heater doesn't use renewable fuels</ins></li>
 <li><del datetime="2008-02-20T21:15Z"><ins datetime="2008-02-16T14:25Z">Bug 232:
 Carbon dioxide emissions detected after startup</ins></del></li>
</ol>

In the following example, a list that started with just fruit was replaced by a list with just colors.

<h1>List of <del>fruits</del><ins>colors</ins></h1>
<ul>
 <li><del>Lime</del><ins>Green</ins></li>
 <li><del>Apple</del></li>
 <li>Orange</li>
 <li><del>Pear</del></li>
 <li><ins>Teal</ins></li>
 <li><del>Lemon</del><ins>Yellow</ins></li>
 <li>Olive</li>
 <li><ins>Purple</ins></li>
</ul>

4.8 Embedded content

4.8.1 The img element

Categories
Flow content.
Phrasing content.
Embedded content.
If the element has a usemap attribute: Interactive content.
Contexts in which this element can be used:
Where embedded content is expected.
Content model:
Empty.
Content attributes:
Global attributes
alt
src
usemap
ismap
width
height
DOM interface:
[NamedConstructor=Image(),
 NamedConstructor=Image(in unsigned long width),
 NamedConstructor=Image(in unsigned long width, in unsigned long height)]
interface HTMLImageElement : HTMLElement {
           attribute DOMString alt;
           attribute DOMString src;
           attribute DOMString useMap;
           attribute boolean isMap;
           attribute unsigned long width;
           attribute unsigned long height;
  readonly attribute unsigned long naturalWidth;
  readonly attribute unsigned long naturalHeight;
  readonly attribute boolean complete;
};

An img element represents an image.

The image given by the src attribute is the embedded content, and the value of the alt attribute is the img element's fallback content.

The src attribute must be present, and must contain a valid non-empty URL potentially surrounded by spaces referencing a non-interactive, optionally animated, image resource that is neither paged nor scripted.

Images can thus be static bitmaps (e.g. PNGs, GIFs, JPEGs), single-page vector documents (single-page PDFs, XML files with an SVG root element), animated bitmaps (APNGs, animated GIFs), animated vector graphics (XML files with an SVG root element that use declarative SMIL animation), and so forth. However, this also precludes SVG files with script, multipage PDF files, interactive MNG files, HTML documents, plain text documents, and so forth.

The requirements on the alt attribute's value are described in the next section.

The img must not be used as a layout tool. In particular, img elements should not be used to display transparent images, as they rarely convey meaning and rarely add anything useful to the document.


The usemap attribute, if present, can indicate that the image has an associated image map.

The ismap attribute, when used on an element that is a descendant of an a element with an href attribute, indicates by its presence that the element provides access to a server-side image map. This affects how events are handled on the corresponding a element.

The ismap attribute is a boolean attribute. The attribute must not be specified on an element that does not have an ancestor a element with an href attribute.

The img element supports dimension attributes.

image . width [ = value ]
image . height [ = value ]

These attributes return the actual rendered dimensions of the image, or zero if the dimensions are not known.

They can be set, to change the corresponding content attributes.

image . naturalWidth
image . naturalHeight

These attributes return the intrinsic dimensions of the image, or zero if the dimensions are not known.

image . complete

Returns true if the image has been completely downloaded or if no image is specified; otherwise, returns false.

image = new Image( [ width [, height ] ] )

Returns a new img element, with the width and height attributes set to the values passed in the relevant arguments, if applicable.

A single image can have different appropriate alternative text depending on the context.

In each of the following cases, the same image is used, yet the alt text is different each time. The image is the coat of arms of the Carouge municipality in the canton Geneva in Switzerland.

Here it is used as a supplementary icon:

<p>I lived in <img src="carouge.svg" alt=""> Carouge.</p>

Here it is used as an icon representing the town:

<p>Home town: <img src="carouge.svg" alt="Carouge"></p>

Here it is used as part of a text on the town:

<p>Carouge has a coat of arms.</p>
<p><img src="carouge.svg" alt="The coat of arms depicts a lion, sitting in front of a tree."></p>
<p>It is used as decoration all over the town.</p>

Here it is used as a way to support a similar text where the description is given as well as, instead of as an alternative to, the image:

<p>Carouge has a coat of arms.</p>
<p><img src="carouge.svg" alt=""></p>
<p>The coat of arms depicts a lion, sitting in front of a tree.
It is used as decoration all over the town.</p>

Here it is used as part of a story:

<p>He picked up the folder and a piece of paper fell out.</p>
<p><img src="carouge.svg" alt="Shaped like a shield, the paper had a
red background, a green tree, and a yellow lion with its tongue
hanging out and whose tail was shaped like an S."></p>
<p>He stared at the folder. S! The answer he had been looking for all
this time was simply the letter S! How had he not seen that before? It all
came together now. The phone call where Hector had referred to a lion's tail,
the time Marco had stuck his tongue out...</p>

Here it is not known at the time of publication what the image will be, only that it will be a coat of arms of some kind, and thus no replacement text can be provided, and instead only a brief caption for the image is provided, in the title attribute:

<p>The last user to have uploaded a coat of arms uploaded this one:</p>
<p><img src="last-uploaded-coat-of-arms.cgi" title="User-uploaded coat of arms."></p>

Ideally, the author would find a way to provide real replacement text even in this case, e.g. by asking the previous user. Not providing replacement text makes the document more difficult to use for people who are unable to view images, e.g. blind users, or users or very low-bandwidth connections or who pay by the byte, or users who are forced to use a text-only Web browser.

Here are some more examples showing the same picture used in different contexts, with different appropriate alternate texts each time.

<article>
 <h1>My cats</h1>
 <h2>Fluffy</h2>
 <p>Fluffy is my favorite.</p>
 <img src="fluffy.jpg" alt="She likes playing with a ball of yarn.">
 <p>She's just too cute.</p>
 <h2>Miles</h2>
 <p>My other cat, Miles just eats and sleeps.</p>
</article>
<article>
 <h1>Photography</h1>
 <h2>Shooting moving targets indoors</h2>
 <p>The trick here is to know how to anticipate; to know at what speed and
 what distance the subject will pass by.</p>
 <img src="fluffy.jpg" alt="A cat flying by, chasing a ball of yarn, can be
 photographed quite nicely using this technique.">
 <h2>Nature by night</h2>
 <p>To achieve this, you'll need either an extremely sensitive film, or
 immense flash lights.</p>
</article>
<article>
 <h1>About me</h1>
 <h2>My pets</h2>
 <p>I've got a cat named Fluffy and a dog named Miles.</p>
 <img src="fluffy.jpg" alt="Fluffy, my cat, tends to keep itself busy.">
 <p>My dog Miles and I like go on long walks together.</p>
 <h2>music</h2>
 <p>After our walks, having emptied my mind, I like listening to Bach.</p>
</article>
<article>
 <h1>Fluffy and the Yarn</h1>
 <p>Fluffy was a cat who liked to play with yarn. He also liked to jump.</p>
 <aside><img src="fluffy.jpg" alt="" title="Fluffy"></aside>
 <p>He would play in the morning, he would play in the evening.</p>
</article>
4.8.1.1 Requirements for providing text to act as an alternative for images

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

4.8.1.1.1 General guidelines

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

Except where otherwise specified, the alt attribute must be specified and its value must not be empty; the value must be an appropriate replacement for the image. The specific requirements for the alt attribute depend on what the image is intended to represent, as described in the following sections.

The most general rule to consider when writing alternative text is the following: the intent is that replacing every image with the text of its alt attribute not change the meaning of the page.

So, in general, alternative text can be written by considering what one would have written had one not been able to include the image.

A corollary to this is that the alt attribute's value should never contain text that could be considered the image's caption, title, or legend. It is supposed to contain replacement text that could be used by users instead of the image; it is not meant to supplement the image. The title attribute can be used for supplemental information.

One way to think of alternative text is to think about how you would read the page containing the image to someone over the phone, without mentioning that there is an image present. Whatever you say instead of the image is typically a good start for writing the alternative text.

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

When an a element that creates a hyperlink, or a button element, has no textual content but contains one or more images, the alt attributes must contain text that together convey the purpose of the link or button.

In this example, a user is asked to pick his preferred color from a list of three. Each color is given by an image, but for users who have configured their user agent not to display images, the color names are used instead:

<h1>Pick your color</h1>
<ul>
 <li><a href="green.html"><img src="green.jpeg" alt="Green"></a></li>
 <li><a href="blue.html"><img src="blue.jpeg" alt="Blue"></a></li>
 <li><a href="red.html"><img src="red.jpeg" alt="Red"></a></li>
</ul>

In this example, each button has a set of images to indicate the kind of color output desired by the user. The first image is used in each case to give the alternative text.

<button name="rgb"><img src="red" alt="RGB"><img src="green" alt=""><img src="blue" alt=""></button>
<button name="cmyk"><img src="cyan" alt="CMYK"><img src="magenta" alt=""><img src="yellow" alt=""><img src="black" alt=""></button>

Since each image represents one part of the text, it could also be written like this:

<button name="rgb"><img src="red" alt="R"><img src="green" alt="G"><img src="blue" alt="B"></button>
<button name="cmyk"><img src="cyan" alt="C"><img src="magenta" alt="M"><img src="yellow" alt="Y"><img src="black" alt="K"></button>

However, with other alternative text, this might not work, and putting all the alternative text into one image in each case might make more sense:

<button name="rgb"><img src="red" alt="sRGB profile"><img src="green" alt=""><img src="blue" alt=""></button>
<button name="cmyk"><img src="cyan" alt="CMYK profile"><img src="magenta" alt=""><img src="yellow" alt=""><img src="black" alt=""></button>
4.8.1.1.3 A phrase or paragraph with an alternative graphical representation: charts, diagrams, graphs, maps, illustrations

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

Sometimes something can be more clearly stated in graphical form, for example as a flowchart, a diagram, a graph, or a simple map showing directions. In such cases, an image can be given using the img element, but the lesser textual version must still be given, so that users who are unable to view the image (e.g. because they have a very slow connection, or because they are using a text-only browser, or because they are listening to the page being read out by a hands-free automobile voice Web browser, or simply because they are blind) are still able to understand the message being conveyed.

The text must be given in the alt attribute, and must convey the same message as the image specified in the src attribute.

It is important to realize that the alternative text is a replacement for the image, not a description of the image.

In the following example we have a flowchart in image form, with text in the alt attribute rephrasing the flowchart in prose form:

<p>In the common case, the data handled by the tokenization stage
comes from the network, but it can also come from script.</p>
<p><img src="http://dev.w3.org/html5/spec/images/parsing-model-overview.png" alt="The network
passes data to the Tokenizer stage, which passes data to the Tree
Construction stage. From there, data goes to both the DOM and to
Script Execution. Script Execution is linked to the DOM, and, using
document.write(), passes data to the Tokenizer."></p>

Here's another example, showing a good solution and a bad solution to the problem of including an image in a description.

First, here's the good solution. This sample shows how the alternative text should just be what you would have put in the prose if the image had never existed.

<!-- This is the correct way to do things. -->
<p>
 You are standing in an open field west of a house.
 <img src="house.jpeg" alt="The house is white, with a boarded front door.">
 There is a small mailbox here.
</p>

Second, here's the bad solution. In this incorrect way of doing things, the alternative text is simply a description of the image, instead of a textual replacement for the image. It's bad because when the image isn't shown, the text doesn't flow as well as in the first example.

<!-- This is the wrong way to do things. -->
<p>
 You are standing in an open field west of a house.
 <img src="house.jpeg" alt="A white house, with a boarded front door.">
 There is a small mailbox here.
</p>

Text such as "Photo of white house with boarded door" would be equally bad alternative text (though it could be suitable for the title attribute or in the figcaption element of a figure with this image).

4.8.1.1.4 A short phrase or label with an alternative graphical representation: icons, logos

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

A document can contain information in iconic form. The icon is intended to help users of visual browsers to recognize features at a glance.

In some cases, the icon is supplemental to a text label conveying the same meaning. In those cases, the alt attribute must be present but must be empty.

Here the icons are next to text that conveys the same meaning, so they have an empty alt attribute:

<nav>
 <p><a href="/help/"><img src="/icons/help.png" alt=""> Help</a></p>
 <p><a href="/configure/"><img src="/icons/configuration.png" alt="">
 Configuration Tools</a></p>
</nav>

In other cases, the icon has no text next to it describing what it means; the icon is supposed to be self-explanatory. In those cases, an equivalent textual label must be given in the alt attribute.

Here, posts on a news site are labeled with an icon indicating their topic.

<body>
 <article>
  <header>
   <h1>Ratatouille wins <i>Best Movie of the Year</i> award</h1>
   <p><img src="movies.png" alt="Movies"></p>
  </header>
  <p>Pixar has won yet another <i>Best Movie of the Year</i> award,
  making this its 8th win in the last 12 years.</p>
 </article>
 <article>
  <header>
   <h1>Latest TWiT episode is online</h1>
   <p><img src="podcasts.png" alt="Podcasts"></p>
  </header>
  <p>The latest TWiT episode has been posted, in which we hear
  several tech news stories as well as learning much more about the
  iPhone. This week, the panelists compare how reflective their
  iPhones' Apple logos are.</p>
 </article>
</body>

Many pages include logos, insignia, flags, or emblems, which stand for a particular entity such as a company, organization, project, band, software package, country, or some such.

If the logo is being used to represent the entity, e.g. as a page heading, the alt attribute must contain the name of the entity being represented by the logo. The alt attribute must not contain text like the word "logo", as it is not the fact that it is a logo that is being conveyed, it's the entity itself.

If the logo is being used next to the name of the entity that it represents, then the logo is supplemental, and its alt attribute must instead be empty.

If the logo is merely used as decorative material (as branding, or, for example, as a side image in an article that mentions the entity to which the logo belongs), then the entry below on purely decorative images applies. If the logo is actually being discussed, then it is being used as a phrase or paragraph (the description of the logo) with an alternative graphical representation (the logo itself), and the first entry above applies.

In the following snippets, all four of the above cases are present. First, we see a logo used to represent a company:

<h1><img src="XYZ.gif" alt="The XYZ company"></h1>

Next, we see a paragraph which uses a logo right next to the company name, and so doesn't have any alternative text:

<article>
 <h2>News</h2>
 <p>We have recently been looking at buying the <img src="alpha.gif"
 alt=""> ΑΒΓ company, a small Greek company
 specializing in our type of product.</p>

In this third snippet, we have a logo being used in an aside, as part of the larger article discussing the acquisition:

 <aside><p><img src="alpha-large.gif" alt=""></p></aside>
 <p>The ΑΒΓ company has had a good quarter, and our
 pie chart studies of their accounts suggest a much bigger blue slice
 than its green and orange slices, which is always a good sign.</p>
</article>

Finally, we have an opinion piece talking about a logo, and the logo is therefore described in detail in the alternative text.

<p>Consider for a moment their logo:</p>

<p><img src="/images/logo" alt="It consists of a green circle with a
green question mark centered inside it."></p>

<p>How unoriginal can you get? I mean, oooooh, a question mark, how
<em>revolutionary</em>, how utterly <em>ground-breaking</em>, I'm
sure everyone will rush to adopt those specifications now! They could
at least have tried for some sort of, I don't know, sequence of
rounded squares with varying shades of green and bold white outlines,
at least that would look good on the cover of a blue book.</p>

This example shows how the alternative text should be written such that if the image isn't available, and the text is used instead, the text flows seamlessly into the surrounding text, as if the image had never been there in the first place.

4.8.1.1.5 Text that has been rendered to a graphic for typographical effect

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

Sometimes, an image just consists of text, and the purpose of the image is not to highlight the actual typographic effects used to render the text, but just to convey the text itself.

In such cases, the alt attribute must be present but must consist of the same text as written in the image itself.

Consider a graphic containing the text "Earth Day", but with the letters all decorated with flowers and plants. If the text is merely being used as a heading, to spice up the page for graphical users, then the correct alternative text is just the same text "Earth Day", and no mention need be made of the decorations:

<h1><img src="earthdayheading.png" alt="Earth Day"></h1>
4.8.1.1.6 A graphical representation of some of the surrounding text

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

In many cases, the image is actually just supplementary, and its presence merely reinforces the surrounding text. In these cases, the alt attribute must be present but its value must be the empty string.

In general, an image falls into this category if removing the image doesn't make the page any less useful, but including the image makes it a lot easier for users of visual browsers to understand the concept.

A flowchart that repeats the previous paragraph in graphical form:

<p>The network passes data to the Tokenizer stage, which
passes data to the Tree Construction stage. From there, data goes
to both the DOM and to Script Execution. Script Execution is
linked to the DOM, and, using document.write(), passes data to
the Tokenizer.</p>
<p><img src="http://dev.w3.org/html5/spec/images/parsing-model-overview.png" alt=""></p>

In these cases, it would be wrong to include alternative text that consists of just a caption. If a caption is to be included, then either the title attribute can be used, or the figure and figcaption elements can be used. In the latter case, the image would in fact be a phrase or paragraph with an alternative graphical representation, and would thus require alternative text.

<!-- Using the title="" attribute -->
<p>The network passes data to the Tokenizer stage, which
passes data to the Tree Construction stage. From there, data goes
to both the DOM and to Script Execution. Script Execution is
linked to the DOM, and, using document.write(), passes data to
the Tokenizer.</p>
<p><img src="http://dev.w3.org/html5/spec/images/parsing-model-overview.png" alt=""
        title="Flowchart representation of the parsing model."></p>
<!-- Using <figure> and <figcaption> -->
<p>The network passes data to the Tokenizer stage, which
passes data to the Tree Construction stage. From there, data goes
to both the DOM and to Script Execution. Script Execution is
linked to the DOM, and, using document.write(), passes data to
the Tokenizer.</p>
<figure>
 <img src="http://dev.w3.org/html5/spec/images/parsing-model-overview.png" alt="The Network leads
 to the Tokenizer, which leads to the Tree Construction. The Tree
 Construction leads to two items. The first is Script Execution, which
 leads via document.write() back to the Tokenizer. The second item
 from which Tree Construction leads is the DOM. The DOM is related to
 the Script Execution.">
 <figcaption>Flowchart representation of the parsing model.</figcaption>
</figure>
<!-- This is WRONG. Do not do this. Instead, do what the above examples do. -->
<p>The network passes data to the Tokenizer stage, which
passes data to the Tree Construction stage. From there, data goes
to both the DOM and to Script Execution. Script Execution is
linked to the DOM, and, using document.write(), passes data to
the Tokenizer.</p>
<p><img src="http://dev.w3.org/html5/spec/images/parsing-model-overview.png"
        alt="Flowchart representation of the parsing model."></p>
<!-- Never put the image's caption in the alt="" attribute! -->

A graph that repeats the previous paragraph in graphical form:

<p>According to a study covering several billion pages,
about 62% of documents on the Web in 2007 triggered the Quirks
rendering mode of Web browsers, about 30% triggered the Almost
Standards mode, and about 9% triggered the Standards mode.</p>
<p><img src="rendering-mode-pie-chart.png" alt=""></p>
4.8.1.1.7 A purely decorative image that doesn't add any information

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

In general, if an image is decorative but isn't especially page-specific, for example an image that forms part of a site-wide design scheme, the image should be specified in the site's CSS, not in the markup of the document.

However, a decorative image that isn't discussed by the surrounding text but still has some relevance can be included in a page using the img element. Such images are decorative, but still form part of the content. In these cases, the alt attribute must be present but its value must be the empty string.

Examples where the image is purely decorative despite being relevant would include things like a photo of the Black Rock City landscape in a blog post about an event at Burning Man, or an image of a painting inspired by a poem, on a page reciting that poem. The following snippet shows an example of the latter case (only the first verse is included in this snippet):

<h1>The Lady of Shalott</h1>
<p><img src="shalott.jpeg" alt=""></p>
<p>On either side the river lie<br>
Long fields of barley and of rye,<br>
That clothe the wold and meet the sky;<br>
And through the field the road run by<br>
To many-tower'd Camelot;<br>
And up and down the people go,<br>
Gazing where the lilies blow<br>
Round an island there below,<br>
The island of Shalott.</p>

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

When a picture has been sliced into smaller image files that are then displayed together to form the complete picture again, one of the images must have its alt attribute set as per the relevant rules that would be appropriate for the picture as a whole, and then all the remaining images must have their alt attribute set to the empty string.

In the following example, a picture representing a company logo for XYZ Corp has been split into two pieces, the first containing the letters "XYZ" and the second with the word "Corp". The alternative text ("XYZ Corp") is all in the first image.

<h1><img src="logo1.png" alt="XYZ Corp"><img src="logo2.png" alt=""></h1>

In the following example, a rating is shown as three filled stars and two empty stars. While the alternative text could have been "★★★☆☆", the author has instead decided to more helpfully give the rating in the form "3 out of 5". That is the alternative text of the first image, and the rest have blank alternative text.

<p>Rating: <meter max=5 value=3><img src="1" alt="3 out of 5"
  ><img src="1" alt=""><img src="1" alt=""><img src="0" alt=""
  ><img src="0" alt=""></meter></p>

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

Generally, image maps should be used instead of slicing an image for links.

However, if an image is indeed sliced and any of the components of the sliced picture are the sole contents of links, then one image per link must have alternative text in its alt attribute representing the purpose of the link.

In the following example, a picture representing the flying spaghetti monster emblem, with each of the left noodly appendages and the right noodly appendages in different images, so that the user can pick the left side or the right side in an adventure.

<h1>The Church</h1>
<p>You come across a flying spaghetti monster. Which side of His
Noodliness do you wish to reach out for?</p>
<p><a href="?go=left" ><img src="fsm-left.png"  alt="Left side. "></a
  ><img src="fsm-middle.png" alt=""
  ><a href="?go=right"><img src="fsm-right.png" alt="Right side."></a></p>
4.8.1.1.10 A key part of the content

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

In some cases, the image is a critical part of the content. This could be the case, for instance, on a page that is part of a photo gallery. The image is the whole point of the page containing it.

How to provide alternative text for an image that is a key part of the content depends on the image's provenance.

The general case

When it is possible for detailed alternative text to be provided, for example if the image is part of a series of screenshots in a magazine review, or part of a comic strip, or is a photograph in a blog entry about that photograph, text that can serve as a substitute for the image must be given as the contents of the alt attribute.

A screenshot in a gallery of screenshots for a new OS, with some alternative text:

<figure>
 <img src="KDE%20Light%20desktop.png"
      alt="The desktop is blue, with icons along the left hand side in
           two columns, reading System, Home, K-Mail, etc. A window is
           open showing that menus wrap to a second line if they
           cannot fit in the window. The window has a list of icons
           along the top, with an address bar below it, a list of
           icons for tabs along the left edge, a status bar on the
           bottom, and two panes in the middle. The desktop has a bar
           at the bottom of the screen with a few buttons, a pager, a
           list of open applications, and a clock.">
 <figcaption>Screenshot of a KDE desktop.</figcaption>
</figure>

A graph in a financial report:

<img src="sales.gif"
     title="Sales graph"
     alt="From 1998 to 2005, sales increased by the following percentages
     with each year: 624%, 75%, 138%, 40%, 35%, 9%, 21%">

Note that "sales graph" would be inadequate alternative text for a sales graph. Text that would be a good caption is not generally suitable as replacement text.

Images that defy a complete description

In certain cases, the nature of the image might be such that providing thorough alternative text is impractical. For example, the image could be indistinct, or could be a complex fractal, or could be a detailed topographical map.

In these cases, the alt attribute must contain some suitable alternative text, but it may be somewhat brief.

Sometimes there simply is no text that can do justice to an image. For example, there is little that can be said to usefully describe a Rorschach inkblot test. However, a description, even if brief, is still better than nothing:

<figure>
 <img src="/commons/a/a7/Rorschach1.jpg" alt="A shape with left-right
 symmetry with indistinct edges, with a small gap in the center, two
 larger gaps offset slightly from the center, with two similar gaps
 under them. The outline is wider in the top half than the bottom
 half, with the sides extending upwards higher than the center, and
 the center extending below the sides.">
 <figcaption>A black outline of the first of the ten cards
 in the Rorschach inkblot test.</figcaption>
</figure>

Note that the following would be a very bad use of alternative text:

<!-- This example is wrong. Do not copy it. -->
<figure>
 <img src="/commons/a/a7/Rorschach1.jpg" alt="A black outline
 of the first of the ten cards in the Rorschach inkblot test.">
 <figcaption>A black outline of the first of the ten cards
 in the Rorschach inkblot test.</figcaption>
</figure>

Including the caption in the alternative text like this isn't useful because it effectively duplicates the caption for users who don't have images, taunting them twice yet not helping them any more than if they had only read or heard the caption once.

Another example of an image that defies full description is a fractal, which, by definition, is infinite in detail.

The following example shows one possible way of providing alternative text for the full view of an image of the Mandelbrot set.

<img src="ms1.jpeg" alt="The Mandelbrot set appears as a cardioid with
its cusp on the real axis in the positive direction, with a smaller
bulb aligned along the same center line, touching it in the negative
direction, and with these two shapes being surrounded by smaller bulbs
of various sizes.">
Images whose contents are not known

In some unfortunate cases, there might be no alternative text available at all, either because the image is obtained in some automated fashion without any associated alternative text (e.g. a Webcam), or because the page is being generated by a script using user-provided images where the user did not provide suitable or usable alternative text (e.g. photograph sharing sites), or because the author does not himself know what the images represent (e.g. a blind photographer sharing an image on his blog).

In such cases, the alt attribute may be omitted, but one of the following conditions must be met as well:

Such cases are to be kept to an absolute minimum. If there is even the slightest possibility of the author having the ability to provide real alternative text, then it would not be acceptable to omit the alt attribute.

A photo on a photo-sharing site, if the site received the image with no metadata other than the caption, could be marked up as follows:

<figure>
 <img src="1100670787_6a7c664aef.jpg">
 <figcaption>Bubbles traveled everywhere with us.</figcaption>
</figure>

It would be better, however, if a detailed description of the important parts of the image obtained from the user and included on the page.

A blind user's blog in which a photo taken by the user is shown. Initially, the user might not have any idea what the photo he took shows:

<article>
 <h1>I took a photo</h1>
 <p>I went out today and took a photo!</p>
 <figure>
  <img src="photo2.jpeg">
  <figcaption>A photograph taken blindly from my front porch.</figcaption>
 </figure>
</article>

Eventually though, the user might obtain a description of the image from his friends and could then include alternative text:

<article>
 <h1>I took a photo</h1>
 <p>I went out today and took a photo!</p>
 <figure>
  <img src="photo2.jpeg" alt="The photograph shows my hummingbird
  feeder hanging from the edge of my roof. It is half full, but there
  are no birds around. In the background, out-of-focus trees fill the
  shot. The feeder is made of wood with a metal grate, and it contains
  peanuts. The edge of the roof is wooden too, and is painted white
  with light blue streaks.">
  <figcaption>A photograph taken blindly from my front porch.</figcaption>
 </figure>
</article>

Sometimes the entire point of the image is that a textual description is not available, and the user is to provide the description. For instance, the point of a CAPTCHA image is to see if the user can literally read the graphic. Here is one way to mark up a CAPTCHA (note the title attribute):

<p><label>What does this image say?
<img src="captcha.cgi?id=8934" title="CAPTCHA">
<input type=text name=captcha></label>
(If you cannot see the image, you can use an <a
href="?audio">audio</a> test instead.)</p>

Another example would be software that displays images and asks for alternative text precisely for the purpose of then writing a page with correct alternative text. Such a page could have a table of images, like this:

<table>
 <thead>
  <tr> <th> Image <th> Description
 <tbody>
  <tr>
   <td> <img src="2421.png" title="Image 640 by 100, filename 'banner.gif'">
   <td> <input name="alt2421">
  <tr>
   <td> <img src="2422.png" title="Image 200 by 480, filename 'ad3.gif'">
   <td> <input name="alt2422">
</table>

Notice that even in this example, as much useful information as possible is still included in the title attribute.

Since some users cannot use images at all (e.g. because they have a very slow connection, or because they are using a text-only browser, or because they are listening to the page being read out by a hands-free automobile voice Web browser, or simply because they are blind), the alt attribute is only allowed to be omitted rather than being provided with replacement text when no alternative text is available and none can be made available, as in the above examples. Lack of effort from the part of the author is not an acceptable reason for omitting the alt attribute.

4.8.1.1.11 An image not intended for the user

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

Generally authors should avoid using img elements for purposes other than showing images.

If an img element is being used for purposes other than showing an image, e.g. as part of a service to count page views, then the alt attribute must be the empty string.

In such cases, the width and height attributes should both be set to zero.

4.8.1.1.12 An image in an e-mail or private document intended for a specific person who is known to be able to view images

ISSUE-31 (alt-conformance-requirements) blocks progress to Last Call

This section does not apply to documents that are publicly accessible, or whose target audience is not necessarily personally known to the author, such as documents on a Web site, e-mails sent to public mailing lists, or software documentation.

When an image is included in a private communication (such as an HTML e-mail) aimed at a specific person who is known to be able to view images, the alt attribute may be omitted. However, even in such cases it is strongly recommended that alternative text be included (as appropriate according to the kind of image involved, as described in the above entries), so that the e-mail is still usable should the user use a mail client that does not support images, or should the document be forwarded on to other users whose abilities might not include easily seeing images.

4.8.2 The iframe element

Categories
Flow content.
Phrasing content.
Embedded content.
Interactive content.
Contexts in which this element can be used:
Where embedded content is expected.
Content model:
Text that conforms to the requirements given in the prose.
Content attributes:
Global attributes
src
srcdoc
name
sandbox
seamless
width
height
DOM interface:
interface HTMLIFrameElement : HTMLElement {
           attribute DOMString src;
           attribute DOMString srcdoc;
           attribute DOMString name;
  [PutForwards=value] readonly attribute DOMSettableTokenList sandbox;
           attribute boolean seamless;
           attribute DOMString width;
           attribute DOMString height;
  readonly attribute Document contentDocument;
  readonly attribute WindowProxy contentWindow;
};

The iframe element represents a nested browsing context.

The src attribute gives the address of a page that the nested browsing context is to contain. The attribute, if present, must be a valid non-empty URL potentially surrounded by spaces.

The srcdoc attribute gives the content of the page that the nested browsing context is to contain. The value of the attribute is the source of an iframe srcdoc document.

For iframe elements in HTML documents, the attribute, if present, must have a value using the HTML syntax that consists of the following syntactic components, in the given order:

  1. Any number of comments and space characters.
  2. Optionally, a DOCTYPE.
  3. Any number of comments and space characters.
  4. The root element, in the form of an html element.
  5. Any number of comments and space characters.

For iframe elements in XML documents, the attribute, if present, must have a value that matches the production labeled document in the XML specification. [XML]

If the src attribute and the srcdoc attribute are both specified together, the srcdoc attribute takes priority. This allows authors to provide a fallback URL for legacy user agents that do not support the srcdoc attribute.

If, when the element is created, the srcdoc attribute is not set, and the src attribute is either also not set or set but its value cannot be resolved, the browsing context will remain at the initial about:blank page.

If the user navigates away from this page, the iframe's corresponding WindowProxy object will proxy new Window objects for new Document objects, but the src attribute will not change.

Here a blog uses the srcdoc attribute in conjunction with the sandbox and seamless attributes described below to provide users of user agents that support this feature with an extra layer of protection from script injection in the blog post comments:

<article>
 <h1>I got my own magazine!</h1>
 <p>After much effort, I've finally found a publisher, and so now I
 have my own magazine! Isn't that awesome?! The first issue will come
 out in September, and we have articles about getting food, and about
 getting in boxes, it's going to be great!</p>
 <footer>
  <p>Written by <a href="/users/cap">cap</a>.
  <time pubdate>2009-08-21T23:32Z</time></p>
 </footer>
 <article>
  <footer> At <time pubdate>2009-08-21T23:35Z</time>, <a href="/users/ch">ch</a> writes: </footer>
  <iframe seamless sandbox srcdoc="<p>did you get a cover picture yet?"></iframe>
 </article>
 <article>
  <footer> At <time pubdate>2009-08-21T23:44Z</time>, <a href="/users/cap">cap</a> writes: </footer>
  <iframe seamless sandbox srcdoc="<p>Yeah, you can see it <a href=&quot;/gallery?mode=cover&amp;amp;page=1&quot;>in my gallery</a>."></iframe>
 </article>
 <article>
  <footer> At <time pubdate>2009-08-21T23:58Z</time>, <a href="/users/ch">ch</a> writes: </footer>
  <iframe seamless sandbox srcdoc="<p>hey that's earl's table.
<p>you should get earl&amp;amp;me on the next cover."></iframe>
 </article>

Notice the way that quotes have to be escaped (otherwise the sandbox attribute would end prematurely), and the way raw ampersands (e.g. in URLs or in prose) mentioned in the sandboxed content have to be doubly escaped — once so that the ampersand is preserved when originally parsing the sandbox attribute, and once more to prevent the ampersand from being misinterpreted when parsing the sandboxed content.

In the HTML syntax, authors need only remember to use U+0022 QUOTATION MARK characters (") to wrap the attribute contents and then to escape all U+0022 QUOTATION MARK (") and U+0026 AMPERSAND (&) characters, and to specify the sandbox attribute, to ensure safe embedding of content.

Due to restrictions of the XML syntax, in XML the U+003C LESS-THAN SIGN character (<) needs to be escaped as well. In order to prevent attribute-value normalization, XML's whitespace characters — U+0009 CHARACTER TABULATION (HT), U+000A LINE FEED (LF), U+000D CARRIAGE RETURN (CR) and U+0020 SPACE — also need to be escaped. [XML]


The name attribute, if present, must be a valid browsing context name. The given value is used to name the nested browsing context.


The sandbox attribute, when specified, enables a set of extra restrictions on any content hosted by the iframe. Its value must be an unordered set of unique space-separated tokens that are ASCII case-insensitive. The allowed values are allow-same-origin, allow-top-navigation, allow-forms, and allow-scripts. When the attribute is set, the content is treated as being from a unique origin, forms and scripts are disabled, links are prevented from targeting other browsing contexts, and plugins are disabled. The allow-same-origin keyword allows the content to be treated as being from the same origin instead of forcing it into a unique origin, the allow-top-navigation keyword allows the content to navigate its top-level browsing context, and the allow-forms and allow-scripts keywords re-enable forms and scripts respectively (though scripts are still prevented from creating popups).

Setting both the allow-scripts and allow-same-origin keywords together when the embedded page has the same origin as the page containing the iframe allows the embedded page to simply remove the sandbox attribute.

Sandboxing hostile content is of minimal help if an attacker can convince the user to just visit the hostile content directly, rather than in the iframe. To limit the damage that can be caused by hostile HTML content, it should be served using the text/html-sandboxed MIME type.

In this example, some completely-unknown, potentially hostile, user-provided HTML content is embedded in a page. Because it is sandboxed, it is treated by the user agent as being from a unique origin, despite the content being served from the same site. Thus it is affected by all the normal cross-site restrictions. In addition, the embedded page has scripting disabled, plugins disabled, forms disabled, and it cannot navigate any frames or windows other than itself (or any frames or windows it itself embeds).

<p>We're not scared of you! Here is your content, unedited:</p>
<iframe sandbox src="getusercontent.cgi?id=12193"></iframe>

Note that cookies are still sent to the server in the getusercontent.cgi request, though they are not visible in the document.cookie IDL attribute.

It is important that the server serve the user-provided HTML using the text/html-sandboxed MIME type so that if the attacker convinces the user to visit that page directly, the page doesn't run in the context of the site's origin, which would make the user vulnerable to any attack found in the page.

In this example, a gadget from another site is embedded. The gadget has scripting and forms enabled, and the origin sandbox restrictions are lifted, allowing the gadget to communicate with its originating server. The sandbox is still useful, however, as it disables plugins and popups, thus reducing the risk of the user being exposed to malware and other annoyances.

<iframe sandbox="allow-same-origin allow-forms allow-scripts"
        src="http://maps.example.com/embedded.html"></iframe>

Suppose a file A contained the following fragment:

<iframe sandbox="allow-same-origin allow-forms" src=B></iframe>

Suppose that file B contained an iframe also:

<iframe sandbox="allow-scripts" src=C></iframe>

Further, suppose that file C contained a link:

<a href=D>Link</a>

For this example, suppose all the files were served as text/html.

Page C in this scenario has all the sandboxing flags set. Scripts are disabled, because the iframe in A has scripts disabled, and this overrides the allow-scripts keyword set on the iframe in B. Forms are also disabled, because the inner iframe (in B) does not have the allow-forms keyword set.

Suppose now that a script in A removes all the sandbox attributes in A and B. This would change nothing immediately. If the user clicked the link in C, loading page D into the iframe in B, page D would now act as if the iframe in B had the allow-same-origin and allow-forms keywords set, because that was the state of the nested browsing context in the iframe in A when page B was loaded.

Generally speaking, dynamically removing or changing the sandbox attribute is ill-advised, because it can make it quite hard to reason about what will be allowed and what will not.

Potentially hostile files can be served from the same server as the file containing the iframe element by labeling them as text/html-sandboxed instead of text/html. This ensures that scripts in the files are unable to attack the site (as if they were actually served from another server), even if the user is tricked into visiting those pages directly, without the protection of the sandbox attribute.

If the allow-scripts keyword is set along with allow-same-origin keyword, and the file is from the same origin as the iframe's Document, then a script in the "sandboxed" iframe could just reach out, remove the sandbox attribute, and then reload itself, effectively breaking out of the sandbox altogether.


The seamless attribute is a boolean attribute. When specified, it indicates that the iframe element's browsing context is to be rendered in a manner that makes it appear to be part of the containing document (seamlessly included in the parent document).

The attribute can be set or removed dynamically, with the rendering updating in tandem.

In this example, the site's navigation is embedded using a client-side include using an iframe. Any links in the iframe will, in new user agents, be automatically opened in the iframe's parent browsing context; for legacy user agents, the site could also include a base element with a target attribute with the value _parent. Similarly, in new user agents the styles of the parent page will be automatically applied to the contents of the frame, but to support legacy user agents authors might wish to include the styles explicitly.

<nav><iframe seamless src="nav.include.html"></iframe></nav>

The iframe element supports dimension attributes for cases where the embedded content has specific dimensions (e.g. ad units have well-defined dimensions).

An iframe element never has fallback content, as it will always create a nested browsing context, regardless of whether the specified initial contents are successfully used.

Descendants of iframe elements represent nothing. (In legacy user agents that do not support iframe elements, the contents would be parsed as markup that could act as fallback content.)

When used in HTML documents, the allowed content model of iframe elements is text, except that invoking the HTML fragment parsing algorithm with the iframe element as the context element and the text contents as the input must result in a list of nodes that are all phrasing content, with no parse errors having occurred, with no script elements being anywhere in the list or as descendants of elements in the list, and with all the elements in the list (including their descendants) being themselves conforming.

The iframe element must be empty in XML documents.

The HTML parser treats markup inside iframe elements as text.

Here is an example of a page using an iframe to include advertising from an advertising broker:

<iframe src="http://ads.example.com/?customerid=923513721&amp;format=banner"
        width="468" height="60"></iframe>

4.8.3 The embed element

Categories
Flow content.
Phrasing content.
Embedded content.
Interactive content.
Contexts in which this element can be used:
Where embedded content is expected.
Content model:
Empty.
Content attributes:
Global attributes
src
type
width
height
Any other attribute that has no namespace (see prose).
DOM interface:
interface HTMLEmbedElement : HTMLElement {
           attribute DOMString src;
           attribute DOMString type;
           attribute DOMString width;
           attribute DOMString height;
};

The embed element represents an integration point for an external (typically non-HTML) application or interactive content.

The src attribute gives the address of the resource being embedded. The attribute, if present, must contain a valid non-empty URL potentially surrounded by spaces.

The type attribute, if present, gives the MIME type by which the plugin to instantiate is selected. The value must be a valid MIME type. If both the type attribute and the src attribute are present, then the type attribute must specify the same type as the explicit Content-Type metadata of the resource given by the src attribute.

Any namespace-less attribute other than name, align, hspace, and vspace may be specified on the embed element, so long as its name is XML-compatible and contains no characters in the range U+0041 to U+005A (LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z). These attributes are then passed as parameters to the plugin.

All attributes in HTML documents get lowercased automatically, so the restriction on uppercase letters doesn't affect such documents.

The four exceptions are to exclude legacy attributes that have side-effects beyond just sending parameters to the plugin.

The embed element supports dimension attributes.

Here's a way to embed a resource that requires a proprietary plug-in, like Flash:

<embed src="catgame.swf">

If the user does not have the plug-in (for example if the plug-in vendor doesn't support the user's platform), then the user will be unable to use the resource.

To pass the plugin a parameter "quality" with the value "high", an attribute can be specified:

<embed src="catgame.swf" quality="high">

This would be equivalent to the following, when using an object element instead:

<object data="catgame.swf">
 <param name="quality" value="high">
</object>

4.8.4 The object element

Categories
Flow content.
Phrasing content.
Embedded content.
If the element has a usemap attribute: Interactive content.
Listed, submittable, form-associated element.
Contexts in which this element can be used:
Where embedded content is expected.
Content model:
Zero or more param elements, then, transparent.
Content attributes:
Global attributes
data
type
name
usemap
form
width
height
DOM interface:
interface HTMLObjectElement : HTMLElement {
           attribute DOMString data;
           attribute DOMString type;
           attribute DOMString name;
           attribute DOMString useMap;
  readonly attribute HTMLFormElement form;
           attribute DOMString width;
           attribute DOMString height;
  readonly attribute Document contentDocument;
  readonly attribute WindowProxy contentWindow;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);
};

The object element can represent an external resource, which, depending on the type of the resource, will either be treated as an image, as a nested browsing context, or as an external resource to be processed by a plugin.

The data attribute, if present, specifies the address of the resource. If present, the attribute must be a valid non-empty URL potentially surrounded by spaces.

The type attribute, if present, specifies the type of the resource. If present, the attribute must be a valid MIME type.

At least one of either the data attribute or the type attribute must be present.

The name attribute, if present, must be a valid browsing context name. The given value is used to name the nested browsing context, if applicable.

The usemap attribute, if present while the object element represents an image, can indicate that the object has an associated image map.

The form attribute is used to explicitly associate the object element with its form owner.

The object element supports dimension attributes.

In the following example, a Java applet is embedded in a page using the object element. (Generally speaking, it is better to avoid using applets like these and instead use native JavaScript and HTML to provide the functionality, since that way the application will work on all Web browsers without requiring a third-party plugin. Many devices, especially embedded devices, do not support third-party technologies like Java.)

<figure>
 <object type="application/x-java-applet">
  <param name="code" value="MyJavaClass">
  <p>You do not have Java available, or it is disabled.</p>
 </object>
 <figcaption>My Java Clock</figcaption>
</figure>

In this example, an HTML page is embedded in another using the object element.

<figure>
 <object data="clock.html"></object>
 <figcaption>My HTML Clock</figcaption>
</figure>

The following example shows how a plugin can be used in HTML (in this case the Flash plugin, to show a video file). Fallback is provided for users who do not have Flash enabled, in this case using the video element to show the video for those using user agents that support video, and finally providing a link to the video for those who have neither Flash nor a video-capable browser.

<p>Look at my video:
 <object type="application/x-shockwave-flash">
  <param name=movie value="http://video.example.com/library/watch.swf">
  <param name=allowfullscreen value=true>
  <param name=flashvars value="http://video.example.com/vids/315981">
  <video controls src="http://video.example.com/vids/315981">
   <a href="http://video.example.com/vids/315981">View video</a>.
  </video>
 </object>
</p>

4.8.5 The param element

Categories
None.
Contexts in which this element can be used:
As a child of an object element, before any flow content.
Content model:
Empty.
Content attributes:
Global attributes
name
value
DOM interface:
interface HTMLParamElement : HTMLElement {
           attribute DOMString name;
           attribute DOMString value;
};

The param element defines parameters for plugins invoked by object elements. It does not represent anything on its own.

The name attribute gives the name of the parameter.

The value attribute gives the value of the parameter.

Both attributes must be present. They may have any value.

The following example shows how the param element can be used to pass a parameter to a plugin, in this case the O3D plugin.

<!DOCTYPE HTML>
<html lang="en">
  <head>
   <title>O3D Utah Teapot</title>
  </head>
  <body>
   <p>
    <object type="application/vnd.o3d.auto">
     <param name="o3d_features" value="FloatingPointTextures">
     <img src="o3d-teapot.png"
          title="3D Utah Teapot illustration rendered using O3D."
          alt="When O3D renders the Utah Teapot, it appears as a squat
          teapot with a shiny metallic finish on which the
          surroundings are reflected, with a faint shadow caused by
          the lighting.">
     <p>To see the teapot actually rendered by O3D on your
     computer, please download and install the <a
     href="http://code.google.com/apis/o3d/docs/gettingstarted.html#install">O3D plugin</a>.</p>
    </object>
    <script src="o3d-teapot.js"></script>
   </p>
  </body>
</html>

4.8.6 The video element

ISSUE-9 (video-accessibility) blocks progress to Last Call

Categories
Flow content.
Phrasing content.
Embedded content.
If the element has a controls attribute: Interactive content.
Contexts in which this element can be used:
Where embedded content is expected.
Content model:
If the element has a src attribute: zero or more track elements, then transparent, but with no media element descendants.
If the element does not have a src attribute: one or more source elements, then zero or more track elements, then transparent, but with no media element descendants.
Content attributes:
Global attributes
src
poster
preload
autoplay
loop
audio
controls
width
height
DOM interface:
interface HTMLVideoElement : HTMLMediaElement {
           attribute unsigned long width;
           attribute unsigned long height;
  readonly attribute unsigned long videoWidth;
  readonly attribute unsigned long videoHeight;
           attribute DOMString poster;
  [PutForwards=value attribute DOMSettableTokenList audio; 
};

A video element is used for playing videos or movies.

Content may be provided inside the video element; it is intended for older Web browsers which do not support video, so that legacy video plugins can be tried, or to show text to the users of these older browsers informing them of how to access the video contents.

In particular, this content is not intended to address accessibility concerns. To make video content accessible to the blind, deaf, and those with other physical or cognitive disabilities, authors are expected to provide alternative media streams and/or to embed accessibility aids (such as caption or subtitle tracks, audio description tracks, or sign-language overlays) into their media streams.

The video element is a media element whose media data is ostensibly video data, possibly with associated audio data.

The src, preload, autoplay, loop, and controls attributes are the attributes common to all media elements. The audio attribute controls the audio channel.

The poster attribute gives the address of an image file that the user agent can show while no video data is available. The attribute, if present, must contain a valid non-empty URL potentially surrounded by spaces.

The image given by the poster attribute, the poster frame, is intended to be a representative frame of the video (typically one of the first non-blank frames) that gives the user an idea of what the video is like.

video . videoWidth
video . videoHeight

These attributes return the intrinsic dimensions of the video, or zero if the dimensions are not known.

The video element supports dimension attributes.

This example shows how to detect when a video has failed to play correctly:

<script>
 function failed(e) {
   // video playback failed - show a message saying why
   switch (e.target.error.code) {
     case e.target.error.MEDIA_ERR_ABORTED:
       alert('You aborted the video playback.');
       break;
     case e.target.error.MEDIA_ERR_NETWORK:
       alert('A network error caused the video download to fail part-way.');
       break;
     case e.target.error.MEDIA_ERR_DECODE:
       alert('The video playback was aborted due to a corruption problem or because the video used features your browser did not support.');
       break;
     case e.target.error.MEDIA_ERR_SRC_NOT_SUPPORTED:
       alert('The video could not be loaded, either because the server or network failed or because the format is not supported.');
       break;
     default:
       alert('An unknown error occurred.');
       break;
   }
 }
</script>
<p><video src="tgif.vid" autoplay controls onerror="failed(event)"></video></p>
<p><a href="tgif.vid">Download the video file</a>.</p>

4.8.7 The audio element

Categories
Flow content.
Phrasing content.
Embedded content.
If the element has a controls attribute: Interactive content.
Contexts in which this element can be used:
Where embedded content is expected.
Content model:
If the element has a src attribute: zero or more track elements, then transparent, but with no media element descendants.
If the element does not have a src attribute: one or more source elements, then zero or more track elements, then transparent, but with no media element descendants.
Content attributes:
Global attributes
src
preload
autoplay
loop
controls
DOM interface:
[NamedConstructor=Audio(),
 NamedConstructor=Audio(in DOMString src)]
interface HTMLAudioElement : HTMLMediaElement {};

An audio element represents a sound or audio stream.

Content may be provided inside the audio element; it is intended for older Web browsers which do not support audio, so that legacy audio plugins can be tried, or to show text to the users of these older browsers informing them of how to access the audio contents.

In particular, this content is not intended to address accessibility concerns. To make audio content accessible to the deaf or to those with other physical or cognitive disabilities, authors are expected to provide alternative media streams and/or to embed accessibility aids (such as transcriptions) into their media streams.

The audio element is a media element whose media data is ostensibly audio data.

The src, preload, autoplay, loop, and controls attributes are the attributes common to all media elements.

audio = new Audio( [ url ] )

Returns a new audio element, with the src attribute set to the value passed in the argument, if applicable.

4.8.8 The source element

Categories
None.
Contexts in which this element can be used:
As a child of a media element, before any flow content or track elements.
Content model:
Empty.
Content attributes:
Global attributes
src
type
media
DOM interface:
interface HTMLSourceElement : HTMLElement {
           attribute DOMString src;
           attribute DOMString type;
           attribute DOMString media;
};

The source element allows authors to specify multiple alternative media resources for media elements. It does not represent anything on its own.

The src attribute gives the address of the media resource. The value must be a valid non-empty URL potentially surrounded by spaces. This attribute must be present.

Dynamically modifying a source element and its attribute when the element is already inserted in a video or audio element will have no effect. To change what is playing, either just use the src attribute on the media element directly, or call the load() method on the media element after manipulating the source elements.

The type attribute gives the type of the media resource, to help the user agent determine if it can play this media resource before fetching it. If specified, its value must be a valid MIME type. The codecs parameter, which certain MIME types define, might be necessary to specify exactly how the resource is encoded. [RFC4281]

The following list shows some examples of how to use the codecs= MIME parameter in the type attribute.

H.264 Constrained baseline profile video (main and extended video compatible) level 3 and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="avc1.42E01E, mp4a.40.2"'>
H.264 Extended profile video (baseline-compatible) level 3 and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="avc1.58A01E, mp4a.40.2"'>
H.264 Main profile video level 3 and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="avc1.4D401E, mp4a.40.2"'>
H.264 'High' profile video (incompatible with main, baseline, or extended profiles) level 3 and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="avc1.64001E, mp4a.40.2"'>
MPEG-4 Visual Simple Profile Level 0 video and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="mp4v.20.8, mp4a.40.2"'>
MPEG-4 Advanced Simple Profile Level 0 video and Low-Complexity AAC audio in MP4 container
<source src='video.mp4' type='video/mp4; codecs="mp4v.20.240, mp4a.40.2"'>
MPEG-4 Visual Simple Profile Level 0 video and AMR audio in 3GPP container
<source src='video.3gp' type='video/3gpp; codecs="mp4v.20.8, samr"'>
Theora video and Vorbis audio in Ogg container
<source src='video.ogv' type='video/ogg; codecs="theora, vorbis"'>
Theora video and Speex audio in Ogg container
<source src='video.ogv' type='video/ogg; codecs="theora, speex"'>
Vorbis audio alone in Ogg container
<source src='audio.ogg' type='audio/ogg; codecs=vorbis'>
Speex audio alone in Ogg container
<source src='audio.spx' type='audio/ogg; codecs=speex'>
FLAC audio alone in Ogg container
<source src='audio.oga' type='audio/ogg; codecs=flac'>
Dirac video and Vorbis audio in Ogg container
<source src='video.ogv' type='video/ogg; codecs="dirac, vorbis"'>
Theora video and Vorbis audio in Matroska container
<source src='video.mkv' type='video/x-matroska; codecs="theora, vorbis"'>

The media attribute gives the intended media type of the media resource, to help the user agent determine if this media resource is useful to the user before fetching it. Its value must be a valid media query.

The default, if the media attribute is omitted, is "all", meaning that by default the media resource is suitable for all media.

If the author isn't sure if the user agents will all be able to render the media resources provided, the author can listen to the error event on the last source element and trigger fallback behavior:

<script>
 function fallback(video) {
   // replace <video> with its contents
   while (video.hasChildNodes()) {
     if (video.firstChild instanceof HTMLSourceElement)
       video.removeChild(video.firstChild);
     else
       video.parentNode.insertBefore(video.firstChild, video);
   }
   video.parentNode.removeChild(video);
 }
</script>
<video controls autoplay>
 <source src='video.mp4' type='video/mp4; codecs="avc1.42E01E, mp4a.40.2"'>
 <source src='video.ogv' type='video/ogg; codecs="theora, vorbis"'
         onerror="fallback(parentNode)">
 ...
</video>

4.8.9 The track element

ISSUE-9 (video-accessibility) blocks progress to Last Call

Categories
None.
Contexts in which this element can be used:
As a child of a media element, before any flow content.
Content model:
Empty.
Content attributes:
Global attributes
kind
src
srclang
label
default
DOM interface:
interface HTMLTrackElement : HTMLElement {
           attribute DOMString kind;
           attribute DOMString src;
           attribute DOMString srclang;
           attribute DOMString label;
           attribute boolean default;

  readonly attribute TextTrack track;
};

The track element allows authors to specify explicit external timed text tracks for media elements. It does not represent anything on its own.

The kind attribute is an enumerated attribute. The following table lists the keywords defined for this attribute. The keyword given in the first cell of each row maps to the state given in the second cell.

Keyword State Brief description
subtitles Subtitles Transcription or translation of the dialogue, suitable for when the sound is available but not understood (e.g. because the user does not understand the language of the media resource's soundtrack). Displayed over the video.
captions Captions Transcription or translation of the dialogue, sound effects, relevant musical cues, and other relevant audio information, suitable for when the soundtrack is unavailable (e.g. because it is muted or because the user is deaf). Displayed over the video; labeled as appropriate for the hard-of-hearing.
descriptions Descriptions Textual descriptions of the video component of the media resource, intended for audio synthesis when the visual component is unavailable (e.g. because the user is interacting with the application without a screen while driving, or because the user is blind). Synthesized as separate audio track.
chapters Chapters Chapter titles, intended to be used for navigating the media resource. Displayed as an interactive list in the user agent's interface.
metadata Metadata Tracks intended for use from script. Not displayed by the user agent.

The attribute may be omitted. The missing value default is the subtitles state.

The src attribute gives the address of the text track data. The value must be a valid non-empty URL potentially surrounded by spaces. This attribute must be present.

The srclang attribute gives the language of the text track data. The value must be a valid BCP 47 language tag. This attribute must be present if the element's kind attribute is in the subtitles state. [BCP47]

The label attribute gives a user-readable title for the track. This title is used by user agents when listing subtitle, caption, and audio description tracks in their user interface.

The value of the label attribute, if the attribute is present, must not be the empty string. Furthermore, there must not be two track element children of the same media element whose kind attributes are in the same state, whose srclang attributes are both missing or have values that represent the same language, and whose label attributes are again both missing or both have the same value.

The default attribute, if specified, indicates that the track is to be enabled if the user's preferences do not indicate that another track would be more appropriate. There must not be more than one track element with the same parent node with the default attribute specified.

track . track

Returns the TextTrack object corresponding to the text track of the track element.

This video has subtitles in several languages:

<video src="brave.webm">
 <track kind=subtitles src=brave.en.vtt srclang=en label="English">
 <track kind=captions src=brave.en.vtt srclang=en label="English for the Hard of Hearing">
 <track kind=subtitles src=brave.fr.vtt srclang=fr label="Français">
 <track kind=subtitles src=brave.de.vtt srclang=de label="Deutsch">
</video>

4.8.10 Media elements

Media elements (audio and video, in this specification) implement the following interface:

interface HTMLMediaElement : HTMLElement {

  // error state
  readonly attribute MediaError error;

  // network state
           attribute DOMString src;
  readonly attribute DOMString currentSrc;
  const unsigned short NETWORK_EMPTY = 0;
  const unsigned short NETWORK_IDLE = 1;
  const unsigned short NETWORK_LOADING = 2;
  const unsigned short NETWORK_NO_SOURCE = 3;
  readonly attribute unsigned short networkState;
           attribute DOMString preload;
  readonly attribute TimeRanges buffered;
  void load();
  DOMString canPlayType(in DOMString type);

  // ready state
  const unsigned short HAVE_NOTHING = 0;
  const unsigned short HAVE_METADATA = 1;
  const unsigned short HAVE_CURRENT_DATA = 2;
  const unsigned short HAVE_FUTURE_DATA = 3;
  const unsigned short HAVE_ENOUGH_DATA = 4;
  readonly attribute unsigned short readyState;
  readonly attribute boolean seeking;

  // playback state
           attribute double currentTime;
  readonly attribute double initialTime;
  readonly attribute double duration;
  readonly attribute Date startOffsetTime;
  readonly attribute boolean paused;
           attribute double defaultPlaybackRate;
           attribute double playbackRate;
  readonly attribute TimeRanges played;
  readonly attribute TimeRanges seekable;
  readonly attribute boolean ended;
           attribute boolean autoplay;
           attribute boolean loop;
  void play();
  void pause();

  // controls
           attribute boolean controls;
           attribute double volume;
           attribute boolean muted;

  // text tracks
  readonly attribute TextTrack[] tracks;
  MutableTextTrack addTrack(in DOMString kind, in optional DOMString label, in optional DOMString language);

};

The media element attributes, src, preload, autoplay, loop, and controls, apply to all media elements. They are defined in this section.

Media elements are used to present audio data, or video and audio data, to the user. This is referred to as media data in this section, since this section applies equally to media elements for audio or for video. The term media resource is used to refer to the complete set of media data, e.g. the complete video file, or complete audio file.

4.8.10.1 Error codes
media . error

Returns a MediaError object representing the current error state of the element.

Returns null if there is no error.

interface MediaError {
  const unsigned short MEDIA_ERR_ABORTED = 1;
  const unsigned short MEDIA_ERR_NETWORK = 2;
  const unsigned short MEDIA_ERR_DECODE = 3;
  const unsigned short MEDIA_ERR_SRC_NOT_SUPPORTED = 4;
  readonly attribute unsigned short code;
};
media . error . code

Returns the current error's error code, from the list below.

MEDIA_ERR_ABORTED (numeric value 1)
The fetching process for the media resource was aborted by the user agent at the user's request.
MEDIA_ERR_NETWORK (numeric value 2)
A network error of some description caused the user agent to stop fetching the media resource, after the resource was established to be usable.
MEDIA_ERR_DECODE (numeric value 3)
An error of some description occurred while decoding the media resource, after the resource was established to be usable.
MEDIA_ERR_SRC_NOT_SUPPORTED (numeric value 4)
The media resource indicated by the src attribute was not suitable.
4.8.10.2 Location of the media resource

The src content attribute on media elements gives the address of the media resource (video, audio) to show. The attribute, if present, must contain a valid non-empty URL potentially surrounded by spaces.

media . currentSrc

Returns the address of the current media resource.

Returns the empty string when there is no media resource.

There are two ways to specify a media resource, the src attribute, or source elements. The attribute overrides the elements.

4.8.10.3 MIME types

A media resource can be described in terms of its type, specifically a MIME type, in some cases with a codecs parameter. (Whether the codecs parameter is allowed or not depends on the MIME type.) [RFC4281]

Types are usually somewhat incomplete descriptions; for example "video/mpeg" doesn't say anything except what the container type is, and even a type like "video/mp4; codecs="avc1.42E01E, mp4a.40.2"" doesn't include information like the actual bitrate (only the maximum bitrate). Thus, given a type, a user agent can often only know whether it might be able to play media of that type (with varying levels of confidence), or whether it definitely cannot play media of that type.

A type that the user agent knows it cannot render is one that describes a resource that the user agent definitely does not support, for example because it doesn't recognize the container type, or it doesn't support the listed codecs.

The MIME type "application/octet-stream" with no parameters is never a type that the user agent knows it cannot render. User agents must treat that type as equivalent to the lack of any explicit Content-Type metadata when it is used to label a potential media resource.

In the absence of a specification to the contrary, the MIME type "application/octet-stream" when used with parameters, e.g. "application/octet-stream;codecs=theora", is a type that the user agent knows it cannot render, since that parameter is not defined for that type.

media . canPlayType(type)

Returns the empty string (a negative response), "maybe", or "probably" based on how confident the user agent is that it can play media resources of the given type.

This script tests to see if the user agent supports a (fictional) new format to dynamically decide whether to use a video element or a plugin:

<section id="video">
 <p><a href="playing-cats.nfv">Download video</a></p>
</section>
<script>
 var videoSection = document.getElementById('video');
 var videoElement = document.createElement('video');
 var support = videoElement.canPlayType('video/x-new-fictional-format;codecs="kittens,bunnies"');
 if (support != "probably" && "New Fictional Video Plug-in" in navigator.plugins) {
   // not confident of browser support
   // but we have a plugin
   // so use plugin instead
   videoElement = document.createElement("embed");
 } else if (support == "") {
   // no support from browser and no plugin
   // do nothing
   videoElement = null;
 }
 if (videoElement) {
   while (videoSection.hasChildNodes())
     videoSection.removeChild(videoSection.firstChild);
   videoElement.setAttribute("src", "playing-cats.nfv");
   videoSection.appendChild(videoElement);
 }
</script>

The type attribute of the source element allows the user agent to avoid downloading resources that use formats it cannot render.

4.8.10.4 Network states
media . networkState

Returns the current state of network activity for the element, from the codes in the list below.

NETWORK_EMPTY (numeric value 0)
The element has not yet been initialized. All attributes are in their initial states.
NETWORK_IDLE (numeric value 1)
The element has selected a resource, but it is not actually using the network at this time.
NETWORK_LOADING (numeric value 2)
The user agent is actively trying to download data.
NETWORK_NO_SOURCE (numeric value 3)
The element has so not yet found a resource to use.
4.8.10.5 Loading the media resource
media . load()

Causes the element to reset and start selecting and loading a new media resource from scratch.


The preload attribute is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.

Keyword State Brief description
none None Hints to the user agent that either the author does not expect the user to need the media resource, or that the server wants to minimise unnecessary traffic.
metadata Metadata Hints to the user agent that the author does not expect the user to need the media resource, but that fetching the resource metadata (dimensions, first frame, track list, duration, etc) is reasonable.
auto Automatic Hints to the user agent that the user agent can put the user's needs first without risk to the server, up to and including optimistically downloading the entire resource.

The empty string is also a valid keyword, and maps to the Automatic state. The attribute's missing value default is user-agent defined, though the Metadata state is suggested as a compromise between reducing server load and providing an optimal user experience.

The autoplay attribute can override the preload attribute (since if the media plays, it naturally has to buffer first, regardless of the hint given by the preload attribute). Including both is not an error, however.


media . buffered

Returns a TimeRanges object that represents the ranges of the media resource that the user agent has buffered.

4.8.10.6 Offsets into the media resource
media . duration

Returns the length of the media resource, in seconds, assuming that the start of the media resource is at time zero.

Returns NaN if the duration isn't available.

Returns Infinity for unbounded streams.

media . currentTime [ = value ]

Returns the current playback position, in seconds.

Can be set, to seek to the given time.

Will throw an INVALID_STATE_ERR exception if there is no selected media resource. Will throw an INDEX_SIZE_ERR exception if the given time is not within the ranges to which the user agent can seek.

media . initialTime

Returns the initial playback position, that is, time to which the media resource was automatically seeked when it was loaded. Returns zero if the initial playback position is still unknown.


The loop attribute is a boolean attribute that, if specified, indicates that the media element is to seek back to the start of the media resource upon reaching the end.

4.8.10.7 The ready states
media . readyState

Returns a value that expresses the current state of the element with respect to rendering the current playback position, from the codes in the list below.

HAVE_NOTHING (numeric value 0)
No information regarding the media resource is available. No data for the current playback position is available. Media elements whose networkState attribute are set to NETWORK_EMPTY are always in the HAVE_NOTHING state.
HAVE_METADATA (numeric value 1)
Enough of the resource has been obtained that the duration of the resource is available. In the case of a video element, the dimensions of the video are also available. The API will no longer raise an exception when seeking. No media data is available for the immediate current playback position. The text tracks are ready.
HAVE_CURRENT_DATA (numeric value 2)
Data for the immediate current playback position is available, but either not enough data is available that the user agent could successfully advance the current playback position in the direction of playback at all without immediately reverting to the HAVE_METADATA state, or there is no more data to obtain in the direction of playback. For example, in video this corresponds to the user agent having data from the current frame, but not the next frame; and to when playback has ended.
HAVE_FUTURE_DATA (numeric value 3)
Data for the immediate current playback position is available, as well as enough data for the user agent to advance the current playback position in the direction of playback at least a little without immediately reverting to the HAVE_METADATA state. For example, in video this corresponds to the user agent having data for at least the current frame and the next frame. The user agent cannot be in this state if playback has ended, as the current playback position can never advance in this case.
HAVE_ENOUGH_DATA (numeric value 4)
All the conditions described for the HAVE_FUTURE_DATA state are met, and, in addition, the user agent estimates that data is being fetched at a rate where the current playback position, if it were to advance at the rate given by the defaultPlaybackRate attribute, would not overtake the available data before playback reaches the end of the media resource.

It is possible for the ready state of a media element to jump between these states discontinuously. For example, the state of a media element can jump straight from HAVE_METADATA to HAVE_ENOUGH_DATA without passing through the HAVE_CURRENT_DATA and HAVE_FUTURE_DATA states.

The autoplay attribute is a boolean attribute. When present, the user agent will automatically begin playback of the media resource as soon as it can do so without stopping.

Authors are urged to use the autoplay attribute rather than using script to trigger automatic playback, as this allows the user to override the automatic playback when it is not desired, e.g. when using a screen reader. Authors are also encouraged to consider not using the automatic playback behavior at all, and instead to let the user agent wait for the user to start playback explicitly.

4.8.10.8 Playing the media resource
media . paused

Returns true if playback is paused; false otherwise.

media . ended

Returns true if playback has reached the end of the media resource.

media . defaultPlaybackRate [ = value ]

Returns the default rate of playback, for when the user is not fast-forwarding or reversing through the media resource.

Can be set, to change the default rate of playback.

The default rate has no direct effect on playback, but if the user switches to a fast-forward mode, when they return to the normal playback mode, it is expected that the rate of playback will be returned to the default rate of playback.

media . playbackRate [ = value ]

Returns the current rate playback, where 1.0 is normal speed.

Can be set, to change the rate of playback.

media . played

Returns a TimeRanges object that represents the ranges of the media resource that the user agent has played.

media . play()

Sets the paused attribute to false, loading the media resource and beginning playback if necessary. If the playback had ended, will restart it from the start.

media . pause()

Sets the paused attribute to true, loading the media resource if necessary.

4.8.10.9 Seeking
media . seeking

Returns true if the user agent is currently seeking.

media . seekable

Returns a TimeRanges object that represents the ranges of the media resource to which it is possible for the user agent to seek.

4.8.10.10 Timed text tracks
4.8.10.10.1 Text track model

A media element can have a group of associated text tracks, known as the media element's list of text tracks. The text tracks are sorted as follows:

  1. The text tracks corresponding to track element children of the media element, in tree order.
  2. Any text tracks added using the addTrack() method, in the order they were added, oldest first.
  3. Any media-resource-specific text tracks (text tracks corresponding to data in the media resource), in the order defined by the media resource's format specification.

A text track consists of:

The kind of text track

This decides how the track is handled by the user agent. The kind is represented by a string. The possible strings are:

The kind of track can change dynamically, in the case of a text track corresponding to a track element.

A label

This is a human-readable string intended to identify the track for the user. In certain cases, the label might be generated automatically.

The label of a track can change dynamically, in the case of a text track corresponding to a track element or in the case of an automatically-generated label whose value depends on variable factors such as the user's preferred user interface language.

A language

This is a string (a BCP 47 language tag) representing the language of the text track's cues. [BCP47]

The language of a text track can change dynamically, in the case of a text track corresponding to a track element.

A readiness state

One of the following:

Not loaded

Indicates that the text track is known to exist (e.g. it has been declared with a track element), but its cues have not been obtained.

Loading

Indicates that the text track is loading and there have been no fatal errors encountered so far. Further cues might still be added to the track.

Loaded

Indicates that the text track has been loaded with no fatal errors. No new cues will be added to the track except if the text track corresponds to a MutableTextTrack object.

Failed to load

Indicates that the text track was enabled, but when the user agent attempted to obtain it, this failed in some way (e.g. URL could not be resolved, network error, unknown text track format). Some or all of the cues are likely missing and will not be obtained.

The readiness state of a text track changes dynamically as the track is obtained.

A mode

One of the following:

Disabled

Indicates that the text track is not active. Other than for the purposes of exposing the track in the DOM, the user agent is ignoring the text track. No cues are active, no events are fired, and the user agent will not attempt to obtain the track's cues.

Hidden

Indicates that the text track is active, but that the user agent is not actively displaying the cues. If no attempt has yet been made to obtain the track's cues, the user agent will perform such an attempt momentarily. The user agent is maintaining a list of which cues are active, and events are being fired accordingly.

Showing
Showing by default

Indicates that the text track is active. If no attempt has yet been made to obtain the track's cues, the user agent will perform such an attempt momentarily. The user agent is maintaining a list of which cues are active, and events are being fired accordingly. In addition, for text tracks whose kind is subtitles or captions, the cues are being displayed over the video as appropriate; for text tracks whose kind is descriptions, the user agent is making the cues available to the user in a non-visual fashion; and for text tracks whose kind is chapters, the user agent is making available to the user a mechanism by which the user can navigate to any point in the media resource by selecting a cue.

The showing by default state is used in conjunction with the default attribute on track elements to indicate that the text track was enabled due to that attribute. This allows the user agent to override the state if a later track is discovered that is more appropriate per the user's preferences.

A list of zero or more cues

A list of text track cues, along with rules for updating the text track rendering.

The list of cues of a text track can change dynamically, either because the text track has not yet been loaded or is still loading, or because the text track corresponds to a MutableTextTrack object, whose API allows individual cues can be added or removed dynamically.

Each text track has a corresponding TextTrack object.

The text tracks of a media element are ready if all the text tracks whose mode was not in the disabled state when the element's resource selection algorithm last started now have a text track readiness state of loaded or failed to load.


A text track cue is the unit of time-sensitive data in a text track, corresponding for instance for subtitles and captions to the text that appears at a particular time and disappears at another time.

Each text track cue consists of:

An identifier

An arbitrary string.

A start time

A time, in seconds and fractions of a second, at which the cue becomes relevant.

An end time

A time, in seconds and fractions of a second, at which the cue stops being relevant.

A pause-on-exit flag

A boolean indicating whether playback of the media resource is to pause when the cue stops being relevant.

A writing direction

A writing direction, either horizontal (a line extends horizontally and is positioned vertically, with consecutive lines displayed below each other), vertical growing left (a line extends vertically and is positioned horizontally, with consecutive lines displayed to the left of each other), or vertical growing right (a line extends vertically and is positioned horizontally, with consecutive lines displayed to the right of each other).

A size

A number giving the size of the box within which the text of each line of the cue is to be aligned, to be interpreted as a percentage of the video, as defined by the writing direction.

The text of the cue

The raw text of the cue, and rules for its interpretation, allowing the text to be rendered and converted to a DOM fragment.

A text track cue is immutable.

Each text track cue has a corresponding TextTrackCue object, and can be associated with a particular text track. Once a text track cue is associated with a particular text track, the association is permanent.

In addition, each text track cue has two pieces of dynamic information:

The active flag

This flag must be initially unset. The flag is used to ensure events are fired appropriately when the cue becomes active or inactive, and to make sure the right cues are rendered.

The user agent must synchronously unset this flag whenever the text track cue is removed from its text track's text track list of cues; whenever the text track itself is removed from its media element's list of text tracks or has its text track mode changed to disabled; and whenever the media element's readyState is changed back to HAVE_NOTHING. When the flag is unset in this way for one or more cues in text tracks that were showing or showing by default prior to the relevant incident, the user agent must, after having unset the flag for all the affected cues, apply the rules for updating the text track rendering of those text tracks.

The display state

This is used as part of the rendering model, to keep cues in a consistent position. It must initially be empty. Whenever the text track cue active flag is unset, the user agent must empty the text track cue display state.

The text track cues of a media element's text tracks are ordered relative to each other in the text track cue order, which is determined as follows: first group the cues by their text track, with the groups being sorted in the same order as their text tracks appear in the media element's list of text tracks; then, within each group, cues must be sorted by their start time, earliest first; then, any cues with the same start time must be sorted by their end time, earliest first; and finally, any cues with identical end times must be sorted in the order they were created (so e.g. for cues from a WebVTT file, that would be the order in which the cues were listed in the file).

4.8.10.10.2 Sourcing in-band text tracks

A media-resource-specific text track is a text track that corresponds to data found in the media resource.

4.8.10.10.3 Text track API
media . tracks . length

Returns the number of text tracks associated with the media element (e.g. from track elements). This is the number of text tracks in the media element's list of text tracks.

media . tracks[ n ]

Returns the TextTrack object representing the nth text track in the media element's list of text tracks.

track . track

Returns the TextTrack object representing the track element's text track.


interface TextTrack {
  readonly attribute DOMString kind;
  readonly attribute DOMString label;
  readonly attribute DOMString language;

  const unsigned short NONE = 0;
  const unsigned short LOADING = 1;
  const unsigned short LOADED = 2;
  const unsigned short ERROR = 3;
  readonly attribute unsigned short readyState;
  readonly attribute Function onload;
  readonly attribute Function onerror;

  const unsigned short OFF = 0;
  const unsigned short HIDDEN = 1;
  const unsigned short SHOWING = 2;
           attribute unsigned short mode;

  readonly attribute TextTrackCueList cues;
  readonly attribute TextTrackCueList activeCues;

  readonly attribute Function oncuechange;
};
timedTrack . kind

Returns the text track kind string.

timedTrack . label

Returns the text track label.

timedTrack . language

Returns the text track language string.

timedTrack . readyState

Returns the text track readiness state, represented by a number from the following list:

TextTrack . NONE (0)

The text track not loaded state.

TextTrack . LOADING (1)

The text track loading state.

TextTrack . LOADED (2)

The text track loaded state.

TextTrack . ERROR (3)

The text track failed to load state.

timedTrack . mode

Returns the text track mode, represented by a number from the following list:

TextTrack . OFF (0)

The text track disabled mode.

TextTrack . HIDDEN (1)

The text track hidden mode.

TextTrack . SHOWING (2)

The text track showing and showing by default modes.

Can be set, to change the mode.

timedTrack . cues

Returns the text track list of cues, as a TextTrackCueList object.

timedTrack . activeCues

Returns the text track cues from the text track list of cues that are currently active (i.e. that start before the current playback position and end after it), as a TextTrackCueList object.


interface MutableTextTrack : TextTrack {
 void addCue(in TextTrackCue cue);
 void removeCue(in TextTrackCue cue);
};
mutableTextTrack = media . addTrack( kind [, label [, language ] ] )

Creates and returns a new MutableTextTrack object, which is also added to the media element's list of text tracks.

mutableTextTrack . addCue( cue )

Adds the given cue to mutableTextTrack's text track list of cues.

Raises an exception if the argument is null, associated with another text track, or already in the list of cues.

mutableTextTrack . removeCue( cue )

Removes the given cue from mutableTextTrack's text track list of cues.

Raises an exception if the argument is null, associated with another text track, or not in the list of cues.

In this example, an audio element is used to play a specific sound-effect from a sound file containing many sound effects. A cue is used to pause the audio, so that it ends exactly at the end of the clip, even if the browser is busy running some script. If the page had relied on script to pause the audio, then the start of the next clip might be heard if the browser was not able to run the script at the exact time specified.

var sfx = new Audio('sfx.wav');
var sounds = a.addTrack('metadata');
// add sounds we care about
sounds.addCue(new TextTrackCue('dog bark', 12.783, 13.612, '', '', '', true));
sounds.addCue(new TextTrackCue('kitten mew', 13.612, 15.091, '', '', '', true));

function playSound(id) {
  sfx.currentTime = sounds.getCueById(id).startTime;
  sfx.play();
}

sfx.oncanplaythrough = function () {
  playSound('dog bark');
}
window.onbeforeunload = function () {
  playSound('kitten mew');
  return 'Are you sure you want to leave this awesome page?';
}

interface TextTrackCueList {
  readonly attribute unsigned long length;
  getter TextTrackCue (in unsigned long index);
  TextTrackCue getCueById(in DOMString id);
};
cuelist . length

Returns the number of cues in the list.

cuelist[index]

Returns the text track cue with index index in the list. The cues are sorted in text track cue order.

cuelist . getCueById( id )

Returns the first text track cue (in text track cue order) with text track cue identifier id.

Returns null if none of the cues have the given identifier or if the argument is the empty string.


interface TextTrackCue {
  readonly attribute TextTrack track;
  readonly attribute DOMString id;

  readonly attribute double startTime;
  readonly attribute double endTime;
  readonly attribute boolean pauseOnExit;


  DOMString getCueAsSource();
  DocumentFragment getCueAsHTML();

  readonly attribute Function onenter;
  readonly attribute Function onexit;
};
cue . track

Returns the TextTrack object to which this text track cue belongs, if any, or null otherwise.

cue . id

Returns the text track cue identifier.

cue . startTime

Returns the text track cue start time, in seconds.

cue . endTime

Returns the text track cue end time, in seconds.

cue . pauseOnExit

Returns true if the text track cue pause-on-exit flag is set, false otherwise.

source = cue . getCueAsSource()

Returns the text track cue text in raw unparsed form.

fragment = cue . getCueAsHTML()

Returns the text track cue text as a DocumentFragment of HTML elements and other DOM nodes.

4.8.10.11 User interface

The controls attribute is a boolean attribute. If present, it indicates that the author has not provided a scripted controller and would like the user agent to provide its own set of controls.

media . volume [ = value ]

Returns the current playback volume, as a number in the range 0.0 to 1.0, where 0.0 is the quietest and 1.0 the loudest.

Can be set, to change the volume.

Throws an INDEX_SIZE_ERR if the new value is not in the range 0.0 .. 1.0.

media . muted [ = value ]

Returns true if audio is muted, overriding the volume attribute, and false if the volume attribute is being honored.

Can be set, to change whether the audio is muted or not.

The audio attribute on the video element controls the default state of the audio channel of the media resource, potentially overriding user preferences.

The audio attribute, if specified, must have a value that is an unordered set of unique space-separated tokens, which are ASCII case-insensitive. The tokens must be from the following list (currently, only one allowed token is defined):

muted

Causes the user agent to override the user's preferences, if any, and always default the video to muted.

A future version of this specification will probably introduce new values here, e.g. to control the default volume, or to select a default audio track.

This attribute has no dynamic effect (it only controls the default state of the element).

This video (an advertisment) autoplays, but to avoid annoying users, it does so without sound, and allows the user to turn the sound on.

<video src="adverts.cgi?kind=video" controls autoplay loop audio=muted></video>
4.8.10.12 Time ranges

Objects implementing the TimeRanges interface represent a list of ranges (periods) of time.

interface TimeRanges {
  readonly attribute unsigned long length;
  double start(in unsigned long index);
  double end(in unsigned long index);
};
media . length

Returns the number of ranges in the object.

time = media . start(index)

Returns the time for the start of the range with the given index.

Throws an INDEX_SIZE_ERR if the index is out of range.

time = media . end(index)

Returns the time for the end of the range with the given index.

Throws an INDEX_SIZE_ERR if the index is out of range.

4.8.10.13 Event summary

This section is non-normative.

The following events fire on media elements as part of the processing model described above:

Event name Interface Dispatched when... Preconditions
loadstart Event The user agent begins looking for media data, as part of the resource selection algorithm. networkState equals NETWORK_LOADING
progress Event The user agent is fetching media data. networkState equals NETWORK_LOADING
suspend Event The user agent is intentionally not currently fetching media data, but does not have the entire media resource downloaded. networkState equals NETWORK_IDLE
abort Event The user agent stops fetching the media data before it is completely downloaded, but not due to an error. error is an object with the code MEDIA_ERR_ABORTED. networkState equals either NETWORK_EMPTY or NETWORK_IDLE, depending on when the download was aborted.
error Event An error occurs while fetching the media data. error is an object with the code MEDIA_ERR_NETWORK or higher. networkState equals either NETWORK_EMPTY or NETWORK_IDLE, depending on when the download was aborted.
emptied Event A media element whose networkState was previously not in the NETWORK_EMPTY state has just switched to that state (either because of a fatal error during load that's about to be reported, or because the load() method was invoked while the resource selection algorithm was already running). networkState is NETWORK_EMPTY; all the IDL attributes are in their initial states.
stalled Event The user agent is trying to fetch media data, but data is unexpectedly not forthcoming. networkState is NETWORK_LOADING.
play Event Playback has begun. Fired after the play() method has returned, or when the autoplay attribute has caused playback to begin. paused is newly false.
pause Event Playback has been paused. Fired after the pause() method has returned. paused is newly true.
loadedmetadata Event The user agent has just determined the duration and dimensions of the media resource and the text tracks are ready. readyState is newly equal to HAVE_METADATA or greater for the first time.
loadeddata Event The user agent can render the media data at the current playback position for the first time. readyState newly increased to HAVE_CURRENT_DATA or greater for the first time.
waiting Event Playback has stopped because the next frame is not available, but the user agent expects that frame to become available in due course. readyState is newly equal to or less than HAVE_CURRENT_DATA, and paused is false. Either seeking is true, or the current playback position is not contained in any of the ranges in buffered. It is possible for playback to stop for two other reasons without paused being false, but those two reasons do not fire this event: maybe playback ended, or playback stopped due to errors.
playing Event Playback has started. readyState is newly equal to or greater than HAVE_FUTURE_DATA, paused is false, seeking is false, or the current playback position is contained in one of the ranges in buffered.
canplay Event The user agent can resume playback of the media data, but estimates that if playback were to be started now, the media resource could not be rendered at the current playback rate up to its end without having to stop for further buffering of content. readyState newly increased to HAVE_FUTURE_DATA or greater.
canplaythrough Event The user agent estimates that if playback were to be started now, the media resource could be rendered at the current playback rate all the way to its end without having to stop for further buffering. readyState is newly equal to HAVE_ENOUGH_DATA.
seeking Event The seeking IDL attribute changed to true and the seek operation is taking long enough that the user agent has time to fire the event.
seeked Event The seeking IDL attribute changed to false.
timeupdate Event The current playback position changed as part of normal playback or in an especially interesting way, for example discontinuously.
ended Event Playback has stopped because the end of the media resource was reached. currentTime equals the end of the media resource; ended is true.
ratechange Event Either the defaultPlaybackRate or the playbackRate attribute has just been updated.
durationchange Event The duration attribute has just been updated.
volumechange Event Either the volume attribute or the muted attribute has changed. Fired after the relevant attribute's setter has returned.
4.8.10.14 Best practices for authors using media elements

This section is non-normative.

Playing audio and video resources on small devices such as set-top boxes or mobile phones is often constrained by limited hardware resources in the device. For example, a device might only support three simultaneous videos. For this reason, it is a good practice to release resources held by media elements when they are done playing, either by being very careful about removing all references to the element and allowing it to be garbage collected, or, even better, by removing the element's src attribute and any source element descendants, and invoking the element's load() method.

4.8.11 The canvas element

Categories
Flow content.
Phrasing content.
Embedded content.
Contexts in which this element can be used:
Where embedded content is expected.
Content model:
Transparent.
Content attributes:
Global attributes
width
height
DOM interface:
interface HTMLCanvasElement : HTMLElement {
           attribute unsigned long width;
           attribute unsigned long height;

  DOMString toDataURL(in optional DOMString type, in any... args);

  object getContext(in DOMString contextId, in any... args);
};

The canvas element provides scripts with a resolution-dependent bitmap canvas, which can be used for rendering graphs, game graphics, or other visual images on the fly.

Authors should not use the canvas element in a document when a more suitable element is available. For example, it is inappropriate to use a canvas element to render a page heading: if the desired presentation of the heading is graphically intense, it should be marked up using appropriate elements (typically h1) and then styled using CSS and supporting technologies such as XBL.

When authors use the canvas element, they must also provide content that, when presented to the user, conveys essentially the same function or purpose as the bitmap canvas. This content may be placed as content of the canvas element. The contents of the canvas element, if any, are the element's fallback content.

In interactive visual media, if scripting is enabled for the canvas element, and if support for canvas elements has been enabled, the canvas element represents embedded content consisting of a dynamically created image.

In non-interactive, static, visual media, if the canvas element has been previously painted on (e.g. if the page was viewed in an interactive visual medium and is now being printed, or if some script that ran during the page layout process painted on the element), then the canvas element represents embedded content with the current image and size. Otherwise, the element represents its fallback content instead.

In non-visual media, and in visual media if scripting is disabled for the canvas element or if support for canvas elements has been disabled, the canvas element represents its fallback content instead.

When a canvas element represents embedded content, the user can still focus descendants of the canvas element (in the fallback content). This allows authors to make an interactive canvas keyboard-focusable: authors should have a one-to-one mapping of interactive regions to focusable elements in the fallback content.

The canvas element has two attributes to control the size of the coordinate space: width and height. These attributes, when specified, must have values that are valid non-negative integers. The width attribute defaults to 300, and the height attribute defaults to 150.

The intrinsic dimensions of the canvas element equal the size of the coordinate space, with the numbers interpreted in CSS pixels. However, the element can be sized arbitrarily by a style sheet. During rendering, the image is scaled to fit this layout size.

Only one square appears to be drawn in the following example:

  // canvas is a reference to a <canvas> element
  var context = canvas.getContext('2d');
  context.fillRect(0,0,50,50);
  canvas.setAttribute('width', '300'); // clears the canvas
  context.fillRect(0,100,50,50);
  canvas.width = canvas.width; // clears the canvas
  context.fillRect(100,0,50,50); // only this square remains

context = canvas . getContext(contextId [, ... ])

Returns an object that exposes an API for drawing on the canvas. The first argument specifies the desired API. Subsequent arguments are handled by that API.

The list of defined contexts is given on the WHATWG Wiki CanvasContexts page. [WHATWGWIKI]

Returns null if the given context ID is not supported or if the canvas has already been initialised with some other (incompatible) context type (e.g. trying to get a "2d" context after getting a "webgl" context).


url = canvas . toDataURL( [ type, ... ])

Returns a data: URL for the image in the canvas.

The first argument, if provided, controls the type of the image to be returned (e.g. PNG or JPEG). The default is image/png; that type is also used if the given type isn't supported. The other arguments are specific to the type, and control the way that the image is generated, as given in the table below.

When trying to use types other than image/png, authors can check if the image was really returned in the requested format by checking to see if the returned string starts with one of the exact strings "data:image/png," or "data:image/png;". If it does, the image is PNG, and thus the requested type was not supported. (The one exception to this is if the canvas has either no height or no width, in which case the result might simply be "data:,".)

Type Other arguments
image/jpeg The second argument is a number in the range 0.0 to 1.0 inclusive treated as the desired quality level.

4.8.12 The map element

Categories
Flow content.
When the element only contains phrasing content: phrasing content.
Contexts in which this element can be used:
When the element only contains phrasing content: where phrasing content is expected.
Otherwise: where flow content is expected.
Content model:
Transparent.
Content attributes:
Global attributes
name
DOM interface:
interface HTMLMapElement : HTMLElement {
           attribute DOMString name;
  readonly attribute HTMLCollection areas;
  readonly attribute HTMLCollection images;
};

The map element, in conjunction with any area element descendants, defines an image map. The element represents its children.

The name attribute gives the map a name so that it can be referenced. The attribute must be present and must have a non-empty value with no space characters. The value of the name attribute must not be a compatibility-caseless match for the value of the name attribute of another map element in the same document. If the id attribute is also specified, both attributes must have the same value.

map . areas

Returns an HTMLCollection of the area elements in the map.

map . images

Returns an HTMLCollection of the img and object elements that use the map.

Image maps can be defined in conjunction with other content on the page, to ease maintenance. This example is of a page with an image map at the top of the page and a corresponding set of text links at the bottom.

<!DOCTYPE HTML>
<TITLE>Babies™: Toys</TITLE>
<HEADER>
 <H1>Toys</H1>
 <IMG SRC="/images/menu.gif"
      ALT="Babies™ navigation menu. Select a department to go to its page."
      USEMAP="#NAV">
</HEADER>
 ...
<FOOTER>
 <MAP NAME="NAV">
  <P>
   <A HREF="/clothes/">Clothes</A>
   <AREA ALT="Clothes" COORDS="0,0,100,50" HREF="/clothes/"> |
   <A HREF="/toys/">Toys</A>
   <AREA ALT="Toys" COORDS="0,0,100,50" HREF="/toys/"> |
   <A HREF="/food/">Food</A>
   <AREA ALT="Food" COORDS="0,0,100,50" HREF="/food/"> |
   <A HREF="/books/">Books</A>
   <AREA ALT="Books" COORDS="0,0,100,50" HREF="/books/">
 </MAP>
</FOOTER>

4.8.13 The area element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected, but only if there is a map element ancestor.
Content model:
Empty.
Content attributes:
Global attributes
alt
coords
shape
href
target
rel
media
hreflang
type
DOM interface:
interface HTMLAreaElement : HTMLElement {
           attribute DOMString alt;
           attribute DOMString coords;
           attribute DOMString shape;
  stringifier attribute DOMString href;
           attribute DOMString target;
           attribute DOMString rel;
  readonly attribute DOMTokenList relList;
           attribute DOMString media;
           attribute DOMString hreflang;
           attribute DOMString type;

  // URL decomposition IDL attributes
           attribute DOMString protocol;
           attribute DOMString host;
           attribute DOMString hostname;
           attribute DOMString port;
           attribute DOMString pathname;
           attribute DOMString search;
           attribute DOMString hash;
};

The area element represents either a hyperlink with some text and a corresponding area on an image map, or a dead area on an image map.

If the area element has an href attribute, then the area element represents a hyperlink. In this case, the alt attribute must be present. It specifies the text of the hyperlink. Its value must be text that, when presented with the texts specified for the other hyperlinks of the image map, and with the alternative text of the image, but without the image itself, provides the user with the same kind of choice as the hyperlink would when used without its text but with its shape applied to the image. The alt attribute may be left blank if there is another area element in the same image map that points to the same resource and has a non-blank alt attribute.

If the area element has no href attribute, then the area represented by the element cannot be selected, and the alt attribute must be omitted.

In both cases, the shape and coords attributes specify the area.

The shape attribute is an enumerated attribute. The following table lists the keywords defined for this attribute. The states given in the first cell of the rows with keywords give the states to which those keywords map.

State Keywords
Circle state circle
Default state default
Polygon state poly
Rectangle state rect

The attribute may be omitted. The missing value default is the rectangle state.

The coords attribute must, if specified, contain a valid list of integers. This attribute gives the coordinates for the shape described by the shape attribute.

In the circle state, area elements must have a coords attribute present, with three integers, the last of which must be non-negative. The first integer must be the distance in CSS pixels from the left edge of the image to the center of the circle, the second integer must be the distance in CSS pixels from the top edge of the image to the center of the circle, and the third integer must be the radius of the circle, again in CSS pixels.

In the default state state, area elements must not have a coords attribute. (The area is the whole image.)

In the polygon state, area elements must have a coords attribute with at least six integers, and the number of integers must be even. Each pair of integers must represent a coordinate given as the distances from the left and the top of the image in CSS pixels respectively, and all the coordinates together must represent the points of the polygon, in order.

In the rectangle state, area elements must have a coords attribute with exactly four integers, the first of which must be less than the third, and the second of which must be less than the fourth. The four points must represent, respectively, the distance from the left edge of the image to the left side of the rectangle, the distance from the top edge to the top side, the distance from the left edge to the right side, and the distance from the top edge to the bottom side, all in CSS pixels.

The target, rel, media, hreflang, and type attributes must be omitted if the href attribute is not present.

4.8.14 Image maps

An image map allows geometric areas on an image to be associated with hyperlinks.

An image, in the form of an img element or an object element representing an image, may be associated with an image map (in the form of a map element) by specifying a usemap attribute on the img or object element. The usemap attribute, if specified, must be a valid hash-name reference to a map element.

Consider an image that looks as follows:

A line with four shapes in it, equally spaced: a red hollow box, a green circle, a blue triangle, and a yellow four-pointed star.

If we wanted just the colored areas to be clickable, we could do it as follows:

<p>
 Please select a shape:
 <img src="shapes.png" usemap="#shapes"
      alt="Four shapes are available: a red hollow box, a green circle, a blue triangle, and a yellow four-pointed star.">
 <map name="shapes">
  <area shape=rect coords="50,50,100,100"> <!-- the hole in the red box -->
  <area shape=rect coords="25,25,125,125" href="red.html" alt="Red box.">
  <area shape=circle coords="200,75,50" href="green.html" alt="Green circle.">
  <area shape=poly coords="325,25,262,125,388,125" href="blue.html" alt="Blue triangle.">
  <area shape=poly coords="450,25,435,60,400,75,435,90,450,125,465,90,500,75,465,60"
        href="yellow.html" alt="Yellow star.">
 </map>
</p>

4.8.15 MathML

The math element from the MathML namespace falls into the embedded content, phrasing content, and flow content categories for the purposes of the content models in this specification.

The semantics of MathML elements are defined by the MathML specification and other applicable specifications. [MATHML]

Here is an example of the use of MathML in an HTML document:

<!DOCTYPE html>
<html>
 <head>
  <title>The quadratic formula</title>
 </head>
 <body>
  <h1>The quadratic formula</h1>
  <p>
   <math>
    <mi>x</mi>
    <mo>=</mo>
    <mfrac>
     <mrow>
      <mo form="prefix">−</mo> <mi>b</mi>
      <mo>±</mo>
      <msqrt>
       <msup> <mi>b</mi> <mn>2</mn> </msup>
       <mo>−</mo>
       <mn>4</mn> <mo>⁢</mo> <mi>a</mi> <mo>⁢</mo> <mi>c</mi>
      </msqrt>
     </mrow>
     <mrow>
      <mn>2</mn> <mo>⁢</mo> <mi>a</mi>
     </mrow>
    </mfrac>
   </math>
  </p>
 </body>
</html>

4.8.16 SVG

The svg element from the SVG namespace falls into the embedded content, phrasing content, and flow content categories for the purposes of the content models in this specification.

When the SVG foreignObject element contains elements from the HTML namespace, such elements must all be flow content. [SVG]

The content model for title elements in the SVG namespace inside HTML documents is phrasing content. (This further constrains the requirements given in the SVG specification.)

The semantics of SVG elements are defined by the SVG specification and other applicable specifications. [SVG]

The SVG specification includes requirements regarding the handling of elements in the DOM that are not in the SVG namespace, that are in SVG fragments, and that are not included in a foreignObject element. This specification does not define any processing for elements in SVG fragments that are not in the HTML namespace; they are considered neither conforming nor non-conforming from the perspective of this specification.

4.8.17 Dimension attributes

The width and height attributes on img, iframe, embed, object, video, and, when their type attribute is in the Image Button state, input elements may be specified to give the dimensions of the visual content of the element (the width and height respectively, relative to the nominal direction of the output medium), in CSS pixels. The attributes, if specified, must have values that are valid non-negative integers.

The specified dimensions given may differ from the dimensions specified in the resource itself, since the resource may have a resolution that differs from the CSS pixel resolution. (On screens, CSS pixels have a resolution of 96ppi, but in general the CSS pixel resolution depends on the reading distance.) If both attributes are specified, then one of the following statements must be true:

The target ratio is the ratio of the intrinsic width to the intrinsic height in the resource. The specified width and specified height are the values of the width and height attributes respectively.

The two attributes must be omitted if the resource in question does not have both an intrinsic width and an intrinsic height.

If the two attributes are both zero, it indicates that the element is not intended for the user (e.g. it might be a part of a service to count page views).

The dimension attributes are not intended to be used to stretch the image.

4.9 Tabular data

ISSUE-32 (table-summary) blocks progress to Last Call

4.9.1 The table element

ISSUE-92 (cleanuptable) blocks progress to Last Call

Categories
Flow content.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
In this order: optionally a caption element, followed by zero or more colgroup elements, followed optionally by a thead element, followed optionally by a tfoot element, followed by either zero or more tbody elements or one or more tr elements, followed optionally by a tfoot element (but there can only be one tfoot element child in total).
Content attributes:
Global attributes
summary (but see prose)
DOM interface:
interface HTMLTableElement : HTMLElement {
           attribute HTMLTableCaptionElement caption;
  HTMLElement createCaption();
  void deleteCaption();
           attribute HTMLTableSectionElement tHead;
  HTMLElement createTHead();
  void deleteTHead();
           attribute HTMLTableSectionElement tFoot;
  HTMLElement createTFoot();
  void deleteTFoot();
  readonly attribute HTMLCollection tBodies;
  HTMLElement createTBody();
  readonly attribute HTMLCollection rows;
  HTMLElement insertRow(in optional long index);
  void deleteRow(in long index);
           attribute DOMString summary;
};

The table element represents data with more than one dimension, in the form of a table.

Tables must not be used as layout aids. Historically, some Web authors have misused tables in HTML as a way to control their page layout. This usage is non-conforming, because tools attempting to extract tabular data from such documents would obtain very confusing results. In particular, users of accessibility tools like screen readers are likely to find it very difficult to navigate pages with tables used for layout.

There are a variety of alternatives to using HTML tables for layout, primarily using CSS positioning and the CSS table model.

Tables have rows, columns, and cells given by their descendants. The rows and columns form a grid; a table's cells must completely cover that grid without overlap.

For tables that consist of more than just a grid of cells with headers in the first row and headers in the first column, and for any table in general where the reader might have difficulty understanding the content, authors should include explanatory information introducing the table. This information is useful for all users, but is especially useful for users who cannot see the table, e.g. users of screen readers.

Such explanatory information should introduce the purpose of the table, outline its basic cell structure, highlight any trends or patterns, and generally teach the user how to use the table.

For instance, the following table:

Characteristics with positive and negative sides
Negative Characteristic Positive
Sad Mood Happy
Failing Grade Passing

...might benefit from a description explaining the way the table is laid out, something like "Characteristics are given in the second column, with the negative side in the left column and the positive side in the right column".

There are a variety of ways to include this information, such as:

In prose, surrounding the table
<p>In the following table, characteristics are given in the second
column, with the negative side in the left column and the positive
side in the right column.</p>
<table>
 <caption>Characteristics with positive and negative sides</caption>
 <thead>
  <tr>
   <th id="n"> Negative
   <th> Characteristic
   <th> Positive
 <tbody>
  <tr>
   <td headers="n r1"> Sad
   <th id="r1"> Mood
   <td> Happy
  <tr>
   <td headers="n r2"> Failing
   <th id="r2"> Grade
   <td> Passing
</table>
In the table's caption
<table>
 <caption>
  <strong>Characteristics with positive and negative sides.</strong>
  <p>Characteristics are given in the second column, with the
  negative side in the left column and the positive side in the right
  column.</p>
 </caption>
 <thead>
  <tr>
   <th id="n"> Negative
   <th> Characteristic
   <th> Positive
 <tbody>
  <tr>
   <td headers="n r1"> Sad
   <th id="r1"> Mood
   <td> Happy
  <tr>
   <td headers="n r2"> Failing
   <th id="r2"> Grade
   <td> Passing
</table>
In the table's caption, in a details element
<table>
 <caption>
  <strong>Characteristics with positive and negative sides.</strong>
  <details>
   <summary>Help</summary>
   <p>Characteristics are given in the second column, with the
   negative side in the left column and the positive side in the right
   column.</p>
  </details>
 </caption>
 <thead>
  <tr>
   <th id="n"> Negative
   <th> Characteristic
   <th> Positive
 <tbody>
  <tr>
   <td headers="n r1"> Sad
   <th id="r1"> Mood
   <td> Happy
  <tr>
   <td headers="n r2"> Failing
   <th id="r2"> Grade
   <td> Passing
</table>
Next to the table, in the same figure
<figure>
 <figcaption>Characteristics with positive and negative sides</figcaption>
 <p>Characteristics are given in the second column, with the
 negative side in the left column and the positive side in the right
 column.</p>
 <table>
  <thead>
   <tr>
    <th id="n"> Negative
    <th> Characteristic
    <th> Positive
  <tbody>
   <tr>
    <td headers="n r1"> Sad
    <th id="r1"> Mood
    <td> Happy
   <tr>
    <td headers="n r2"> Failing
    <th id="r2"> Grade
    <td> Passing
 </table>
</figure>
Next to the table, in a figure's figcaption
<figure>
 <figcaption>
  <strong>Characteristics with positive and negative sides</strong>
  <p>Characteristics are given in the second column, with the
  negative side in the left column and the positive side in the right
  column.</p>
 </figcaption>
 <table>
  <thead>
   <tr>
    <th id="n"> Negative
    <th> Characteristic
    <th> Positive
  <tbody>
   <tr>
    <td headers="n r1"> Sad
    <th id="r1"> Mood
    <td> Happy
   <tr>
    <td headers="n r2"> Failing
    <th id="r2"> Grade
    <td> Passing
 </table>
</figure>

Authors may also use other techniques, or combinations of the above techniques, as appropriate.

The best option, of course, rather than writing a description explaining the way the table is laid out, is to adjust the table such that no explanation is needed.

In the case of the table used in the examples above, a simple rearrangement of the table so that the headers are on the top and left sides removes the need for an explanation as well as removing the need for the use of headers attributes:

<table>
 <caption>Characteristics with positive and negative sides</caption>
 <thead>
  <tr>
   <th> Characteristic
   <th> Negative
   <th> Positive
 <tbody>
  <tr>
   <th> Mood
   <td> Sad
   <td> Happy
  <tr>
   <th> Grade
   <td> Failing
   <td> Passing
</table>

The summary attribute on table elements was suggested in earlier versions of the language as a technique for providing explanatory text for complex tables for users of screen readers. One of the techniques described above should be used instead.

In particular, authors are encouraged to consider whether their explanatory text for tables is likely to be useful to the visually impaired: if their text would not be useful, then it is best to not include a summary attribute. Similarly, if their explanatory text could help someone who is not visually impaired, e.g. someone who is seeing the table for the first time, then the text would be more useful before the table or in the caption. For example, describing the conclusions of the data in a table is useful to everyone; explaining how to read the table, if not obvious from the headers alone, is useful to everyone; describing the structure of the table, if it is easy to grasp visually, may not be useful to everyone, but it might also not be useful to users who can quickly navigate the table with an accessibility tool.

table . caption [ = value ]

Returns the table's caption element.

Can be set, to replace the caption element. If the new value is not a caption element, throws a HIERARCHY_REQUEST_ERR exception.

caption = table . createCaption()

Ensures the table has a caption element, and returns it.

table . deleteCaption()

Ensures the table does not have a caption element.

table . tHead [ = value ]

Returns the table's thead element.

Can be set, to replace the thead element. If the new value is not a thead element, throws a HIERARCHY_REQUEST_ERR exception.

thead = table . createTHead()

Ensures the table has a thead element, and returns it.

table . deleteTHead()

Ensures the table does not have a thead element.

table . tFoot [ = value ]

Returns the table's tfoot element.

Can be set, to replace the tfoot element. If the new value is not a tfoot element, throws a HIERARCHY_REQUEST_ERR exception.

tfoot = table . createTFoot()

Ensures the table has a tfoot element, and returns it.

table . deleteTFoot()

Ensures the table does not have a tfoot element.

table . tBodies

Returns an HTMLCollection of the tbody elements of the table.

tbody = table . createTBody()

Creates a tbody element, inserts it into the table, and returns it.

table . rows

Returns an HTMLCollection of the tr elements of the table.

tr = table . insertRow(index)

Creates a tr element, along with a tbody if required, inserts them into the table at the position given by the argument, and returns the tr.

The position is relative to the rows in the table. The index −1 is equivalent to inserting at the end of the table.

If the given position is less than −1 or greater than the number of rows, throws an INDEX_SIZE_ERR exception.

table . deleteRow(index)

Removes the tr element with the given position in the table.

The position is relative to the rows in the table. The index −1 is equivalent to deleting the last row of the table.

If the given position is less than −1 or greater than the index of the last row, or if there are no rows, throws an INDEX_SIZE_ERR exception.

Here is an example of a table being used to mark up a Sudoku puzzle. Observe the lack of headers, which are not necessary in such a table.

<section>
 <style scoped>
  table { border-collapse: collapse; border: solid thick }
  colgroup, tbody { border: solid medium; }
  td { border: solid thin; height: 1.4em; width: 1.4em; text-align: center; padding: 0; }
 </style>
 <h1>Today's Sudoku</h1>
 <table>
  <colgroup><col><col><col>
  <colgroup><col><col><col>
  <colgroup><col><col><col>
  <tbody>
   <tr> <td> 1 <td>   <td> 3 <td> 6 <td>   <td> 4 <td> 7 <td>   <td> 9
   <tr> <td>   <td> 2 <td>   <td>   <td> 9 <td>   <td>   <td> 1 <td>
   <tr> <td> 7 <td>   <td>   <td>   <td>   <td>   <td>   <td>   <td> 6
  <tbody>
   <tr> <td> 2 <td>   <td> 4 <td>   <td> 3 <td>   <td> 9 <td>   <td> 8
   <tr> <td>   <td>   <td>   <td>   <td>   <td>   <td>   <td>   <td>
   <tr> <td> 5 <td>   <td>   <td> 9 <td>   <td> 7 <td>   <td>   <td> 1
  <tbody>
   <tr> <td> 6 <td>   <td>   <td>   <td> 5 <td>   <td>   <td>   <td> 2
   <tr> <td>   <td>   <td>   <td>   <td> 7 <td>   <td>   <td>   <td>
   <tr> <td> 9 <td>   <td>   <td> 8 <td>   <td> 2 <td>   <td>   <td> 5
 </table>
</section>

4.9.2 The caption element

Categories
None.
Contexts in which this element can be used:
As the first element child of a table element.
Content model:
Flow content, but with no descendant table elements.
Content attributes:
Global attributes
DOM interface:
interface HTMLTableCaptionElement : HTMLElement {};

The caption element represents the title of the table that is its parent, if it has a parent and that is a table element.

When a table element is the only content in a figure element other than the figcaption, the caption element should be omitted in favor of the figcaption.

A caption can introduce context for a table, making it significantly easier to understand.

Consider, for instance, the following table:

1 2 3 4 5 6
1 2 3 4 5 6 7
2 3 4 5 6 7 8
3 4 5 6 7 8 9
4 5 6 7 8 9 10
5 6 7 8 9 10 11
6 7 8 9 10 11 12

In the abstract, this table is not clear. However, with a caption giving the table's number (for reference in the main prose) and explaining its use, it makes more sense:

<caption>
<p>Table 1.
<p>This table shows the total score obtained from rolling two
six-sided dice. The first row represents the value of the first die,
the first column the value of the second die. The total is given in
the cell that corresponds to the values of the two dice.
</caption>

4.9.3 The colgroup element

Categories
None.
Contexts in which this element can be used:
As a child of a table element, after any caption elements and before any thead, tbody, tfoot, and tr elements.
Content model:
If the span attribute is present: Empty.
If the span attribute is absent: Zero or more col elements.
Content attributes:
Global attributes
span
DOM interface:
interface HTMLTableColElement : HTMLElement {
           attribute unsigned long span;
};

The colgroup element represents a group of one or more columns in the table that is its parent, if it has a parent and that is a table element.

If the colgroup element contains no col elements, then the element may have a span content attribute specified, whose value must be a valid non-negative integer greater than zero.

4.9.4 The col element

Categories
None.
Contexts in which this element can be used:
As a child of a colgroup element that doesn't have a span attribute.
Content model:
Empty.
Content attributes:
Global attributes
span
DOM interface:

HTMLTableColElement, same as for colgroup elements. This interface defines one member, span.

If a col element has a parent and that is a colgroup element that itself has a parent that is a table element, then the col element represents one or more columns in the column group represented by that colgroup.

The element may have a span content attribute specified, whose value must be a valid non-negative integer greater than zero.

4.9.5 The tbody element

Categories
None.
Contexts in which this element can be used:
As a child of a table element, after any caption, colgroup, and thead elements, but only if there are no tr elements that are children of the table element.
Content model:
Zero or more tr elements
Content attributes:
Global attributes
DOM interface:
interface HTMLTableSectionElement : HTMLElement {
  readonly attribute HTMLCollection rows;
  HTMLElement insertRow(in optional long index);
  void deleteRow(in long index);
};

The HTMLTableSectionElement interface is also used for thead and tfoot elements.

The tbody element represents a block of rows that consist of a body of data for the parent table element, if the tbody element has a parent and it is a table.

tbody . rows

Returns an HTMLCollection of the tr elements of the table section.

tr = tbody . insertRow( [ index ] )

Creates a tr element, inserts it into the table section at the position given by the argument, and returns the tr.

The position is relative to the rows in the table section. The index −1, which is the default if the argument is omitted, is equivalent to inserting at the end of the table section.

If the given position is less than −1 or greater than the number of rows, throws an INDEX_SIZE_ERR exception.

tbody . deleteRow(index)

Removes the tr element with the given position in the table section.

The position is relative to the rows in the table section. The index −1 is equivalent to deleting the last row of the table section.

If the given position is less than −1 or greater than the index of the last row, or if there are no rows, throws an INDEX_SIZE_ERR exception.

4.9.6 The thead element

Categories
None.
Contexts in which this element can be used:
As a child of a table element, after any caption, and colgroup elements and before any tbody, tfoot, and tr elements, but only if there are no other thead elements that are children of the table element.
Content model:
Zero or more tr elements
Content attributes:
Global attributes
DOM interface:
HTMLTableSectionElement, as defined for tbody elements.

The thead element represents the block of rows that consist of the column labels (headers) for the parent table element, if the thead element has a parent and it is a table.

This example shows a thead element being used. Notice the use of both th and td elements in the thead element: the first row is the headers, and the second row is an explanation of how to fill in the table.

<table>
 <caption> School auction sign-up sheet </caption>
 <thead>
  <tr>
   <th><label for=e1>Name</label>
   <th><label for=e2>Product</label>
   <th><label for=e3>Picture</label>
   <th><label for=e4>Price</label>
  <tr>
   <td>Your name here
   <td>What are you selling?
   <td>Link to a picture
   <td>Your reserve price
 <tbody>
  <tr>
   <td>Ms Danus
   <td>Doughnuts
   <td><img src="http://example.com/mydoughnuts.png" title="Doughnuts from Ms Danus">
   <td>$45
  <tr>
   <td><input id=e1 type=text name=who required form=f>
   <td><input id=e2 type=text name=what required form=f>
   <td><input id=e3 type=url name=pic form=f>
   <td><input id=e4 type=number step=0.01 min=0 value=0 required form=f>
</table>
<form id=f action="/auction.cgi">
 <input type=button name=add value="Submit">
</form>

4.9.7 The tfoot element

Categories
None.
Contexts in which this element can be used:
As a child of a table element, after any caption, colgroup, and thead elements and before any tbody and tr elements, but only if there are no other tfoot elements that are children of the table element.
As a child of a table element, after any caption, colgroup, thead, tbody, and tr elements, but only if there are no other tfoot elements that are children of the table element.
Content model:
Zero or more tr elements
Content attributes:
Global attributes
DOM interface:
HTMLTableSectionElement, as defined for tbody elements.

The tfoot element represents the block of rows that consist of the column summaries (footers) for the parent table element, if the tfoot element has a parent and it is a table.

4.9.8 The tr element

Categories
None.
Contexts in which this element can be used:
As a child of a thead element.
As a child of a tbody element.
As a child of a tfoot element.
As a child of a table element, after any caption, colgroup, and thead elements, but only if there are no tbody elements that are children of the table element.
Content model:
Zero or more td or th elements
Content attributes:
Global attributes
DOM interface:
interface HTMLTableRowElement : HTMLElement {
  readonly attribute long rowIndex;
  readonly attribute long sectionRowIndex;
  readonly attribute HTMLCollection cells;
  HTMLElement insertCell(in optional long index);
  void deleteCell(in long index);
};

The tr element represents a row of cells in a table.

tr . rowIndex

Returns the position of the row in the table's rows list.

Returns −1 if the element isn't in a table.

tr . sectionRowIndex

Returns the position of the row in the table section's rows list.

Returns −1 if the element isn't in a table section.

tr . cells

Returns an HTMLCollection of the td and th elements of the row.

cell = tr . insertCell( [ index ] )

Creates a td element, inserts it into the table row at the position given by the argument, and returns the td.

The position is relative to the cells in the row. The index −1, which is the default if the argument is omitted, is equivalent to inserting at the end of the row.

If the given position is less than −1 or greater than the number of cells, throws an INDEX_SIZE_ERR exception.

tr . deleteCell(index)

Removes the td or th element with the given position in the row.

The position is relative to the cells in the row. The index −1 is equivalent to deleting the last cell of the row.

If the given position is less than −1 or greater than the index of the last cell, or if there are no cells, throws an INDEX_SIZE_ERR exception.

4.9.9 The td element

Categories
Sectioning root.
Contexts in which this element can be used:
As a child of a tr element.
Content model:
Flow content.
Content attributes:
Global attributes
colspan
rowspan
headers
DOM interface:
interface HTMLTableDataCellElement : HTMLTableCellElement {};

The td element represents a data cell in a table.

4.9.10 The th element

Categories
None.
Contexts in which this element can be used:
As a child of a tr element.
Content model:
Phrasing content.
Content attributes:
Global attributes
colspan
rowspan
headers
scope
DOM interface:
interface HTMLTableHeaderCellElement : HTMLTableCellElement {
           attribute DOMString scope;
};

The th element represents a header cell in a table.

The th element may have a scope content attribute specified. The scope attribute is an enumerated attribute with five states, four of which have explicit keywords:

The row keyword, which maps to the row state
The row state means the header cell applies to some of the subsequent cells in the same row(s).
The col keyword, which maps to the column state
The column state means the header cell applies to some of the subsequent cells in the same column(s).
The rowgroup keyword, which maps to the row group state
The row group state means the header cell applies to all the remaining cells in the row group. A th element's scope attribute must not be in the row group state if the element is not anchored in a row group.
The colgroup keyword, which maps to the column group state
The column group state means the header cell applies to all the remaining cells in the column group. A th element's scope attribute must not be in the column group state if the element is not anchored in a column group.
The auto state
The auto state makes the header cell apply to a set of cells selected based on context.

The scope attribute's missing value default is the auto state.

The following example shows how the scope attribute's rowgroup value affects which data cells a header cell applies to.

Here is a markup fragment showing a table:

<table>
 <thead>
  <tr> <th> ID <th> Measurement <th> Average <th> Maximum
 <tbody>
  <tr> <td> <th scope=rowgroup> Cats <td> <td>
  <tr> <td> 93 <th> Legs <td> 3.5 <td> 4
  <tr> <td> 10 <th> Tails <td> 1 <td> 1
 <tbody>
  <tr> <td> <th scope=rowgroup> English speakers <td> <td>
  <tr> <td> 32 <th> Legs <td> 2.67 <td> 4
  <tr> <td> 35 <th> Tails <td> 0.33 <td> 1
</table>

This would result in the following table:

ID Measurement Average Maximum
Cats
93 Legs 3.5 4
10 Tails 1 1
English speakers
32 Legs 2.67 4
35 Tails 0.33 1

The headers in the first row all apply directly down to the rows in their column.

The headers with the explicit scope attributes apply to all the cells in their row group other than the cells in the first column.

The remaining headers apply just to the cells to the right of them.

4.9.11 Attributes common to td and th elements

The td and th elements may have a colspan content attribute specified, whose value must be a valid non-negative integer greater than zero.

The td and th elements may also have a rowspan content attribute specified, whose value must be a valid non-negative integer.

These attributes give the number of columns and rows respectively that the cell is to span. These attributes must not be used to overlap cells.


The td and th element may have a headers content attribute specified. The headers attribute, if specified, must contain a string consisting of an unordered set of unique space-separated tokens that are case-sensitive, each of which must have the value of an ID of a th element taking part in the same table as the td or th element.

A th element with ID id is said to be directly targeted by all td and th elements in the same table that have headers attributes whose values include as one of their tokens the ID id. A th element A is said to be targeted by a th or td element B if either A is directly targeted by B or if there exists an element C that is itself targeted by the element B and A is directly targeted by C.

A th element must not be targeted by itself.


The td and th elements implement interfaces that inherit from the HTMLTableCellElement interface:

interface HTMLTableCellElement : HTMLElement {
           attribute unsigned long colSpan;
           attribute unsigned long rowSpan;
  [PutForwards=value] readonly attribute DOMSettableTokenList headers;
  readonly attribute long cellIndex;
};
cell . cellIndex

Returns the position of the cell in the row's cells list. This does not necessarily correspond to the x-position of the cell in the table, since earlier cells might cover multiple rows or columns.

Returns 0 if the element isn't in a row.

4.9.12 Examples

This section is non-normative.

The following shows how might one mark up the bottom part of table 45 of the Smithsonian physical tables, Volume 71:

<table>
 <caption>Specification values: <b>Steel</b>, <b>Castings</b>,
 Ann. A.S.T.M. A27-16, Class B;* P max. 0.06; S max. 0.05.</caption>
 <thead>
  <tr>
   <th rowspan=2>Grade.</th>
   <th rowspan=2>Yield Point.</th>
   <th colspan=2>Ultimate tensile strength</th>
   <th rowspan=2>Per cent elong. 50.8mm or 2 in.</th>
   <th rowspan=2>Per cent reduct. area.</th>
  </tr>
  <tr>
   <th>kg/mm<sup>2</sup></th>
   <th>lb/in<sup>2</sup></th>
  </tr>
 </thead>
 <tbody>
  <tr>
   <td>Hard</td>
   <td>0.45 ultimate</td>
   <td>56.2</td>
   <td>80,000</td>
   <td>15</td>
   <td>20</td>
  </tr>
  <tr>
   <td>Medium</td>
   <td>0.45 ultimate</td>
   <td>49.2</td>
   <td>70,000</td>
   <td>18</td>
   <td>25</td>
  </tr>
  <tr>
   <td>Soft</td>
   <td>0.45 ultimate</td>
   <td>42.2</td>
   <td>60,000</td>
   <td>22</td>
   <td>30</td>
  </tr>
 </tbody>
</table>

This table could look like this:

Specification values: Steel, Castings, Ann. A.S.T.M. A27-16, Class B;* P max. 0.06; S max. 0.05.
Grade. Yield Point. Ultimate tensile strength Per cent elong. 50.8 mm or 2 in. Per cent reduct. area.
kg/mm2 lb/in2
Hard 0.45 ultimate 56.2 80,000 15 20
Medium 0.45 ultimate 49.2 70,000 18 25
Soft 0.45 ultimate 42.2 60,000 22 30

The following shows how one might mark up the gross margin table on page 46 of Apple, Inc's 10-K filing for fiscal year 2008:

<table>
 <thead>
  <tr>
   <th>
   <th>2008
   <th>2007
   <th>2006
 <tbody>
  <tr>
   <th>Net sales
   <td>$ 32,479
   <td>$ 24,006
   <td>$ 19,315
  <tr>
   <th>Cost of sales
   <td>  21,334
   <td>  15,852
   <td>  13,717
 <tbody>
  <tr>
   <th>Gross margin
   <td>$ 11,145
   <td>$  8,154
   <td>$  5,598
 <tfoot>
  <tr>
   <th>Gross margin percentage
   <td>34.3%
   <td>34.0%
   <td>29.0%
</table>

The following shows how one might mark up the operating expenses table from lower on the same page of that document:

<table>
 <colgroup> <col>
 <colgroup> <col> <col> <col>
 <thead>
  <tr> <th> <th>2008 <th>2007 <th>2006
 <tbody>
  <tr> <th scope=rowgroup> Research and development
       <td> $ 1,109 <td> $ 782 <td> $ 712
  <tr> <th scope=row> Percentage of net sales
       <td> 3.4% <td> 3.3% <td> 3.7%
 <tbody>
  <tr> <th scope=rowgroup> Selling, general, and administrative
       <td> $ 3,761 <td> $ 2,963 <td> $ 2,433
  <tr> <th scope=row> Percentage of net sales
       <td> 11.6% <td> 12.3% <td> 12.6%
</table>

This table could look like this:

2008 2007 2006
Research and development $ 1,109 $ 782 $ 712
Percentage of net sales 3.4% 3.3% 3.7%
Selling, general, and administrative $ 3,761 $ 2,963 $ 2,433
Percentage of net sales 11.6% 12.3% 12.6%

4.10 Forms

4.10.1 Introduction

This section is non-normative.

A form is a component of a Web page that has form controls, such as text fields, buttons, check boxes, range controls, or color pickers. A user can interact with such a form, providing data that can then be sent to the server for further processing (e.g. returning the results of a search or calculation). No client-side scripting is needed in many cases, though an API is available so that scripts can augment the user experience or use forms for purposes other than submitting data to a server.

Writing a form consists of several steps, which can be performed in any order: writing the user interface, implementing the server-side processing, and configuring the user interface to communicate with the server.

4.10.1.1 Writing a form's user interface

This section is non-normative.

For the purposes of this brief introduction, we will create a pizza ordering form.

Any form starts with a form element, inside which are placed the controls. Most controls are represented by the input element, which by default provides a one-line text field. To label a control, the label element is used; the label text and the control itself go inside the label element. Each part of a form is considered a paragraph, and is typically separated from other parts using p elements. Putting this together, here is how one might ask for the customer's name:

<form>
 <p><label>Customer name: <input></label></p>
</form>

To let the user select the size of the pizza, we can use a set of radio buttons. Radio buttons also use the input element, this time with a type attribute with the value radio. To make the radio buttons work as a group, they are given a common name using the name attribute. To group a batch of controls together, such as, in this case, the radio buttons, one can use the fieldset element. The title of such a group of controls is given by the first element in the fieldset, which has to be a legend element.

<form>
 <p><label>Customer name: <input></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
</form>

Changes from the previous step are highlighted.

To pick toppings, we can use checkboxes. These use the input element with a type attribute with the value checkbox:

<form>
 <p><label>Customer name: <input></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
</form>

The pizzeria for which this form is being written is always making mistakes, so it needs a way to contact the customer. For this purpose, we can use form controls specifically for telephone numbers (input elements with their type attribute set to tel) and e-mail addresses (input elements with their type attribute set to email):

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
</form>

We can use an input element with its type attribute set to time to ask for a delivery time. Many of these form controls have attributes to control exactly what values can be specified; in this case, three attributes of particular interest are min, max, and step. These set the minimum time, the maximum time, and the interval between allowed values (in seconds). This pizzeria only delivers between 11am and 9pm, and doesn't promise anything better than 15 minute increments, which we can mark up as follows:

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p>
</form>

The textarea element can be used to provide a free-form text field. In this instance, we are going to use it to provide a space for the customer to give delivery instructions:

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p>
 <p><label>Delivery instructions: <textarea></textarea></label></p>
</form>

Finally, to make the form submittable we use the button element:

<form>
 <p><label>Customer name: <input></label></p>
 <p><label>Telephone: <input type=tel></label></p>
 <p><label>E-mail address: <input type=email></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size> Small </label></p>
  <p><label> <input type=radio name=size> Medium </label></p>
  <p><label> <input type=radio name=size> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox> Bacon </label></p>
  <p><label> <input type=checkbox> Extra Cheese </label></p>
  <p><label> <input type=checkbox> Onion </label></p>
  <p><label> <input type=checkbox> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900"></label></p>
 <p><label>Delivery instructions: <textarea></textarea></label></p>
 <p><button>Submit order</button></p>
</form>
4.10.1.2 Implementing the server-side processing for a form

This section is non-normative.

The exact details for writing a server-side processor are out of scope for this specification. For the purposes of this introduction, we will assume that the script at https://pizza.example.com/order.cgi is configured to accept submissions using the application/x-www-form-urlencoded format, expecting the following parameters sent in an HTTP POST body:

custname
Customer's name
custtel
Customer's telephone number
custemail
Customer's e-mail address
size
The pizza size, either small, medium, or large
toppings
The topping, specified once for each selected topping, with the allowed values being bacon, cheese, onion, and mushroom
delivery
The requested delivery time
comments
The delivery instructions
4.10.1.3 Configuring a form to communicate with a server

This section is non-normative.

Form submissions are exposed to servers in a variety of ways, most commonly as HTTP GET or POST requests. To specify the exact method used, the method attribute is specified on the form element. This doesn't specify how the form data is encoded, though; to specify that, you use the enctype attribute. You also have to specify the URL of the service that will handle the submitted data, using the action attribute.

For each form control you want submitted, you then have to give a name that will be used to refer to the data in the submission. We already specified the name for the group of radio buttons; the same attribute (name) also specifies the submission name. Radio buttons can be distinguished from each other in the submission by giving them different values, using the value attribute.

Multiple controls can have the same name; for example, here we give all the checkboxes the same name, and the server distinguishes which checkbox was checked by seeing which values are submitted with that name — like the radio buttons, they are also given unique values with the value attribute.

Given the settings in the previous section, this all becomes:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname"></label></p>
 <p><label>Telephone: <input type=tel name="custtel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size value="small"> Small </label></p>
  <p><label> <input type=radio name=size value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery"></label></p>
 <p><label>Delivery instructions: <textarea name="comments"></textarea></label></p>
 <p><button>Submit order</button><p>
</form>

For example, if the customer entered "Denise Lawrence" as their name, "555-321-8642" as their telephone number, did not specify an e-mail address, asked for a medium-sized pizza, selected the Extra Cheese and Mushroom toppings, entered a delivery time of 7pm, and left the delivery instructions text field blank, the user agent would submit the following to the online Web service:

custname=Denise+Lawrence&custtel=555-321-8624&custemail=&size=medium&topping=cheese&topping=mushroom&delivery=19%3A00&comments=
4.10.1.4 Client-side form validation

This section is non-normative.

Forms can be annotated in such a way that the user agent will check the user's input before the form is submitted. The server still has to verify the input is valid (since hostile users can easily bypass the form validation), but it allows the user to avoid the wait incurred by having the server be the sole checker of the user's input.

The simplest annotation is the required attribute, which can be specified on input elements to indicate that the form is not to be submitted until a value is given. By adding this attribute to the customer name and delivery time fields, we allow the user agent to notify the user when the user submits the form without filling in those fields:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname" required></label></p>
 <p><label>Telephone: <input type=tel name="custtel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size value="small"> Small </label></p>
  <p><label> <input type=radio name=size value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery" required></label></p>
 <p><label>Delivery instructions: <textarea name="comments"></textarea></label></p>
 <p><button>Submit order</button><p>
</form>

It is also possible to limit the length of the input, using the maxlength attribute. By adding this to the textarea element, we can limit users to 1000 characters, preventing them from writing huge essays to the busy delivery drivers instead of staying focused and to the point:

<form method="post"
      enctype="application/x-www-form-urlencoded"
      action="https://pizza.example.com/order.cgi">
 <p><label>Customer name: <input name="custname" required></label></p>
 <p><label>Telephone: <input type=tel name="custtel"></label></p>
 <p><label>E-mail address: <input type=email name="custemail"></label></p>
 <fieldset>
  <legend> Pizza Size </legend>
  <p><label> <input type=radio name=size value="small"> Small </label></p>
  <p><label> <input type=radio name=size value="medium"> Medium </label></p>
  <p><label> <input type=radio name=size value="large"> Large </label></p>
 </fieldset>
 <fieldset>
  <legend> Pizza Toppings </legend>
  <p><label> <input type=checkbox name="topping" value="bacon"> Bacon </label></p>
  <p><label> <input type=checkbox name="topping" value="cheese"> Extra Cheese </label></p>
  <p><label> <input type=checkbox name="topping" value="onion"> Onion </label></p>
  <p><label> <input type=checkbox name="topping" value="mushroom"> Mushroom </label></p>
 </fieldset>
 <p><label>Preferred delivery time: <input type=time min="11:00" max="21:00" step="900" name="delivery" required></label></p>
 <p><label>Delivery instructions: <textarea name="comments" maxlength=1000></textarea></label></p>
 <p><button>Submit order</button><p>
</form>

4.10.2 Categories

Mostly for historical reasons, elements in this section fall into several overlapping (but subtly different) categories in addition to the usual ones like flow content, phrasing content, and interactive content.

A number of the elements are form-associated elements, which means they can have a form owner and, to expose this, have a form content attribute with a matching form IDL attribute.

The form-associated elements fall into several subcategories:

Listed elements

Denotes elements that are listed in the form.elements and fieldset.elements APIs.

Labelable elements

Denotes elements that can be associated with label elements.

Submittable elements

Denotes elements that can be used for constructing the form data set when a form element is submitted.

Resettable elements

Denotes elements that can be affected when a form element is reset.

In addition, some submittable elements can be, depending on their attributes, buttons. The prose below defines when an element is a button. Some buttons are specifically submit buttons.

The object element is also a form-associated element and can, with the use of a suitable plugin, partake in form submission.

4.10.3 The form element

Categories
Flow content.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Flow content, but with no form element descendants.
Content attributes:
Global attributes
accept-charset
action
autocomplete
enctype
method
name
novalidate
target
DOM interface:
[OverrideBuiltins]
interface HTMLFormElement : HTMLElement {
           attribute DOMString acceptCharset;
           attribute DOMString action;
           attribute DOMString autocomplete;
           attribute DOMString enctype;
           attribute DOMString encoding;
           attribute DOMString method;
           attribute DOMString name;
           attribute boolean noValidate;
           attribute DOMString target;

  readonly attribute HTMLFormControlsCollection elements;
  readonly attribute long length;
  caller getter any (in unsigned long index);
  caller getter any (in DOMString name);

  void submit();
  void reset();
  boolean checkValidity();

  void dispatchFormInput();
  void dispatchFormChange();
};

The form element represents a collection of form-associated elements, some of which can represent editable values that can be submitted to a server for processing.

The accept-charset attribute gives the character encodings that are to be used for the submission. If specified, the value must be an ordered set of unique space-separated tokens that are ASCII case-insensitive, and each token must be an ASCII case-insensitive match for the preferred MIME name of an ASCII-compatible character encoding. [IANACHARSET]

The name attribute represents the form's name within the forms collection. The value must not be the empty string, and the value must be unique amongst the form elements in the forms collection that it is in, if any.

The autocomplete attribute is an enumerated attribute. The attribute has two states. The on keyword maps to the on state, and the off keyword maps to the off state. The attribute may also be omitted. The missing value default is the on state. The off state indicates that by default, input elements in the form will have their resulting autocompletion state set to off; the on state indicates that by default, input elements in the form will have their resulting autocompletion state set to on.

The action, enctype, method, novalidate, and target attributes are attributes for form submission.

form . elements

Returns an HTMLCollection of the form controls in the form (excluding image buttons for historical reasons).

form . length

Returns the number of form controls in the form (excluding image buttons for historical reasons).

form[index]
form(index)

Returns the indexth element in the form (excluding image buttons for historical reasons).

form[name]
form(name)

Returns the form control in the form with the given ID or name (excluding image buttons for historical reasons).

Once an element has been referenced using a particular name, that name will continue being available as a way to reference that element in this method, even if the element's actual ID or name changes, for as long as the element remains in the Document.

If there are multiple matching items, then a NodeList object containing all those elements is returned.

Returns null if no element with that ID or name could be found.

form . submit()

Submits the form.

form . reset()

Resets the form.

form . checkValidity()

Returns true if the form's controls are all valid; otherwise, returns false.

form . dispatchFormInput()

Dispatches a forminput event at all the form controls.

form . dispatchFormChange()

Dispatches a formchange event at all the form controls.

This example shows two search forms:

<form action="http://www.google.com/search" method="get">
 <label>Google: <input type="search" name="q"></label> <input type="submit" value="Search...">
</form>
<form action="http://www.bing.com/search" method="get">
 <label>Bing: <input type="search" name="q"></label> <input type="submit" value="Search...">
</form>

4.10.4 The fieldset element

Categories
Flow content.
Sectioning root.
Listed form-associated element.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Optionally a legend element, followed by flow content.
Content attributes:
Global attributes
disabled
form
name
DOM interface:
interface HTMLFieldSetElement : HTMLElement {
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute DOMString name;

  readonly attribute DOMString type;

  readonly attribute HTMLFormControlsCollection elements;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);
};

The fieldset element represents a set of form controls optionally grouped under a common name.

The name of the group is given by the first legend element that is a child of the fieldset element, if any. The remainder of the descendants form the group.

The disabled attribute, when specified, causes all the form control descendants of the fieldset element, excluding those that are descendants of the fieldset element's first legend element child, if any, to be disabled.

The form attribute is used to explicitly associate the fieldset element with its form owner. The name attribute represents the element's name.

fieldset . type

Returns the string "fieldset".

fieldset . elements

Returns an HTMLCollection of the form controls in the element.

The following snippet shows a fieldset with a checkbox in the legend that controls whether or not the fieldset is enabled. The contents of the fieldset consist of two required text fields and an optional year/month control.

<fieldset name="clubfields" disabled>
 <legend> <label>
  <input type=checkbox name=club onchange="form.clubfields.disabled = !checked">
  Use Club Card
 </label> </legend>
 <p><label>Name on card: <input name=clubname required></label></p>
 <p><label>Card number: <input name=clubnum required pattern="[-0-9]+"></label></p>
 <p><label>Expiry date: <input name=clubexp type=month></label></p>
</fieldset>

You can also nest fieldset elements. Here is an example expanding on the previous one that does so:

<fieldset name="clubfields" disabled>
 <legend> <label>
  <input type=checkbox name=club onchange="form.clubfields.disabled = !checked">
  Use Club Card
 </label> </legend>
 <p><label>Name on card: <input name=clubname required></label></p>
 <fieldset name="numfields">
  <legend> <label>
   <input type=radio checked name=clubtype onchange="form.numfields.disabled = !checked">
   My card has numbers on it
  </label> </legend>
  <p><label>Card number: <input name=clubnum required pattern="[-0-9]+"></label></p>
 </fieldset>
 <fieldset name="letfields" disabled>
  <legend> <label>
   <input type=radio name=clubtype onchange="form.letfields.disabled = !checked">
   My card has letters on it
  </label> </legend>
  <p><label>Card code: <input name=clublet required pattern="[A-Za-z]+"></label></p>
 </fieldset>
</fieldset>

In this example, if the outer "Use Club Card" checkbox is not checked, everything inside the outer fieldset, including the two radio buttons in the legends of the two nested fieldsets, will be disabled. However, if the checkbox is checked, then the radio buttons will both be enabled and will let you select which of the two inner fieldsets is to be enabled.

4.10.5 The legend element

Categories
None.
Contexts in which this element can be used:
As the first child of a fieldset element.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
interface HTMLLegendElement : HTMLElement {
  readonly attribute HTMLFormElement form;
};

The legend element represents a caption for the rest of the contents of the legend element's parent fieldset element.

legend . form

Returns the element's form element, if any, or null otherwise.

4.10.6 The label element

Categories
Flow content.
Phrasing content.
Interactive content.
Form-associated element.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content, but with no descendant labelable form-associated elements unless it is the element's labeled control, and no descendant label elements.
Content attributes:
Global attributes
form
for
DOM interface:
interface HTMLLabelElement : HTMLElement {
  readonly attribute HTMLFormElement form;
           attribute DOMString htmlFor;
  readonly attribute HTMLElement control;
};

The label represents a caption in a user interface. The caption can be associated with a specific form control, either using for attribute, or by putting the form control inside the label element itself.

The for attribute may be specified to indicate a form control with which the caption is to be associated. If the attribute is specified, the attribute's value must be the ID of a labelable form-associated element in the same Document as the label element.

label . control

Returns the form control that is associated with this element.

The form attribute is used to explicitly associate the label element with its form owner.


control . labels

Returns a NodeList of all the label elements that the form control is associated with.

The following example shows three form controls each with a label, two of which have small text showing the right format for users to use.

<p><label>Full name: <input name=fn> <small>Format: First Last</small></label></p>
<p><label>Age: <input name=age type=number min=0></label></p>
<p><label>Post code: <input name=pc> <small>Format: AB12 3CD</small></label></p>

4.10.7 The input element

Categories
Flow content.
Phrasing content.
If the type attribute is not in the Hidden state: Interactive content.
If the type attribute is not in the Hidden state: Listed, labelable, submittable, and resettable form-associated element.
If the type attribute is in the Hidden state: Listed, submittable, and resettable form-associated element.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Empty.
Content attributes:
Global attributes
accept
alt
autocomplete
autofocus
checked
dirname
disabled
form
formaction
formenctype
formmethod
formnovalidate
formtarget
height
list
max
maxlength
min
multiple
name
pattern
placeholder
readonly
required
size
src
step
type
value
width
DOM interface:
interface HTMLInputElement : HTMLElement {
           attribute DOMString accept;
           attribute DOMString alt;
           attribute DOMString autocomplete;
           attribute boolean autofocus;
           attribute boolean defaultChecked;
           attribute boolean checked;
           attribute DOMString dirName;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
  readonly attribute FileList files;
           attribute DOMString formAction;
           attribute DOMString formEnctype;
           attribute DOMString formMethod;
           attribute boolean formNoValidate;
           attribute DOMString formTarget;
           attribute DOMString height;
           attribute boolean indeterminate;
  readonly attribute HTMLElement list;
           attribute DOMString max;
           attribute long maxLength;
           attribute DOMString min;
           attribute boolean multiple;
           attribute DOMString name;
           attribute DOMString pattern;
           attribute DOMString placeholder;
           attribute boolean readOnly;
           attribute boolean required;
           attribute unsigned long size;
           attribute DOMString src;
           attribute DOMString step;
           attribute DOMString type;
           attribute DOMString defaultValue;
           attribute DOMString value;
           attribute Date valueAsDate;
           attribute double valueAsNumber;
  readonly attribute HTMLOptionElement selectedOption;
           attribute DOMString width;

  void stepUp(in optional long n);
  void stepDown(in optional long n);

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;

  void select();
           attribute unsigned long selectionStart;
           attribute unsigned long selectionEnd;
  void setSelectionRange(in unsigned long start, in unsigned long end);
};

The input element represents a typed data field, usually with a form control to allow the user to edit the data.

The type attribute controls the data type (and associated control) of the element. It is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.

Keyword State Data type Control type
hidden Hidden An arbitrary string n/a
text Text Text with no line breaks Text field
search Search Text with no line breaks Search field
tel Telephone Text with no line breaks A text field
url URL An absolute IRI A text field
email E-mail An e-mail address or list of e-mail addresses A text field
password Password Text with no line breaks (sensitive information) Text field that obscures data entry
datetime Date and Time A date and time (year, month, day, hour, minute, second, fraction of a second) with the time zone set to UTC A date and time control
date Date A date (year, month, day) with no time zone A date control
month Month A date consisting of a year and a month with no time zone A month control
week Week A date consisting of a week-year number and a week number with no time zone A week control
time Time A time (hour, minute, seconds, fractional seconds) with no time zone A time control
datetime-local Local Date and Time A date and time (year, month, day, hour, minute, second, fraction of a second) with no time zone A date and time control
number Number A numerical value A text field or spinner control
range Range A numerical value, with the extra semantic that the exact value is not important A slider control or similar
color Color An sRGB color with 8-bit red, green, and blue components A color well
checkbox Checkbox A set of zero or more values from a predefined list A checkbox
radio Radio Button An enumerated value A radio button
file File Upload Zero or more files each with a MIME type and optionally a file name A label and a button
submit Submit Button An enumerated value, with the extra semantic that it must be the last value selected and initiates form submission A button
image Image Button A coordinate, relative to a particular image's size, with the extra semantic that it must be the last value selected and initiates form submission Either a clickable image, or a button
reset Reset Button n/a A button
button Button n/a A button

The missing value default is the Text state.

Which of the accept, alt, autocomplete, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, required, size, src, step, and width content attributes, the checked, files, valueAsDate, valueAsNumber, list, and selectedOption IDL attributes, the select() method, the selectionStart and selectionEnd IDL attributes, the setSelectionRange() method, the stepUp() and stepDown() methods, and the input and change events apply to an input element depends on the state of its type attribute. The following table summarizes which of those content attributes, IDL attributes, methods, and events apply to each state:

Hidden Text, Search URL, Telephone E-mail Password Date and Time, Date, Month, Week, Time Local Date and Time, Number Range Color Checkbox, Radio Button File Upload Submit Button Image Button Reset Button, Button
Content attributes
accept · · · · · · · · · · Yes · · ·
alt · · · · · · · · · · · · Yes ·
autocomplete · Yes Yes Yes Yes Yes Yes Yes Yes · · · · ·
checked · · · · · · · · · Yes · · · ·
dirname · Yes · · · · · · · · · · · ·
formaction · · · · · · · · · · · Yes Yes ·
formenctype · · · · · · · · · · · Yes Yes ·
formmethod · · · · · · · · · · · Yes Yes ·
formnovalidate · · · · · · · · · · · Yes Yes ·
formtarget · · · · · · · · · · · Yes Yes ·
height · · · · · · · · · · · · Yes ·
list · Yes Yes Yes · Yes Yes Yes Yes · · · · ·
max · · · · · Yes Yes Yes · · · · · ·
maxlength · Yes Yes Yes Yes · · · · · · · · ·
min · · · · · Yes Yes Yes · · · · · ·
multiple · · · Yes · · · · · · Yes · · ·
pattern · Yes Yes Yes Yes · · · · · · · · ·
placeholder · Yes Yes Yes Yes · · · · · · · · ·
readonly · Yes Yes Yes Yes Yes Yes · · · · · · ·
required · Yes Yes Yes Yes Yes Yes · · Yes Yes · · ·
size · Yes Yes Yes Yes · · · · · · · · ·
src · · · · · · · · · · · · Yes ·
step · · · · · Yes Yes Yes · · · · · ·
width · · · · · · · · · · · · Yes ·
IDL attributes and methods
checked · · · · · · · · · Yes · · · ·
files · · · · · · · · · · Yes · · ·
valueAsDate · · · · · Yes · · · · · · · ·
valueAsNumber · · · · · Yes Yes Yes · · · · · ·
list · Yes Yes Yes · Yes Yes Yes Yes · · · · ·
selectedOption · Yes Yes Yes† · Yes Yes Yes Yes · · · · ·
select() · Yes Yes · Yes · · · · · · · · ·
selectionStart · Yes Yes · Yes · · · · · · · · ·
selectionEnd · Yes Yes · Yes · · · · · · · · ·
setSelectionRange() · Yes Yes · Yes · · · · · · · · ·
stepDown() · · · · · Yes Yes Yes · · · · · ·
stepUp() · · · · · Yes Yes Yes · · · · · ·
Events
input event · Yes Yes Yes Yes Yes Yes Yes Yes · · · · ·
change event · Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes · · ·

† The dagger symbol (†) indicates that the feature only applies when the multiple attribute is not specified.

The value content attribute gives the default value of the input element.

The checked content attribute is a boolean attribute that gives the default checkedness of the input element.


The form attribute is used to explicitly associate the input element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

4.10.7.1 States of the type attribute
4.10.7.1.1 Hidden state

The input element represents a value that is not intended to be examined or manipulated by the user.

If the name attribute is present and has a value that is a case-sensitive match for the string "_charset_", then the element's value attribute must be omitted.

The value IDL attribute applies to this element and is in mode default.

The following content attributes must not be specified and do not apply to the element: accept, alt, autocomplete, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, required, size, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input and change events do not apply.

4.10.7.1.2 Text state and Search state

The input element represents a one line plain text edit control for the element's value.

The difference between the Text state and the Search state is primarily stylistic: on platforms where search fields are distinguished from regular text fields, the Search state might result in an appearance consistent with the platform's search fields rather than appearing like a regular text field.

The value attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, dirname, list, maxlength, pattern, placeholder, readonly, required, and size content attributes; list, selectedOption, selectionStart, selectionEnd, and value IDL attributes; select() and setSelectionRange() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, formaction, formenctype, formmethod, formnovalidate, formtarget, height, max, min, multiple, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, valueAsDate, and valueAsNumber IDL attributes; stepDown() and stepUp() methods.

4.10.7.1.3 Telephone state

The input element represents a control for editing a telephone number given in the element's value.

The value attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

Unlike the URL and E-mail types, the Telephone type does not enforce a particular syntax. This is intentional; in practice, telephone number fields tend to be free-form fields, because there are a wide variety of valid phone numbers. Systems that need to enforce a particular format are encouraged to use the pattern attribute or the setCustomValidity() method to hook into the client-side validation mechanism.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, maxlength, pattern, placeholder, readonly, required, and size content attributes; list, selectedOption, selectionStart, selectionEnd, and value IDL attributes; select() and setSelectionRange() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, max, min, multiple, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, valueAsDate, and valueAsNumber IDL attributes; stepDown() and stepUp() methods.

4.10.7.1.4 URL state

The input element represents a control for editing a single absolute URL given in the element's value.

The value attribute, if specified, must have a value that is a valid URL potentially surrounded by spaces that is also an absolute URL.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, maxlength, pattern, placeholder, readonly, required, and size content attributes; list, selectedOption, selectionStart, selectionEnd, and value IDL attributes; select() and setSelectionRange() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, max, min, multiple, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, valueAsDate, and valueAsNumber IDL attributes; stepDown() and stepUp() methods.

If a document contained the following markup:

<input type="url" name="location" list="urls">
<datalist id="urls">
 <option label="MIME: Format of Internet Message Bodies" value="http://tools.ietf.org/html/rfc2045">
 <option label="HTML 4.01 Specification" value="http://www.w3.org/TR/html4/">
 <option label="Form Controls" value="http://www.w3.org/TR/xforms/slice8.html#ui-commonelems-hint">
 <option label="Scalable Vector Graphics (SVG) 1.1 Specification" value="http://www.w3.org/TR/SVG/">
 <option label="Feature Sets - SVG 1.1 - 20030114" value="http://www.w3.org/TR/SVG/feature.html">
 <option label="The Single UNIX Specification, Version 3" value="http://www.unix-systems.org/version3/">
</datalist>

...and the user had typed "www.w3", and the user agent had also found that the user had visited http://www.w3.org/Consortium/#membership and http://www.w3.org/TR/XForms/ in the recent past, then the rendering might look like this:

A text box with an icon on the left followed by the text "www.w3" and a cursor, with a drop down button on the right hand side; with, below, a drop down box containing a list of six URIs on the left, with the first four having grayed out labels on the right; and a scroll bar to the right of the drow down box, indicating further values are available.

The first four URIs in this sample consist of the four URIs in the author-specified list that match the text the user has entered, sorted lexically. Note how the UA is using the knowledge that the values are URIs to allow the user to omit the scheme part and perform intelligent matching on the domain name.

The last two URIs (and probably many more, given the scrollbar's indications of more values being available) are the matches from the user agent's session history data. This data is not made available to the page DOM. In this particular case, the UA has no titles to provide for those values.

4.10.7.1.5 E-mail state

How the E-mail state operates depends on whether the multiple attribute is specified or not.

When the multiple attribute is not specified on the element

The input element represents a control for editing an e-mail address given in the element's value.

The value attribute, if specified, must have a value that is a single valid e-mail address.

When the multiple attribute is specified on the element

The input element represents a control for adding, removing, and editing the e-mail addresses given in the element's values.

The value attribute, if specified, must have a value that is a valid e-mail address list.

A valid e-mail address is a string that matches the ABNF production 1*( atext / "." ) "@" ldh-str 1*( "." ldh-str ) where atext is defined in RFC 5322 section 3.2.3, and ldh-str is defined in RFC 1034 section 3.5. [ABNF] [RFC5322] [RFC1034]

This requirement is a willful violation of RFC 5322, which defines a syntax for e-mail addresses that is simultaneously too strict (before the "@" character), too vague (after the "@" character), and too lax (allowing comments, white space characters, and quoted strings in manners unfamiliar to most users) to be of practical use here.

A valid e-mail address list is a set of comma-separated tokens, where each token is itself a valid e-mail address.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, maxlength, multiple, pattern, placeholder, readonly, required, and size content attributes; list and value IDL attributes.

The following common input element content attributes, IDL attributes, and methods apply to the element when the multiple attribute is not specified: selectedOption IDL attribute.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, max, min, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown() and stepUp() methods.

4.10.7.1.6 Password state

The input element represents a one line plain text edit control for the element's value. The user agent should obscure the value so that people other than the user cannot see it.

The value attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, maxlength, pattern, placeholder, readonly, required, and size content attributes; selectionStart, selectionEnd, and value IDL attributes; select(), and setSelectionRange() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, min, multiple, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, list, selectedOption, valueAsDate, and valueAsNumber IDL attributes; stepDown() and stepUp() methods.

4.10.7.1.7 Date and Time state

The input element represents a control for setting the element's value to a string representing a specific global date and time.

The format shown to the user is independent of the format used for form submission. Browsers are encouraged to use user interfaces that present dates and times according to the conventions of the user's preferred locale.

The value attribute, if specified, must have a value that is a valid global date and time string.

The min attribute, if specified, must have a value that is a valid global date and time string. The max attribute, if specified, must have a value that is a valid global date and time string.

The step attribute is expressed in seconds. The default step is 60 seconds.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, readonly, required, and step content attributes; list, value, valueAsDate, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, maxlength, multiple, pattern, placeholder, size, src, and width.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, and selectionEnd IDL attributes; select() and setSelectionRange() methods.

The following fragment shows part of a calendar application. A user can specify a date and time for a meeting (in his local time zone, probably, though the user agent can allow the user to change that), and since the submitted data includes the time-zone offset, the application can ensure that the meeting is shown at the correct time regardless of the time zones used by all the participants.

<fieldset>
 <legend>Add Meeting</legend>
 <p><label>Meeting name: <input type=text name="meeting.label"></label>
 <p><label>Meeting time: <input type=datetime name="meeting.start"></label>
</fieldset>

Had the application used the datetime-local type instead, the calendar application would have also had to explicitly determine which time zone the user intended.

4.10.7.1.8 Date state

The input element represents a control for setting the element's value to a string representing a specific date.

The format shown to the user is independent of the format used for form submission. Browsers are encouraged to use user interfaces that present dates according to the conventions of the user's preferred locale.

The value attribute, if specified, must have a value that is a valid date string.

The min attribute, if specified, must have a value that is a valid date string. The max attribute, if specified, must have a value that is a valid date string.

The step attribute is expressed in days. The default step is 1 day.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, readonly, required, and step content attributes; list, value, valueAsDate, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, maxlength, multiple, pattern, placeholder, size, src, and width.

The following IDL attributes and methods do not apply to the element: checked, selectionStart, and selectionEnd IDL attributes; select() and setSelectionRange() methods.

4.10.7.1.9 Month state

The input element represents a control for setting the element's value to a string representing a specific month.

The format shown to the user is independent of the format used for form submission. Browsers are encouraged to use user interfaces that present months according to the conventions of the user's preferred locale.

The value attribute, if specified, must have a value that is a valid month string.

The min attribute, if specified, must have a value that is a valid month string. The max attribute, if specified, must have a value that is a valid month string.

The step attribute is expressed in months. The default step is 1 month.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, readonly, required, and step content attributes; list, value, valueAsDate, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, maxlength, multiple, pattern, placeholder, size, src, and width.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, and selectionEnd IDL attributes; select() and setSelectionRange() methods.

4.10.7.1.10 Week state

The input element represents a control for setting the element's value to a string representing a specific week.

The format shown to the user is independent of the format used for form submission. Browsers are encouraged to use user interfaces that present weeks according to the conventions of the user's preferred locale.

The value attribute, if specified, must have a value that is a valid week string.

The min attribute, if specified, must have a value that is a valid week string. The max attribute, if specified, must have a value that is a valid week string.

The step attribute is expressed in weeks. The default step is 1 week.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, readonly, required, and step content attributes; list, value, valueAsDate, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, maxlength, multiple, pattern, placeholder, size, src, and width.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, and selectionEnd IDL attributes; select() and setSelectionRange() methods.

4.10.7.1.11 Time state

The input element represents a control for setting the element's value to a string representing a specific time.

The format shown to the user is independent of the format used for form submission. Browsers are encouraged to use user interfaces that present times according to the conventions of the user's preferred locale.

The value attribute, if specified, must have a value that is a valid time string.

The min attribute, if specified, must have a value that is a valid time string. The max attribute, if specified, must have a value that is a valid time string.

The step attribute is expressed in seconds. The default step is 60 seconds.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, readonly, required, and step content attributes; list, value, valueAsDate, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, maxlength, multiple, pattern, placeholder, size, src, and width.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, and selectionEnd IDL attributes; select() and setSelectionRange() methods.

4.10.7.1.12 Local Date and Time state

The input element represents a control for setting the element's value to a string representing a local date and time, with no time-zone offset information.

The format shown to the user is independent of the format used for form submission. Browsers are encouraged to use user interfaces that present dates and times according to the conventions of the user's preferred locale.

The value attribute, if specified, must have a value that is a valid local date and time string.

The min attribute, if specified, must have a value that is a valid local date and time string. The max attribute, if specified, must have a value that is a valid local date and time string.

The step attribute is expressed in seconds. The default step is 60 seconds.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, readonly, required, and step content attributes; list, value, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, maxlength, multiple, pattern, placeholder, size, src, and width.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, selectionEnd, and valueAsDate IDL attributes; select() and setSelectionRange() methods.

The following example shows part of a flight booking application. The application uses an input element with its type attribute set to datetime-local, and it then interprets the given date and time in the time zone of the selected airport.

<fieldset>
 <legend>Destination</legend>
 <p><label>Airport: <input type=text name=to list=airports></label></p>
 <p><label>Departure time: <input type=datetime-local name=totime step=3600></label></p>
</fieldset>
<datalist id=airports>
 <option value=ATL label="Atlanta">
 <option value=MEM label="Memphis">
 <option value=LHR label="London Heathrow">
 <option value=LAX label="Los Angeles">
 <option value=FRA label="Frankfurt">
</datalist>

If the application instead used the datetime type, then the user would have to work out the time-zone conversions himself, which is clearly not a good user experience!

4.10.7.1.13 Number state

The input element represents a control for setting the element's value to a string representing a number.

The value attribute, if specified, must have a value that is a valid floating point number.

The min attribute, if specified, must have a value that is a valid floating point number. The max attribute, if specified, must have a value that is a valid floating point number.

The default step is 1 (allowing only integers, unless the min attribute has a non-integer value).

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, readonly, required, and step content attributes; list, value, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, maxlength, multiple, pattern, placeholder, size, src, and width.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, selectionEnd, and valueAsDate IDL attributes; select() and setSelectionRange() methods.

4.10.7.1.14 Range state

The input element represents a control for setting the element's value to a string representing a number, but with the caveat that the exact value is not important, letting UAs provide a simpler interface than they do for the Number state.

The value attribute, if specified, must have a value that is a valid floating point number.

The min attribute, if specified, must have a value that is a valid floating point number. The default minimum is 0. The max attribute, if specified, must have a value that is a valid floating point number. The default maximum is 100.

The default value is the minimum plus half the difference between the minimum and the maximum, unless the maximum is less than the minimum, in which case the default value is the minimum.

The default step is 1 (allowing only integers, unless the min attribute has a non-integer value).

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete, list, max, min, and step content attributes; list, value, valueAsNumber, and selectedOption IDL attributes; stepDown() and stepUp() methods.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, maxlength, multiple, pattern, placeholder, readonly, required, size, src, and width.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, selectionEnd, and valueAsDate IDL attributes; select() and setSelectionRange() methods.

Here is an example of a range control using an autocomplete list with the list attribute. This could be useful if there are values along the full range of the control that are especially important, such as preconfigured light levels or typical speed limits in a range control used as a speed control. The following markup fragment:

<input type="range" min="-100" max="100" value="0" step="10" name="power" list="powers">
<datalist id="powers">
 <option value="0">
 <option value="-30">
 <option value="30">
 <option value="+50">
</datalist>

...with the following style sheet applied:

input { height: 75px; width: 49px; background: #D5CCBB; color: black; }

...might render as:

A vertical slider control whose primary color is black and whose background color is beige, with the slider having five tick marks, one long one at each extremity, and three short ones clustered around the midpoint.

Note how the UA determined the orientation of the control from the ratio of the style-sheet-specified height and width properties. The colors were similiarly derived from the style sheet. The tick marks, however, were derived from the markup. In particular, the step attribute has not affected the placement of tick marks, the UA deciding to only use the author-specified completion values and then adding longer tick marks at the extremes.

Note also how the invalid value +50 was completely ignored.

For another example, consider the following markup fragment:

<input name=x type=range min=100 max=700 step=9.09090909 value=509.090909>

A user agent could display in a variety of ways, for instance:

As a dial.

Or, alternatively, for instance:

As a long horizontal slider with tick marks.

The user agent could pick which one to display based on the dimensions given in the style sheet. This would allow it to maintain the same resolution for the tick marks, despite the differences in width.

4.10.7.1.15 Color state

The input element represents a color well control, for setting the element's value to a string representing a simple color.

The value attribute, if specified, must have a value that is a valid simple color.

The following common input element content attributes, IDL attributes, and methods apply to the element: autocomplete and list content attributes; list, value, and selectedOption IDL attributes.

The value IDL attribute is in mode value.

The input and change events apply.

The following content attributes must not be specified and do not apply to the element: accept, alt, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, maxlength, max, min, multiple, pattern, placeholder, readonly, required, size, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

4.10.7.1.16 Checkbox state

The input element represents a two-state control that represents the element's checkedness state. If the element's checkedness state is true, the control represents a positive selection, and if it is false, a negative selection. If the element's indeterminate IDL attribute is set to true, then the control's selection should be obscured as if the control was in a third, indeterminate, state.

The control is never a true tri-state control, even if the element's indeterminate IDL attribute is set to true. The indeterminate IDL attribute only gives the appearance of a third state.

input . indeterminate [ = value ]

When set, overrides the rendering of checkbox controls so that the current value is not visible.

The following common input element content attributes and IDL attributes apply to the element: checked, and required content attributes; checked and value IDL attributes.

The value IDL attribute is in mode default/on.

The change event applies.

The following content attributes must not be specified and do not apply to the element: accept, alt, autocomplete, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, size, src, step, and width.

The following IDL attributes and methods do not apply to the element: files, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input event does not apply.

4.10.7.1.17 Radio Button state

The input element represents a control that, when used in conjunction with other input elements, forms a radio button group in which only one control can have its checkedness state set to true. If the element's checkedness state is true, the control represents the selected control in the group, and if it is false, it indicates a control in the group that is not selected.

The radio button group that contains an input element a also contains all the other input elements b that fulfill all of the following conditions:

A document must not contain an input element whose radio button group contains only that element.

If none of the radio buttons in a radio button group are checked when they are inserted into the document, then they will all be initially unchecked in the interface, until such time as one of them is checked (either by the user or by script).

The following common input element content attributes and IDL attributes apply to the element: checked and required content attributes; checked and value IDL attributes.

The value IDL attribute is in mode default/on.

The change event applies.

The following content attributes must not be specified and do not apply to the element: accept, alt, autocomplete, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, size, src, step, and width.

The following IDL attributes and methods do not apply to the element: files, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input event does not apply.

4.10.7.1.18 File Upload state

The input element represents a list of selected files, each file consisting of a file name, a file type, and a file body (the contents of the file).


The accept attribute may be specified to provide user agents with a hint of what file types will be accepted.

If specified, the attribute must consist of a set of comma-separated tokens, each of which must be an ASCII case-insensitive match for one of the following:

The string audio/*
Indicates that sound files are accepted.
The string video/*
Indicates that video files are accepted.
The string image/*
Indicates that image files are accepted.
A valid MIME type with no parameters
Indicates that files of the specified type are accepted.

The tokens must not be ASCII case-insensitive matches for any of the other tokens (i.e. duplicates are not allowed).

For historical reasons, the value IDL attribute prefixes the filename with the string "C:\fakepath\". Some legacy user agents actually included the full path (which was a security vulnerability). As a result of this, obtaining the filename from the value IDL attribute in a backwards-compatible way is non-trivial. The following function extracts the filename in a suitably compatible manner:

function extractFilename(path) {
  var x;
  x = path.lastIndexOf('\\');
  if (x >= 0) // Windows-based path
    return path.substr(x+1);
  x = path.lastIndexOf('/');
  if (x >= 0) // Unix-based path
    return path.substr(x+1);
  return path; // just the filename
}

This can be used as follows:

<p><input type=file name=image onchange="updateFilename(this.value)"></p>
<p>The name of the file you picked is: <span id="filename">(none)</span></p>
<script>
 function updateFilename(path) {
   var name = extractFilename(path);
   document.getElementById('filename').textContent = name;
 }
</script>

The following common input element content attributes apply to the element:

The following common input element content attributes and IDL attributes apply to the element: accept, multiple, and required; files and value IDL attributes.

The value IDL attribute is in mode filename.

The change event applies.

The following content attributes must not be specified and do not apply to the element: alt, autocomplete, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, pattern, placeholder, readonly, size, src, step, and width.

The element's value attribute must be omitted.

The following IDL attributes and methods do not apply to the element: checked, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input event does not apply.

4.10.7.1.19 Submit Button state

The input element represents a button that, when activated, submits the form. The element is a button, specifically a submit button.

The formaction, formenctype, formmethod, formnovalidate, and formtarget attributes are attributes for form submission.

The formnovalidate attribute can be used to make submit buttons that do not trigger the constraint validation.

The following common input element content attributes and IDL attributes apply to the element: formaction, formenctype, formmethod, formnovalidate, and formtarget content attributes; value IDL attribute.

The value IDL attribute is in mode default.

The following content attributes must not be specified and do not apply to the element: accept, alt, autocomplete, checked, dirname, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, required, size, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input and change events do not apply.

4.10.7.1.20 Image Button state

The input element represents either an image from which a user can select a coordinate and submit the form, or alternatively a button from which the user can submit the form. The element is a button, specifically a submit button.


The image is given by the src attribute. The src attribute must be present, and must contain a valid non-empty URL potentially surrounded by spaces referencing a non-interactive, optionally animated, image resource that is neither paged nor scripted.

The alt attribute provides the textual label for the alternative button for users and user agents who cannot use the image. The alt attribute must also be present, and must contain a non-empty string.

The input element supports dimension attributes.

The formaction, formenctype, formmethod, formnovalidate, and formtarget attributes are attributes for form submission.

The following common input element content attributes and IDL attributes apply to the element: alt, formaction, formenctype, formmethod, formnovalidate, formtarget, height, src, and width content attributes; value IDL attribute.

The value IDL attribute is in mode default.

The following content attributes must not be specified and do not apply to the element: accept, autocomplete, checked, dirname, list, max, maxlength, min, multiple, pattern, placeholder, readonly, required, size, and step.

The element's value attribute must be omitted.

The following IDL attributes and methods do not apply to the element: checked, files, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input and change events do not apply.

Many aspects of this state's behavior are similar to the behavior of the img element. Readers are encouraged to read that section, where many of the same requirements are described in more detail.

4.10.7.1.21 Reset Button state

The input element represents a button that, when activated, resets the form. The element is a button.

The value IDL attribute applies to this element and is in mode default.

The following content attributes must not be specified and do not apply to the element: accept, alt, autocomplete, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, required, size, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input and change events do not apply.

4.10.7.1.22 Button state

The input element represents a button with no default behavior. A label for the button must be provided in the value attribute. The element is a button.

The value IDL attribute applies to this element and is in mode default.

The following content attributes must not be specified and do not apply to the element: accept, alt, autocomplete, checked, dirname, formaction, formenctype, formmethod, formnovalidate, formtarget, height, list, max, maxlength, min, multiple, pattern, placeholder, readonly, required, size, src, step, and width.

The following IDL attributes and methods do not apply to the element: checked, files, list, selectedOption, selectionStart, selectionEnd, valueAsDate, and valueAsNumber IDL attributes; select(), setSelectionRange(), stepDown(), and stepUp() methods.

The input and change events do not apply.

4.10.7.2 Common input element attributes
4.10.7.2.1 The autocomplete attribute

User agents sometimes have features for helping users fill forms in, for example prefilling the user's address based on earlier user input.

The autocomplete attribute is an enumerated attribute. The attribute has three states. The on keyword maps to the on state, and the off keyword maps to the off state. The attribute may also be omitted. The missing value default is the default state.

The off state indicates either that the control's input data is particularly sensitive (for example the activation code for a nuclear weapon); or that it is a value that will never be reused (for example a one-time-key for a bank login) and the user will therefore have to explicitly enter the data each time, instead of being able to rely on the UA to prefill the value for him; or that the document provides its own autocomplete mechanism and does not want the user agent to provide autocompletion values.

Conversely, the on state indicates that the value is not particularly sensitive and the user can expect to be able to rely on his user agent to remember values he has entered for that control.

The default state indicates that the user agent is to use the autocomplete attribute on the element's form owner instead. (By default, the autocomplete attribute of form elements is in the on state.)

Banks frequently do not want UAs to prefill login information:

<p><label>Account: <input type="text" name="ac" autocomplete="off"></label></p>
<p><label>PIN: <input type="password" name="pin" autocomplete="off"></label></p>
4.10.7.2.2 The dirname attribute

The dirname attribute, when it applies, is a form control dirname attribute.

In this example, a form contains a text field and a submission button:

<form action="addcomment.cgi" method=post>
 <p><label>Comment: <input type=text name="comment" dirname="comment.dir" required></label></p>
 <p><button name="mode" type=submit value="add">Post Comment</button></p>
</form>

When the user submits the form, the user agent includes three fields, one called "comment", one called "comment.dir", and one called "mode"; so if the user types "Hello", the submission body might be something like:

comment=Hello&comment.dir=ltr&mode=add

If the user manually switches to a right-to-left writing direction and enters "مرحبًا", the submission body might be something like:

comment=%D9%85%D8%B1%D8%AD%D8%A8%D9%8B%D8%A7&comment.dir=rtl&mode=add
4.10.7.2.3 The list attribute

The list attribute is used to identify an element that lists predefined options suggested to the user.

If present, its value must be the ID of a datalist element in the same document.

This URL field offers some suggestions.

<label>Homepage: <input name=hp type=url list=hpurls></label>
<datalist id=hpurls>
 <option value="http://www.google.com/" label="Google">
 <option value="http://www.reddit.com/" label="Reddit">
</datalist>

Other URLs from the user's history might show also; this is up to the user agent.

This example demonstrates how to design a form that uses the autocompletion list feature while still degrading usefully in legacy user agents.

If the autocompletion list is merely an aid, and is not important to the content, then simply using a datalist element with children option elements is enough. To prevent the values from being rendered in legacy user agents, they should be placed inside the value attribute instead of inline.

<p>
 <label>
  Enter a breed:
  <input type="text" name="breed" list="breeds">
  <datalist id="breeds">
   <option value="Abyssinian">
   <option value="Alpaca">
   <!-- ... -->
  </datalist>
 </label>
</p>

However, if the values need to be shown in legacy UAs, then fallback content can be placed inside the datalist element, as follows:

<p>
 <label>
  Enter a breed:
  <input type="text" name="breed" list="breeds">
 </label>
 <datalist id="breeds">
  <label>
   or select one from the list:
   <select name="breed">
    <option value=""> (none selected)
    <option>Abyssinian
    <option>Alpaca
    <!-- ... -->
   </select>
  </label>
 </datalist>
</p>

The fallback content will only be shown in UAs that don't support datalist. The options, on the other hand, will be detected by all UAs, even though they are not direct children of the datalist element.

Note that if an option element used in a datalist is selected, it will be selected by default by legacy UAs (because it affects the select), but it will not have any effect on the input element in UAs that support datalist.

4.10.7.2.4 The readonly attribute

The readonly attribute is a boolean attribute that controls whether or not the user can edit the form control.

In the following example, the existing product identifiers cannot be modified, but they are still displayed as part of the form, for consistency with the row representing a new product (where the identifier is not yet filled in).

<form action="products.cgi" method=post enctype="multipart/form-data">
 <table>
  <tr> <th> Product ID <th> Product name <th> Price <th> Action
  <tr>
   <td> <input readonly name="1.pid" value="H412">
   <td> <input required name="1.pname" value="Floor lamp Ulke">
   <td> $<input required type=number min=0 step=0.01 name="1.pprice" value="49.99">
   <td> <button formnovalidate name="action" value="delete:1">Delete</button>
  <tr>
   <td> <input readonly name="2.pid" value="FG28">
   <td> <input required name="2.pname" value="Table lamp Ulke">
   <td> $<input required type=number min=0 step=0.01 name="2.pprice" value="24.99">
   <td> <button formnovalidate name="action" value="delete:2">Delete</button>
  <tr>
   <td> <input required name="3.pid" value="" pattern="[A-Z0-9]+">
   <td> <input required name="3.pname" value="">
   <td> $<input required type=number min=0 step=0.01 name="3.pprice" value="">
   <td> <button formnovalidate name="action" value="delete:3">Delete</button>
 </table>
 <p> <button formnovalidate name="action" value="add">Add</button> </p>
 <p> <button name="action" value="update">Save</button> </p>
</form>
4.10.7.2.5 The size attribute

The size attribute gives the number of characters that, in a visual rendering, the user agent is to allow the user to see while editing the element's value.

The size attribute, if specified, must have a value that is a valid non-negative integer greater than zero.

4.10.7.2.6 The required attribute

The required attribute is a boolean attribute. When specified, the element is required.

The following form has two required fields, one for an e-mail address and one for a password. It also has a third field that is only considerd valid if the user types the same password in the password field and this third field.

<h1>Create new account</h1>
<form action="/newaccount" method=post>
 <p>
  <label for="username">E-mail address:</label>
  <input id="username" type=email required name=un>
 <p>
  <label for="password1">Password:</label>
  <input id="password1" type=password required name=up>
 <p>
  <label for="password2">Confirm password:</label>
  <input id="password2" type=password onforminput="setCustomValidity(value != password1.value ? 'Passwords do not match.' : '')">
 <p>
  <input type=submit value="Create account">
</form>
4.10.7.2.7 The multiple attribute

The multiple attribute is a boolean attribute that indicates whether the user is to be allowed to specify more than one value.

The following extract shows how an e-mail client's "Cc" field could accept multiple e-mail addresses.

<label>Cc: <input type=email multiple name=cc></label>

If the user had, amongst many friends in his user contacts database, two friends "Arthur Dent" (with address "art@example.net") and "Adam Josh" (with address "adamjosh@example.net"), then, after the user has typed "a", the user agent might suggest these two e-mail addresses to the user.

The page could also link in the user's contacts database from the site:

<label>Cc: <input type=email multiple name=cc list=contacts></label>
...
<datalist id="contacts">
 <option value="hedral@damowmow.com">
 <option value="pillar@example.com">
 <option value="astrophy@cute.example">
 <option value="astronomy@science.example.org">
</datalist>

Suppose the user had entered "bob@example.net" into this text field, and then started typing a second e-mail address starting with "a". The user agent might show both the two friends mentioned earlier, as well as the "astrophy" and "astronomy" values given in the datalist element.

The following extract shows how an e-mail client's "Attachments" field could accept multiple files for upload.

<label>Attachments: <input type=file multiple name=att></label>
4.10.7.2.8 The maxlength attribute

The maxlength attribute is a form control maxlength attribute.

If the input element has a maximum allowed value length, then the code-point length of the value of the element's value attribute must be equal to or less than the element's maximum allowed value length.

The following extract shows how a messaging client's text entry could be arbitrarily restricted to a fixed number of characters, thus forcing any conversation through this medium to be terse and discouraging intelligent discourse.

What are you doing? <input name=status maxlength=140>
4.10.7.2.9 The pattern attribute

The pattern attribute specifies a regular expression against which the control's value, or, when the multiple attribute applies and is set, the control's values, are to be checked.

If specified, the attribute's value must match the JavaScript Pattern production. [ECMA262]

When an input element has a pattern attribute specified, authors should include a title attribute to give a description of the pattern. User agents may use the contents of this attribute, if it is present, when informing the user that the pattern is not matched, or at any other suitable time, such as in a tooltip or read out by assistive technology when the control gains focus.

For example, the following snippet:

<label> Part number:
 <input pattern="[0-9][A-Z]{3}" name="part"
        title="A part number is a digit followed by three uppercase letters."/>
</label>

...could cause the UA to display an alert such as:

A part number is a digit followed by three uppercase letters.
You cannot submit this form when the field is incorrect.

When a control has a pattern attribute, the title attribute, if used, must describe the pattern. Additional information could also be included, so long as it assists the user in filling in the control. Otherwise, assistive technology would be impaired.

For instance, if the title attribute contained the caption of the control, assistive technology could end up saying something like The text you have entered does not match the required pattern. Birthday, which is not useful.

UAs may still show the title in non-error situations (for example, as a tooltip when hovering over the control), so authors should be careful not to word titles as if an error has necessarily occurred.

4.10.7.2.10 The min and max attributes

The min and max attributes indicate the allowed range of values for the element.

The max attribute's value (the maximum) must not be less than the min attribute's value (its minimum).

The following date control limits input to dates that are before the 1980s:

<input name=bday type=date max="1979-12-31">

The following number control limits input to whole numbers greater than zero:

<input name=quantity required type=number min=1 value=1>
4.10.7.2.11 The step attribute

The step attribute indicates the granularity that is expected (and required) of the value, by limiting the allowed values.

The step attribute, if specified, must either have a value that is a valid floating point number that parses to a number that is greater than zero, or must have a value that is an ASCII case-insensitive match for the string "any".

The following range control only accepts values in the range 0..1, and allows 256 steps in that range:

<input name=opacity type=range min=0 max=1 step=0.00392156863>

The following control allows any time in the day to be selected, with any accuracy (e.g. thousandth-of-a-second accuracy or more):

<input name=favtime type=time step=any>

Normally, time controls are limited to an accuracy of one minute.

4.10.7.2.12 The placeholder attribute

The placeholder attribute represents a short hint (a word or short phrase) intended to aid the user with data entry. A hint could be a sample value or a brief description of the expected format. The attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

For a longer hint or other advisory text, the title attribute is more appropriate.

The placeholder attribute should not be used as an alternative to a label.

Here is an example of a mail configuration user interface that uses the placeholder attribute:

<fieldset>
 <legend>Mail Account</legend>
 <p><label>Name: <input type="text" name="fullname" placeholder="John Ratzenberger"></label></p>
 <p><label>Address: <input type="email" name="address" placeholder="john@example.net"></label></p>
 <p><label>Password: <input type="password" name="password"></label></p>
 <p><label>Description: <input type="text" name="desc" placeholder="My Email Account"></label></p>
</fieldset>
4.10.7.3 Common input element APIs
input . value [ = value ]

Returns the current value of the form control.

Can be set, to change the value.

Throws an INVALID_STATE_ERR exception if it is set to any value other than the empty string when the control is a file upload control.

input . checked [ = value ]

Returns the current checkedness of the form control.

Can be set, to change the checkedness.

input . files

Returns a FileList object listing the selected files of the form control.

Returns null if the control isn't a file control.

input . valueAsDate [ = value ]

Returns a Date object representing the form control's value, if applicable; otherwise, returns null.

Can be set, to change the value.

Throws an INVALID_STATE_ERR exception if the control isn't date- or time-based.

input . valueAsNumber [ = value ]

Returns a number representing the form control's value, if applicable; otherwise, returns null.

Can be set, to change the value.

Throws an INVALID_STATE_ERR exception if the control is neither date- or time-based nor numeric.

input . stepUp( [ n ] )
input . stepDown( [ n ] )

Changes the form control's value by the value given in the step attribute, multiplied by n. The default value for n is 1.

Throws INVALID_STATE_ERR exception if the control is neither date- or time-based nor numeric, if the step attribute's value is "any", if the current value could not be parsed, or if stepping in the given direction by the given amount would take the value out of range.

input . list

Returns the datalist element indicated by the list attribute.

input . selectedOption

Returns the option element from the datalist element indicated by the list attribute that matches the form control's value.

4.10.8 The button element

Categories
Flow content.
Phrasing content.
Interactive content.
Listed, labelable, and submittable form-associated element.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content, but there must be no interactive content descendant.
Content attributes:
Global attributes
autofocus
disabled
form
formaction
formenctype
formmethod
formnovalidate
formtarget
name
type
value
DOM interface:
interface HTMLButtonElement : HTMLElement {
           attribute boolean autofocus;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute DOMString formAction;
           attribute DOMString formEnctype;
           attribute DOMString formMethod;
           attribute DOMString formNoValidate;
           attribute DOMString formTarget;
           attribute DOMString name;
           attribute DOMString type;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The button element represents a button.

The element is a button.

The type attribute controls the behavior of the button when it is activated. It is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.

Keyword State Brief description
submit Submit Button Submits the form.
reset Reset Button Resets the form.
button Button Does nothing.

The missing value default is the Submit Button state.

If the type attribute is in the Submit Button state, the element is specifically a submit button.

The form attribute is used to explicitly associate the button element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus. The formaction, formenctype, formmethod, formnovalidate, and formtarget attributes are attributes for form submission.

The formnovalidate attribute can be used to make submit buttons that do not trigger the constraint validation.

The formaction, formenctype, formmethod, formnovalidate, and formtarget must not be specified if the element's type attribute is not in the Submit Button state.

The value attribute gives the element's value for the purposes of form submission. The element's value is the value of the element's value attribute, if there is one, or the empty string otherwise.

A button (and its value) is only included in the form submission if the button itself was used to initiate the form submission.

The following button is labeled "Show hint" and pops up a dialog box when activated:

<button type=button
        onclick="alert('This 15-20 minute piece was composed by George Gershwin.')">
 Show hint
</button>

4.10.9 The select element

Categories
Flow content.
Phrasing content.
Interactive content.
Listed, labelable, submittable, and resettable form-associated element.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Zero or more option or optgroup elements.
Content attributes:
Global attributes
autofocus
disabled
form
multiple
name
required
size
DOM interface:
interface HTMLSelectElement : HTMLElement {
           attribute boolean autofocus;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute boolean multiple;
           attribute DOMString name;
           attribute boolean required;
           attribute unsigned long size;

  readonly attribute DOMString type;

  readonly attribute HTMLOptionsCollection options;
           attribute unsigned long length;
  getter any item(in unsigned long index);
  any namedItem(in DOMString name);
  void add(in HTMLElement element, in optional HTMLElement before);
  void add(in HTMLElement element, in long before);
  void remove(in long index);

  readonly attribute HTMLCollection selectedOptions;
           attribute long selectedIndex;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The select element represents a control for selecting amongst a set of options.

The multiple attribute is a boolean attribute. If the attribute is present, then the select element represents a control for selecting zero or more options from the list of options. If the attribute is absent, then the select element represents a control for selecting a single option from the list of options.

The size attribute gives the number of options to show to the user. The size attribute, if specified, must have a value that is a valid non-negative integer greater than zero. If the multiple attribute is present, then the size attribute's default value is 4. If the multiple attribute is absent, then the size attribute's default value is 1.

The list of options for a select element consists of all the option element children of the select element, and all the option element children of all the optgroup element children of the select element, in tree order.

The required attribute is a boolean attribute. When specified, the user will be required to select a value before submitting the form.

If a select element has a required attribute specified, does not have a multiple attribute specified, and has a display size of 1; and if the value of the first option element in the select element's list of options (if any) is the empty string, and that option is not disabled, and, finally, that option element's parent node is the select element (and not an optgroup element), then that option is the select element's placeholder label option.

The form attribute is used to explicitly associate the select element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

select . type

Returns "select-multiple" if the element has a multiple attribute, and "select-one" otherwise.

select . options

Returns an HTMLOptionsCollection of the list of options.

select . length [ = value ]

Returns the number of elements in the list of options.

When set to a smaller number, truncates the number of option elements in the select.

When set to a greater number, adds new blank option elements to the select.

element = select . item(index)
select[index]

Returns the item with index index from the list of options. The items are sorted in tree order.

Returns null if index is out of range.

element = select . namedItem(name)

Returns the item with ID or name name from the list of options.

If there are multiple matching items, then a NodeList object containing all those elements is returned.

Returns null if no element with that ID could be found.

select . add(element [, before ])

Inserts element before the node given by before.

The before argument can be a number, in which case element is inserted before the item with that number, or an element from the list of options, in which case element is inserted before that element.

If before is omitted, null, or a number out of range, then element will be added at the end of the list.

This method will throw a HIERARCHY_REQUEST_ERR exception if element is an ancestor of the element into which it is to be inserted. If element is not an option or optgroup element, then the method does nothing.

select . selectedOptions

Returns an HTMLCollection of the list of options that are selected.

select . selectedIndex [ = value ]

Returns the index of the first selected item, if any, or −1 if there is no selected item.

Can be set, to change the selection.

select . value [ = value ]

Returns the value of the first selected item, if any, or the empty string if there is no selected item.

Can be set, to change the selection.

The following example shows how a select element can be used to offer the user with a set of options from which the user can select a single option. The default option is preselected.

<p>
 <label for="unittype">Select unit type:</label>
 <select id="unittype" name="unittype">
  <option value="1"> Miner </option>
  <option value="2"> Puffer </option>
  <option value="3" selected> Snipey </option>
  <option value="4"> Max </option>
  <option value="5"> Firebot </option>
 </select>
</p>

Here, the user is offered a set of options from which he can select any number. By default, all five options are selected.

<p>
 <label for="allowedunits">Select unit types to enable on this map:</label>
 <select id="allowedunits" name="allowedunits" multiple>
  <option value="1" selected> Miner </option>
  <option value="2" selected> Puffer </option>
  <option value="3" selected> Snipey </option>
  <option value="4" selected> Max </option>
  <option value="5" selected> Firebot </option>
 </select>
</p>

4.10.10 The datalist element

Categories
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Either: phrasing content.
Or: Zero or more option elements.
Content attributes:
Global attributes
DOM interface:
interface HTMLDataListElement : HTMLElement {
  readonly attribute HTMLCollection options;
};

The datalist element represents a set of option elements that represent predefined options for other controls. The contents of the element represents fallback content for legacy user agents, intermixed with option elements that represent the predefined options. In the rendering, the datalist element represents nothing.

The datalist element is hooked up to an input element using the list attribute on the input element.

Each option element that is a descendant of the datalist element, that is not disabled, and whose value is a string that isn't the empty string, represents a suggestion. Each suggestion has a value and a label.

datalist . options

Returns an HTMLCollection of the options elements of the table.

4.10.11 The optgroup element

Categories
None.
Contexts in which this element can be used:
As a child of a select element.
Content model:
Zero or more option elements.
Content attributes:
Global attributes
disabled
label
DOM interface:
interface HTMLOptGroupElement : HTMLElement {
           attribute boolean disabled;
           attribute DOMString label;
};

The optgroup element represents a group of option elements with a common label.

The element's group of option elements consists of the option elements that are children of the optgroup element.

The disabled attribute is a boolean attribute and can be used to disable a group of option elements together.

The label attribute must be specified. Its value gives the name of the group, for the purposes of the user interface.

The following snippet shows how a set of lessons from three courses could be offered in a select drop-down widget:

<form action="courseselector.dll" method="get">
 <p>Which course would you like to watch today?
 <p><label>Course:
  <select name="c">
   <optgroup label="8.01 Physics I: Classical Mechanics">
    <option value="8.01.1">Lecture 01: Powers of Ten
    <option value="8.01.2">Lecture 02: 1D Kinematics
    <option value="8.01.3">Lecture 03: Vectors
   <optgroup label="8.02 Electricity and Magnestism">
    <option value="8.02.1">Lecture 01: What holds our world together?
    <option value="8.02.2">Lecture 02: Electric Field
    <option value="8.02.3">Lecture 03: Electric Flux
   <optgroup label="8.03 Physics III: Vibrations and Waves">
    <option value="8.03.1">Lecture 01: Periodic Phenomenon
    <option value="8.03.2">Lecture 02: Beats
    <option value="8.03.3">Lecture 03: Forced Oscillations with Damping
  </select>
 </label>
 <p><input type=submit value="▶ Play">
</form>

4.10.12 The option element

Categories
None.
Contexts in which this element can be used:
As a child of a select element.
As a child of a datalist element.
As a child of an optgroup element.
Content model:
Text.
Content attributes:
Global attributes
disabled
label
selected
value
DOM interface:
[NamedConstructor=Option(),
 NamedConstructor=Option(in DOMString text),
 NamedConstructor=Option(in DOMString text, in DOMString value),
 NamedConstructor=Option(in DOMString text, in DOMString value, in boolean defaultSelected),
 NamedConstructor=Option(in DOMString text, in DOMString value, in boolean defaultSelected, in boolean selected)]
interface HTMLOptionElement : HTMLElement {
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute DOMString label;
           attribute boolean defaultSelected;
           attribute boolean selected;
           attribute DOMString value;

           attribute DOMString text;
  readonly attribute long index;
};

The option element represents an option in a select element or as part of a list of suggestions in a datalist element.

In certain circumstances described in the definition of the select element, an option element can be a select element's placeholder label option. A placeholder label option does not represent an actual option, but instead represents a label for the select control.

The disabled attribute is a boolean attribute. An option element is disabled if its disabled attribute is present or if it is a child of an optgroup element whose disabled attribute is present.

The label attribute provides a label for element. The label of an option element is the value of the label attribute, if there is one, or the textContent of the element, if there isn't.

The value attribute provides a value for element. The value of an option element is the value of the value attribute, if there is one, or the textContent of the element, if there isn't.

The selected attribute is a boolean attribute. It represents the default selectedness of the element.

A select element whose multiple attribute is not specified must not have more than one descendant option element with its selected attribute set.

option . selected

Returns true if the element is selected, and false otherwise.

Can be set, to override the current state of the element.

option . index

Returns the index of the element in its select element's options list.

option . form

Returns the element's form element, if any, or null otherwise.

option . text

Same as textContent, except that spaces are collapsed.

option = new Option( [ text [, value [, defaultSelected [, selected ] ] ] ] )

Returns a new option element.

The text argument sets the contents of the element.

The value argument sets the value attribute.

The defaultSelected argument sets the selected attribute.

The selected argument sets whether or not the element is selected. If it is omitted, even if the defaultSelected argument is true, the element is not selected.

4.10.13 The textarea element

Categories
Flow content.
Phrasing content.
Interactive content.
Listed, labelable, submittable, and resettable form-associated element.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Text.
Content attributes:
Global attributes
autofocus
cols
disabled
dirname
form
maxlength
name
placeholder
readonly
required
rows
wrap
DOM interface:
interface HTMLTextAreaElement : HTMLElement {
           attribute boolean autofocus;
           attribute unsigned long cols;
           attribute boolean disabled;
           attribute DOMString dirName;
  readonly attribute HTMLFormElement form;
           attribute long maxLength;
           attribute DOMString name;
           attribute DOMString placeholder;
           attribute boolean readOnly;
           attribute boolean required;
           attribute unsigned long rows;
           attribute DOMString wrap;

  readonly attribute DOMString type;
           attribute DOMString defaultValue;
           attribute DOMString value;
  readonly attribute unsigned long textLength;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;

  void select();
           attribute unsigned long selectionStart;
           attribute unsigned long selectionEnd;
  void setSelectionRange(in unsigned long start, in unsigned long end);
};

The textarea element represents a multiline plain text edit control. The contents of the control represent the control's default value.

The readonly attribute is a boolean attribute used to control whether the text can be edited by the user or not.

The cols attribute specifies the expected maximum number of characters per line. If the cols attribute is specified, its value must be a valid non-negative integer greater than zero.

The rows attribute specifies the number of lines to show. If the rows attribute is specified, its value must be a valid non-negative integer greater than zero.

The wrap attribute is an enumerated attribute with two keywords and states: the soft keyword which maps to the Soft state, and the hard keyword which maps to the Hard state. The missing value default is the Soft state.

The Soft state indicates that the text in the textarea is not to be wrapped when it is submitted (though it can still be wrapped in the rendering).

The Hard state indicates that the text in the textarea is to have newlines added by the user agent so that the text is wrapped when it is submitted.

If the element's wrap attribute is in the Hard state, the cols attribute must be specified.

The maxlength attribute is a form control maxlength attribute controlled by the textarea element's dirty value flag.

If the textarea element has a maximum allowed value length, then the element's children must be such that the code-point length of the value of the element's textContent IDL attribute is equal to or less than the element's maximum allowed value length.

The required attribute is a boolean attribute. When specified, the user will be required to enter a value before submitting the form.

The placeholder attribute represents a hint (a word or short phrase) intended to aid the user with data entry. A hint could be a sample value or a brief description of the expected format. The attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

For a longer hint or other advisory text, the title attribute is more appropriate.

The placeholder attribute should not be used as an alternative to a label.

The dirname attribute is a form control dirname attribute.

The form attribute is used to explicitly associate the textarea element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

textarea . type

Returns the string "textarea".

textarea . value

Returns the current value of the element.

Can be set, to change the value.

Here is an example of a textarea being used for unrestricted free-form text input in a form:

<p>If you have any comments, please let us know: <textarea cols=80 name=comments></textarea></p>

To specify that a maximum length for the comments, one can use the maxlength attribute:

<p>If you have any short comments, please let us know: <textarea cols=80 name=comments maxlength=200></textarea></p>

To give a default value, text can be included inside the element:

<p>If you have any comments, please let us know: <textarea cols=80 name=comments>You rock!</textarea></p>

To have the browser submit the directionality of the element along with the value, the dirname attribute can be specified:

<p>If you have any comments, please let us know (you may use either English or Hebrew for your comments):
<textarea cols=80 name=comments dirname=comments.dir></textarea></p>

4.10.14 The keygen element

Categories
Flow content.
Phrasing content.
Interactive content.
Listed, labelable, submittable, and resettable form-associated element.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Empty.
Content attributes:
Global attributes
autofocus
challenge
disabled
form
keytype
name
DOM interface:
interface HTMLKeygenElement : HTMLElement {
           attribute boolean autofocus;
           attribute DOMString challenge;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute DOMString keytype;
           attribute DOMString name;

  readonly attribute DOMString type;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The keygen element represents a key pair generator control. When the control's form is submitted, the private key is stored in the local keystore, and the public key is packaged and sent to the server.

The challenge attribute may be specified. Its value will be packaged with the submitted key.

The keytype attribute is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states listed in the cell in the second column on the same row as the keyword. User agents are not required to support these values, and must only recognize values whose corresponding algorithms they support.

Keyword State
rsa RSA

The invalid value default state is the unknown state. The missing value default state is the RSA state, if it is supported, or the unknown state otherwise.

This specification does not specify what key types user agents are to support — it is possible for a user agent to not support any key types at all.

The form attribute is used to explicitly associate the keygen element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

keygen . type

Returns the string "keygen".

This specification does not specify how the private key generated is to be used. It is expected that after receiving the SignedPublicKeyAndChallenge (SPKAC) structure, the server will generate a client certificate and offer it back to the user for download; this certificate, once downloaded and stored in the key store along with the private key, can then be used to authenticate to services that use TLS and certificate authentication.

To generate a key pair, add the private key to the user's key store, and submit the public key to the server, markup such as the following can be used:

<form action="processkey.cgi" method="post" enctype="multipart/form-data">
 <p><keygen name="key"></p>
 <p><input type=submit value="Submit key..."></p>
</form>

The server will then receive a form submission with a packaged RSA public key as the value of "key". This can then be used for various purposes, such as generating a client certificate, as mentioned above.

4.10.15 The output element

Categories
Flow content.
Phrasing content.
Listed, labelable, and resettable form-associated element.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content.
Content attributes:
Global attributes
for
form
name
DOM interface:
interface HTMLOutputElement : HTMLElement {
  [PutForwards=value] readonly attribute DOMSettableTokenList htmlFor;
  readonly attribute HTMLFormElement form;
           attribute DOMString name;

  readonly attribute DOMString type;
           attribute DOMString defaultValue;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The output element represents the result of a calculation.

The for content attribute allows an explicit relationship to be made between the result of a calculation and the elements that represent the values that went into the calculation or that otherwise influenced the calculation. The for attribute, if specified, must contain a string consisting of an unordered set of unique space-separated tokens that are case-sensitive, each of which must have the value of an ID of an element in the same Document.

The form attribute is used to explicitly associate the output element with its form owner. The name attribute represents the element's name.

output . value [ = value ]

Returns the element's current value.

Can be set, to change the value.

output . defaultValue [ = value ]

Returns the element's current default value.

Can be set, to change the default value.

output . type

Returns the string "output".

A simple calculator could use output for its display of calculated results:

<form onsubmit="return false">
 <input name=a type=number step=any> +
 <input name=b type=number step=any> =
 <output onforminput="value = a.valueAsNumber + b.valueAsNumber"></output>
</form>

4.10.16 The progress element

ISSUE-96 (progress) blocks progress to Last Call

Categories
Flow content.
Phrasing content.
Labelable form-associated element.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content, but there must be no progress element descendants.
Content attributes:
Global attributes
value
max
form
DOM interface:
interface HTMLProgressElement : HTMLElement {
           attribute double value;
           attribute double max;
  readonly attribute double position;
  readonly attribute HTMLFormElement form;
  readonly attribute NodeList labels;
};

The progress element represents the completion progress of a task. The progress is either indeterminate, indicating that progress is being made but that it is not clear how much more work remains to be done before the task is complete (e.g. because the task is waiting for a remote host to respond), or the progress is a number in the range zero to a maximum, giving the fraction of work that has so far been completed.

There are two attributes that determine the current task completion represented by the element. The value attribute specifies how much of the task has been completed, and the max attribute specifies how much work the task requires in total. The units are arbitrary and not specified.

Authors are encouraged to also include the current value and the maximum value inline as text inside the element, so that the progress is made available to users of legacy user agents.

Here is a snippet of a Web application that shows the progress of some automated task:

<section>
 <h2>Task Progress</h2>
 <p>Progress: <progress id="p" max=100><span>0</span>%</progress></p>
 <script>
  var progressBar = document.getElementById('p');
  function updateProgress(newValue) {
    progressBar.value = newValue;
    progressBar.getElementsByTagName('span')[0].textContent = newValue;
  }
 </script>
</section>

(The updateProgress() method in this example would be called by some other code on the page to update the actual progress bar as the task progressed.)

The value and max attributes, when present, must have values that are valid floating point numbers. The value attribute, if present, must have a value equal to or greater than zero, and less than or equal to the value of the max attribute, if present, or 1.0, otherwise. The max attribute, if present, must have a value greater than zero.

The progress element is the wrong element to use for something that is just a gauge, as opposed to task progress. For instance, indicating disk space usage using progress would be inappropriate. Instead, the meter element is available for such use cases.

progress . position

For a determinate progress bar (one with known current and maximum values), returns the result of dividing the current value by the maximum value.

For an indeterminate progress bar, returns −1.

4.10.17 The meter element

Categories
Flow content.
Phrasing content.
Labelable form-associated element.
Contexts in which this element can be used:
Where phrasing content is expected.
Content model:
Phrasing content, but there must be no meter element descendants.
Content attributes:
Global attributes
value
min
max
low
high
optimum
form
DOM interface:
interface HTMLMeterElement : HTMLElement {
           attribute double value;
           attribute double min;
           attribute double max;
           attribute double low;
           attribute double high;
           attribute double optimum;
  readonly attribute HTMLFormElement form;
  readonly attribute NodeList labels;
};

The meter element represents a scalar measurement within a known range, or a fractional value; for example disk usage, the relevance of a query result, or the fraction of a voting population to have selected a particular candidate.

This is also known as a gauge.

The meter element should not be used to indicate progress (as in a progress bar). For that role, HTML provides a separate progress element.

The meter element also does not represent a scalar value of arbitrary range — for example, it would be wrong to use this to report a weight, or height, unless there is a known maximum value.

There are six attributes that determine the semantics of the gauge represented by the element.

The min attribute specifies the lower bound of the range, and the max attribute specifies the upper bound. The value attribute specifies the value to have the gauge indicate as the "measured" value.

The other three attributes can be used to segment the gauge's range into "low", "medium", and "high" parts, and to indicate which part of the gauge is the "optimum" part. The low attribute specifies the range that is considered to be the "low" part, and the high attribute specifies the range that is considered to be the "high" part. The optimum attribute gives the position that is "optimum"; if that is higher than the "high" value then this indicates that the higher the value, the better; if it's lower than the "low" mark then it indicates that lower values are better, and naturally if it is in between then it indicates that neither high nor low values are good.

The value attribute must be specified. The value, min, low, high, max, and optimum attributes, when present, must have values that are valid floating point numbers.

In addition, the attributes' values are further constrained:

Let value be the value attribute's number.

If the min attribute attribute is specified, then let minimum be that attribute's value; otherwise, let it be zero.

If the max attribute attribute is specified, then let maximum be that attribute's value; otherwise, let it be 1.0.

The following inequalities must hold, as applicable:

If no minimum or maximum is specified, then the range is assumed to be 0..1, and the value thus has to be within that range.

Authors are encouraged to include a textual representation of the gauge's state in the element's contents, for users of user agents that do not support the meter element.

The following examples show three gauges that would all be three-quarters full:

Storage space usage: <meter value=6 max=8>6 blocks used (out of 8 total)</meter>
Voter turnout: <meter value=0.75><img alt="75%" src="graph75.png"></meter>
Tickets sold: <meter min="0" max="100" value="75"></meter>

The following example is incorrect use of the element, because it doesn't give a range (and since the default maximum is 1, both of the gauges would end up looking maxed out):

<p>The grapefruit pie had a radius of <meter value=12>12cm</meter>
and a height of <meter value=2>2cm</meter>.</p> <!-- BAD! -->

Instead, one would either not include the meter element, or use the meter element with a defined range to give the dimensions in context compared to other pies:

<p>The grapefruit pie had a radius of 12cm and a height of
2cm.</p>
<dl>
 <dt>Radius: <dd> <meter min=0 max=20 value=12>12cm</meter>
 <dt>Height: <dd> <meter min=0 max=10 value=2>2cm</meter>
</dl>

There is no explicit way to specify units in the meter element, but the units may be specified in the title attribute in free-form text.

The example above could be extended to mention the units:

<dl>
 <dt>Radius: <dd> <meter min=0 max=20 value=12 title="centimeters">12cm</meter>
 <dt>Height: <dd> <meter min=0 max=10 value=2 title="centimeters">2cm</meter>
</dl>

The following markup:

<h3>Suggested groups</h3>
<menu type="toolbar">
 <a href="?cmd=hsg" onclick="hideSuggestedGroups()">Hide suggested groups</a>
</menu>
<ul>
 <li>
  <p><a href="/group/comp.infosystems.www.authoring.stylesheets/view">comp.infosystems.www.authoring.stylesheets</a> -
     <a href="/group/comp.infosystems.www.authoring.stylesheets/subscribe">join</a></p>
  <p>Group description: <strong>Layout/presentation on the WWW.</strong></p>
  <p><meter value="0.5">Moderate activity,</meter> Usenet, 618 subscribers</p>
 </li>
 <li>
  <p><a href="/group/netscape.public.mozilla.xpinstall/view">netscape.public.mozilla.xpinstall</a> -
     <a href="/group/netscape.public.mozilla.xpinstall/subscribe">join</a></p>
  <p>Group description: <strong>Mozilla XPInstall discussion.</strong></p>
  <p><meter value="0.25">Low activity,</meter> Usenet, 22 subscribers</p>
 </li>
 <li>
  <p><a href="/group/mozilla.dev.general/view">mozilla.dev.general</a> -
     <a href="/group/mozilla.dev.general/subscribe">join</a></p>
  <p><meter value="0.25">Low activity,</meter> Usenet, 66 subscribers</p>
 </li>
</ul>

Might be rendered as follows:

With the <meter> elements rendered as inline green bars of varying lengths.

User agents combine the value of the title attribute and the other attributes to provide context-sensitive help or inline text detailing the actual values.

For example, the following snippet:

<meter min=0 max=60 value=23.2 title=seconds></meter>

...might cause the user agent to display a gauge with a tooltip saying "Value: 23.2 out of 60." on one line and "seconds" on a second line.

The form attribute is used to explicitly associate the meter element with its form owner.

The following example shows how a gauge could fall back to localized or pretty-printed text.

<p>Disk usage: <meter min=0 value=170261928 max=233257824>170 261 928 bytes used
out of 233 257 824 bytes available</meter></p>

4.10.18 Association of controls and forms

A form-associated element can have a relationship with a form element, which is called the element's form owner. If a form-associated element is not associated with a form element, its form owner is said to be null.

A form-associated element is, by default, associated with its ancestor form element, but may have a form attribute specified to override this.

This feature allows authors to work around the lack of support for nested form elements.

If a form-associated element has a form attribute specified, then that attribute's value must be the ID of a form element in the element's owner Document.

element . form

Returns the element's form owner.

Returns null if there isn't one.

4.10.19 Attributes common to form controls

4.10.19.1 Naming form controls

The name content attribute gives the name of the form control, as used in form submission and in the form element's elements object. If the attribute is specified, its value must not be the empty string.

Any non-empty value for name is allowed, but the names "_charset_" and "isindex" are special:

isindex

This value, if used as the name of a Text control that is the only control in a form that is submitted using the application/x-www-form-urlencoded mechanism, causes the submission to only include the value of this control, with no name.

_charset_

This value, if used as the name of a Hidden control with no value attribute, is automatically given a value during submission consisting of the submission character encoding.

4.10.19.2 Enabling and disabling form controls

The disabled content attribute is a boolean attribute.

A form control is disabled if its disabled attribute is set, or if it is a descendant of a fieldset element whose disabled attribute is set and is not a descendant of that fieldset element's first legend element child, if any.

4.10.19.3 Autofocusing a form control

The autofocus content attribute allows the author to indicate that a control is to be focused as soon as the page is loaded, allowing the user to just start typing without having to manually focus the main control.

The autofocus attribute is a boolean attribute.

There must not be more than one element in the document with the autofocus attribute specified.

In the following snippet, the text control would be focused when the document was loaded.

<input maxlength="256" name="q" value="" autofocus>
<input type="submit" value="Search">
4.10.19.4 Limiting user input length

A form control maxlength attribute, controlled by a dirty value flag declares a limit on the number of characters a user can input.

If an element has its form control maxlength attribute specified, the attribute's value must be a valid non-negative integer. If the attribute is specified and applying the rules for parsing non-negative integers to its value results in a number, then that number is the element's maximum allowed value length. If the attribute is omitted or parsing its value results in an error, then there is no maximum allowed value length.

4.10.19.5 Form submission

Attributes for form submission can be specified both on form elements and on submit buttons (elements that represent buttons that submit forms, e.g. an input element whose type attribute is in the Submit Button state).

The attributes for form submission that may be specified on form elements are action, enctype, method, novalidate, and target.

The corresponding attributes for form submission that may be specified on submit buttons are formaction, formenctype, formmethod, formnovalidate, and formtarget. When omitted, they default to the values given on the corresponding attributes on the form element.


The action and formaction content attributes, if specified, must have a value that is a valid URL potentially surrounded by spaces.

The action of an element is the value of the element's formaction attribute, if the element is a submit button and has such an attribute, or the value of its form owner's action attribute, if it has one, or else the empty string.


The method and formmethod content attributes are enumerated attributes with the following keywords and states:

The missing value default for these attributes is the GET state.

The method of an element is one of those states. If the element is a submit button and has a formmethod attribute, then the element's method is that attribute's state; otherwise, it is the form owner's method attribute's state.


The enctype and formenctype content attributes are enumerated attributes with the following keywords and states:

The missing value default for these attributes is the application/x-www-form-urlencoded state.

The enctype of an element is one of those three states. If the element is a submit button and has a formenctype attribute, then the element's enctype is that attribute's state; otherwise, it is the form owner's enctype attribute's state.


The target and formtarget content attributes, if specified, must have values that are valid browsing context names or keywords.

The target of an element is the value of the element's formtarget attribute, if the element is a submit button and has such an attribute; or the value of its form owner's target attribute, if it has such an attribute; or, if the Document contains a base element with a target attribute, then the value of the target attribute of the first such base element; or, if there is no such element, the empty string.


The novalidate and formnovalidate content attributes are boolean attributes. If present, they indicate that the form is not to be validated during submission.

The no-validate state of an element is true if the element is a submit button and the element's formnovalidate attribute is present, or if the element's form owner's novalidate attribute is present, and false otherwise.

This attribute is useful to include "save" buttons on forms that have validation constraints, to allow users to save their progress even though they haven't fully entered the data in the form. The following example shows a simple form that has two required fields. There are three buttons: one to submit the form, which requires both fields to be filled in; one to save the form so that the user can come back and fill it in later; and one to cancel the form altogether.

<form action="editor.cgi" method="post">
 <p><label>Name: <input required name=fn></label></p>
 <p><label>Essay: <textarea required name=essay></textarea></label></p>
 <p><input type=submit name=submit value="Submit essay"></p>
 <p><input type=submit formnovalidate name=save value="Save essay"></p>
 <p><input type=submit formnovalidate name=cancel value="Cancel"></p>
</form>
4.10.19.6 Submitting element directionality

A form control dirname attribute on a form control element enables the submission of the directionality of the element, and gives the name of the field that contains this value during form submission. If such an attribute is specified, its value must not be the empty string.

4.10.20 APIs for the text field selections

The input and textarea elements define the following members in their DOM interfaces for handling their selection:

  void select();
           attribute unsigned long selectionStart;
           attribute unsigned long selectionEnd;
  void setSelectionRange(in unsigned long start, in unsigned long end);

These methods and attributes expose and control the selection of input and textarea text fields.

element . select()

Selects everything in the text field.

element . selectionStart [ = value ]

Returns the offset to the start of the selection.

Can be set, to change the start of the selection.

element . selectionEnd [ = value ]

Returns the offset to the end of the selection.

Can be set, to change the end of the selection.

element . setSelectionRange(start, end)

Changes the selection to cover the given substring.

To obtain the currently selected text, the following JavaScript suffices:

var selectionText = control.value.substring(control.selectionStart, control.selectionEnd);

...where control is the input or textarea element.

Characters with no visible rendering, such as U+200D ZERO WIDTH JOINER, still count as characters. Thus, for instance, the selection can include just an invisible character, and the text insertion cursor can be placed to one side or another of such a character.

4.10.21 Constraints

4.10.21.1 Definitions
4.10.21.2 The constraint validation API
element . willValidate

Returns true if the element will be validated when the form is submitted; false otherwise.

element . setCustomValidity(message)

Sets a custom error, so that the element would fail to validate. The given message is the message to be shown to the user when reporting the problem to the user.

If the argument is the empty string, clears the custom error.

element . validity . valueMissing

Returns true if the element has no value but is a required field; false otherwise.

element . validity . typeMismatch

Returns true if the element's value is not in the correct syntax; false otherwise.

element . validity . patternMismatch

Returns true if the element's value doesn't match the provided pattern; false otherwise.

element . validity . tooLong

Returns true if the element's value is longer than the provided maximum length; false otherwise.

element . validity . rangeUnderflow

Returns true if the element's value is lower than the provided minimum; false otherwise.

element . validity . rangeOverflow

Returns true if the element's value is higher than the provided maximum; false otherwise.

element . validity . stepMismatch

Returns true if the element's value doesn't fit the rules given by the step attribute; false otherwise.

element . validity . customError

Returns true if the element has a custom error; false otherwise.

element . validity . valid

Returns true if the element's value has no validity problems; false otherwise.

valid = element . checkValidity()

Returns true if the element's value has no validity problems; false otherwise. Fires an invalid event at the element in the latter case.

element . validationMessage

Returns the error message that would be shown to the user if the element was to be checked for validity.

In the following example, a script checks the value of a form control each time it is edited, and whenever it is not a valid value, uses the setCustomValidity() method to set an appropriate message.

<label>Feeling: <input name=f type="text" oninput="check(this)"></label>
<script>
 function check(input) {
   if (input.value == "good" ||
       input.value == "fine" ||
       input.value == "tired") {
     input.setCustomValidity('"' + input.value + '" is not a feeling.');
   } else {
     // input is fine -- reset the error message
     input.setCustomValidity('');
   }
 }
</script>
4.10.21.3 Security

Servers should not rely on client-side validation. Client-side validation can be intentionally bypassed by hostile users, and unintentionally bypassed by users of older user agents or automated tools that do not implement these features. The constraint validation features are only intended to improve the user experience, not to provide any kind of security mechanism.

4.10.22 Form submission

This section is non-normative.

When a form is submitted, the data in the form is converted into the structure specified by the enctype, and then sent to the destination specified by the action using the given method.

For example, take the following form:

<form action="/find.cgi" method=get>
 <input type=text name=t>
 <input type=search name=q>
 <input type=submit>
</form>

If the user types in "cats" in the first field and "fur" in the second, and then hits the submit button, then the user agent will load /find.cgi?t=cats&q=fur.

On the other hand, consider this form:

<form action="/find.cgi" method=post enctype="multipart/form-data">
 <input type=text name=t>
 <input type=search name=q>
 <input type=submit>
</form>

Given the same user input, the result on submission is quite different: the user agent instead does an HTTP POST to the given URL, with as the entity body something like the following text:

------kYFrd4jNJEgCervE
Content-Disposition: form-data; name="t"

cats
------kYFrd4jNJEgCervE
Content-Disposition: form-data; name="q"

fur
------kYFrd4jNJEgCervE--

4.11 Interactive elements

4.11.1 The details element

Categories
Flow content.
Sectioning root.
Interactive content.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
One summary element followed by flow content.
Content attributes:
Global attributes
open
DOM interface:
interface HTMLDetailsElement : HTMLElement {
           attribute boolean open;
};

The details element represents a disclosure widget from which the user can obtain additional information or controls.

The details element is not appropriate for footnotes. Please see the section on footnotes for details on how to mark up footnotes.

The summary element child of the element, if any, represents the summary or legend of the details.

The open content attribute is a boolean attribute. If present, it indicates that the details are to be shown to the user. If the attribute is absent, the details are not to be shown.

The following example shows the details element being used to hide technical details in a progress report.

<section class="progress window">
 <h1>Copying "Really Achieving Your Childhood Dreams"</h1>
 <details>
  <summary>Copying... <progress max="375505392" value="97543282"></progress> 25%</summary>
  <dl>
   <dt>Transfer rate:</dt> <dd>452KB/s</dd>
   <dt>Local filename:</dt> <dd>/home/rpausch/raycd.m4v</dd>
   <dt>Remote filename:</dt> <dd>/var/www/lectures/raycd.m4v</dd>
   <dt>Duration:</dt> <dd>01:16:27</dd>
   <dt>Color profile:</dt> <dd>SD (6-1-6)</dd>
   <dt>Dimensions:</dt> <dd>320×240</dd>
  </dl>
 </details>
</section>

The following shows how a details element can be used to hide some controls by default:

<details>
 <summary><label for=fn>Name & Extension:</label></summary>
 <p><input type=text id=fn name=fn value="Pillar Magazine.pdf">
 <p><label><input type=checkbox name=ext checked> Hide extension</label>
</details>

One could use this in conjuction with other details in a list to allow the user to collapse a set of fields down to a small set of headings, with the ability to open each one.

In these examples, the summary really just summarises what the controls can change, and not the actual values, which is less than ideal.

4.11.2 The summary element

Categories
None.
Contexts in which this element can be used:
As the first child of a details element.
Content model:
Phrasing content.
Content attributes:
Global attributes
DOM interface:
Uses HTMLElement.

The summary element represents a summary, caption, or legend for the rest of the contents of the summary element's parent details element.

4.11.3 The command element

Categories
Metadata content.
Flow content.
Phrasing content.
Contexts in which this element can be used:
Where metadata content is expected.
Where phrasing content is expected.
Content model:
Empty.
Content attributes:
Global attributes
type
label
icon
disabled
checked
radiogroup
Also, the title attribute has special semantics on this element.
DOM interface:
interface HTMLCommandElement : HTMLElement {
           attribute DOMString type;
           attribute DOMString label;
           attribute DOMString icon;
           attribute boolean disabled;
           attribute boolean checked;
           attribute DOMString radiogroup;
};

The command element represents a command that the user can invoke.

A command can be part of a context menu or toolbar, using the menu element, or can be put anywhere else in the page, to define a keyboard shortcut.

The type attribute indicates the kind of command: either a normal command with an associated action, or a state or option that can be toggled, or a selection of one item from a list of items.

The attribute is an enumerated attribute with three keywords and states. The "command" keyword maps to the Command state, the "checkbox" keyword maps to the Checkbox state, and the "radio" keyword maps to the Radio state. The missing value default is the Command state.

The Command state

The element represents a normal command with an associated action.

The Checkbox state

The element represents a state or option that can be toggled.

The Radio state

The element represents a selection of one item from a list of items.

The label attribute gives the name of the command, as shown to the user. The label attribute must be specified and must have a value that is not the empty string.

The title attribute gives a hint describing the command, which might be shown to the user to help him.

The icon attribute gives a picture that represents the command. If the attribute is specified, the attribute's value must contain a valid non-empty URL potentially surrounded by spaces.

The disabled attribute is a boolean attribute that, if present, indicates that the command is not available in the current state.

The distinction between disabled and hidden is subtle. A command would be disabled if, in the same context, it could be enabled if only certain aspects of the situation were changed. A command would be marked as hidden if, in that situation, the command will never be enabled. For example, in the context menu for a water faucet, the command "open" might be disabled if the faucet is already open, but the command "eat" would be marked hidden since the faucet could never be eaten.

The checked attribute is a boolean attribute that, if present, indicates that the command is selected. The attribute must be omitted unless the type attribute is in either the Checkbox state or the Radio state.

The radiogroup attribute gives the name of the group of commands that will be toggled when the command itself is toggled, for commands whose type attribute has the value "radio". The scope of the name is the child list of the parent element. The attribute must be omitted unless the type attribute is in the Radio state.

command elements are not rendered unless they form part of a menu.

Here is an example of a toolbar with three buttons that let the user toggle between left, center, and right alignment. One could imagine such a toolbar as part of a text editor. The toolbar also has a separator followed by another button labeled "Publish", though that button is disabled.

<menu type="toolbar">
 <command type="radio" radiogroup="alignment" checked="checked"
          label="Left" icon="icons/alL.png" onclick="setAlign('left')">
 <command type="radio" radiogroup="alignment"
          label="Center" icon="icons/alC.png" onclick="setAlign('center')">
 <command type="radio" radiogroup="alignment"
          label="Right" icon="icons/alR.png" onclick="setAlign('right')">
 <hr>
 <command type="command" disabled
          label="Publish" icon="icons/pub.png" onclick="publish()">
</menu>
Categories
Flow content.
If the element's type attribute is in the toolbar state: Interactive content.
Contexts in which this element can be used:
Where flow content is expected.
Content model:
Either: Zero or more li elements.
Or: Flow content.
Content attributes:
Global attributes
type
label
DOM interface:
interface HTMLMenuElement : HTMLElement {
           attribute DOMString type;
           attribute DOMString label;
};

The menu element represents a list of commands.

The type attribute is an enumerated attribute indicating the kind of menu being declared. The attribute has three states. The context keyword maps to the context menu state, in which the element is declaring a context menu. The toolbar keyword maps to the toolbar state, in which the element is declaring a toolbar. The attribute may also be omitted. The missing value default is the list state, which indicates that the element is merely a list of commands that is neither declaring a context menu nor defining a toolbar.

If a menu element's type attribute is in the context menu state, then the element represents the commands of a context menu, and the user can only interact with the commands if that context menu is activated.

If a menu element's type attribute is in the toolbar state, then the element represents a list of active commands that the user can immediately interact with.

If a menu element's type attribute is in the list state, then the element either represents an unordered list of items (each represented by an li element), each of which represents a command that the user can perform or activate, or, if the element has no li element children, flow content describing available commands.

The label attribute gives the label of the menu. It is used by user agents to display nested menus in the UI. For example, a context menu containing another menu would use the nested menu's label attribute for the submenu's menu label.

This section is non-normative.

The menu element is used to define context menus and toolbars.

For example, the following represents a toolbar with three menu buttons on it, each of which has a dropdown menu with a series of options:

<menu type="toolbar">
 <li>
  <menu label="File">
   <button type="button" onclick="fnew()">New...</button>
   <button type="button" onclick="fopen()">Open...</button>
   <button type="button" onclick="fsave()">Save</button>
   <button type="button" onclick="fsaveas()">Save as...</button>
  </menu>
 </li>
 <li>
  <menu label="Edit">
   <button type="button" onclick="ecopy()">Copy</button>
   <button type="button" onclick="ecut()">Cut</button>
   <button type="button" onclick="epaste()">Paste</button>
  </menu>
 </li>
 <li>
  <menu label="Help">
   <li><a href="help.html">Help</a></li>
   <li><a href="about.html">About</a></li>
  </menu>
 </li>
</menu>

In a supporting user agent, this might look like this:

A toolbar with three buttons, labeled 'File', 'Edit', and 'Help'; where if you select the 'Edit' button you get a drop-down menu with three more options, 'Copy', 'Cut', and 'Paste'.

In a legacy user agent, the above would look like a bulleted list with three items, the first of which has four buttons, the second of which has three, and the third of which has two nested bullet points with two items consisting of links.


The following implements a similar toolbar, with a single button whose values, when selected, redirect the user to Web sites.

<form action="redirect.cgi">
 <menu type="toolbar">
  <label for="goto">Go to...</label>
  <menu label="Go">
   <select id="goto">
    <option value="" selected="selected"> Select site: </option>
    <option value="http://www.apple.com/"> Apple </option>
    <option value="http://www.mozilla.org/"> Mozilla </option>
    <option value="http://www.opera.com/"> Opera </option>
   </select>
   <span><input type="submit" value="Go"></span>
  </menu>
 </menu>
</form>

The behavior in supporting user agents is similar to the example above, but here the legacy behavior consists of a single select element with a submit button. The submit button doesn't appear in the toolbar, because it is not a direct child of the menu element or of its li children.

4.11.4.2 Context menus

The contextmenu attribute gives the element's context menu. The value must be the ID of a menu element in the DOM.

Here is an example of a context menu for an input control:

<form name="npc">
 <label>Character name: <input name=char type=text contextmenu=namemenu required></label>
 <menu type=context id=namemenu>
  <command label="Pick random name" onclick="document.forms.npc.elements.char.value = getRandomName()">
  <command label="Prefill other fields based on name" onclick="prefillFields(document.forms.npc.elements.char.value)">
 </menu>
</form>

This adds two items to the control's context menu, one called "Pick random name", and one called "Prefill other fields based on name". They invoke scripts that are not shown in the example above.

4.11.5 Commands

A command is the abstraction behind menu items, buttons, and links.

Commands are defined to have the following facets:

Type
The kind of command: "command", meaning it is a normal command; "radio", meaning that triggering the command will, amongst other things, set the Checked State to true (and probably uncheck some other commands); or "checkbox", meaning that triggering the command will, amongst other things, toggle the value of the Checked State.
ID
The name of the command, for referring to the command from the markup or from script. If a command has no ID, it is an anonymous command.
Label
The name of the command as seen by the user.
Hint
A helpful or descriptive string that can be shown to the user.
Icon
An absolute URL identifying a graphical image that represents the action. A command might not have an Icon.
Access Key
A key combination selected by the user agent that triggers the command. A command might not have an Access Key.
Hidden State
Whether the command is hidden or not (basically, whether it should be shown in menus).
Disabled State
Whether the command is relevant and can be triggered or not.
Checked State
Whether the command is checked or not.
Action
The actual effect that triggering the command will have. This could be a scripted event handler, a URL to which to navigate, or a form submission.

These facets are exposed on elements using the command API:

element . commandType

Exposes the Type facet of the command.

element . id

Exposes the ID facet of the command.

element . label

Exposes the Label facet of the command.

element . title

Exposes the Hint facet of the command.

element . icon

Exposes the Icon facet of the command.

element . accessKeyLabel

Exposes the Access Key facet of the command.

element . hidden

Exposes the state of the element's hidden attribute, which is generally equivalent to the Hidden State facet of the command. For label and legend elements (used in conjunction with the accesskey attribute), the Hidden State facet is derived from another element (the one that the assigned access key will trigger), and cannot be directly accessed from the element.

element . disabled

Exposes the Disabled State facet of the command.

element . checked

Exposes the Checked State facet of the command.

element . click()

Triggers the Action of the command.


document . commands

Returns an HTMLCollection of the elements in the Document that define commands and have IDs.


User agents may expose the commands whose Hidden State facet is false (visible), e.g. in the user agent's menu bar. User agents are encouraged to do this especially for commands that have Access Keys, as a way to advertise those keys to the user.

4.12.1 Introduction

Links are a conceptual construct, created by a, area, and link elements, that represent a connection between two resources, one of which is the current Document. There are two kinds of links in HTML:

Links to external resources

These are links to resources that are to be used to augment the current document, generally automatically processed by the user agent.

Hyperlinks

These are links to other resources that are generally exposed to the user by the user agent so that the user can cause the user agent to navigate to those resources, e.g. to visit them in a browser or download them.

For link elements with an href attribute and a rel attribute, links must be created for the keywords of the rel attribute, as defined for those keywords in the link types section.

Similarly, for a and area elements with an href attribute and a rel attribute, links must be created for the keywords of the rel attribute as defined for those keywords in the link types section. Unlike link elements, however, a and area element with an href attribute that either do not have a rel attribute, or whose rel attribute has no keywords that are defined as specifying hyperlinks, must also create a hyperlink. This implied hyperlink has no special meaning (it has no link type) beyond linking the element's document to the resource given by the element's href attribute.

A hyperlink can have one or more hyperlink annotations that modify the processing semantics of that hyperlink.

The href attribute on a and area elements must have a value that is a valid URL potentially surrounded by spaces.

The href attribute on a and area elements is not required; when those elements do not have href attributes they do not create hyperlinks.

The target attribute, if present, must be a valid browsing context name or keyword. It gives the name of the browsing context that will be used.

The rel attribute on a and area elements controls what kinds of links the elements create. The attribue's value must be a set of space-separated tokens. The allowed keywords and their meanings are defined below.

The rel attribute has no default value. If the attribute is omitted or if none of the values in the attribute are recognized by the user agent, then the document has no particular relationship with the destination resource other than there being a hyperlink between the two.

The media attribute describes for which media the target document was designed. It is purely advisory. The value must be a valid media query. The default, if the media attribute is omitted, is "all".

The hreflang attribute on a and area elements that create hyperlinks, if present, gives the language of the linked resource. It is purely advisory. The value must be a valid BCP 47 language tag. [BCP47]

The type attribute, if present, gives the MIME type of the linked resource. It is purely advisory. The value must be a valid MIME type.

4.12.3 Link types

The following table summarizes the link types that are defined by this specification. This table is non-normative; the actual definitions for the link types are given in the next few sections.

In this section, the term referenced document refers to the resource identified by the element representing the link, and the term current document refers to the resource within which the element representing the link finds itself.

Except where otherwise specified, a keyword must not be specified more than once per rel attribute.

The link types that contain no U+003A COLON characters (:), including all those defined in this specification, are ASCII case-insensitive values.

Thus, rel="next" is the same as rel="NEXT".

Link type Effect on... Brief description
link a and area
alternate Hyperlink Hyperlink Gives alternate representations of the current document.
archives Hyperlink Hyperlink Provides a link to a collection of records, documents, or other materials of historical interest.
author Hyperlink Hyperlink Gives a link to the current document's author.
bookmark not allowed Hyperlink Gives the permalink for the nearest ancestor section.
external not allowed Hyperlink Indicates that the referenced document is not part of the same site as the current document.
first Hyperlink Hyperlink Indicates that the current document is a part of a series, and that the first document in the series is the referenced document.
help Hyperlink Hyperlink Provides a link to context-sensitive help.
icon External Resource not allowed Imports an icon to represent the current document.
index Hyperlink Hyperlink Gives a link to the document that provides a table of contents or index listing the current document.
last Hyperlink Hyperlink Indicates that the current document is a part of a series, and that the last document in the series is the referenced document.
license Hyperlink Hyperlink Indicates that the main content of the current document is covered by the copyright license described by the referenced document.
next Hyperlink Hyperlink Indicates that the current document is a part of a series, and that the next document in the series is the referenced document.
nofollow not allowed Annotation Indicates that the current document's original author or publisher does not endorse the referenced document.
noreferrer not allowed Annotation Requires that the user agent not send an HTTP Referer (sic) header if the user follows the hyperlink.
pingback External Resource not allowed Gives the address of the pingback server that handles pingbacks to the current document.
prefetch External Resource External Resource Specifies that the target resource should be preemptively cached.
Hyperlink Hyperlink Indicates that the current document is a part of a series, and that the previous document in the series is the referenced document.
search Hyperlink Hyperlink Gives a link to a resource that can be used to search through the current document and its related pages.
stylesheet External Resource not allowed Imports a stylesheet.
sidebar Hyperlink Hyperlink Specifies that the referenced document, if retrieved, is intended to be shown in the browser's sidebar (if it has one).
tag Hyperlink Hyperlink Gives a tag (identified by the given address) that applies to the current document.
up Hyperlink Hyperlink Provides a link to a document giving the context for the current document.
4.12.3.1 Link type "alternate"

The alternate keyword may be used with link, a, and area elements.

The meaning of this keyword depends on the values of the other attributes.

If the element is a link element and the rel attribute also contains the keyword stylesheet

The alternate keyword modifies the meaning of the stylesheet keyword in the way described for that keyword. The alternate keyword does not create a link of its own.

The alternate keyword is used with the type attribute set to the value application/rss+xml or the value application/atom+xml

The keyword creates a hyperlink referencing a syndication feed (though not necessarily syndicating exactly the same content as the current page).

Otherwise

The keyword creates a hyperlink referencing an alternate representation of the current document.

The nature of the referenced document is given by the media, hreflang, and type attributes.

If the alternate keyword is used with the media attribute, it indicates that the referenced document is intended for use with the media specified.

If the alternate keyword is used with the hreflang attribute, and that attribute's value differs from the root element's language, it indicates that the referenced document is a translation.

If the alternate keyword is used with the type attribute, it indicates that the referenced document is a reformulation of the current document in the specified format.

The media, hreflang, and type attributes can be combined when specified with the alternate keyword.

For example, the following link is a French translation that uses the PDF format:

<link rel=alternate type=application/pdf hreflang=fr href=manual-fr>

This relationship is transitive — that is, if a document links to two other documents with the link type "alternate", then, in addition to implying that those documents are alternative representations of the first document, it is also implying that those two documents are alternative representations of each other.

4.12.3.2 Link type "archives"

The archives keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The archives keyword indicates that the referenced document describes a collection of records, documents, or other materials of historical interest.

A blog's index page could link to an index of the blog's past posts with rel="archives".

The author keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

For a and area elements, the author keyword indicates that the referenced document provides further information about the author of the nearest article element ancestor of the element defining the hyperlink, if there is one, or of the page as a whole, otherwise.

For link elements, the author keyword indicates that the referenced document provides further information about the author for the page as a whole.

The "referenced document" can be, and often is, a mailto: URL giving the e-mail address of the author. [MAILTO]

The bookmark keyword may be used with a and area elements. This keyword creates a hyperlink.

The bookmark keyword gives a permalink for the nearest ancestor article element of the linking element in question, or of the section the linking element is most closely associated with, if there are no ancestor article elements.

The following snippet has three permalinks. A user agent could determine which permalink applies to which part of the spec by looking at where the permalinks are given.

 ...
 <body>
  <h1>Example of permalinks</h1>
  <div id="a">
   <h2>First example</h2>
   <p><a href="a.html" rel="bookmark">This</a> permalink applies to
   only the content from the first H2 to the second H2. The DIV isn't
   exactly that section, but it roughly corresponds to it.</p>
  </div>
  <h2>Second example</h2>
  <article id="b">
   <p><a href="b.html" rel="bookmark">This</a> permalink applies to
   the outer ARTICLE element (which could be, e.g., a blog post).</p>
   <article id="c">
    <p><a href="c.html" rel="bookmark">This</a> permalink applies to
    the inner ARTICLE element (which could be, e.g., a blog comment).</p>
   </article>
  </article>
 </body>
 ...

The external keyword may be used with a and area elements. This keyword creates a hyperlink.

The external keyword indicates that the link is leading to a document that is not part of the site that the current document forms a part of.

The help keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

For a and area elements, the help keyword indicates that the referenced document provides further help information for the parent of the element defining the hyperlink, and its children.

In the following example, the form control has associated context-sensitive help. The user agent could use this information, for example, displaying the referenced document if the user presses the "Help" or "F1" key.

 <p><label> Topic: <input name=topic> <a href="help/topic.html" rel="help">(Help)</a></label></p>

For link elements, the help keyword indicates that the referenced document provides help for the page as a whole.

4.12.3.7 Link type "icon"

The icon keyword may be used with link elements. This keyword creates an external resource link.

Icons could be auditory icons, visual icons, or other kinds of icons.

The sizes attribute gives the sizes of icons for visual media.

If specified, the attribute must have a value that is an unordered set of unique space-separated tokens, which are ASCII case-insensitive. The values must all be either an ASCII case-insensitive match for the string "any", or a value that consists of two valid non-negative integers that do not have a leading U+0030 DIGIT ZERO (0) character and that are separated by a single U+0078 LATIN SMALL LETTER X or U+0058 LATIN CAPITAL LETTER X character.

The keywords represent icon sizes.

The any keyword represents that the resource contains a scalable icon, e.g. as provided by an SVG image.

The keywords specified on the sizes attribute must not represent icon sizes that are not actually available in the linked resource.

The following snippet shows the top part of an application with several icons.

<!DOCTYPE HTML>
<html>
 <head>
  <title>lsForums — Inbox</title>
  <link rel=icon href=favicon.png sizes="16x16" type="image/png">
  <link rel=icon href=windows.ico sizes="32x32 48x48" type="image/vnd.microsoft.icon">
  <link rel=icon href=mac.icns sizes="128x128 512x512 8192x8192 32768x32768">
  <link rel=icon href=iphone.png sizes="57x57" type="image/png">
  <link rel=icon href=gnome.svg sizes="any" type="image/svg+xml">
  <link rel=stylesheet href=lsforums.css>
  <script src=lsforums.js></script>
  <meta name=application-name content="lsForums">
 </head>
 <body>
  ...

The license keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The license keyword indicates that the referenced document provides the copyright license terms under which the main content of the current document is provided.

This specification does not specify how to distinguish between the main content of a document and content that is not deemed to be part of that main content. The distinction should be made clear to the user.

Consider a photo sharing site. A page on that site might describe and show a photograph, and the page might be marked up as follows:

<!DOCTYPE HTML>
<html>
 <head>
  <title>Exampl Pictures: Kissat</title>
  <link rel="stylesheet" href="/style/default">
 </head>
 <body>
  <h1>Kissat</h1>
  <nav>
   <a href="../">Return to photo index</a>
  </nav>
  <figure>
   <img src="/pix/39627052_fd8dcd98b5.jpg">
   <figcaption>Kissat</figcaption>
  </figure>
  <p>One of them has six toes!</p>
  <p><small><a rel="license" href="http://www.opensource.org/licenses/mit-license.php">MIT Licensed</a></small></p>
  <footer>
   <a href="/">Home</a> | <a href="../">Photo index</a>
   <p><small>© copyright 2009 Exampl Pictures. All Rights Reserved.</small></p>
  </footer>
 </body>
</html>

In this case the license applies to just the photo (the main content of the document), not the whole document. In particular not the design of the page itself, which is covered by the copyright given at the bottom of the document. This could be made clearer in the styling (e.g. making the license link prominently positioned near the photograph, while having the page copyright in light small text at the foot of the page.

ISSUE-124 (rel-limits) blocks progress to Last Call

The nofollow keyword may be used with a and area elements. This keyword does not create a hyperlink, but annotates any other hyperlinks created by the element (the implied hyperlink, if no other keywords create one).

The nofollow keyword indicates that the link is not endorsed by the original author or publisher of the page, or that the link to the referenced document was included primarily because of a commercial relationship between people affiliated with the two pages.

ISSUE-124 (rel-limits) blocks progress to Last Call

The noreferrer keyword may be used with a and area elements. This keyword does not create a hyperlink, but annotates any other hyperlinks created by the element (the implied hyperlink, if no other keywords create one).

It indicates that no referrer information is to be leaked when following the link.

The pingback keyword may be used with link elements. This keyword creates an external resource link.

For the semantics of the pingback keyword, see the Pingback 1.0 specification. [PINGBACK]

The prefetch keyword may be used with link, a, and area elements. This keyword creates an external resource link.

The prefetch keyword indicates that preemptively fetching and caching the specified resource is likely to be beneficial, as it is highly likely that the user will require this resource.

There is no default type for resources given by the prefetch keyword.

The search keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The search keyword indicates that the referenced document provides an interface specifically for searching the document and its related resources.

OpenSearch description documents can be used with link elements and the search link type to enable user agents to autodiscover search interfaces. [OPENSEARCH]

The stylesheet keyword may be used with link elements. This keyword creates an external resource link that contributes to the styling processing model.

The specified resource is a resource that describes how to present the document. Exactly how the resource is to be processed depends on the actual type of the resource.

If the alternate keyword is also specified on the link element, then the link is an alternative stylesheet; in this case, the title attribute must be specified on the link element, with a non-empty value.

The default type for resources given by the stylesheet keyword is text/css.

The sidebar keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The sidebar keyword indicates that the referenced document, if retrieved, is intended to be shown in a secondary browsing context (if possible), instead of in the current browsing context.

A hyperlink with the sidebar keyword specified is a sidebar hyperlink.

The tag keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The tag keyword indicates that the tag that the referenced document represents applies to the current document.

Since it indicates that the tag applies to the current document, it would be inappropriate to use this keyword in the markup of a tag cloud, which lists the popular tag across a set of pages.

Some documents form part of a hierarchical structure of documents.

A hierarchical structure of documents is one where each document can have various subdocuments. The document of which a document is a subdocument is said to be the document's parent. A document with no parent forms the top of the hierarchy.

A document may be part of multiple hierarchies.

ISSUE-118 (broken-link-types) blocks progress to Last Call

The index keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The index keyword indicates that the document is part of a hierarchical structure, and that the link is leading to the document that is the top of the hierarchy. It conveys more information when used with the up keyword (q.v.).

ISSUE-119 (rel-repetition) blocks progress to Last Call

The up keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The up keyword indicates that the document is part of a hierarchical structure, and that the link is leading to a document that is an ancestor of the current document.

The up keyword may be repeated within a rel attribute to indicate the hierarchical distance from the current document to the referenced document. If it occurs only once, then the link is leading to the current document's parent; each additional occurrence of the keyword represents one further level. If the index keyword is also present, then the number of up keywords is the depth of the current page relative to the top of the hierarchy. Only one link is created for the set of one or more up keywords and, if present, the index keyword.

If the page is part of multiple hierarchies, then they should be described in different paragraphs.

This can be used to mark up a navigation style sometimes known as bread crumbs. In the following example, the current page can be reached via two paths.

<nav>
 <p>
  <a href="/" rel="index up up up">Main</a> >
  <a href="/products/" rel="up up">Products</a> >
  <a href="/products/dishwashers/" rel="up">Dishwashers</a> >
  <a>Second hand</a>
 </p>
 <p>
  <a href="/" rel="index up up">Main</a> >
  <a href="/second-hand/" rel="up">Second hand</a> >
  <a>Dishwashers</a>
 </p>
</nav>

The relList IDL attribute (e.g. on the a element) does not currently represent multiple up keywords (the interface hides duplicates).

Some documents form part of a sequence of documents.

A sequence of documents is one where each document can have a previous sibling and a next sibling. A document with no previous sibling is the start of its sequence, a document with no next sibling is the end of its sequence.

A document may be part of multiple sequences.

ISSUE-118 (broken-link-types) blocks progress to Last Call

The first keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The first keyword indicates that the document is part of a sequence, and that the link is leading to the document that is the first logical document in the sequence.

The last keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The last keyword indicates that the document is part of a sequence, and that the link is leading to the document that is the last logical document in the sequence.

The next keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The next keyword indicates that the document is part of a sequence, and that the link is leading to the document that is the next logical document in the sequence.

The prev keyword may be used with link, a, and area elements. This keyword creates a hyperlink.

The prev keyword indicates that the document is part of a sequence, and that the link is leading to the document that is the previous logical document in the sequence.

ISSUE-127 (link-type-flags) blocks progress to Last Call

Extensions to the predefined set of link types may be registered in the WHATWG Wiki RelExtensions page. [WHATWGWIKI]

Anyone is free to edit the WHATWG Wiki RelExtensions page at any time to add a type. Extension types must be specified with the following information:

Keyword

The actual value being defined. The value should not be confusingly similar to any other defined value (e.g. differing only in case).

If the value contains a U+003A COLON character (:), it must also be an absolute URL.

Effect on... link

One of the following:

Not allowed
The keyword must not be specified on link elements.
Hyperlink
The keyword may be specified on a link element; it creates a hyperlink.
External Resource
The keyword may be specified on a link element; it creates an external resource link.
Effect on... a and area

One of the following:

Not allowed
The keyword must not be specified on a and area elements.
Hyperlink
The keyword may be specified on a and area elements; it creates a hyperlink.
External Resource
The keyword may be specified on a a and area elements; it creates an external resource link.
Hyperlink Annotation
The keyword may be specified on a a and area elements; it annotates other hyperlinks created by the element.
Brief description

A short non-normative description of what the keyword's meaning is.

Specification

A link to a more detailed description of the keyword's semantics and requirements. It could be another page on the Wiki, or a link to an external page.

Synonyms

A list of other keyword values that have exactly the same processing requirements. Authors should not use the values defined to be synonyms, they are only intended to allow user agents to support legacy content. Anyone may remove synonyms that are not used in practice; only names that need to be processed as synonyms for compatibility with legacy content are to be registered in this way.

Status

One of the following:

Proposed
The keyword has not received wide peer review and approval. Someone has proposed it and is, or soon will be, using it.
Ratified
The keyword has received wide peer review and approval. It has a specification that unambiguously defines how to handle pages that use the keyword, including when they use it in incorrect ways.
Discontinued
The keyword has received wide peer review and it has been found wanting. Existing pages are using this keyword, but new pages should avoid it. The "brief description" and "specification" entries will give details of what authors should use instead, if anything.

If a keyword is found to be redundant with existing values, it should be removed and listed as a synonym for the existing value.

If a keyword is registered in the "proposed" state for a period of a month or more without being used or specified, then it may be removed from the registry.

If a keyword is added with the "proposed" status and found to be redundant with existing values, it should be removed and listed as a synonym for the existing value. If a keyword is added with the "proposed" status and found to be harmful, then it should be changed to "discontinued" status.

Anyone can change the status at any time, but should only do so in accordance with the definitions above.

Types defined as extensions in the WHATWG Wiki RelExtensions page with the status "proposed" or "ratified" may be used with the rel attribute on link, a, and area elements in accordance to the "Effect on..." field. [WHATWGWIKI]

4.13 Common idioms without dedicated elements

ISSUE-89 (idioms) blocks progress to Last Call

4.13.1 The main part of the content

The main content of a page — not including headers and footers, navigation links, sidebars, advertisements, and so forth — can be marked up in a variety of ways, depending on the needs of the author.

The simplest solution is to not mark up the main content at all, and just leave it as implicit. Another way to think of this is that the body elements marks up the main content of the page, and the bits that aren't main content are excluded through the use of more appropriate elements like aside and nav.

Here is a short Web page marked up along this minimalistic school of thought. The main content is highlighted. Notice how all the other content in the body is marked up with elements to indicate that it's not part of the main content, in this case header, nav, and footer.

<!DOCTYPE HTML>
<html>
 <head>
  <title> My Toys </title>
 </head>
 <body>
  <header>
   <h1>My toys</h1>
  </header>
  <nav>
   <p><a href="/">Home</a></p>
   <p><a href="/contact">Contact</a></p>
  </nav>
  <p>I really like my chained book and my telephone. I'm not such a
  fan of my big ball.</p>
  <p>Another toy I like is my mirror.</p>
  <footer>
   <p>© copyright 2010 by the boy</p>
  </footer>
 </body>
</html>

If the main content is an independent unit of content that one could imagine syndicating independently, then the article element would be appropriate to mark up the main content of the document.

The document in the previous example is here recast as a blog post:

<!DOCTYPE HTML>
<html>
 <head>
  <title> The Boy Blog: My Toys </title>
 </head>
 <body>
  <header>
   <h1>The Boy Blog</h1>
  </header>
  <nav>
   <p><a href="/">Home</a></p>
   <p><a href="/contact">Contact</a></p>
  </nav>
  <article>
   <header>
    <h1>My toys</h1>
    <p>Published <time pubdate datetime="2010-08-04">August 4th</time></p>
   </header>
   <p>I really like my chained book and my telephone. I'm not such a
   fan of my big ball.</p>
   <p>Another toy I like is my mirror.</p>
  </article>
  <footer>
   <p>© copyright 2010 by the boy</p>
  </footer>
 </body>
</html>

If the main content is not an independent unit of content so much as a section of a larger work, for instance a chapter, then the section element would be appropriate to mark up the main content of the document.

Here is the same document, case as a chapter in an online book:

<!DOCTYPE HTML>
<html>
 <head>
  <title> Chapter 2: My Toys — The Book of the Boy </title>
 </head>
 <body>
  <header>
   <h1>Chapter 2: My Toys</h1>
  </header>
  <nav>
   <p><a href="/">Front Page</a></p>
   <p><a href="/toc">Table of Contents</a></p>
   <p><a href="/c1">Chapter 1</a> — <a href="/c3">Chapter 3</a></p>
  </nav>
  <section>
   <p>I really like my chained book and my telephone. I'm not such a
   fan of my big ball.</p>
   <p>Another toy I like is my mirror.</p>
  </section>
  <footer>
   <p>© copyright 2010 by the boy</p>
  </footer>
 </body>
</html>

If neither article nor section would be appropriate, but the main content still needs an explicit element, for example for styling purposes, then the div element can be used.

This is the same as the original example, but using div for the main content instead of leaving it implied:

<!DOCTYPE HTML>
<html>
 <head>
  <title> My Toys </title>
  <style>
   body > div { background: navy; color: yellow; }
  </style>
 </head>
 <body>
  <header>
   <h1>My toys</h1>
  </header>
  <nav>
   <p><a href="/">Home</a></p>
   <p><a href="/contact">Contact</a></p>
  </nav>
  <div>
   <p>I really like my chained book and my telephone. I'm not such a
   fan of my big ball.</p>
   <p>Another toy I like is my mirror.</p>
  </div>
  <footer>
   <p>© copyright 2010 by the boy</p>
  </footer>
 </body>
</html>

4.13.2 Tag clouds

This specification does not define any markup specifically for marking up lists of keywords that apply to a group of pages (also known as tag clouds). In general, authors are encouraged to either mark up such lists using ul elements with explicit inline counts that are then hidden and turned into a presentational effect using a style sheet, or to use SVG.

Here, three tags are included in a short tag cloud:

<style>
@media screen, print, handheld, tv {
  /* should be ignored by non-visual browsers */
  .tag-cloud > li > span { display: none; }
  .tag-cloud > li { display: inline; }
  .tag-cloud-1 { font-size: 0.7em; }
  .tag-cloud-2 { font-size: 0.9em; }
  .tag-cloud-3 { font-size: 1.1em; }
  .tag-cloud-4 { font-size: 1.3em; }
  .tag-cloud-5 { font-size: 1.5em; }
}
</style>
...
<ul class="tag-cloud">
 <li class="tag-cloud-4"><a title="28 instances" href="/t/apple">apple</a> <span>(popular)</span>
 <li class="tag-cloud-2"><a title="6 instances"  href="/t/kiwi">kiwi</a> <span>(rare)</span>
 <li class="tag-cloud-5"><a title="41 instances" href="/t/pear">pear</a> <span>(very popular)</span>
</ul>

The actual frequency of each tag is given using the title attribute. A CSS style sheet is provided to convert the markup into a cloud of differently-sized words, but for user agents that do not support CSS or are not visual, the markup contains annotations like "(popular)" or "(rare)" to categorize the various tags by frequency, thus enabling all users to benefit from the information.

The ul element is used (rather than ol) because the order is not particularly important: while the list is in fact ordered alphabetically, it would convey the same information if ordered by, say, the length of the tag.

The tag rel-keyword is not used on these a elements because they do not represent tags that apply to the page itself; they are just part of an index listing the tags themselves.

4.13.3 Conversations

This specification does not define a specific element for marking up conversations, meeting minutes, chat transcripts, dialogues in screenplays, instant message logs, and other situations where different players take turns in discourse.

Instead, authors are encouraged to mark up conversations using p elements and punctuation. Authors who need to mark the speaker for styling purposes are encouraged to use span or b. Paragraphs with their text wrapped in the i element can be used for marking up stage directions.

This example demonstrates this using an extract from Abbot and Costello's famous sketch, Who's on first:

<p> Costello: Look, you gotta first baseman?
<p> Abbott: Certainly.
<p> Costello: Who's playing first?
<p> Abbott: That's right.
<p> Costello becomes exasperated.
<p> Costello: When you pay off the first baseman every month, who gets the money?
<p> Abbott: Every dollar of it.

The following extract shows how an IM conversation log could be marked up.

<p> <time>14:22</time> <b>egof</b> I'm not that nerdy, I've only seen 30% of the star trek episodes
<p> <time>14:23</time> <b>kaj</b> if you know what percentage of the star trek episodes you have seen, you are inarguably nerdy
<p> <time>14:23</time> <b>egof</b> it's unarguably
<p> <time>14:23</time> <i>* kaj blinks</i>
<p> <time>14:24</time> <b>kaj</b> you are not helping your case

4.13.4 Footnotes

HTML does not have a dedicated mechanism for marking up footnotes. Here are the recommended alternatives.


For short inline annotations, the title attribute should be used.

In this example, two parts of a dialogue are annotated with footnote-like content using the title attribute.

<p> <b>Customer</b>: Hello! I wish to register a complaint. Hello. Miss?
<p> <b>Shopkeeper</b>: <span title="Colloquial pronunciation of 'What do you'"
>Watcha</span> mean, miss?
<p> <b>Customer</b>: Uh, I'm sorry, I have a cold. I wish to make a complaint.
<p> <b>Shopkeeper</b>: Sorry, <span title="This is, of course, a lie.">we're
closing for lunch</span>.

For longer annotations, the a element should be used, pointing to an element later in the document. The convention is that the contents of the link be a number in square brackets.

In this example, a footnote in the dialogue links to a paragraph below the dialogue. The paragraph then reciprocally links back to the dialogue, allowing the user to return to the location of the footnote.

<p> Announcer: Number 16: The <i>hand</i>.
<p> Interviewer: Good evening. I have with me in the studio tonight
Mr Norman St John Polevaulter, who for the past few years has been
contradicting people. Mr Polevaulter, why <em>do</em> you
contradict people?
<p> Norman: I don't. <sup><a href="#fn1" id="r1">[1]</a></sup>
<p> Interviewer: You told me you did!
...
<section>
 <p id="fn1"><a href="#r1">[1]</a> This is, naturally, a lie,
 but paradoxically if it were true he could not say so without
 contradicting the interviewer and thus making it false.</p>
</section>

For side notes, longer annotations that apply to entire sections of the text rather than just specific words or sentences, the aside element should be used.

In this example, a sidebar is given after a dialogue, giving it some context.

<p> <span class="speaker">Customer</span>: I will not buy this record, it is scratched.
<p> <span class="speaker">Shopkeeper</span>: I'm sorry?
<p> <span class="speaker">Customer</span>: I will not buy this record, it is scratched.
<p> <span class="speaker">Shopkeeper</span>: No no no, this's'a tobacconist's.
<aside>
 <p>In 1970, the British Empire lay in ruins, and foreign
 nationalists frequented the streets — many of them Hungarians
 (not the streets — the foreign nationals). Sadly, Alexander
 Yalt has been publishing incompetently-written phrase books.
</aside>

For figures or tables, footnotes can be included in the relevant figcaption or caption element, or in surrounding prose.

In this example, a table has cells with footnotes that are given in prose. A figure element is used to give a single legend to the combination of the table and its footnotes.

<figure>
 <figcaption>Table 1. Alternative activities for knights.</figcaption>
 <table>
  <tr>
   <th> Activity
   <th> Location
   <th> Cost
  <tr>
   <td> Dance
   <td> Wherever possible
   <td> £0<sup><a href="#fn1">1</a></sup>
  <tr>
   <td> Routines, chorus scenes<sup><a href="#fn2">2</a></sup>
   <td> Undisclosed
   <td> Undisclosed
  <tr>
   <td> Dining<sup><a href="#fn3">3</a></sup>
   <td> Camelot
   <td> Cost of ham, jam, and spam<sup><a href="#fn4">4</a></sup>
 </table>
 <p id="fn1">1. Assumed.</p>
 <p id="fn2">2. Footwork impeccable.</p>
 <p id="fn3">3. Quality described as "well".</p>
 <p id="fn4">4. A lot.</p>
</figure>

5 Loading Web pages

5.1 Browsing contexts

A browsing context is an environment in which Document objects are presented to the user.

A tab or window in a Web browser typically contains a browsing context, as does an iframe.

Each browsing context has a corresponding WindowProxy object.

A browsing context has a session history, which lists the Document objects that that browsing context has presented, is presenting, or will present. At any time, one Document in each browsing context is designated the active document.

Each Document is associated with a Window object. A browsing context's WindowProxy object forwards everything to the browsing context's active document's Window object.

In general, there is a 1-to-1 mapping from the Window object to the Document object. In one particular case, a Window can be reused for the presentation of a second Document in the same browsing context, such that the mapping is then 2-to-1. This occurs when a browsing context is navigated from the initial about:blank Document to another, with replacement enabled.

A Document does not necessarily have a browsing context associated with it. In particular, data mining tools are likely to never instantiate browsing contexts.


A browsing context can have a creator browsing context, the browsing context that was responsible for its creation. If a browsing context has a parent browsing context, then that is its creator browsing context. Otherwise, if the browsing context has an opener browsing context, then that is its creator browsing context. Otherwise, the browsing context has no creator browsing context.

If a browsing context A has a creator browsing context, then the Document that was the active document of that creator browsing context at the time A was created is the creator Document.

5.1.1 Nested browsing contexts

Certain elements (for example, iframe elements) can instantiate further browsing contexts. These are called nested browsing contexts. If a browsing context P has a Documents D with an element E that nests another browsing context C inside it, then C is said to be nested through D, and E is said to be the browsing context container of C. If the browsing context container element E is in the Document D, then P is said to be the parent browsing context of C and C is said to be a child browsing context of P. Otherwise, the nested browsing context C has no parent browsing context.

A browsing context A is said to be an ancestor of a browsing context B if there exists a browsing context A' that is a child browsing context of A and that is itself an ancestor of B, or if there is a browsing context P that is a child browsing context of A and that is the parent browsing context of B.

A browsing context that is not a nested browsing context has no parent browsing context, and is the top-level browsing context of all the browsing contexts for which it is an ancestor browsing context.

The transitive closure of parent browsing contexts for a nested browsing context gives the list of ancestor browsing contexts.

The list of the descendant browsing contexts of a Document d is the (ordered) list returned by the following algorithm:

  1. Let list be an empty list.

  2. For each child browsing context of d that is nested through an element that is in the Document d, in the tree order of the elements nesting those browsing contexts, run these substeps:

    1. Append that child browsing context to the list list.

    2. Append the list of the descendant browsing contexts of the active document of that child browsing context to the list list.

  3. Return the constructed list.

A Document is said to be fully active when it is the active document of its browsing context, and either its browsing context is a top-level browsing context, or it has a parent browsing context and the Document through which it is nested is itself fully active.

Because they are nested through an element, child browsing contexts are always tied to a specific Document in their parent browsing context. User agents must not allow the user to interact with child browsing contexts of elements that are in Documents that are not themselves fully active.

A nested browsing context can have a seamless browsing context flag set, if it is embedded through an iframe element with a seamless attribute.

A nested browsing context can in some cases be taken out of its parent browsing context (e.g. if an iframe element is removed from its Document). In such a situation, the nested browsing context has no parent browsing context, but it still has the same browsing context container and is still nested through that element's Document. Such a nested browsing context is not a top-level browsing context, and cannot contain Documents that are fully active. Furthermore, if a browsing context container (such as an iframe) is moved to another Document, then the parent browsing context of its nested browsing context will change.

window . top

Returns the WindowProxy for the top-level browsing context.

window . parent

Returns the WindowProxy for the parent browsing context.

window . frameElement

Returns the Element for the browsing context container.

Returns null if there isn't one.

Throws a SECURITY_ERR exception in cross-origin situations.

5.1.2 Auxiliary browsing contexts

It is possible to create new browsing contexts that are related to a top-level browsing context without being nested through an element. Such browsing contexts are called auxiliary browsing contexts. Auxiliary browsing contexts are always top-level browsing contexts.

An auxiliary browsing context has an opener browsing context, which is the browsing context from which the auxiliary browsing context was created.

The opener IDL attribute on the Window object must return the WindowProxy object of the browsing context from which the current browsing context was created (its opener browsing context), if there is one and it is still available.

5.1.3 Secondary browsing contexts

User agents may support secondary browsing contexts, which are browsing contexts that form part of the user agent's interface, apart from the main content area.

5.1.4 Browsing context names

Browsing contexts can have a browsing context name. By default, a browsing context has no name (its name is not set).

A valid browsing context name is any string with at least one character that does not start with a U+005F LOW LINE character. (Names starting with an underscore are reserved for special keywords.)

A valid browsing context name or keyword is any string that is either a valid browsing context name or that is an ASCII case-insensitive match for one of: _blank, _self, _parent, or _top.

5.2 The Window object

[ReplaceableNamedProperties] 
interface Window {
  // the current browsing context
  readonly attribute WindowProxy window;
  readonly attribute WindowProxy self;
  readonly attribute Document document;
           attribute DOMString name; 
  [PutForwards=href] readonly attribute Location location;
  readonly attribute History history;
  [Replaceable] readonly attribute BarProp locationbar;
  [Replaceable] readonly attribute BarProp menubar;
  [Replaceable] readonly attribute BarProp personalbar;
  [Replaceable] readonly attribute BarProp scrollbars;
  [Replaceable] readonly attribute BarProp statusbar;
  [Replaceable] readonly attribute BarProp toolbar;
  void close();
  void stop();
  void focus();
  void blur();

  // other browsing contexts
  [Replaceable] readonly attribute WindowProxy frames;
  [Replaceable] readonly attribute unsigned long length;
  readonly attribute WindowProxy top;
  [Replaceable] readonly attribute WindowProxy opener;
  readonly attribute WindowProxy parent;
  readonly attribute Element frameElement;
  WindowProxy open(in optional DOMString url, in optional DOMString target, in optional DOMString features, in optional DOMString replace);
  getter WindowProxy (in unsigned long index);
  getter any (in DOMString name);

  // the user agent
  readonly attribute Navigator navigator; 
  readonly attribute ApplicationCache applicationCache;

  // user prompts
  void alert(in DOMString message);
  boolean confirm(in DOMString message);
  DOMString prompt(in DOMString message, in optional DOMString default);
  void print();
  any showModalDialog(in DOMString url, in optional any argument);

  // event handler IDL attributes
           attribute Function onabort;
           attribute Function onafterprint;
           attribute Function onbeforeprint;
           attribute Function onbeforeunload;
           attribute Function onblur;
           attribute Function oncanplay;
           attribute Function oncanplaythrough;
           attribute Function onchange;
           attribute Function onclick;
           attribute Function oncontextmenu;

           attribute Function oncuechange;

           attribute Function ondblclick;
           attribute Function ondrag;
           attribute Function ondragend;
           attribute Function ondragenter;
           attribute Function ondragleave;
           attribute Function ondragover;
           attribute Function ondragstart;
           attribute Function ondrop;
           attribute Function ondurationchange;
           attribute Function onemptied;
           attribute Function onended;
           attribute Function onerror;
           attribute Function onfocus;
           attribute Function onformchange;
           attribute Function onforminput;
           attribute Function onhashchange;
           attribute Function oninput;
           attribute Function oninvalid;
           attribute Function onkeydown;
           attribute Function onkeypress;
           attribute Function onkeyup;
           attribute Function onload;
           attribute Function onloadeddata;
           attribute Function onloadedmetadata;
           attribute Function onloadstart;
           attribute Function onmessage;
           attribute Function onmousedown;
           attribute Function onmousemove;
           attribute Function onmouseout;
           attribute Function onmouseover;
           attribute Function onmouseup;
           attribute Function onmousewheel;
           attribute Function onoffline;
           attribute Function ononline;
           attribute Function onpause;
           attribute Function onplay;
           attribute Function onplaying;
           attribute Function onpagehide;
           attribute Function onpageshow;
           attribute Function onpopstate;
           attribute Function onprogress;
           attribute Function onratechange;
           attribute Function onreadystatechange;
           attribute Function onredo;
           attribute Function onreset;
           attribute Function onresize;
           attribute Function onscroll;
           attribute Function onseeked;
           attribute Function onseeking;
           attribute Function onselect;
           attribute Function onshow;
           attribute Function onstalled;
           attribute Function onstorage;
           attribute Function onsubmit;
           attribute Function onsuspend;
           attribute Function ontimeupdate;
           attribute Function onundo;
           attribute Function onunload;
           attribute Function onvolumechange;
           attribute Function onwaiting;
};
Window implements EventTarget;
window . window
window . frames
window . self

These attributes all return window.

window . document

Returns the active document.

document . defaultView

Returns the Window object of the active document.

5.2.1 APIs for creating and navigating browsing contexts by name

window = window . open( [ url [, target [, features [, replace ] ] ] ] )

Opens a window to show url (defaults to about:blank), and returns it. The target argument gives the name of the new window. If a window exists with that name already, it is reused. The replace attribute, if true, means that whatever page is currently open in that window will be removed from the window's session history. The features argument is ignored.

window . name [ = value ]

Returns the name of the window.

Can be set, to change the name.

window . close()

Closes the window.

window . stop()

Cancels the document load.

5.2.2 Accessing other browsing contexts

window . length

Returns the number of child browsing contexts.

window[index]

Returns the indicated child browsing context.

5.2.3 Named access on the Window object

window[name]

Returns the indicated element or collection of elements.

5.2.4 Browser interface elements

To allow Web pages to integrate with Web browsers, certain Web browser interface elements are exposed in a limited way to scripts in Web pages.

Each interface element is represented by a BarProp object:

interface BarProp {
           attribute boolean visible;
};
window . locationbar . visible

Returns true if the location bar is visible; otherwise, returns false.

window . menubar . visible

Returns true if the menu bar is visible; otherwise, returns false.

window . personalbar . visible

Returns true if the personal bar is visible; otherwise, returns false.

window . scrollbars . visible

Returns true if the scroll bars are visible; otherwise, returns false.

window . statusbar . visible

Returns true if the status bar is visible; otherwise, returns false.

window . toolbar . visible

Returns true if the toolbar is visible; otherwise, returns false.

5.3 Origin

The origin of a resource and the effective script origin of a resource are both either opaque identifiers or tuples consisting of a scheme component, a host component, a port component, and optionally extra data.

The extra data could include the certificate of the site when using encrypted connections, to ensure that if the site's secure certificate changes, the origin is considered to change as well.

5.3.1 Relaxing the same-origin restriction

document . domain [ = domain ]

Returns the current domain used for security checks.

Can be set to a value that removes subdomains, to change the effective script origin to allow pages on other subdomains of the same domain (if they do the same thing) to access each other.

The domain attribute is used to enable pages on different hosts of a domain to access each others' DOMs.

Do not use the document.domain attribute when using shared hosting. If an untrusted third party is able to host an HTTP server at the same IP address but on a different port, then the same-origin protection that normally protects two different sites on the same host will fail, as the ports are ignored when comparing origins after the document.domain attribute has been used.

5.4 Session history and navigation

5.4.1 The session history of browsing contexts

The sequence of Documents in a browsing context is its session history.

History objects provide a representation of the pages in the session history of browsing contexts. Each browsing context, including nested browsing contexts, has a distinct session history.

Each Document object in a browsing context's session history is associated with a unique instance of the History object, although they all must model the same underlying session history.

History objects represent their browsing context's session history as a flat list of session history entries. Each session history entry consists of either a URL or a state object, or both.

Titles associated with session history entries need not have any relation with the current title of the Document. The title of a session history entry is intended to explain the state of the document at that point, so that the user can navigate the document's history.

URLs without associated state objects are added to the session history as the user (or script) navigates from page to page.

A state object is an object representing a user interface state.

Pages can add state objects between their entry in the session history and the next ("forward") entry. These are then returned to the script when the user (or script) goes back in the history, thus enabling authors to use the "navigation" metaphor even in one-page applications.

State objects are intended to be used for two main purposes: first, storing a preparsed description of the state in the URL so that in the simple case an author doesn't have to do the parsing (though one would still need the parsing for handling URLs passed around by users, so it's only a minor optimization), and second, so that the author can store state that one wouldn't store in the URL because it only applies to the current Document instance and it would have to be reconstructed if a new Document were opened.

An example of the latter would be something like keeping track of the precise coordinate from which a popup div was made to animate, so that if the user goes back, it can be made to animate to the same location. Or alternatively, it could be used to keep a pointer into a cache of data that would be fetched from the server based on the information in the URL, so that when going back and forward, the information doesn't have to be fetched again.


At any point, one of the entries in the session history is the current entry. This is the entry representing the active document of the browsing context. The current entry is usually an entry for the location of the Document. However, it can also be one of the entries for state objects added to the history by that document.

An entry with persisted user state is one that also has user-agent defined state. This specification does not specify what kind of state can be stored.

For example, some user agents might want to persist the scroll position, or the values of form controls.

Entries that consist of state objects share the same Document as the entry for the page that was active when they were added.

Contiguous entries that differ just by fragment identifier also share the same Document.

All entries that share the same Document (and that are therefore merely different states of one particular document) are contiguous by definition.

5.4.2 The History interface

interface History {
  readonly attribute long length;
  void go(in optional long delta);
  void back();
  void forward();
  void pushState(in any data, in DOMString title, in optional DOMString url);
  void replaceState(in any data, in DOMString title, in optional DOMString url);
};
window . history . length

Returns the number of entries in the joint session history.

window . history . go( [ delta ] )

Goes back or forward the specified number of steps in the joint session history.

A zero delta will reload the current page.

If the delta is out of range, does nothing.

window . history . back()

Goes back one step in the joint session history.

If there is no previous page, does nothing.

window . history . forward()

Goes forward one step in the joint session history.

If there is no next page, does nothing.

window . history . pushState(data, title [, url ] )

Pushes the given data onto the session history, with the given title, and, if provided, the given URL.

window . history . replaceState(data, title [, url ] )

Updates the current entry in the session history to have the given data, title, and, if provided, URL.

The joint session history of a History object is the union of all the session histories of all browsing contexts of all the fully active Document objects that share the History object's top-level browsing context, with all the entries that are current entries in their respective session histories removed except for the current entry of the joint session history.

The current entry of the joint session history is the entry that most recently became a current entry in its session history.

Entries in the joint session history are ordered chronologically by the time they were added to their respective session histories. (Since all these browsing contexts by definition share an event loop, there is always a well-defined sequential order in which their session histories had their entries added.) Each entry has an index; the earliest entry has index 0, and the subsequent entries are numbered with consecutively increasing integers (1, 2, 3, etc).

Consider a game where the user can navigate along a line, such that the user is always at some coordinate, and such that the user can bookmark the page corresponding to a particular coordinate, to return to it later.

A static page implementing the x=5 position in such a game could look like the following:

<!DOCTYPE HTML>
<!-- this is http://example.com/line?x=5 -->
<title>Line Game - 5</title>
<p>You are at coordinate 5 on the line.</p>
<p>
 <a href="?x=6">Advance to 6</a> or
 <a href="?x=4">retreat to 4</a>?
</p>

The problem with such a system is that each time the user clicks, the whole page has to be reloaded. Here instead is another way of doing it, using script:

<!DOCTYPE HTML>
<!-- this starts off as http://example.com/line?x=5 -->
<title>Line Game - 5</title>
<p>You are at coordinate <span id="coord">5</span> on the line.</p>
<p>
 <a href="?x=6" onclick="go(1); return false;">Advance to 6</a> or
 <a href="?x=4" onclick="go(-1); return false;">retreat to 4</a>?
</p>
<script>
 var currentPage = 5; // prefilled by server
 function go(d) {
   setupPage(currentPage + d);
   history.pushState(currentPage, document.title, '?x=' + currentPage);
 }
 onpopstate = function(event) {
   setupPage(event.state);
 }
 function setupPage(page) {
   currentPage = page;
   document.title = 'Line Game - ' + currentPage;
   document.getElementById('coord').textContent = currentPage;
   document.links[0].href = '?x=' + (currentPage+1);
   document.links[0].textContent = 'Advance to ' + (currentPage+1);
   document.links[1].href = '?x=' + (currentPage-1);
   document.links[1].textContent = 'retreat to ' + (currentPage-1);
 }
</script>

In systems without script, this still works like the previous example. However, users that do have script support can now navigate much faster, since there is no network access for the same experience. Furthermore, contrary to the experience the user would have with just a naïve script-based approach, bookmarking and navigating the session history still work.

In the example above, the data argument to the pushState() method is the same information as would be sent to the server, but in a more convenient form, so that the script doesn't have to parse the URL each time the user navigates.

Applications might not use the same title for a session history entry as the value of the document's title element at that time. For example, here is a simple page that shows a block in the title element. Clearly, when navigating backwards to a previous state the user does not go back in time, and therefore it would be inappropriate to put the time in the session history title.

<!DOCTYPE HTML>
<TITLE>Line</TITLE>
<SCRIPT>
 setInterval(function () { document.title = 'Line - ' + new Date(); }, 1000);
 var i = 1;
 function inc() {
   set(i+1);
   history.pushState(i, 'Line - ' + i);
 }
 function set(newI) {
   i = newI;
   document.forms.F.I.value = newI;
 }
</SCRIPT>
<BODY ONPOPSTATE="recover(event.state)">
<FORM NAME=F>
State: <OUTPUT NAME=I>1</OUTPUT> <INPUT VALUE="Increment" TYPE=BUTTON ONCLICK="inc()">
</FORM>

5.4.3 The Location interface

Each Document object in a browsing context's session history is associated with a unique instance of a Location object.

document . location [ = value ]
window . location [ = value ]

Returns a Location object with the current page's location.

Can be set, to navigate to another page.

Location objects provide a representation of their document's current address, and allow the current entry of the browsing context's session history to be changed, by adding or replacing entries in the history object.

interface Location {
  stringifier attribute DOMString href;
  void assign(in DOMString url);
  void replace(in DOMString url);
  void reload();

  // URL decomposition IDL attributes 
           attribute DOMString protocol;
           attribute DOMString host;
           attribute DOMString hostname;
           attribute DOMString port;
           attribute DOMString pathname;
           attribute DOMString search;
           attribute DOMString hash;

  // resolving relative URLs
  DOMString resolveURL(in DOMString url);
};
location . href [ = value ]

Returns the current page's location.

Can be set, to navigate to another page.

location . assign(url)

Navigates to the given page.

location . replace(url)

Removes the current page from the session history and navigates to the given page.

location . reload()

Reloads the current page.

url = location . resolveURL(url)

Resolves the given relative URL to an absolute URL.

The Location interface also has the complement of URL decomposition IDL attributes, protocol, host, port, hostname, pathname, search, and hash.

5.5 Browsing the Web

5.5.1 History traversal

The popstate event is fired in certain cases when navigating to a session history entry.

interface PopStateEvent : Event {
  readonly attribute any state;
  void initPopStateEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in any stateArg);
};
event . state

Returns a copy of the information that was provided to pushState() or replaceState().


The hashchange event is fired when navigating to a session history entry whose URL differs from that of the previous one only in the fragment identifier.

interface HashChangeEvent : Event {
  readonly attribute DOMString oldURL;
  readonly attribute DOMString newURL;
  void initHashChangeEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in DOMString oldURLArg, in DOMString newURLArg);
};
event . oldURL

Returns the URL of the session history entry that was previously current.

event . newURL

Returns the URL of the session history entry that is now current.


The pageshow event is fired when traversing to a session history entry.

The pagehide event is fired when traversing from a session history entry.

interface PageTransitionEvent : Event {
  readonly attribute boolean persisted;
  void initPageTransitionEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in boolean persistedArg);
};
event . persisted

Returns false if the page is newly being loaded (and the load event will fire). Otherwise, returns true.

5.5.2 Unloading documents

interface BeforeUnloadEvent : Event {
           attribute DOMString returnValue;
};
event . returnValue [ = value ]

Returns the current return value of the event (the message to show the user).

Can be set, to update the message.

There are no BeforeUnloadEvent-specific initialization methods.

5.6 Offline Web applications

5.6.1 Introduction

This section is non-normative.

In order to enable users to continue interacting with Web applications and documents even when their network connection is unavailable — for instance, because they are traveling outside of their ISP's coverage area — authors can provide a manifest which lists the files that are needed for the Web application to work offline and which causes the user's browser to keep a copy of the files for use offline.

To illustrate this, consider a simple clock applet consisting of an HTML page "clock.html", a CSS style sheet "clock.css", and a JavaScript script "clock.js".

Before adding the manifest, these three files might look like this:

<!-- clock.html -->
<!DOCTYPE HTML>
<html>
 <head>
  <title>Clock</title>
  <script src="clock.js"></script>
  <link rel="stylesheet" href="clock.css">
 </head>
 <body>
  <p>The time is: <output id="clock"></output></p>
 </body>
</html>
/* clock.css */
output { font: 2em sans-serif; }
/* clock.js */
setTimeout(function () {
    document.getElementById('clock').value = new Date();
}, 1000);

If the user tries to open the "clock.html" page while offline, though, the user agent (unless it happens to have it still in the local cache) will fail with an error.

The author can instead provide a manifest of the three files:

CACHE MANIFEST
clock.html
clock.css
clock.js

With a small change to the HTML file, the manifest (served as text/cache-manifest) is linked to the application:

<!-- clock.html -->
<!DOCTYPE HTML>
<html manifest="clock.manifest">
 <head>
  <title>Clock</title>
  <script src="clock.js"></script>
  <link rel="stylesheet" href="clock.css">
 </head>
 <body>
  <p>The time is: <output id="clock"></output></p>
 </body>
</html>

Now, if the user goes to the page, the browser will cache the files and make them available even when the user is offline.

Authors are encouraged to include the main page in the manifest also, but in practice the page that referenced the manifest is automatically cached even if it isn't explicitly mentioned.

HTTP cache headers and restrictions on caching pages served over TLS (encrypted, using https:) are overridden by manifests. Thus, pages will not expire from an application cache before the user agent has updated it, and even applications served over TLS can be made to work offline.

5.6.1.1 Event summary

This section is non-normative.

When the user visits a page that declares a manifest, the browser will try to update the cache. It does this by fetching a copy of the manifest and, if the manifest has changed since the user agent last saw it, redownloading all the resources it mentions and caching them anew.

As this is going on, a number of events get fired on the ApplicationCache object to keep the script updated as to the state of the cache update, so that the user can be notified appropriately. The events are as follows:

Event name Interface Dispatched when... Next events
checking Event The user agent is checking for an update, or attempting to download the manifest for the first time. This is always the first event in the sequence. noupdate, downloading, obsolete, error
noupdate Event The manifest hadn't changed. Last event in sequence.
downloading Event The user agent has found an update and is fetching it, or is downloading the resources listed by the manifest for the first time. progress, error, cached, updateready
progress ProgressEvent The user agent is downloading resources listed by the manifest. progress, error, cached, updateready
cached Event The resources listed in the manifest have been downloaded, and the application is now cached. Last event in sequence.
updateready Event The resources listed in the manifest have been newly redownloaded, and the script can use swapCache() to switch to the new cache. Last event in sequence.
obsolete Event The manifest was found to have become a 404 or 410 page, so the application cache is being deleted. Last event in sequence.
error Event The manifest was a 404 or 410 page, so the attempt to cache the application has been aborted. Last event in sequence.
The manifest hadn't changed, but the page referencing the manifest failed to download properly.
A fatal error occurred while fetching the resources listed in the manifest.
The manifest changed while the update was being run. The user agent will try fetching the files again momentarily.

5.6.2 The cache manifest syntax

5.6.2.1 Some sample manifests

This section is non-normative.

This example manifest requires two images and a style sheet to be cached and whitelists a CGI script.

CACHE MANIFEST
# the above line is required

# this is a comment
# there can be as many of these anywhere in the file
# they are all ignored
  # comments can have spaces before them
  # but must be alone on the line

# blank lines are ignored too

# these are files that need to be cached they can either be listed
# first, or a "CACHE:" header could be put before them, as is done
# lower down.
images/sound-icon.png
images/background.png
# note that each file has to be put on its own line

# here is a file for the online whitelist -- it isn't cached, and
# references to this file will bypass the cache, always hitting the
# network (or trying to, if the user is offline).
NETWORK:
comm.cgi

# here is another set of files to cache, this time just the CSS file.
CACHE:
style/default.css

It could equally well be written as follows:

CACHE MANIFEST
NETWORK:
comm.cgi
CACHE:
style/default.css
images/sound-icon.png
images/background.png

Offline application cache manifests can use absolute paths or even absolute URLs:

CACHE MANIFEST

/main/home
/main/app.js
/settings/home
/settings/app.js
http://img.example.com/logo.png
http://img.example.com/check.png
http://img.example.com/cross.png

The following manifest defines a catch-all error page that is displayed for any page on the site while the user is offline. It also specifies that the online whitelist wildcard flag is open, meaning that accesses to resources on other sites will not be blocked. (Resources on the same site are already not blocked because of the catch-all fallback namespace.)

So long as all pages on the site reference this manifest, they will get cached locally as they are fetched, so that subsequent hits to the same page will load the page immediately from the cache. Until the manifest is changed, those pages will not be fetched from the server again. When the manifest changes, then all the files will be redownloaded.

Subresources, such as style sheets, images, etc, would only be cached using the regular HTTP caching semantics, however.

CACHE MANIFEST
FALLBACK:
/ /offline.html
NETWORK:
*
5.6.2.2 Writing cache manifests

Manifests must be served using the text/cache-manifest MIME type. All resources served using the text/cache-manifest MIME type must follow the syntax of application cache manifests, as described in this section.

An application cache manifest is a text file, whose text is encoded using UTF-8. Data in application cache manifests is line-based. Newlines must be represented by U+000A LINE FEED (LF) characters, U+000D CARRIAGE RETURN (CR) characters, or U+000D CARRIAGE RETURN (CR) U+000A LINE FEED (LF) pairs. [RFC3629]

This is a willful violation of RFC 2046, which requires all text/* types to only allow CRLF line breaks. This requirement, however, is outdated; the use of CR, LF, and CRLF line breaks is commonly supported and indeed sometimes CRLF is not supported by text editors. [RFC2046]

The first line of an application cache manifest must consist of the string "CACHE", a single U+0020 SPACE character, the string "MANIFEST", and either a U+0020 SPACE character, a U+0009 CHARACTER TABULATION (tab) character, a U+000A LINE FEED (LF) character, or a U+000D CARRIAGE RETURN (CR) character. The first line may optionally be preceded by a U+FEFF BYTE ORDER MARK (BOM) character. If any other text is found on the first line, it is ignored.

Subsequent lines, if any, must all be one of the following:

A blank line

Blank lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters only.

A comment

Comment lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, followed by a single U+0023 NUMBER SIGN character (#), followed by zero or more characters other than U+000A LINE FEED (LF) and U+000D CARRIAGE RETURN (CR) characters.

Comments must be on a line on their own. If they were to be included on a line with a URL, the "#" would be mistaken for part of a fragment identifier.

A section header

Section headers change the current section. There are three possible section headers:

CACHE:
Switches to the explicit section.
FALLBACK:
Switches to the fallback section.
NETWORK:
Switches to the online whitelist section.

Section header lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, followed by one of the names above (including the U+003A COLON character (:)) followed by zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters.

Ironically, by default, the current section is the explicit section.

Data for the current section

The format that data lines must take depends on the current section.

When the current section is the explicit section, data lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, a valid URL identifying a resource other than the manifest itself, and then zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters.

When the current section is the fallback section, data lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, a valid URL identifying a resource other than the manifest itself, one or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, another valid URL identifying a resource other than the manifest itself, and then zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters.

When the current section is the online whitelist section, data lines must consist of zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters, either a single U+002A ASTERISK character (*) or a valid URL identifying a resource other than the manifest itself, and then zero or more U+0020 SPACE and U+0009 CHARACTER TABULATION (tab) characters.

Manifests may contain sections more than once. Sections may be empty.

If the manifest's <scheme> is https: or another scheme intended for encrypted data transfer, then all URLs in explicit sections must have the same origin as the manifest itself.

URLs that are to be fallback pages associated with fallback namespaces, and those namespaces themselves, must be given in fallback sections, with the namespace being the first URL of the data line, and the corresponding fallback page being the second URL. All the other pages to be cached must be listed in explicit sections.

Fallback namespaces and fallback entries must have the same origin as the manifest itself.

A fallback namespace must not be listed more than once.

Namespaces that the user agent is to put into the online whitelist must all be specified in online whitelist sections. (This is needed for any URL that the page is intending to use to communicate back to the server.) To specify that all URLs are automatically whitelisted in this way, a U+002A ASTERISK character (*) may be specified as one of the URLs.

Authors should not include namespaces in the online whitelist for which another namespace in the online whitelist is a prefix match.

Relative URLs must be given relative to the manifest's own URL. All URLs in the manifest must have the same <scheme> as the manifest itself (either explicitly or implicitly, through the use of relative URLs).

URLs in manifests must not have fragment identifiers (i.e. the U+0023 NUMBER SIGN character isn't allowed in URLs in manifests).

Fallback namespaces and namespaces in the online whitelist are matched by prefix match.

5.6.3 Application cache API

interface ApplicationCache {

  // update status
  const unsigned short UNCACHED = 0;
  const unsigned short IDLE = 1;
  const unsigned short CHECKING = 2;
  const unsigned short DOWNLOADING = 3;
  const unsigned short UPDATEREADY = 4;
  const unsigned short OBSOLETE = 5;
  readonly attribute unsigned short status;

  // updates
  void update();
  void swapCache();

  // events
           attribute Function onchecking;
           attribute Function onerror;
           attribute Function onnoupdate;
           attribute Function ondownloading;
           attribute Function onprogress;
           attribute Function onupdateready;
           attribute Function oncached;
           attribute Function onobsolete;
};
ApplicationCache implements EventTarget;
cache = window . applicationCache

(In a window.) Returns the ApplicationCache object that applies to the active document of that Window.

cache = self . applicationCache

(In a shared worker.) Returns the ApplicationCache object that applies to the current shared worker. [WEBWORKERS]

cache . status

Returns the current status of the application cache, as given by the constants defined below.

cache . update()

Invokes the application cache download process.

Throws an INVALID_STATE_ERR exception if there is no application cache to update.

cache . swapCache()

Switches to the most recent application cache, if there is a newer one. If there isn't, throws an INVALID_STATE_ERR exception.

This does not cause previously-loaded resources to be reloaded; for example, images do not suddenly get reloaded and style sheets and scripts do not get reparsed or reevaluated. The only change is that subsequent requests for cached resources will obtain the newer copies.

UNCACHED (numeric value 0)

The ApplicationCache object's cache host is not associated with an application cache at this time.

IDLE (numeric value 1)

The ApplicationCache object's cache host is associated with an application cache whose application cache group's update status is idle, and that application cache is the newest cache in its application cache group, and the application cache group is not marked as obsolete.

CHECKING (numeric value 2)

The ApplicationCache object's cache host is associated with an application cache whose application cache group's update status is checking.

DOWNLOADING (numeric value 3)

The ApplicationCache object's cache host is associated with an application cache whose application cache group's update status is downloading.

UPDATEREADY (numeric value 4)

The ApplicationCache object's cache host is associated with an application cache whose application cache group's update status is idle, and whose application cache group is not marked as obsolete, but that application cache is not the newest cache in its group.

OBSOLETE (numeric value 5)

The ApplicationCache object's cache host is associated with an application cache whose application cache group is marked as obsolete.

5.6.4 Browser state

window . navigator . onLine

Returns false if the user agent is definitely offline (disconnected from the network). Returns true if the user agent might be online.

The events online and offline are fired when the value of this attribute changes.

This attribute is inherently unreliable. A computer can be connected to a network without having Internet access.

In this example, an indicator is updated as the browser goes online and offline.

<!DOCTYPE HTML>
<html>
 <head>
  <title>Online status</title>
  <script>
   function updateIndicator() {
     document.getElementById('indicator').textContext = navigator.onLine ? 'online' : 'offline';
   }
  </script>
 </head>
 <body onload="updateIndicator()" ononline="updateIndicator()" onoffline="updateIndicator()">
  <p>The network is: <span id="indicator">(state unknown)</span>
 </body>
</html>

6 Web application APIs

6.1 Scripting

6.1.1 Introduction

Various mechanisms can cause author-provided executable code to run in the context of a document. These mechanisms include, but are probably not limited to:

6.1.2 Events

Many objects can have event handlers specified. These act as bubbling event listeners for the object on which they are specified.

An event handler can either have the value null or be set to a Function object.

Event handlers are exposed in one or two ways.

The first way, common to all event handlers, is as an event handler IDL attribute.

The second way is as an event handler content attribute. Event handlers on HTML elements and some of the event handlers on Window objects are exposed in this way.

Event handler content attributes, when specified, must contain valid JavaScript code matching the FunctionBody production. [ECMA262]

When an event handler content attribute is set on an element owned by a Document that is not in a browsing context, the corresponding event handler is not changed.

Event handlers always fire before event listeners attached using addEventListener().


The Function interface represents a function in the scripting language being used. It is represented in IDL as follows:

[Callback=FunctionOnly, NoInterfaceObject]
interface Function {
  any call(in any... arguments);
};

The call(...) method is the object's callback.

In JavaScript, any Function object implements this interface.

If the Function object is a JavaScript Function, then when it is invoked by the user agent, the user agent must set the thisArg (as defined by ECMAScript edition 5 section 10.4.3 Entering Function Code) to the event handler's object. [ECMA262]

For example, the following document fragment:

<body onload="alert(this)" onclick="alert(this)">

...leads to an alert saying "[object Window]" when the document is loaded, and an alert saying "[object HTMLBodyElement]" whenever the user clicks something in the page.

The return value of the function affects whether the event is canceled or not: if the return value is false, the event is canceled (except for mouseover events, where the return value has to be true to cancel the event). With beforeunload events, the value is instead used to determine the message to show the user.

6.2 Timers

The setTimeout() and setInterval() methods allow authors to schedule timer-based callbacks.

[Supplemental, NoInterfaceObject]
interface WindowTimers {
  long setTimeout(in any handler, in optional any timeout, in any... args);
  void clearTimeout(in long handle);
  long setInterval(in any handler, in optional any timeout, in any... args);
  void clearInterval(in long handle);
};
Window implements WindowTimers;
handle = window . setTimeout( handler [, timeout [, arguments ] ] )

Schedules a timeout to run handler after timeout milliseconds. Any arguments are passed straight through to the handler.

handle = window . setTimeout( code [, timeout ] )

Schedules a timeout to compile and run code after timeout milliseconds.

window . clearTimeout( handle )

Cancels the timeout set with setTimeout() identified by handle.

handle = window . setInterval( handler [, timeout [, arguments ] ] )

Schedules a timeout to run handler every timeout milliseconds. Any arguments are passed straight through to the handler.

handle = window . setInterval( code [, timeout ] )

Schedules a timeout to compile and run code every timeout milliseconds.

window . clearInterval( handle )

Cancels the timeout set with setInterval() identified by handle.

This API does not guarantee that timers will fire exactly on schedule. Delays due to CPU load, other tasks, etc, are to be expected.

6.3 User prompts

6.3.1 Simple dialogs

window . alert(message)

Displays a modal alert with the given message, and waits for the user to dismiss it.

A call to the navigator.yieldForStorageUpdates() method is implied when this method is invoked.

result = window . confirm(message)

Displays a modal OK/Cancel prompt with the given message, waits for the user to dismiss it, and returns true if the user clicks OK and false if the user clicks Cancel.

A call to the navigator.yieldForStorageUpdates() method is implied when this method is invoked.

result = window . prompt(message [, default] )

Displays a modal text field prompt with the given message, waits for the user to dismiss it, and returns the value that the user entered. If the user cancels the prompt, then returns null instead. If the second argument is present, then the given value is used as a default.

A call to the navigator.yieldForStorageUpdates() method is implied when this method is invoked.

6.3.2 Printing

window . print()

Prompts the user to print the page.

A call to the navigator.yieldForStorageUpdates() method is implied when this method is invoked.

6.3.3 Dialogs implemented using separate documents

result = window . showModalDialog(url [, argument] )

Prompts the user with the given page, waits for that page to close, and returns the return value.

A call to the navigator.yieldForStorageUpdates() method is implied when this method is invoked.

[Supplemental, NoInterfaceObject] interface WindowModal {
  readonly attribute any dialogArguments;
           attribute DOMString returnValue;
};
window . dialogArguments

Returns the argument argument that was passed to the showModalDialog() method.

window . returnValue [ = value ]

Returns the current return value for the window.

Can be set, to change the value that will be returned by the showModalDialog() method.

The window.close() method can be used to close the browsing context.

6.4 System state and capabilities: the Navigator object

interface Navigator {
  // objects implementing this interface also implement the interfaces given below
};
Navigator implements NavigatorID;
Navigator implements NavigatorOnLine;
Navigator implements NavigatorAbilities;

[Supplemental, NoInterfaceObject]
interface NavigatorID {
  readonly attribute DOMString appName;
  readonly attribute DOMString appVersion;
  readonly attribute DOMString platform;
  readonly attribute DOMString userAgent;
};

[Supplemental, NoInterfaceObject]
interface NavigatorOnLine {
  readonly attribute boolean onLine;
};

[Supplemental, NoInterfaceObject]
interface NavigatorAbilities {
  // content handler registration
  void registerProtocolHandler(in DOMString scheme, in DOMString url, in DOMString title);
  void registerContentHandler(in DOMString mimeType, in DOMString url, in DOMString title);
  void yieldForStorageUpdates();
};

6.4.1 Client identification

In certain cases, despite the best efforts of the entire industry, Web browsers have bugs and limitations that Web authors are forced to work around.

This section defines a collection of attributes that can be used to determine, from script, the kind of user agent in use, in order to work around these issues.

Client detection should always be limited to detecting known current versions; future versions and unknown versions should always be assumed to be fully compliant.

window . navigator . appName

Returns the name of the browser.

window . navigator . appVersion

Returns the version of the browser.

window . navigator . platform

Returns the name of the platform.

window . navigator . userAgent

Returns the complete User-Agent header.

6.4.2 Custom scheme and content handlers

The registerProtocolHandler() method allows Web sites to register themselves as possible handlers for particular schemes. For example, an online telephone messaging service could register itself as a handler of the sms: scheme ([RFC5724]), so that if the user clicks on such a link, he is given the opportunity to use that Web site. Analogously, the registerContentHandler() method allows Web sites to register themselves as possible handlers for content in a particular MIME type. For example, the same online telephone messaging service could register itself as a handler for text/directory files ([RFC2425]), so that if the user has no native application capable of handling vCards ([RFC2426]), his Web browser can instead suggest he use that site to view contact information stored on vCards that he opens.

window . navigator . registerProtocolHandler(scheme, url, title)
window . navigator . registerContentHandler(mimeType, url, title)

Registers a handler for the given scheme or content type, at the given URL, with the given title.

The string "%s" in the URL is used as a placeholder for where to put the URL of the content to be handled.

Throws a SECURITY_ERR exception if the user agent blocks the registration (this might happen if trying to register as a handler for "http", for instance).

Throws a SYNTAX_ERR if the "%s" string is missing in the URL.

6.4.3 Manually releasing the storage mutex

window . navigator . yieldForStorageUpdates()

If a script uses the document.cookie API, or the localStorage API, the browser will block other scripts from accessing cookies or storage until the first script finishes. [WEBSTORAGE]

Calling the navigator.yieldForStorageUpdates() method tells the user agent to unblock any other scripts that may be blocked, even though the script hasn't returned.

Values of cookies and items in the Storage objects of localStorage attributes can change after calling this method, whence its name. [WEBSTORAGE]

7 User interaction

7.1 The hidden attribute

All HTML elements may have the hidden content attribute set. The hidden attribute is a boolean attribute. When specified on an element, it indicates that the element is not yet, or is no longer, relevant.

In the following skeletal example, the attribute is used to hide the Web game's main screen until the user logs in:

  <h1>The Example Game</h1>
  <section id="login">
   <h2>Login</h2>
   <form>
    ...
    <!-- calls login() once the user's credentials have been checked -->
   </form>
   <script>
    function login() {
      // switch screens
      document.getElementById('login').hidden = true;
      document.getElementById('game').hidden = false;
    }
   </script>
  </section>
  <section id="game" hidden>
   ...
  </section>

The hidden attribute must not be used to hide content that could legitimately be shown in another presentation. For example, it is incorrect to use hidden to hide panels in a tabbed dialog, because the tabbed interface is merely a kind of overflow presentation — one could equally well just show all the form controls in one big page with a scrollbar. It is similarly incorrect to use this attribute to hide content just from one presentation — if something is marked hidden, it is hidden from all presentations, including, for instance, screen readers.

Elements that are not hidden should not link to or refer to elements that are hidden.

For example, it would be incorrect to use the href attribute to link to a section marked with the hidden attribute. If the content is not applicable or relevant, then there is no reason to link to it.

It would similarly be incorrect to use the ARIA aria-describedby attribute to refer to descriptions that are themselves hidden. Hiding a section means that it is not applicable or relevant to anyone at the current time, so clearly it cannot be a valid description of content the user can interact with.

Elements in a section hidden by the hidden attribute are still active, e.g. scripts and form controls in such sections still execute and submit respectively. Only their presentation to the user changes.

7.2 Activation

element . click()

Acts as if the element was clicked.

7.3 Focus

7.3.1 Sequential focus navigation and the tabindex attribute

The tabindex content attribute specifies whether the element is focusable, whether it can be reached using sequential focus navigation, and the relative order of the element for the purposes of sequential focus navigation. The name "tab index" comes from the common use of the "tab" key to navigate through the focusable elements. The term "tabbing" refers to moving forward through the focusable elements that can be reached using sequential focus navigation.

The tabindex attribute, if specified, must have a value that is a valid integer.

7.3.2 Document-level focus APIs

document . activeElement

Returns the currently focused element.

document . hasFocus()

Returns true if the document has focus; otherwise, returns false.

window . focus()

Focuses the window. Use of this method is discouraged. Allow the user to control window focus instead.

window . blur()

Unfocuses the window. Use of this method is discouraged. Allow the user to control window focus instead.

7.3.3 Element-level focus APIs

element . focus()

Focuses the element.

element . blur()

Unfocuses the element. Use of this method is discouraged. Focus another element instead.

Do not use this method to hide the focus ring if you find the focus ring unsightly. Instead, use a CSS rule to override the 'outline' property.

For example, to hide the outline from links, you could use:

:link:focus, :visited:focus { outline: none; }

7.4 Assigning keyboard shortcuts

7.4.1 Introduction

This section is non-normative.

Each element that can be activated or focused can be assigned a single key combination to activate it, using the accesskey attribute.

The exact shortcut is determined by the user agent, based on information about the user's keyboard, what keyboard shortcuts already exist on the platform, and what other shortcuts have been specified on the page, using the information provided in the accesskey attribute as a guide.

In order to ensure that a relevant keyboard shortcut is available on a wide variety of input devices, the author can provide a number of alternatives in the accesskey attribute.

Each alternative consists of a single character, such as a letter or digit.

User agents can provide users with a list of the keyboard shortcuts, but authors are encouraged to do so also. The accessKeyLabel IDL attribute returns a string representing the actual key combination assigned by the user agent.

7.4.2 The accesskey attribute

All HTML elements may have the accesskey content attribute set. The accesskey attribute's value is used by the user agent as a guide for creating a keyboard shortcut that activates or focuses the element.

If specified, the value must be an ordered set of unique space-separated tokens that are case-sensitive, each of which must be exactly one Unicode code point in length.

In the following example, a variety of links are given with access keys so that keyboard users familiar with the site can more quickly navigate to the relevant pages:

<nav>
 <p>
  <a title="Consortium Activities" accesskey="A" href="/Consortium/activities">Activities</a> |
  <a title="Technical Reports and Recommendations" accesskey="T" href="/TR/">Technical Reports</a> |
  <a title="Alphabetical Site Index" accesskey="S" href="/Consortium/siteindex">Site Index</a> |
  <a title="About This Site" accesskey="B" href="/Consortium/">About Consortium</a> |
  <a title="Contact Consortium" accesskey="C" href="/Consortium/contact">Contact</a>
 </p>
</nav>

In the following example, the search field is given two possible access keys, "s" and "0" (in that order). A user agent on a device with a full keyboard might pick Ctrl+Alt+S as the shortcut key, while a user agent on a small device with just a numeric keypad might pick just the plain unadorned key 0:

<form action="/search">
 <label>Search: <input type="search" name="q" accesskey="s 0"></label>
 <input type="submit">
</form>

In the following example, a button has possible access keys described. A script then tries to update the button's label to advertise the key combination the user agent selected.

<input type=submit accesskey="N @ 1" value="Compose">
...
<script>
 function labelButton(button) {
   if (button.accessKeyLabel)
     button.value += ' (' + button.accessKeyLabel + ')';
 }
 var inputs = document.getElementsByTagName('input');
 for (var i = 0; i < inputs.length; i += 1) {
   if (inputs[i].type == "submit")
     labelButton(inputs[i]);
 }
</script>

On one user agent, the button's label might become "Compose (⌘N)". On another, it might become "Compose (Alt+⇧+1)". If the user agent doesn't assign a key, it will be just "Compose". The exact string depends on what the assigned access key is, and on how the user agent represents that key combination.

7.5 The contenteditable attribute

The contenteditable attribute is an enumerated attribute whose keywords are the empty string, true, and false. The empty string and the true keyword map to the true state. The false keyword maps to the false state. In addition, there is a third state, the inherit state, which is the missing value default (and the invalid value default).

The true state indicates that the element is editable. The inherit state indicates that the element is editable if its parent is. The false state indicates that the element is not editable.

element . contentEditable [ = value ]

Returns "true", "false", or "inherit", based on the state of the contenteditable attribute.

Can be set, to change that state.

Throws a SYNTAX_ERR exception if the new value isn't one of those strings.

element . isContentEditable

Returns true if the element is editable; otherwise, returns false.

7.5.1 Making entire documents editable

document . designMode [ = value ]

Returns "on" if the document is editable, and "off" if it isn't.

Can be set, to change the document's current state.

7.6 Spelling and grammar checking

The spellcheck attribute is an enumerated attribute whose keywords are the empty string, true and false. The empty string and the true keyword map to the true state. The false keyword maps to the false state. In addition, there is a third state, the default state, which is the missing value default (and the invalid value default).

The true state indicates that the element is to have its spelling and grammar checked. The default state indicates that the element is to act according to a default behavior, possibly based on the parent element's own spellcheck state. The false state indicates that the element is not to be checked.

element . spellcheck [ = value ]

Returns true if the element is to have its spelling and grammar checked; otherwise, returns false.

Can be set, to override the default and set the spellcheck content attribute.

This specification does not define the user interface for spelling and grammar checkers. A user agent could offer on-demand checking, could perform continuous checking while the checking is enabled, or could use other interfaces.

7.7 Drag and drop

This section defines an event-based drag-and-drop mechanism.

This specification does not define exactly what a drag-and-drop operation actually is.

On a visual medium with a pointing device, a drag operation could be the default action of a mousedown event that is followed by a series of mousemove events, and the drop could be triggered by the mouse being released.

On media without a pointing device, the user would probably have to explicitly indicate his intention to perform a drag-and-drop operation, stating what he wishes to drag and what he wishes to drop, respectively.

7.7.1 Introduction

This section is non-normative.

To make an element draggable is simple: give the element a draggable attribute, and set an event listener for dragstart that stores the data being dragged.

The event handler typically needs to check that it's not a text selection that is being dragged, and then needs to store data into the DataTransfer object and set the allowed effects (copy, move, link, or some combination).

For example:

<p>What fruits do you like?</p>
<ol ondragstart="dragStartHandler(event)">
 <li draggable="true" data-value="fruit-apple">Apples</li>
 <li draggable="true" data-value="fruit-orange">Oranges</li>
 <li draggable="true" data-value="fruit-pear">Pears</li>
</ol>
<script>
  var internalDNDType = 'text/x-example'; // set this to something specific to your site
  function dragStartHandler(event) {
    if (event.target instanceof HTMLLIElement) {
      // use the element's data-value="" attribute as the value to be moving:
      event.dataTransfer.setData(internalDNDType, event.target.dataset.value);
      event.effectAllowed = 'move'; // only allow moves
    } else {
      event.preventDefault(); // don't allow selection to be dragged
    }
  }
</script>

To accept a drop, the drop target has to listen to at least three events. First, the dragenter event, which is used to determine whether or not the drop target is to accept the drop. If the drop is to be accepted, then this event has to be canceled. Second, the dragover event, which is used to determine what feedback is to be shown to the user. If the event is canceled, then the feedback (typically the cursor) is updated based on the dropEffect attribute's value, as set by the event handler; otherwise, the default behavior (typically to do nothing) is used instead. Finally, the drop event, which allows the actual drop to be performed. This event also needs to be canceled, so that the dropEffect attribute's value can be used by the source (otherwise it's reset).

For example:

<p>Drop your favorite fruits below:</p>
<ol class="dropzone"
    ondragenter="dragEnterHandler(event)"
    ondragover="dragOverHandler(event)"
    ondrop="dropHandler(event)">
</ol>
<script>
  var internalDNDType = 'text/x-example'; // set this to something specific to your site
  function dragEnterHandler(event) {
    // cancel the event if the drag contains data of our type
    if (event.dataTransfer.types.contains(internalDNDType))
      event.preventDefault();
  }
  function dragOverHandler(event) {
    event.dataTransfer.dropEffect = 'move';
    event.preventDefault(); // override default drag feedback
  }
  function dropHandler(event) {
    // drop the data
    var li = document.createElement('li');
    var data = event.dataTransfer.getData(internalDNDType);
    if (data == 'fruit-apple') {
      li.textContent = 'Apples';
    } else if (data == 'fruit-orange') {
      li.textContent = 'Oranges';
    } else if (data == 'fruit-pear') {
      li.textContent = 'Pears';
    } else {
      li.textContent = 'Unknown Fruit';
    }
    event.target.appendChild(li);
  }
</script>

To remove the original element (the one that was dragged) from the display, the dragend event can be used.

For our example here, that means updating the original markup to handle that event:

<p>What fruits do you like?</p>
<ol ondragstart="dragStartHandler(event)" ondragend="dragEndHandler(event)">
 ...as before...
</ol>
<script>
  function dragStartHandler(event) {
    // ...as before...
  }
  function dragEndHandler(event) {
    // remove the dragged element
    event.target.parentNode.removeChild(event.target);
  }
</script>

7.7.2 The drag data store

The data that underlies a drag-and-drop operation, known as the drag data store, consists of the following information:

When a drag data store is created, it must be initialized such that its drag data store item list is empty, it has no drag data store default feedback, its drag data store elements list is empty, it has no drag data store bitmap / drag data store hot spot coordinate, its drag data store mode is protected mode, and its drag data store allowed effects state is the string "uninitialized".

7.7.3 The DataTransfer interface

DataTransfer objects are used to expose the drag data store that underlies a drag-and-drop operation.

interface DataTransfer {
           attribute DOMString dropEffect;
           attribute DOMString effectAllowed;

  readonly attribute DOMStringList types;
  void clearData(in optional DOMString format);
  void setData(in DOMString format, in DOMString data);
  DOMString getData(in DOMString format);
  readonly attribute FileList files;

  void setDragImage(in Element image, in long x, in long y);
  void addElement(in Element element);
};
dataTransfer . dropEffect [ = value ]

Returns the kind of operation that is currently selected. If the kind of operation isn't one of those that is allowed by the effectAllowed attribute, then the operation will fail.

Can be set, to change the selected operation.

The possible values are "none", "copy", "link", and "move".

dataTransfer . effectAllowed [ = value ]

Returns the kinds of operations that are to be allowed.

Can be set, to change the allowed operations.

The possible values are "none", "copy", "copyLink", "copyMove", "link", "linkMove", "move", "all", and "uninitialized",

dataTransfer . types

Returns a DOMStringList listing the formats that were set in the dragstart event. In addition, if any files are being dragged, then one of the types will be the string "Files".

dataTransfer . clearData( [ format ] )

Removes the data of the specified formats. Removes all data if the argument is omitted.

dataTransfer . setData(format, data)

Adds the specified data.

data = dataTransfer . getData(format)

Returns the specified data. If there is no such data, returns the empty string.

dataTransfer . files

Returns a FileList of the files being dragged, if any.

dataTransfer . setDragImage(element, x, y)

Uses the given element to update the drag feedback, replacing any previously specified feedback.

dataTransfer . addElement(element)

Adds the given element to the list of elements used to render the drag feedback.

DataTransfer objects are used during the drag-and-drop events, and are only valid while those events are being dispatched.

7.7.3.1 The DataTransferItems interface

Each DataTransfer object is associated with a DataTransferItems object.

interface DataTransferItems {
  readonly attribute unsigned long length;
  getter DataTransferItem (in unsigned long index);
  deleter void (in unsigned long index);
  void clear();

  DataTransferItem add(in DOMString data, in DOMString type);
  DataTransferItem add(in File data);
};
items . length

Returns the number of items in the drag data store.

items[index]

Returns the DataTransferItem object representing the indexth entry in the drag data store.

delete items[index]

Removes the indexth entry in the drag data store.

items . clear()

Removes all the entries in the drag data store.

items . add(data)
items . add(data, type)

Adds a new entry for the given data to the drag data store. If the data is plain text then a type string has to be provided also.

7.7.3.2 The DataTransferItem interface

Each DataTransferItem object is associated with a DataTransfer object.

interface DataTransferItem {
    readonly attribute DOMString kind;
    readonly attribute DOMString type;
    void getAsString(in FunctionStringCallback callback);
    File getAsFile();
};

[Callback=FunctionOnly, NoInterfaceObject]
interface FunctionStringCallback {
  void handleEvent(in DOMString data);
};
item . kind

Returns the drag data item kind, one of: "string", "file".

item . type

Returns the drag data item type string.

item . getAsString(callback)

Invokes the callback with the string data as the argument, if the drag data item kind is Plain Unicode string.

file = item . getAsFile()

Returns a File object, if the drag data item kind is File.

7.7.4 The DragEvent interface

The drag-and-drop processing model involves several events. They all use the DragEvent interface.

interface DragEvent : MouseEvent {
  readonly attribute DataTransfer dataTransfer;

  void initDragEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in any dummyArg, in long detailArg, in long screenXArg, in long screenYArg, in long clientXArg, in long clientYArg, in boolean ctrlKeyArg, in boolean altKeyArg, in boolean shiftKeyArg, in boolean metaKeyArg, in unsigned short buttonArg, in EventTarget relatedTargetArg, in DataTransfer dataTransferArg);
};
event . dataTransfer

Returns the DataTransfer object for the event.

7.7.5 Events summary

This section is non-normative.

The following events are involved in the drag-and-drop model.

Event Name Target Cancelable? Drag data store mode dropEffect Default Action
dragstart Source node ✓ Cancelable Read/write mode "none" Initiate the drag-and-drop operation
drag Source node ✓ Cancelable Protected mode "none" Continue the drag-and-drop operation
dragenter Immediate user selection or the body element ✓ Cancelable Protected mode Based on effectAllowed value Reject immediate user selection as potential target element
dragleave Previous target element Protected mode "none" None
dragover Current target element ✓ Cancelable Protected mode Based on effectAllowed value Reset the current drag operation to "none"
drop Current target element ✓ Cancelable Read-only mode Current drag operation Varies
dragend Source node Protected mode Current drag operation Varies

Not shown in the above table: all these events bubble, and the effectAllowed attribute always has the value it had after the previous event was fired, defaulting to "uninitialized" in the dragstart event.

7.7.6 The draggable attribute

All HTML elements may have the draggable content attribute set. The draggable attribute is an enumerated attribute. It has three states. The first state is true and it has the keyword true. The second state is false and it has the keyword false. The third state is auto; it has no keywords but it is the missing value default.

The true state means the element is draggable; the false state means that it is not. The auto state uses the default behavior of the user agent.

element . draggable [ = value ]

Returns true if the element is draggable; otherwise, returns false.

Can be set, to override the default and set the draggable content attribute.

7.7.7 The dropzone attribute

All HTML elements may have the dropzone content attribute set. When specified, its value must be an unordered set of unique space-separated tokens that are ASCII case-insensitive. The allowed values are the following:

copy

Indicates that dropping an accepted item on the element will result in a copy of the dragged data.

move

Indicates that dropping an accepted item on the element will result in the dragged data being moved to the new location.

link

Indicates that dropping an accepted item on the element will result in a link to the original data.

Any keyword with three characters or more, beginning with the two characters U+0073 LATIN SMALL LETTER S and U+003A COLON or U+0053 LATIN CAPITAL LETTER S and U+003A COLON (i.e. an ASCII case-insensitive match for the string "s:")

Indicates that items with the drag data item kind Plain Unicode string and the drag data item type string set to a value that matches the remainder of the keyword are accepted.

Any keyword with three characters or more, beginning with the two characters U+0066 LATIN SMALL LETTER F and U+003A COLON or U+0046 LATIN CAPITAL LETTER F and U+003A COLON (i.e. an ASCII case-insensitive match for the string "f:")

Indicates that items with the drag data item kind File and the drag data item type string set to a value that matches the remainder of the keyword are accepted.

The dropzone content attribute's values must not have more than one of the three feedback values (copy, move, and link) specified. If none are specified, the copy value is implied.

In this example, a div element is made into a drop target for image files using the dropzone attribute. Images dropped into the target are then displayed.

<div dropzone="copy f:image/png f:image/gif f:image/jpeg" ondrop="receive(event, this)">
 <p>Drop an image here to have it displayed.</p>
</div>
<script>
 function receive(event, element) {
   var data = event.dataTransfer.items;
   for (var i = 0; i < data.length; i += 1) {
     if ((data[i].kind == 'file') && (data[i].type.match('^image/'))) {
       var img = new Image();
       img.src = window.createObjectURL(data[i].getAsFile());
       element.appendChild(img);
     }
   }
 }
</script>

7.8 Editing APIs

document . execCommand(commandId [, showUI [, value ] ] )

Runs the action specified by the first argument, as described in the list below. The second and third arguments sometimes affect the action. (If they don't they are ignored.)

document . queryCommandEnabled(commandId)

Returns whether the given command is enabled, as described in the list below.

document . queryCommandIndeterm(commandId)

Returns whether the given command is indeterminate, as described in the list below.

document . queryCommandState(commandId)

Returns the state of the command, as described in the list below.

document . queryCommandSupported(commandId)

Returns true if the command is supported; otherwise, returns false.

document . queryCommandValue(commandId)

Returns the value of the command, as described in the list below.

A document is ready for editing host commands if it has a selection that is entirely within an editing host, or if it has no selection but its caret is inside an editing host.

The possible values for commandId, and their corresponding meanings, are as follows.

bold
Summary: Toggles whether the selection is bold.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: True if the selection, or the caret, if there is no selection, is, or is contained within, a b element. False otherwise.
Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.
createLink
Summary: Toggles whether the selection is a link or not. If the second argument is true, and a link is to be added, the user agent will ask the user for the address. Otherwise, the third argument will be used as the address.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
delete
Summary: Deletes the selection or the character before the cursor.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
formatBlock
Summary: Wraps the selection in the element given by the third argument. If the third argument doesn't specify an element that is a formatBlock candidate, does nothing.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
forwardDelete
Summary: Deletes the selection or the character after the cursor.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertImage
Summary: Toggles whether the selection is an image or not. If the second argument is true, and an image is to be added, the user agent will ask the user for the address. Otherwise, the third argument will be used as the address.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertHTML
Summary: Replaces the selection with the value of the third argument parsed as HTML.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertLineBreak
Summary: Inserts a line break.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertOrderedList
Summary: Toggles whether the selection is an ordered list.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertUnorderedList
Summary: Toggles whether the selection is an unordered list.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertParagraph
Summary: Inserts a paragraph break.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
insertText
Summary: Inserts the text given in the third parameter.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
italic
Summary: Toggles whether the selection is italic.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: True if the selection, or the caret, if there is no selection, is, or is contained within, a i element. False otherwise.
Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.
redo
Summary: Acts as if the user had requested a redo.
Enabled When: The undo position is not at the end of the undo transaction history.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
selectAll
Summary: Selects all the editable content.
Enabled When: Always.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
subscript
Summary: Toggles whether the selection is subscripted.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: True if the selection, or the caret, if there is no selection, is, or is contained within, a sub element. False otherwise.
Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.
superscript
Summary: Toggles whether the selection is superscripted.
Enabled When: The document is ready for editing host commands.
Indeterminate When: Never.
State: True if the selection, or the caret, if there is no selection, is, or is contained within, a sup element. False otherwise.
Value: The string "true" if the expression given for the "State" above is true, the string "false" otherwise.
undo
Summary: Acts as if the user had requested an undo.
Enabled When: The undo position is not at the start of the undo transaction history.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
unlink
Summary: Removes all links from the selection.
Enabled When: The document has a selection that is entirely within an editing host and that contains (either partially or completely) at least one a element that has an href attribute.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".
unselect
Summary: Unselects everything.
Enabled When: Always.
Indeterminate When: Never.
State: Always false.
Value: Always the string "false".

8 The HTML syntax

This section only describes the rules for resources labeled with an HTML MIME type. Rules for XML resources are discussed in the section below entitled "The XHTML syntax".

8.1 Writing HTML documents

Documents must consist of the following parts, in the given order:

  1. Optionally, a single U+FEFF BYTE ORDER MARK (BOM) character.
  2. Any number of comments and space characters.
  3. A DOCTYPE.
  4. Any number of comments and space characters.
  5. The root element, in the form of an html element.
  6. Any number of comments and space characters.

The various types of content mentioned above are described in the next few sections.

In addition, there are some restrictions on how character encoding declarations are to be serialized, as discussed in the section on that topic.

Space characters before the root html element, and space characters at the start of the html element and before the head element, will be dropped when the document is parsed; space characters after the root html element will be parsed as if they were at the end of the body element. Thus, space characters around the root element do not round-trip.

It is suggested that newlines be inserted after the DOCTYPE, after any comments that are before the root element, after the html element's start tag (if it is not omitted), and after any comments that are inside the html element but before the head element.

Many strings in the HTML syntax (e.g. the names of elements and their attributes) are case-insensitive, but only for characters in the ranges U+0041 to U+005A (LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z) and U+0061 to U+007A (LATIN SMALL LETTER A to LATIN SMALL LETTER Z). For convenience, in this section this is just referred to as "case-insensitive".

8.1.1 The DOCTYPE

A DOCTYPE is a required preamble.

DOCTYPEs are required for legacy reasons. When omitted, browsers tend to use a different rendering mode that is incompatible with some specifications. Including the DOCTYPE in a document ensures that the browser makes a best-effort attempt at following the relevant specifications.

A DOCTYPE must consist of the following characters, in this order:

  1. A string that is an ASCII case-insensitive match for the string "<!DOCTYPE".
  2. One or more space characters.
  3. A string that is an ASCII case-insensitive match for the string "html".
  4. Optionally, a DOCTYPE legacy string or an obsolete permitted DOCTYPE string (defined below).
  5. Zero or more space characters.
  6. A U+003E GREATER-THAN SIGN character (>).

In other words, <!DOCTYPE html>, case-insensitively.


For the purposes of HTML generators that cannot output HTML markup with the short DOCTYPE "<!DOCTYPE html>", a DOCTYPE legacy string may be inserted into the DOCTYPE (in the position defined above). This string must consist of:

  1. One or more space characters.
  2. A string that is an ASCII case-insensitive match for the string "SYSTEM".
  3. One or more space characters.
  4. A U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (the quote mark).
  5. The literal string "about:legacy-compat".
  6. A matching U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (i.e. the same character as in the earlier step labeled quote mark).

In other words, <!DOCTYPE html SYSTEM "about:legacy-compat"> or <!DOCTYPE html SYSTEM 'about:legacy-compat'>, case-insensitively except for the part in single or double quotes.

The DOCTYPE legacy string should not be used unless the document is generated from a system that cannot output the shorter string.


To help authors transition from HTML4 and XHTML1, an obsolete permitted DOCTYPE string can be inserted into the DOCTYPE (in the position defined above). This string must consist of:

  1. One or more space characters.
  2. A string that is an ASCII case-insensitive match for the string "PUBLIC".
  3. One or more space characters.
  4. A U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (the first quote mark).
  5. The string from one of the cells in the first column of the table below. The row to which this cell belongs is the selected row.
  6. A matching U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (i.e. the same character as in the earlier step labeled first quote mark).
  7. If the cell in the second column of the selected row is not blank, one or more space characters.
  8. If the cell in the second column of the selected row is not blank, a U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (the third quote mark).
  9. If the cell in the second column of the selected row is not blank, the string from the cell in the second column of the selected row.
  10. If the cell in the second column of the selected row is not blank, a matching U+0022 QUOTATION MARK or U+0027 APOSTROPHE character (i.e. the same character as in the earlier step labeled third quote mark).
Allowed values for public and system identifiers in an obsolete permitted DOCTYPE string.
Public identifier System identifier
-//W3C//DTD HTML 4.0//EN
-//W3C//DTD HTML 4.0//EN http://www.w3.org/TR/REC-html40/strict.dtd
-//W3C//DTD HTML 4.01//EN
-//W3C//DTD HTML 4.01//EN http://www.w3.org/TR/html4/strict.dtd
-//W3C//DTD XHTML 1.0 Strict//EN http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd
-//W3C//DTD XHTML 1.1//EN http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd

A DOCTYPE containing an obsolete permitted DOCTYPE string is an obsolete permitted DOCTYPE. Authors should not use obsolete permitted DOCTYPEs, as they are unnecessarily long.

8.1.2 Elements

There are five different kinds of elements: void elements, raw text elements, RCDATA elements, foreign elements, and normal elements.

Void elements
area, base, br, col, command, embed, hr, img, input, keygen, link, meta, param, source, track, wbr
Raw text elements
script, style
RCDATA elements
textarea, title
Foreign elements
Elements from the MathML namespace and the SVG namespace.
Normal elements
All other allowed HTML elements are normal elements.

Tags are used to delimit the start and end of elements in the markup. Raw text, RCDATA, and normal elements have a start tag to indicate where they begin, and an end tag to indicate where they end. The start and end tags of certain normal elements can be omitted, as described later. Those that cannot be omitted must not be omitted. Void elements only have a start tag; end tags must not be specified for void elements. Foreign elements must either have a start tag and an end tag, or a start tag that is marked as self-closing, in which case they must not have an end tag.

The contents of the element must be placed between just after the start tag (which might be implied, in certain cases) and just before the end tag (which again, might be implied in certain cases). The exact allowed contents of each individual element depend on the content model of that element, as described earlier in this specification. Elements must not contain content that their content model disallows. In addition to the restrictions placed on the contents by those content models, however, the five types of elements have additional syntactic requirements.

Void elements can't have any contents (since there's no end tag, no content can be put between the start tag and the end tag).

Raw text elements can have text, though it has restrictions described below.

RCDATA elements can have text and character references, but the text must not contain an ambiguous ampersand. There are also further restrictions described below.

Foreign elements whose start tag is marked as self-closing can't have any contents (since, again, as there's no end tag, no content can be put between the start tag and the end tag). Foreign elements whose start tag is not marked as self-closing can have text, character references, CDATA sections, other elements, and comments, but the text must not contain the character U+003C LESS-THAN SIGN (<) or an ambiguous ampersand.

The HTML syntax does not support namespace declarations, even in foreign elements.

For instance, consider the following HTML fragment:

<p>
 <svg>
  <metadata>
   <!-- this is invalid -->
   <cdr:license xmlns:cdr="http://www.example.com/cdr/metadata" name="MIT"/>
  </metadata>
 </svg>
</p>

The innermost element, cdr:license, is actually in the SVG namespace, as the "xmlns:cdr" attribute has no effect (unlike in XML). In fact, as the comment in the fragment above says, the fragment is actually non-conforming. This is because the SVG specification does not define any elements called "cdr:license" in the SVG namespace.

Normal elements can have text, character references, other elements, and comments, but the text must not contain the character U+003C LESS-THAN SIGN (<) or an ambiguous ampersand. Some normal elements also have yet more restrictions on what content they are allowed to hold, beyond the restrictions imposed by the content model and those described in this paragraph. Those restrictions are described below.

Tags contain a tag name, giving the element's name. HTML elements all have names that only use characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), U+0061 LATIN SMALL LETTER A to U+007A LATIN SMALL LETTER Z, and U+0041 LATIN CAPITAL LETTER A to U+005A LATIN CAPITAL LETTER Z. In the HTML syntax, tag names, even those for foreign elements, may be written with any mix of lower- and uppercase letters that, when converted to all-lowercase, matches the element's tag name; tag names are case-insensitive.

8.1.2.1 Start tags

Start tags must have the following format:

  1. The first character of a start tag must be a U+003C LESS-THAN SIGN character (<).
  2. The next few characters of a start tag must be the element's tag name.
  3. If there are to be any attributes in the next step, there must first be one or more space characters.
  4. Then, the start tag may have a number of attributes, the syntax for which is described below. Attributes must be separated from each other by one or more space characters.
  5. After the attributes, or after the tag name if there are no attributes, there may be one or more space characters. (Some attributes are required to be followed by a space. See the attributes section below.)
  6. Then, if the element is one of the void elements, or if the element is a foreign element, then there may be a single U+002F SOLIDUS character (/). This character has no effect on void elements, but on foreign elements it marks the start tag as self-closing.
  7. Finally, start tags must be closed by a U+003E GREATER-THAN SIGN character (>).
8.1.2.2 End tags

End tags must have the following format:

  1. The first character of an end tag must be a U+003C LESS-THAN SIGN character (<).
  2. The second character of an end tag must be a U+002F SOLIDUS character (/).
  3. The next few characters of an end tag must be the element's tag name.
  4. After the tag name, there may be one or more space characters.
  5. Finally, end tags must be closed by a U+003E GREATER-THAN SIGN character (>).
8.1.2.3 Attributes

Attributes for an element are expressed inside the element's start tag.

Attributes have a name and a value. Attribute names must consist of one or more characters other than the space characters, U+0000 NULL, U+0022 QUOTATION MARK ("), U+0027 APOSTROPHE ('), U+003E GREATER-THAN SIGN (>), U+002F SOLIDUS (/), and U+003D EQUALS SIGN (=) characters, the control characters, and any characters that are not defined by Unicode. In the HTML syntax, attribute names, even those for foreign elements, may be written with any mix of lower- and uppercase letters that are an ASCII case-insensitive match for the attribute's name.

Attribute values are a mixture of text and character references, except with the additional restriction that the text cannot contain an ambiguous ampersand.

Attributes can be specified in four different ways:

Empty attribute syntax

Just the attribute name. The value is implicitly the empty string.

In the following example, the disabled attribute is given with the empty attribute syntax:

<input disabled>

If an attribute using the empty attribute syntax is to be followed by another attribute, then there must be a space character separating the two.

Unquoted attribute value syntax

The attribute name, followed by zero or more space characters, followed by a single U+003D EQUALS SIGN character, followed by zero or more space characters, followed by the attribute value, which, in addition to the requirements given above for attribute values, must not contain any literal space characters, any U+0022 QUOTATION MARK characters ("), U+0027 APOSTROPHE characters ('), U+003D EQUALS SIGN characters (=), U+003C LESS-THAN SIGN characters (<), U+003E GREATER-THAN SIGN characters (>), or U+0060 GRAVE ACCENT characters (`), and must not be the empty string.

In the following example, the value attribute is given with the unquoted attribute value syntax:

<input value=yes>

If an attribute using the unquoted attribute syntax is to be followed by another attribute or by the optional U+002F SOLIDUS character (/) allowed in step 6 of the start tag syntax above, then there must be a space character separating the two.

Single-quoted attribute value syntax

The attribute name, followed by zero or more space characters, followed by a single U+003D EQUALS SIGN character, followed by zero or more space characters, followed by a single U+0027 APOSTROPHE character ('), followed by the attribute value, which, in addition to the requirements given above for attribute values, must not contain any literal U+0027 APOSTROPHE characters ('), and finally followed by a second single U+0027 APOSTROPHE character (').

In the following example, the type attribute is given with the single-quoted attribute value syntax:

<input type='checkbox'>

If an attribute using the single-quoted attribute syntax is to be followed by another attribute, then there must be a space character separating the two.

Double-quoted attribute value syntax

The attribute name, followed by zero or more space characters, followed by a single U+003D EQUALS SIGN character, followed by zero or more space characters, followed by a single U+0022 QUOTATION MARK character ("), followed by the attribute value, which, in addition to the requirements given above for attribute values, must not contain any literal U+0022 QUOTATION MARK characters ("), and finally followed by a second single U+0022 QUOTATION MARK character (").

In the following example, the name attribute is given with the double-quoted attribute value syntax:

<input name="be evil">

If an attribute using the double-quoted attribute syntax is to be followed by another attribute, then there must be a space character separating the two.

There must never be two or more attributes on the same start tag whose names are an ASCII case-insensitive match for each other.


When a foreign element has one of the namespaced attributes given by the local name and namespace of the first and second cells of a row from the following table, it must be written using the name given by the third cell from the same row.

Local name Namespace Attribute name
actuate XLink namespace xlink:actuate
arcrole XLink namespace xlink:arcrole
href XLink namespace xlink:href
role XLink namespace xlink:role
show XLink namespace xlink:show
title XLink namespace xlink:title
type XLink namespace xlink:type
base XML namespace xml:base
lang XML namespace xml:lang
space XML namespace xml:space
xmlns XMLNS namespace xmlns
xlink XMLNS namespace xmlns:xlink

No other namespaced attribute can be expressed in the HTML syntax.

8.1.2.4 Optional tags

Certain tags can be omitted.

Omitting an element's start tag does not mean the element is not present; it is implied, but it is still there. An HTML document always has a root html element, even if the string <html> doesn't appear anywhere in the markup.

An html element's start tag may be omitted if the first thing inside the html element is not a comment.

An html element's end tag may be omitted if the html element is not immediately followed by a comment.

A head element's start tag may be omitted if the element is empty, or if the first thing inside the head element is an element.

A head element's end tag may be omitted if the head element is not immediately followed by a space character or a comment.

A body element's start tag may be omitted if the element is empty, or if the first thing inside the body element is not a space character or a comment, except if the first thing inside the body element is a script or style element.

A body element's end tag may be omitted if the body element is not immediately followed by a comment.

A li element's end tag may be omitted if the li element is immediately followed by another li element or if there is no more content in the parent element.

A dt element's end tag may be omitted if the dt element is immediately followed by another dt element or a dd element.

A dd element's end tag may be omitted if the dd element is immediately followed by another dd element or a dt element, or if there is no more content in the parent element.

A p element's end tag may be omitted if the p element is immediately followed by an address, article, aside, blockquote, dir, div, dl, fieldset, footer, form, h1, h2, h3, h4, h5, h6, header, hgroup, hr, menu, nav, ol, p, pre, section, table, or ul, element, or if there is no more content in the parent element and the parent element is not an a element.

An rt element's end tag may be omitted if the rt element is immediately followed by an rt or rp element, or if there is no more content in the parent element.

An rp element's end tag may be omitted if the rp element is immediately followed by an rt or rp element, or if there is no more content in the parent element.

An optgroup element's end tag may be omitted if the optgroup element is immediately followed by another optgroup element, or if there is no more content in the parent element.

An option element's end tag may be omitted if the option element is immediately followed by another option element, or if it is immediately followed by an optgroup element, or if there is no more content in the parent element.

A colgroup element's start tag may be omitted if the first thing inside the colgroup element is a col element, and if the element is not immediately preceded by another colgroup element whose end tag has been omitted. (It can't be omitted if the element is empty.)

A colgroup element's end tag may be omitted if the colgroup element is not immediately followed by a space character or a comment.

A thead element's end tag may be omitted if the thead element is immediately followed by a tbody or tfoot element.

A tbody element's start tag may be omitted if the first thing inside the tbody element is a tr element, and if the element is not immediately preceded by a tbody, thead, or tfoot element whose end tag has been omitted. (It can't be omitted if the element is empty.)

A tbody element's end tag may be omitted if the tbody element is immediately followed by a tbody or tfoot element, or if there is no more content in the parent element.

A tfoot element's end tag may be omitted if the tfoot element is immediately followed by a tbody element, or if there is no more content in the parent element.

A tr element's end tag may be omitted if the tr element is immediately followed by another tr element, or if there is no more content in the parent element.

A td element's end tag may be omitted if the td element is immediately followed by a td or th element, or if there is no more content in the parent element.

A th element's end tag may be omitted if the th element is immediately followed by a td or th element, or if there is no more content in the parent element.

However, a start tag must never be omitted if it has any attributes.

8.1.2.5 Restrictions on content models

For historical reasons, certain elements have extra restrictions beyond even the restrictions given by their content model.

A table element must not contain tr elements, even though these elements are technically allowed inside table elements according to the content models described in this specification. (If a tr element is put inside a table in the markup, it will in fact imply a tbody start tag before it.)

A single newline may be placed immediately after the start tag of pre and textarea elements. This does not affect the processing of the element. The otherwise optional newline must be included if the element's contents themselves start with a newline (because otherwise the leading newline in the contents would be treated like the optional newline, and ignored).

The following two pre blocks are equivalent:

<pre>Hello</pre>
<pre>
Hello</pre>
8.1.2.6 Restrictions on the contents of raw text and RCDATA elements

The text in raw text and RCDATA elements must not contain any occurrences of the string "</" (U+003C LESS-THAN SIGN, U+002F SOLIDUS) followed by characters that case-insensitively match the tag name of the element followed by one of U+0009 CHARACTER TABULATION, U+000A LINE FEED (LF), U+000C FORM FEED (FF), U+000D CARRIAGE RETURN (CR), U+0020 SPACE, U+003E GREATER-THAN SIGN (>), or U+002F SOLIDUS (/).

8.1.3 Text

Text is allowed inside elements, attribute values, and comments. Text must consist of Unicode characters. Text must not contain U+0000 characters. Text must not contain permanently undefined Unicode characters (noncharacters). Text must not contain control characters other than space characters. Extra constraints are placed on what is and what is not allowed in text based on where the text is to be put, as described in the other sections.

8.1.3.1 Newlines

Newlines in HTML may be represented either as U+000D CARRIAGE RETURN (CR) characters, U+000A LINE FEED (LF) characters, or pairs of U+000D CARRIAGE RETURN (CR), U+000A LINE FEED (LF) characters in that order.

Where character references are allowed, a character reference of a U+000A LINE FEED (LF) character (but not a U+000D CARRIAGE RETURN (CR) character) also represents a newline.

8.1.4 Character references

In certain cases described in other sections, text may be mixed with character references. These can be used to escape characters that couldn't otherwise legally be included in text.

Character references must start with a U+0026 AMPERSAND character (&). Following this, there are three possible kinds of character references:

Named character references
The ampersand must be followed by one of the names given in the named character references section, using the same case.
Decimal numeric character reference
The ampersand must be followed by a U+0023 NUMBER SIGN character (#), followed by one or more digits in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), representing a base-ten integer that corresponds to a Unicode code point that is allowed according to the definition below. The digits must then be followed by a U+003B SEMICOLON character (;).
Hexadecimal numeric character reference
The ampersand must be followed by a U+0023 NUMBER SIGN character (#), which must be followed by either a U+0078 LATIN SMALL LETTER X character (x) or a U+0058 LATIN CAPITAL LETTER X character (X), which must then be followed by one or more digits in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), U+0061 LATIN SMALL LETTER A to U+0066 LATIN SMALL LETTER F, and U+0041 LATIN CAPITAL LETTER A to U+0046 LATIN CAPITAL LETTER F, representing a base-sixteen integer that corresponds to a Unicode code point that is allowed according to the definition below. The digits must then be followed by a U+003B SEMICOLON character (;).

The numeric character reference forms described above are allowed to reference any Unicode code point other than U+0000, U+000D, permanently undefined Unicode characters (noncharacters), and control characters other than space characters.

An ambiguous ampersand is a U+0026 AMPERSAND character (&) that is followed by one or more characters in the range U+0030 DIGIT ZERO (0) to U+0039 DIGIT NINE (9), U+0061 LATIN SMALL LETTER A to U+007A LATIN SMALL LETTER Z, and U+0041 LATIN CAPITAL LETTER A to U+005A LATIN CAPITAL LETTER Z, followed by a U+003B SEMICOLON character (;), where these characters do not match any of the names given in the named character references section.

8.1.5 CDATA sections

CDATA sections must start with the character sequence U+003C LESS-THAN SIGN, U+0021 EXCLAMATION MARK, U+005B LEFT SQUARE BRACKET, U+0043 LATIN CAPITAL LETTER C, U+0044 LATIN CAPITAL LETTER D, U+0041 LATIN CAPITAL LETTER A, U+0054 LATIN CAPITAL LETTER T, U+0041 LATIN CAPITAL LETTER A, U+005B LEFT SQUARE BRACKET (<![CDATA[). Following this sequence, the CDATA section may have text, with the additional restriction that the text must not contain the three character sequence U+005D RIGHT SQUARE BRACKET, U+005D RIGHT SQUARE BRACKET, U+003E GREATER-THAN SIGN (]]>). Finally, the CDATA section must be ended by the three character sequence U+005D RIGHT SQUARE BRACKET, U+005D RIGHT SQUARE BRACKET, U+003E GREATER-THAN SIGN (]]>).

CDATA sections can only be used in foreign content (MathML or SVG). In this example, a CDATA section is used to escape the contents of an ms element:

<p>You can add a string to a number, but this stringifies the number:</p>
<math>
 <ms><![CDATA[x<y]]></ms>
 <mo>+</mo>
 <mn>3</mn>
 <mo>=</mo>
 <ms><![CDATA[x<y3]]></ms>
</math>

8.1.6 Comments

Comments must start with the four character sequence U+003C LESS-THAN SIGN, U+0021 EXCLAMATION MARK, U+002D HYPHEN-MINUS, U+002D HYPHEN-MINUS (<!--). Following this sequence, the comment may have text, with the additional restriction that the text must not start with a single U+003E GREATER-THAN SIGN character (>), nor start with a U+002D HYPHEN-MINUS character (-) followed by a U+003E GREATER-THAN SIGN (>) character, nor contain two consecutive U+002D HYPHEN-MINUS characters (--), nor end with a U+002D HYPHEN-MINUS character (-). Finally, the comment must be ended by the three character sequence U+002D HYPHEN-MINUS, U+002D HYPHEN-MINUS, U+003E GREATER-THAN SIGN (-->).

8.2 Named character references

This table lists the character reference names that are supported by HTML, and the code points to which they refer. It is referenced by the previous sections.

Name Character(s) Glyph
AElig; U+000C6 Æ
AMP; U+00026 &
Aacute; U+000C1 Á
Abreve; U+00102 Ă
Acirc; U+000C2 Â
Acy; U+00410 А
Afr; U+1D504 𝔄
Agrave; U+000C0 À
Alpha; U+00391 Α
Amacr; U+00100 Ā
And; U+02A53
Aogon; U+00104 Ą
Aopf; U+1D538 𝔸
ApplyFunction; U+02061
Aring; U+000C5 Å
Ascr; U+1D49C 𝒜
Assign; U+02254
Atilde; U+000C3 Ã
Auml; U+000C4 Ä
Backslash; U+02216
Barv; U+02AE7
Barwed; U+02306
Bcy; U+00411 Б
Because; U+02235
Bernoullis; U+0212C
Beta; U+00392 Β
Bfr; U+1D505 𝔅
Bopf; U+1D539 𝔹
Breve; U+002D8 ˘
Bscr; U+0212C
Bumpeq; U+0224E
CHcy; U+00427 Ч
COPY; U+000A9 ©
Cacute; U+00106 Ć
Cap; U+022D2
CapitalDifferentialD; U+02145
Cayleys; U+0212D
Ccaron; U+0010C Č
Ccedil; U+000C7 Ç
Ccirc; U+00108 Ĉ
Cconint; U+02230
Cdot; U+0010A Ċ
Cedilla; U+000B8 ¸
CenterDot; U+000B7 ·
Cfr; U+0212D
Chi; U+003A7 Χ
CircleDot; U+02299
CircleMinus; U+02296
CirclePlus; U+02295
CircleTimes; U+02297
ClockwiseContourIntegral; U+02232
CloseCurlyDoubleQuote; U+0201D
CloseCurlyQuote; U+02019
Colon; U+02237
Colone; U+02A74
Congruent; U+02261
Conint; U+0222F
ContourIntegral; U+0222E
Copf; U+02102
Coproduct; U+02210
CounterClockwiseContourIntegral; U+02233
Cross; U+02A2F
Cscr; U+1D49E 𝒞
Cup; U+022D3
CupCap; U+0224D
DD; U+02145
DDotrahd; U+02911
DJcy; U+00402 Ђ
DScy; U+00405 Ѕ
DZcy; U+0040F Џ
Dagger; U+02021
Darr; U+021A1
Dashv; U+02AE4
Dcaron; U+0010E Ď
Dcy; U+00414 Д
Del; U+02207
Delta; U+00394 Δ
Dfr; U+1D507 𝔇
DiacriticalAcute; U+000B4 ´
DiacriticalDot; U+002D9 ˙
DiacriticalDoubleAcute; U+002DD ˝
DiacriticalGrave; U+00060 `
DiacriticalTilde; U+002DC ˜
Diamond; U+022C4
DifferentialD; U+02146
Dopf; U+1D53B 𝔻
Dot; U+000A8 ¨
DotDot; U+020DC ◌⃜
DotEqual; U+02250
DoubleContourIntegral; U+0222F
DoubleDot; U+000A8 ¨
DoubleDownArrow; U+021D3
DoubleLeftArrow; U+021D0
DoubleLeftRightArrow; U+021D4
DoubleLeftTee; U+02AE4
DoubleLongLeftArrow; U+027F8
DoubleLongLeftRightArrow; U+027FA
DoubleLongRightArrow; U+027F9
DoubleRightArrow; U+021D2
DoubleRightTee; U+022A8
DoubleUpArrow; U+021D1
DoubleUpDownArrow; U+021D5
DoubleVerticalBar; U+02225
DownArrow; U+02193
DownArrowBar; U+02913
DownArrowUpArrow; U+021F5
DownBreve; U+00311 ◌̑
DownLeftRightVector; U+02950
DownLeftTeeVector; U+0295E
DownLeftVector; U+021BD
DownLeftVectorBar; U+02956
DownRightTeeVector; U+0295F
DownRightVector; U+021C1
DownRightVectorBar; U+02957
DownTee; U+022A4
DownTeeArrow; U+021A7
Downarrow; U+021D3
Dscr; U+1D49F 𝒟
Dstrok; U+00110 Đ
ENG; U+0014A Ŋ
ETH; U+000D0 Ð
Eacute; U+000C9 É
Ecaron; U+0011A Ě
Ecirc; U+000CA Ê
Ecy; U+0042D Э
Edot; U+00116 Ė
Efr; U+1D508 𝔈
Egrave; U+000C8 È
Element; U+02208
Emacr; U+00112 Ē
EmptySmallSquare; U+025FB
EmptyVerySmallSquare; U+025AB
Eogon; U+00118 Ę
Eopf; U+1D53C 𝔼
Epsilon; U+00395 Ε
Equal; U+02A75
EqualTilde; U+02242
Equilibrium; U+021CC
Escr; U+02130
Esim; U+02A73
Eta; U+00397 Η
Euml; U+000CB Ë
Exists; U+02203
ExponentialE; U+02147
Fcy; U+00424 Ф
Ffr; U+1D509 𝔉
FilledSmallSquare; U+025FC
FilledVerySmallSquare; U+025AA
Fopf; U+1D53D 𝔽
ForAll; U+02200
Fouriertrf; U+02131
Fscr; U+02131
GJcy; U+00403 Ѓ
GT; U+0003E >
Gamma; U+00393 Γ
Gammad; U+003DC Ϝ
Gbreve; U+0011E Ğ
Gcedil; U+00122 Ģ
Gcirc; U+0011C Ĝ
Gcy; U+00413 Г
Gdot; U+00120 Ġ
Gfr; U+1D50A 𝔊
Gg; U+022D9
Gopf; U+1D53E 𝔾
GreaterEqual; U+02265
GreaterEqualLess; U+022DB
GreaterFullEqual; U+02267
GreaterGreater; U+02AA2
GreaterLess; U+02277
GreaterSlantEqual; U+02A7E
GreaterTilde; U+02273
Gscr; U+1D4A2 𝒢
Gt; U+0226B
HARDcy; U+0042A Ъ
Hacek; U+002C7 ˇ
Hat; U+0005E ^
Hcirc; U+00124 Ĥ
Hfr; U+0210C
HilbertSpace; U+0210B
Hopf; U+0210D
HorizontalLine; U+02500
Hscr; U+0210B
Hstrok; U+00126 Ħ
HumpDownHump; U+0224E
HumpEqual; U+0224F
IEcy; U+00415 Е
IJlig; U+00132 IJ
IOcy; U+00401 Ё
Iacute; U+000CD Í
Icirc; U+000CE Î
Icy; U+00418 И
Idot; U+00130 İ
Ifr; U+02111
Igrave; U+000CC Ì
Im; U+02111
Imacr; U+0012A Ī
ImaginaryI; U+02148
Implies; U+021D2
Int; U+0222C
Integral; U+0222B
Intersection; U+022C2
InvisibleComma; U+02063
InvisibleTimes; U+02062
Iogon; U+0012E Į
Iopf; U+1D540 𝕀
Iota; U+00399 Ι
Iscr; U+02110
Itilde; U+00128 Ĩ
Iukcy; U+00406 І
Iuml; U+000CF Ï
Jcirc; U+00134 Ĵ
Jcy; U+00419 Й
Jfr; U+1D50D 𝔍
Jopf; U+1D541 𝕁
Jscr; U+1D4A5 𝒥
Jsercy; U+00408 Ј
Jukcy; U+00404 Є
KHcy; U+00425 Х
KJcy; U+0040C Ќ
Kappa; U+0039A Κ
Kcedil; U+00136 Ķ
Kcy; U+0041A К
Kfr; U+1D50E 𝔎
Kopf; U+1D542 𝕂
Kscr; U+1D4A6 𝒦
LJcy; U+00409 Љ
LT; U+0003C <
Lacute; U+00139 Ĺ
Lambda; U+0039B Λ
Lang; U+027EA
Laplacetrf; U+02112
Larr; U+0219E
Lcaron; U+0013D Ľ
Lcedil; U+0013B Ļ
Lcy; U+0041B Л
LeftAngleBracket; U+027E8
LeftArrow; U+02190
LeftArrowBar; U+021E4
LeftArrowRightArrow; U+021C6
LeftCeiling; U+02308
LeftDoubleBracket; U+027E6
LeftDownTeeVector; U+02961
LeftDownVector; U+021C3
LeftDownVectorBar; U+02959
LeftFloor; U+0230A
LeftRightArrow; U+02194
LeftRightVector; U+0294E
LeftTee; U+022A3
LeftTeeArrow; U+021A4
LeftTeeVector; U+0295A
LeftTriangle; U+022B2
LeftTriangleBar; U+029CF
LeftTriangleEqual; U+022B4
LeftUpDownVector; U+02951
LeftUpTeeVector; U+02960
LeftUpVector; U+021BF
LeftUpVectorBar; U+02958
LeftVector; U+021BC
LeftVectorBar; U+02952
Leftarrow; U+021D0
Leftrightarrow; U+021D4
LessEqualGreater; U+022DA
LessFullEqual; U+02266
LessGreater; U+02276
LessLess; U+02AA1
LessSlantEqual; U+02A7D
LessTilde; U+02272
Lfr; U+1D50F 𝔏
Ll; U+022D8
Lleftarrow; U+021DA
Lmidot; U+0013F Ŀ
LongLeftArrow; U+027F5
LongLeftRightArrow; U+027F7
LongRightArrow; U+027F6
Longleftarrow; U+027F8
Longleftrightarrow; U+027FA
Longrightarrow; U+027F9
Lopf; U+1D543 𝕃
LowerLeftArrow; U+02199
LowerRightArrow; U+02198
Lscr; U+02112
Lsh; U+021B0
Lstrok; U+00141 Ł
Lt; U+0226A
Map; U+02905
Mcy; U+0041C М
MediumSpace; U+0205F
Mellintrf; U+02133
Mfr; U+1D510 𝔐
MinusPlus; U+02213
Mopf; U+1D544 𝕄
Mscr; U+02133
Mu; U+0039C Μ
NJcy; U+0040A Њ
Nacute; U+00143 Ń
Ncaron; U+00147 Ň
Ncedil; U+00145 Ņ
Ncy; U+0041D Н
NegativeMediumSpace; U+0200B
NegativeThickSpace; U+0200B
NegativeThinSpace; U+0200B
NegativeVeryThinSpace; U+0200B
NestedGreaterGreater; U+0226B
NestedLessLess; U+0226A
NewLine; U+0000A
Nfr; U+1D511 𝔑
NoBreak; U+02060
NonBreakingSpace; U+000A0  
Nopf; U+02115
Not; U+02AEC
NotCongruent; U+02262
NotCupCap; U+0226D
NotDoubleVerticalBar; U+02226
NotElement; U+02209
NotEqual; U+02260
NotEqualTilde; U+02242 U+00338 ≂̸
NotExists; U+02204
NotGreater; U+0226F
NotGreaterEqual; U+02271
NotGreaterFullEqual; U+02267 U+00338 ≧̸
NotGreaterGreater; U+0226B U+00338 ≫̸
NotGreaterLess; U+02279
NotGreaterSlantEqual; U+02A7E U+00338 ⩾̸
NotGreaterTilde; U+02275
NotHumpDownHump; U+0224E U+00338 ≎̸
NotHumpEqual; U+0224F U+00338 ≏̸
NotLeftTriangle; U+022EA
NotLeftTriangleBar; U+029CF U+00338 ⧏̸
NotLeftTriangleEqual; U+022EC
NotLess; U+0226E
NotLessEqual; U+02270
NotLessGreater; U+02278
NotLessLess; U+0226A U+00338 ≪̸
NotLessSlantEqual; U+02A7D U+00338 ⩽̸
NotLessTilde; U+02274
NotNestedGreaterGreater; U+02AA2 U+00338 ⪢̸
NotNestedLessLess; U+02AA1 U+00338 ⪡̸
NotPrecedes; U+02280
NotPrecedesEqual; U+02AAF U+00338 ⪯̸
NotPrecedesSlantEqual; U+022E0
NotReverseElement; U+0220C
NotRightTriangle; U+022EB
NotRightTriangleBar; U+029D0 U+00338 ⧐̸
NotRightTriangleEqual; U+022ED
NotSquareSubset; U+0228F U+00338 ⊏̸
NotSquareSubsetEqual; U+022E2
NotSquareSuperset; U+02290 U+00338 ⊐̸
NotSquareSupersetEqual; U+022E3
NotSubset; U+02282 U+020D2 ⊂⃒
NotSubsetEqual; U+02288
NotSucceeds; U+02281
NotSucceedsEqual; U+02AB0 U+00338 ⪰̸
NotSucceedsSlantEqual; U+022E1
NotSucceedsTilde; U+0227F U+00338 ≿̸
NotSuperset; U+02283 U+020D2 ⊃⃒
NotSupersetEqual; U+02289
NotTilde; U+02241
NotTildeEqual; U+02244
NotTildeFullEqual; U+02247
NotTildeTilde; U+02249
NotVerticalBar; U+02224
Nscr; U+1D4A9 𝒩
Ntilde; U+000D1 Ñ
Nu; U+0039D Ν
OElig; U+00152 Œ
Oacute; U+000D3 Ó
Ocirc; U+000D4 Ô
Ocy; U+0041E О
Odblac; U+00150 Ő
Ofr; U+1D512 𝔒
Ograve; U+000D2 Ò
Omacr; U+0014C Ō
Omega; U+003A9 Ω
Omicron; U+0039F Ο
Oopf; U+1D546 𝕆
OpenCurlyDoubleQuote; U+0201C
OpenCurlyQuote; U+02018
Or; U+02A54
Oscr; U+1D4AA 𝒪
Oslash; U+000D8 Ø
Otilde; U+000D5 Õ
Otimes; U+02A37
Ouml; U+000D6 Ö
OverBar; U+0203E
OverBrace; U+023DE
OverBracket; U+023B4
OverParenthesis; U+023DC
PartialD; U+02202
Pcy; U+0041F П
Pfr; U+1D513 𝔓
Phi; U+003A6 Φ
Pi; U+003A0 Π
PlusMinus; U+000B1 ±
Poincareplane; U+0210C
Popf; U+02119
Pr; U+02ABB
Precedes; U+0227A
PrecedesEqual; U+02AAF
PrecedesSlantEqual; U+0227C
PrecedesTilde; U+0227E
Prime; U+02033
Product; U+0220F
Proportion; U+02237
Proportional; U+0221D
Pscr; U+1D4AB 𝒫
Psi; U+003A8 Ψ
QUOT; U+00022 "
Qfr; U+1D514 𝔔
Qopf; U+0211A
Qscr; U+1D4AC 𝒬
RBarr; U+02910
REG; U+000AE ®
Racute; U+00154 Ŕ
Rang; U+027EB
Rarr; U+021A0
Rarrtl; U+02916
Rcaron; U+00158 Ř
Rcedil; U+00156 Ŗ
Rcy; U+00420 Р
Re; U+0211C
ReverseElement; U+0220B
ReverseEquilibrium; U+021CB
ReverseUpEquilibrium; U+0296F
Rfr; U+0211C
Rho; U+003A1 Ρ
RightAngleBracket; U+027E9
RightArrow; U+02192
RightArrowBar; U+021E5
RightArrowLeftArrow; U+021C4
RightCeiling; U+02309
RightDoubleBracket; U+027E7
RightDownTeeVector; U+0295D
RightDownVector; U+021C2
RightDownVectorBar; U+02955
RightFloor; U+0230B
RightTee; U+022A2
RightTeeArrow; U+021A6
RightTeeVector; U+0295B
RightTriangle; U+022B3
RightTriangleBar; U+029D0
RightTriangleEqual; U+022B5
RightUpDownVector; U+0294F
RightUpTeeVector; U+0295C
RightUpVector; U+021BE
RightUpVectorBar; U+02954
RightVector; U+021C0
RightVectorBar; U+02953
Rightarrow; U+021D2
Ropf; U+0211D
RoundImplies; U+02970
Rrightarrow; U+021DB
Rscr; U+0211B
Rsh; U+021B1
RuleDelayed; U+029F4
SHCHcy; U+00429 Щ
SHcy; U+00428 Ш
SOFTcy; U+0042C Ь
Sacute; U+0015A Ś
Sc; U+02ABC
Scaron; U+00160 Š
Scedil; U+0015E Ş
Scirc; U+0015C Ŝ
Scy; U+00421 С
Sfr; U+1D516 𝔖
ShortDownArrow; U+02193
ShortLeftArrow; U+02190
ShortRightArrow; U+02192
ShortUpArrow; U+02191
Sigma; U+003A3 Σ
SmallCircle; U+02218
Sopf; U+1D54A 𝕊
Sqrt; U+0221A
Square; U+025A1
SquareIntersection; U+02293
SquareSubset; U+0228F
SquareSubsetEqual; U+02291
SquareSuperset; U+02290
SquareSupersetEqual; U+02292
SquareUnion; U+02294
Sscr; U+1D4AE 𝒮
Star; U+022C6
Sub; U+022D0
Subset; U+022D0
SubsetEqual; U+02286
Succeeds; U+0227B
SucceedsEqual; U+02AB0
SucceedsSlantEqual; U+0227D
SucceedsTilde; U+0227F
SuchThat; U+0220B
Sum; U+02211
Sup; U+022D1
Superset; U+02283
SupersetEqual; U+02287
Supset; U+022D1
THORN; U+000DE Þ
TRADE; U+02122
TSHcy; U+0040B Ћ
TScy; U+00426 Ц
Tab; U+00009
Tau; U+003A4 Τ
Tcaron; U+00164 Ť
Tcedil; U+00162 Ţ
Tcy; U+00422 Т
Tfr; U+1D517 𝔗
Therefore; U+02234
Theta; U+00398 Θ
ThickSpace; U+0205F U+0200A   
ThinSpace; U+02009
Tilde; U+0223C
TildeEqual; U+02243
TildeFullEqual; U+02245
TildeTilde; U+02248
Topf; U+1D54B 𝕋
TripleDot; U+020DB ◌⃛
Tscr; U+1D4AF 𝒯
Tstrok; U+00166 Ŧ
Uacute; U+000DA Ú
Uarr; U+0219F
Uarrocir; U+02949
Ubrcy; U+0040E Ў
Ubreve; U+0016C Ŭ
Ucirc; U+000DB Û
Ucy; U+00423 У
Udblac; U+00170 Ű
Ufr; U+1D518 𝔘
Ugrave; U+000D9 Ù
Umacr; U+0016A Ū
UnderBar; U+0005F _
UnderBrace; U+023DF
UnderBracket; U+023B5
UnderParenthesis; U+023DD
Union; U+022C3
UnionPlus; U+0228E
Uogon; U+00172 Ų
Uopf; U+1D54C 𝕌
UpArrow; U+02191
UpArrowBar; U+02912
UpArrowDownArrow; U+021C5
UpDownArrow; U+02195
UpEquilibrium; U+0296E
UpTee; U+022A5
UpTeeArrow; U+021A5
Uparrow; U+021D1
Updownarrow; U+021D5
UpperLeftArrow; U+02196
UpperRightArrow; U+02197
Upsi; U+003D2 ϒ
Upsilon; U+003A5 Υ
Uring; U+0016E Ů
Uscr; U+1D4B0 𝒰
Utilde; U+00168 Ũ
Uuml; U+000DC Ü
VDash; U+022AB
Vbar; U+02AEB
Vcy; U+00412 В
Vdash; U+022A9
Vdashl; U+02AE6
Vee; U+022C1
Verbar; U+02016
Vert; U+02016
VerticalBar; U+02223
VerticalLine; U+0007C |
VerticalSeparator; U+02758
VerticalTilde; U+02240
VeryThinSpace; U+0200A
Vfr; U+1D519 𝔙
Vopf; U+1D54D 𝕍
Vscr; U+1D4B1 𝒱
Vvdash; U+022AA
Wcirc; U+00174 Ŵ
Wedge; U+022C0
Wfr; U+1D51A 𝔚
Wopf; U+1D54E 𝕎
Wscr; U+1D4B2 𝒲
Xfr; U+1D51B 𝔛
Xi; U+0039E Ξ
Xopf; U+1D54F 𝕏
Xscr; U+1D4B3 𝒳
YAcy; U+0042F Я
YIcy; U+00407 Ї
YUcy; U+0042E Ю
Yacute; U+000DD Ý
Ycirc; U+00176 Ŷ
Ycy; U+0042B Ы
Yfr; U+1D51C 𝔜
Yopf; U+1D550 𝕐
Yscr; U+1D4B4 𝒴
Yuml; U+00178 Ÿ
ZHcy; U+00416 Ж
Zacute; U+00179 Ź
Zcaron; U+0017D Ž
Zcy; U+00417 З
Zdot; U+0017B Ż
ZeroWidthSpace; U+0200B
Zeta; U+00396 Ζ
Zfr; U+02128
Zopf; U+02124
Zscr; U+1D4B5 𝒵
aacute; U+000E1 á
abreve; U+00103 ă
ac; U+0223E
acE; U+0223E U+00333 ∾̳
acd; U+0223F
acirc; U+000E2 â
acute; U+000B4 ´
acy; U+00430 а
aelig; U+000E6 æ
af; U+02061
afr; U+1D51E 𝔞
agrave; U+000E0 à
alefsym; U+02135
aleph; U+02135
alpha; U+003B1 α
amacr; U+00101 ā
amalg; U+02A3F ⨿
amp; U+00026 &
and; U+02227
andand; U+02A55
andd; U+02A5C
andslope; U+02A58
andv; U+02A5A
ang; U+02220
ange; U+029A4
angle; U+02220
angmsd; U+02221
angmsdaa; U+029A8
angmsdab; U+029A9
angmsdac; U+029AA
angmsdad; U+029AB
angmsdae; U+029AC
angmsdaf; U+029AD
angmsdag; U+029AE
angmsdah; U+029AF
angrt; U+0221F
angrtvb; U+022BE
angrtvbd; U+0299D
angsph; U+02222
angst; U+000C5 Å
angzarr; U+0237C
aogon; U+00105 ą
aopf; U+1D552 𝕒
ap; U+02248
apE; U+02A70
apacir; U+02A6F
ape; U+0224A
apid; U+0224B
apos; U+00027 '
approx; U+02248
approxeq; U+0224A
aring; U+000E5 å
ascr; U+1D4B6 𝒶
ast; U+0002A *
asymp; U+02248
asympeq; U+0224D
atilde; U+000E3 ã
auml; U+000E4 ä
awconint; U+02233
awint; U+02A11
bNot; U+02AED
backcong; U+0224C
backepsilon; U+003F6 ϶
backprime; U+02035
backsim; U+0223D
backsimeq; U+022CD
barvee; U+022BD
barwed; U+02305
barwedge; U+02305
bbrk; U+023B5
bbrktbrk; U+023B6
bcong; U+0224C
bcy; U+00431 б
bdquo; U+0201E
becaus; U+02235
because; U+02235
bemptyv; U+029B0
bepsi; U+003F6 ϶
bernou; U+0212C
beta; U+003B2 β
beth; U+02136
between; U+0226C
bfr; U+1D51F 𝔟
bigcap; U+022C2
bigcirc; U+025EF
bigcup; U+022C3
bigodot; U+02A00
bigoplus; U+02A01
bigotimes; U+02A02
bigsqcup; U+02A06
bigstar; U+02605
bigtriangledown; U+025BD
bigtriangleup; U+025B3
biguplus; U+02A04
bigvee; U+022C1
bigwedge; U+022C0
bkarow; U+0290D
blacklozenge; U+029EB
blacksquare; U+025AA
blacktriangle; U+025B4
blacktriangledown; U+025BE
blacktriangleleft; U+025C2
blacktriangleright; U+025B8
blank; U+02423
blk12; U+02592
blk14; U+02591
blk34; U+02593
block; U+02588
bne; U+0003D U+020E5 =⃥
bnequiv; U+02261 U+020E5 ≡⃥
bnot; U+02310
bopf; U+1D553 𝕓
bot; U+022A5
bottom; U+022A5
bowtie; U+022C8
boxDL; U+02557
boxDR; U+02554
boxDl; U+02556
boxDr; U+02553
boxH; U+02550
boxHD; U+02566
boxHU; U+02569
boxHd; U+02564
boxHu; U+02567
boxUL; U+0255D
boxUR; U+0255A
boxUl; U+0255C
boxUr; U+02559
boxV; U+02551
boxVH; U+0256C
boxVL; U+02563
boxVR; U+02560
boxVh; U+0256B
boxVl; U+02562
boxVr; U+0255F
boxbox; U+029C9
boxdL; U+02555
boxdR; U+02552
boxdl; U+02510
boxdr; U+0250C
boxh; U+02500
boxhD; U+02565
boxhU; U+02568
boxhd; U+0252C
boxhu; U+02534
boxminus; U+0229F
boxplus; U+0229E
boxtimes; U+022A0
boxuL; U+0255B
boxuR; U+02558
boxul; U+02518
boxur; U+02514
boxv; U+02502
boxvH; U+0256A
boxvL; U+02561
boxvR; U+0255E
boxvh; U+0253C
boxvl; U+02524
boxvr; U+0251C
bprime; U+02035
breve; U+002D8 ˘
brvbar; U+000A6 ¦
bscr; U+1D4B7 𝒷
bsemi; U+0204F
bsim; U+0223D
bsime; U+022CD
bsol; U+0005C \
bsolb; U+029C5
bsolhsub; U+027C8
bull; U+02022
bullet; U+02022
bump; U+0224E
bumpE; U+02AAE
bumpe; U+0224F
bumpeq; U+0224F
cacute; U+00107 ć
cap; U+02229
capand; U+02A44
capbrcup; U+02A49
capcap; U+02A4B
capcup; U+02A47
capdot; U+02A40
caps; U+02229 U+0FE00 ∩︀
caret; U+02041
caron; U+002C7 ˇ
ccaps; U+02A4D
ccaron; U+0010D č
ccedil; U+000E7 ç
ccirc; U+00109 ĉ
ccups; U+02A4C
ccupssm; U+02A50
cdot; U+0010B ċ
cedil; U+000B8 ¸
cemptyv; U+029B2
cent; U+000A2 ¢
centerdot; U+000B7 ·
cfr; U+1D520 𝔠
chcy; U+00447 ч
check; U+02713
checkmark; U+02713
chi; U+003C7 χ
cir; U+025CB
cirE; U+029C3
circ; U+002C6 ˆ
circeq; U+02257
circlearrowleft; U+021BA
circlearrowright; U+021BB
circledR; U+000AE ®
circledS; U+024C8
circledast; U+0229B
circledcirc; U+0229A
circleddash; U+0229D
cire; U+02257
cirfnint; U+02A10
cirmid; U+02AEF
cirscir; U+029C2
clubs; U+02663
clubsuit; U+02663
colon; U+0003A :
colone; U+02254
coloneq; U+02254
comma; U+0002C ,
commat; U+00040 @
comp; U+02201
compfn; U+02218
complement; U+02201
complexes; U+02102
cong; U+02245
congdot; U+02A6D
conint; U+0222E
copf; U+1D554 𝕔
coprod; U+02210
copy; U+000A9 ©
copysr; U+02117
crarr; U+021B5
cross; U+02717
cscr; U+1D4B8 𝒸
csub; U+02ACF
csube; U+02AD1
csup; U+02AD0
csupe; U+02AD2
ctdot; U+022EF
cudarrl; U+02938
cudarrr; U+02935
cuepr; U+022DE
cuesc; U+022DF
cularr; U+021B6
cularrp; U+0293D
cup; U+0222A
cupbrcap; U+02A48
cupcap; U+02A46
cupcup; U+02A4A
cupdot; U+0228D
cupor; U+02A45
cups; U+0222A U+0FE00 ∪︀
curarr; U+021B7
curarrm; U+0293C
curlyeqprec; U+022DE
curlyeqsucc; U+022DF
curlyvee; U+022CE
curlywedge; U+022CF
curren; U+000A4 ¤
curvearrowleft; U+021B6
curvearrowright; U+021B7
cuvee; U+022CE
cuwed; U+022CF
cwconint; U+02232
cwint; U+02231
cylcty; U+0232D
dArr; U+021D3
dHar; U+02965
dagger; U+02020
daleth; U+02138
darr; U+02193
dash; U+02010
dashv; U+022A3
dbkarow; U+0290F
dblac; U+002DD ˝
dcaron; U+0010F ď
dcy; U+00434 д
dd; U+02146
ddagger; U+02021
ddarr; U+021CA
ddotseq; U+02A77
deg; U+000B0 °
delta; U+003B4 δ
demptyv; U+029B1
dfisht; U+0297F ⥿
dfr; U+1D521 𝔡
dharl; U+021C3
dharr; U+021C2
diam; U+022C4
diamond; U+022C4
diamondsuit; U+02666
diams; U+02666
die; U+000A8 ¨
digamma; U+003DD ϝ
disin; U+022F2
div; U+000F7 ÷
divide; U+000F7 ÷
divideontimes; U+022C7
divonx; U+022C7
djcy; U+00452 ђ
dlcorn; U+0231E
dlcrop; U+0230D
dollar; U+00024 $
dopf; U+1D555 𝕕
dot; U+002D9 ˙
doteq; U+02250
doteqdot; U+02251
dotminus; U+02238
dotplus; U+02214
dotsquare; U+022A1
doublebarwedge; U+02306
downarrow; U+02193
downdownarrows; U+021CA
downharpoonleft; U+021C3
downharpoonright; U+021C2
drbkarow; U+02910
drcorn; U+0231F
drcrop; U+0230C
dscr; U+1D4B9 𝒹
dscy; U+00455 ѕ
dsol; U+029F6
dstrok; U+00111 đ
dtdot; U+022F1
dtri; U+025BF
dtrif; U+025BE
duarr; U+021F5
duhar; U+0296F
dwangle; U+029A6
dzcy; U+0045F џ
dzigrarr; U+027FF
eDDot; U+02A77
eDot; U+02251
eacute; U+000E9 é
easter; U+02A6E
ecaron; U+0011B ě
ecir; U+02256
ecirc; U+000EA ê
ecolon; U+02255
ecy; U+0044D э
edot; U+00117 ė
ee; U+02147
efDot; U+02252
efr; U+1D522 𝔢
eg; U+02A9A
egrave; U+000E8 è
egs; U+02A96
egsdot; U+02A98
el; U+02A99
elinters; U+023E7
ell; U+02113
els; U+02A95
elsdot; U+02A97
emacr; U+00113 ē
empty; U+02205
emptyset; U+02205
emptyv; U+02205
emsp; U+02003
emsp13; U+02004
emsp14; U+02005
eng; U+0014B ŋ
ensp; U+02002
eogon; U+00119 ę
eopf; U+1D556 𝕖
epar; U+022D5
eparsl; U+029E3
eplus; U+02A71
epsi; U+003B5 ε
epsilon; U+003B5 ε
epsiv; U+003F5 ϵ
eqcirc; U+02256
eqcolon; U+02255
eqsim; U+02242
eqslantgtr; U+02A96
eqslantless; U+02A95
equals; U+0003D =
equest; U+0225F
equiv; U+02261
equivDD; U+02A78
eqvparsl; U+029E5
erDot; U+02253
erarr; U+02971
escr; U+0212F
esdot; U+02250
esim; U+02242
eta; U+003B7 η
eth; U+000F0 ð
euml; U+000EB ë
euro; U+020AC
excl; U+00021 !
exist; U+02203
expectation; U+02130
exponentiale; U+02147
fallingdotseq; U+02252
fcy; U+00444 ф
female; U+02640
ffilig; U+0FB03
fflig; U+0FB00
ffllig; U+0FB04
ffr; U+1D523 𝔣
filig; U+0FB01
fjlig; U+00066 U+0006A fj
flat; U+0266D
fllig; U+0FB02
fltns; U+025B1
fnof; U+00192 ƒ
fopf; U+1D557 𝕗
forall; U+02200
fork; U+022D4
forkv; U+02AD9
fpartint; U+02A0D
frac12; U+000BD ½
frac13; U+02153
frac14; U+000BC ¼
frac15; U+02155
frac16; U+02159
frac18; U+0215B
frac23; U+02154
frac25; U+02156
frac34; U+000BE ¾
frac35; U+02157
frac38; U+0215C
frac45; U+02158
frac56; U+0215A
frac58; U+0215D
frac78; U+0215E
frasl; U+02044
frown; U+02322
fscr; U+1D4BB 𝒻
gE; U+02267
gEl; U+02A8C
gacute; U+001F5 ǵ
gamma; U+003B3 γ
gammad; U+003DD ϝ
gap; U+02A86
gbreve; U+0011F ğ
gcirc; U+0011D ĝ
gcy; U+00433 г
gdot; U+00121 ġ
ge; U+02265
gel; U+022DB
geq; U+02265
geqq; U+02267
geqslant; U+02A7E
ges; U+02A7E
gescc; U+02AA9
gesdot; U+02A80
gesdoto; U+02A82
gesdotol; U+02A84
gesl; U+022DB U+0FE00 ⋛︀
gesles; U+02A94
gfr; U+1D524 𝔤
gg; U+0226B
ggg; U+022D9
gimel; U+02137
gjcy; U+00453 ѓ
gl; U+02277
glE; U+02A92
gla; U+02AA5
glj; U+02AA4
gnE; U+02269
gnap; U+02A8A
gnapprox; U+02A8A
gne; U+02A88
gneq; U+02A88
gneqq; U+02269
gnsim; U+022E7
gopf; U+1D558 𝕘
grave; U+00060 `
gscr; U+0210A
gsim; U+02273
gsime; U+02A8E
gsiml; U+02A90
gt; U+0003E >
gtcc; U+02AA7
gtcir; U+02A7A
gtdot; U+022D7
gtlPar; U+02995
gtquest; U+02A7C
gtrapprox; U+02A86
gtrarr; U+02978
gtrdot; U+022D7
gtreqless; U+022DB
gtreqqless; U+02A8C
gtrless; U+02277
gtrsim; U+02273
gvertneqq; U+02269 U+0FE00 ≩︀
gvnE; U+02269 U+0FE00 ≩︀
hArr; U+021D4
hairsp; U+0200A
half; U+000BD ½
hamilt; U+0210B
hardcy; U+0044A ъ
harr; U+02194
harrcir; U+02948
harrw; U+021AD
hbar; U+0210F
hcirc; U+00125 ĥ
hearts; U+02665
heartsuit; U+02665
hellip; U+02026
hercon; U+022B9
hfr; U+1D525 𝔥
hksearow; U+02925
hkswarow; U+02926
hoarr; U+021FF
homtht; U+0223B
hookleftarrow; U+021A9
hookrightarrow; U+021AA
hopf; U+1D559 𝕙
horbar; U+02015
hscr; U+1D4BD 𝒽
hslash; U+0210F
hstrok; U+00127 ħ
hybull; U+02043
hyphen; U+02010
iacute; U+000ED í
ic; U+02063
icirc; U+000EE î
icy; U+00438 и
iecy; U+00435 е
iexcl; U+000A1 ¡
iff; U+021D4
ifr; U+1D526 𝔦
igrave; U+000EC ì
ii; U+02148
iiiint; U+02A0C
iiint; U+0222D
iinfin; U+029DC
iiota; U+02129
ijlig; U+00133 ij
imacr; U+0012B ī
image; U+02111
imagline; U+02110
imagpart; U+02111
imath; U+00131 ı
imof; U+022B7
imped; U+001B5 Ƶ
in; U+02208
incare; U+02105
infin; U+0221E
infintie; U+029DD
inodot; U+00131 ı
int; U+0222B
intcal; U+022BA
integers; U+02124
intercal; U+022BA
intlarhk; U+02A17
intprod; U+02A3C
iocy; U+00451 ё
iogon; U+0012F į
iopf; U+1D55A 𝕚
iota; U+003B9 ι
iprod; U+02A3C
iquest; U+000BF ¿
iscr; U+1D4BE 𝒾
isin; U+02208
isinE; U+022F9
isindot; U+022F5
isins; U+022F4
isinsv; U+022F3
isinv; U+02208
it; U+02062
itilde; U+00129 ĩ
iukcy; U+00456 і
iuml; U+000EF ï
jcirc; U+00135 ĵ
jcy; U+00439 й
jfr; U+1D527 𝔧
jmath; U+00237 ȷ
jopf; U+1D55B 𝕛
jscr; U+1D4BF 𝒿
jsercy; U+00458 ј
jukcy; U+00454 є
kappa; U+003BA κ
kappav; U+003F0 ϰ
kcedil; U+00137 ķ
kcy; U+0043A к
kfr; U+1D528 𝔨
kgreen; U+00138 ĸ
khcy; U+00445 х
kjcy; U+0045C ќ
kopf; U+1D55C 𝕜
kscr; U+1D4C0 𝓀
lAarr; U+021DA
lArr; U+021D0
lAtail; U+0291B
lBarr; U+0290E
lE; U+02266
lEg; U+02A8B
lHar; U+02962
lacute; U+0013A ĺ
laemptyv; U+029B4
lagran; U+02112
lambda; U+003BB λ
lang; U+027E8
langd; U+02991
langle; U+027E8
lap; U+02A85
laquo; U+000AB «
larr; U+02190
larrb; U+021E4
larrbfs; U+0291F
larrfs; U+0291D
larrhk; U+021A9
larrlp; U+021AB
larrpl; U+02939
larrsim; U+02973
larrtl; U+021A2
lat; U+02AAB
latail; U+02919
late; U+02AAD
lates; U+02AAD U+0FE00 ⪭︀
lbarr; U+0290C
lbbrk; U+02772
lbrace; U+0007B {
lbrack; U+0005B [
lbrke; U+0298B
lbrksld; U+0298F
lbrkslu; U+0298D
lcaron; U+0013E ľ
lcedil; U+0013C ļ
lceil; U+02308
lcub; U+0007B {
lcy; U+0043B л
ldca; U+02936
ldquo; U+0201C
ldquor; U+0201E
ldrdhar; U+02967
ldrushar; U+0294B
ldsh; U+021B2
le; U+02264
leftarrow; U+02190
leftarrowtail; U+021A2
leftharpoondown; U+021BD
leftharpoonup; U+021BC
leftleftarrows; U+021C7
leftrightarrow; U+02194
leftrightarrows; U+021C6
leftrightharpoons; U+021CB
leftrightsquigarrow; U+021AD
leftthreetimes; U+022CB
leg; U+022DA
leq; U+02264
leqq; U+02266
leqslant; U+02A7D
les; U+02A7D
lescc; U+02AA8
lesdot; U+02A7F ⩿
lesdoto; U+02A81
lesdotor; U+02A83
lesg; U+022DA U+0FE00 ⋚︀
lesges; U+02A93
lessapprox; U+02A85
lessdot; U+022D6
lesseqgtr; U+022DA
lesseqqgtr; U+02A8B
lessgtr; U+02276
lesssim; U+02272
lfisht; U+0297C
lfloor; U+0230A
lfr; U+1D529 𝔩
lg; U+02276
lgE; U+02A91
lhard; U+021BD
lharu; U+021BC
lharul; U+0296A
lhblk; U+02584
ljcy; U+00459 љ
ll; U+0226A
llarr; U+021C7
llcorner; U+0231E
llhard; U+0296B
lltri; U+025FA
lmidot; U+00140 ŀ
lmoust; U+023B0
lmoustache; U+023B0
lnE; U+02268
lnap; U+02A89
lnapprox; U+02A89
lne; U+02A87
lneq; U+02A87
lneqq; U+02268
lnsim; U+022E6
loang; U+027EC
loarr; U+021FD
lobrk; U+027E6
longleftarrow; U+027F5
longleftrightarrow; U+027F7
longmapsto; U+027FC
longrightarrow; U+027F6
looparrowleft; U+021AB
looparrowright; U+021AC
lopar; U+02985
lopf; U+1D55D 𝕝
loplus; U+02A2D
lotimes; U+02A34
lowast; U+02217
lowbar; U+0005F _
loz; U+025CA
lozenge; U+025CA
lozf; U+029EB
lpar; U+00028 (
lparlt; U+02993
lrarr; U+021C6
lrcorner; U+0231F
lrhar; U+021CB
lrhard; U+0296D
lrm; U+0200E
lrtri; U+022BF
lsaquo; U+02039
lscr; U+1D4C1 𝓁
lsh; U+021B0
lsim; U+02272
lsime; U+02A8D
lsimg; U+02A8F
lsqb; U+0005B [
lsquo; U+02018
lsquor; U+0201A
lstrok; U+00142 ł
lt; U+0003C <
ltcc; U+02AA6
ltcir; U+02A79
ltdot; U+022D6
lthree; U+022CB
ltimes; U+022C9
ltlarr; U+02976
ltquest; U+02A7B
ltrPar; U+02996
ltri; U+025C3
ltrie; U+022B4
ltrif; U+025C2
lurdshar; U+0294A
luruhar; U+02966
lvertneqq; U+02268 U+0FE00 ≨︀
lvnE; U+02268 U+0FE00 ≨︀
mDDot; U+0223A
macr; U+000AF ¯
male; U+02642
malt; U+02720
maltese; U+02720
map; U+021A6
mapsto; U+021A6
mapstodown; U+021A7
mapstoleft; U+021A4
mapstoup; U+021A5
marker; U+025AE
mcomma; U+02A29
mcy; U+0043C м
mdash; U+02014
measuredangle; U+02221
mfr; U+1D52A 𝔪
mho; U+02127
micro; U+000B5 µ
mid; U+02223
midast; U+0002A *
midcir; U+02AF0
middot; U+000B7 ·
minus; U+02212
minusb; U+0229F
minusd; U+02238
minusdu; U+02A2A
mlcp; U+02ADB
mldr; U+02026
mnplus; U+02213
models; U+022A7
mopf; U+1D55E 𝕞
mp; U+02213
mscr; U+1D4C2 𝓂
mstpos; U+0223E
mu; U+003BC μ
multimap; U+022B8
mumap; U+022B8
nGg; U+022D9 U+00338 ⋙̸
nGt; U+0226B U+020D2 ≫⃒
nGtv; U+0226B U+00338 ≫̸
nLeftarrow; U+021CD
nLeftrightarrow; U+021CE
nLl; U+022D8 U+00338 ⋘̸
nLt; U+0226A U+020D2 ≪⃒
nLtv; U+0226A U+00338 ≪̸
nRightarrow; U+021CF
nVDash; U+022AF
nVdash; U+022AE
nabla; U+02207
nacute; U+00144 ń
nang; U+02220 U+020D2 ∠⃒
nap; U+02249
napE; U+02A70 U+00338 ⩰̸
napid; U+0224B U+00338 ≋̸
napos; U+00149 ʼn
napprox; U+02249
natur; U+0266E
natural; U+0266E
naturals; U+02115
nbsp; U+000A0  
nbump; U+0224E U+00338 ≎̸
nbumpe; U+0224F U+00338 ≏̸
ncap; U+02A43
ncaron; U+00148 ň
ncedil; U+00146 ņ
ncong; U+02247
ncongdot; U+02A6D U+00338 ⩭̸
ncup; U+02A42
ncy; U+0043D н
ndash; U+02013
ne; U+02260
neArr; U+021D7
nearhk; U+02924
nearr; U+02197
nearrow; U+02197
nedot; U+02250 U+00338 ≐̸
nequiv; U+02262
nesear; U+02928
nesim; U+02242 U+00338 ≂̸
nexist; U+02204
nexists; U+02204
nfr; U+1D52B 𝔫
ngE; U+02267 U+00338 ≧̸
nge; U+02271
ngeq; U+02271
ngeqq; U+02267 U+00338 ≧̸
ngeqslant; U+02A7E U+00338 ⩾̸
nges; U+02A7E U+00338 ⩾̸
ngsim; U+02275
ngt; U+0226F
ngtr; U+0226F
nhArr; U+021CE
nharr; U+021AE
nhpar; U+02AF2
ni; U+0220B
nis; U+022FC
nisd; U+022FA
niv; U+0220B
njcy; U+0045A њ
nlArr; U+021CD
nlE; U+02266 U+00338 ≦̸
nlarr; U+0219A
nldr; U+02025
nle; U+02270
nleftarrow; U+0219A
nleftrightarrow; U+021AE
nleq; U+02270
nleqq; U+02266 U+00338 ≦̸
nleqslant; U+02A7D U+00338 ⩽̸
nles; U+02A7D U+00338 ⩽̸
nless; U+0226E
nlsim; U+02274
nlt; U+0226E
nltri; U+022EA
nltrie; U+022EC
nmid; U+02224
nopf; U+1D55F 𝕟
not; U+000AC ¬
notin; U+02209
notinE; U+022F9 U+00338 ⋹̸
notindot; U+022F5 U+00338 ⋵̸
notinva; U+02209
notinvb; U+022F7
notinvc; U+022F6
notni; U+0220C
notniva; U+0220C
notnivb; U+022FE
notnivc; U+022FD
npar; U+02226
nparallel; U+02226
nparsl; U+02AFD U+020E5 ⫽⃥
npart; U+02202 U+00338 ∂̸
npolint; U+02A14
npr; U+02280
nprcue; U+022E0
npre; U+02AAF U+00338 ⪯̸
nprec; U+02280
npreceq; U+02AAF U+00338 ⪯̸
nrArr; U+021CF
nrarr; U+0219B
nrarrc; U+02933 U+00338 ⤳̸
nrarrw; U+0219D U+00338 ↝̸
nrightarrow; U+0219B
nrtri; U+022EB
nrtrie; U+022ED
nsc; U+02281
nsccue; U+022E1
nsce; U+02AB0 U+00338 ⪰̸
nscr; U+1D4C3 𝓃
nshortmid; U+02224
nshortparallel; U+02226
nsim; U+02241
nsime; U+02244
nsimeq; U+02244
nsmid; U+02224
nspar; U+02226
nsqsube; U+022E2
nsqsupe; U+022E3
nsub; U+02284
nsubE; U+02AC5 U+00338 ⫅̸
nsube; U+02288
nsubset; U+02282 U+020D2 ⊂⃒
nsubseteq; U+02288
nsubseteqq; U+02AC5 U+00338 ⫅̸
nsucc; U+02281
nsucceq; U+02AB0 U+00338 ⪰̸
nsup; U+02285
nsupE; U+02AC6 U+00338 ⫆̸
nsupe; U+02289
nsupset; U+02283 U+020D2 ⊃⃒
nsupseteq; U+02289
nsupseteqq; U+02AC6 U+00338 ⫆̸
ntgl; U+02279
ntilde; U+000F1 ñ
ntlg; U+02278
ntriangleleft; U+022EA
ntrianglelefteq; U+022EC
ntriangleright; U+022EB
ntrianglerighteq; U+022ED
nu; U+003BD ν
num; U+00023 #
numero; U+02116
numsp; U+02007
nvDash; U+022AD
nvHarr; U+02904
nvap; U+0224D U+020D2 ≍⃒
nvdash; U+022AC
nvge; U+02265 U+020D2 ≥⃒
nvgt; U+0003E U+020D2 >⃒
nvinfin; U+029DE
nvlArr; U+02902
nvle; U+02264 U+020D2 ≤⃒
nvlt; U+0003C U+020D2 <⃒
nvltrie; U+022B4 U+020D2 ⊴⃒
nvrArr; U+02903
nvrtrie; U+022B5 U+020D2 ⊵⃒
nvsim; U+0223C U+020D2 ∼⃒
nwArr; U+021D6
nwarhk; U+02923
nwarr; U+02196
nwarrow; U+02196
nwnear; U+02927
oS; U+024C8
oacute; U+000F3 ó
oast; U+0229B
ocir; U+0229A
ocirc; U+000F4 ô
ocy; U+0043E о
odash; U+0229D
odblac; U+00151 ő
odiv; U+02A38
odot; U+02299
odsold; U+029BC
oelig; U+00153 œ
ofcir; U+029BF ⦿
ofr; U+1D52C 𝔬
ogon; U+002DB ˛
ograve; U+000F2 ò
ogt; U+029C1
ohbar; U+029B5
ohm; U+003A9 Ω
oint; U+0222E
olarr; U+021BA
olcir; U+029BE
olcross; U+029BB
oline; U+0203E
olt; U+029C0
omacr; U+0014D ō
omega; U+003C9 ω
omicron; U+003BF ο
omid; U+029B6
ominus; U+02296
oopf; U+1D560 𝕠
opar; U+029B7
operp; U+029B9
oplus; U+02295
or; U+02228
orarr; U+021BB
ord; U+02A5D
order; U+02134
orderof; U+02134
ordf; U+000AA ª
ordm; U+000BA º
origof; U+022B6
oror; U+02A56
orslope; U+02A57
orv; U+02A5B
oscr; U+02134
oslash; U+000F8 ø
osol; U+02298
otilde; U+000F5 õ
otimes; U+02297
otimesas; U+02A36
ouml; U+000F6 ö
ovbar; U+0233D
par; U+02225
para; U+000B6
parallel; U+02225
parsim; U+02AF3
parsl; U+02AFD
part; U+02202
pcy; U+0043F п
percnt; U+00025 %
period; U+0002E .
permil; U+02030
perp; U+022A5
pertenk; U+02031
pfr; U+1D52D 𝔭
phi; U+003C6 φ
phiv; U+003D5 ϕ
phmmat; U+02133
phone; U+0260E
pi; U+003C0 π
pitchfork; U+022D4
piv; U+003D6 ϖ
planck; U+0210F
planckh; U+0210E
plankv; U+0210F
plus; U+0002B +
plusacir; U+02A23
plusb; U+0229E
pluscir; U+02A22
plusdo; U+02214
plusdu; U+02A25
pluse; U+02A72
plusmn; U+000B1 ±
plussim; U+02A26
plustwo; U+02A27
pm; U+000B1 ±
pointint; U+02A15
popf; U+1D561 𝕡
pound; U+000A3 £
pr; U+0227A
prE; U+02AB3
prap; U+02AB7
prcue; U+0227C
pre; U+02AAF
prec; U+0227A
precapprox; U+02AB7
preccurlyeq; U+0227C
preceq; U+02AAF
precnapprox; U+02AB9
precneqq; U+02AB5
precnsim; U+022E8
precsim; U+0227E
prime; U+02032
primes; U+02119
prnE; U+02AB5
prnap; U+02AB9
prnsim; U+022E8
prod; U+0220F
profalar; U+0232E
profline; U+02312
profsurf; U+02313
prop; U+0221D
propto; U+0221D
prsim; U+0227E
prurel; U+022B0
pscr; U+1D4C5 𝓅
psi; U+003C8 ψ
puncsp; U+02008
qfr; U+1D52E 𝔮
qint; U+02A0C
qopf; U+1D562 𝕢
qprime; U+02057
qscr; U+1D4C6 𝓆
quaternions; U+0210D
quatint; U+02A16
quest; U+0003F ?
questeq; U+0225F
quot; U+00022 "
rAarr; U+021DB
rArr; U+021D2
rAtail; U+0291C
rBarr; U+0290F
rHar; U+02964
race; U+0223D U+00331 ∽̱
racute; U+00155 ŕ
radic; U+0221A
raemptyv; U+029B3
rang; U+027E9
rangd; U+02992
range; U+029A5
rangle; U+027E9
raquo; U+000BB »
rarr; U+02192
rarrap; U+02975
rarrb; U+021E5
rarrbfs; U+02920
rarrc; U+02933
rarrfs; U+0291E
rarrhk; U+021AA
rarrlp; U+021AC
rarrpl; U+02945
rarrsim; U+02974
rarrtl; U+021A3
rarrw; U+0219D
ratail; U+0291A
ratio; U+02236
rationals; U+0211A
rbarr; U+0290D
rbbrk; U+02773
rbrace; U+0007D }
rbrack; U+0005D ]
rbrke; U+0298C
rbrksld; U+0298E
rbrkslu; U+02990
rcaron; U+00159 ř
rcedil; U+00157 ŗ
rceil; U+02309
rcub; U+0007D }
rcy; U+00440 р
rdca; U+02937
rdldhar; U+02969
rdquo; U+0201D
rdquor; U+0201D
rdsh; U+021B3
real; U+0211C
realine; U+0211B
realpart; U+0211C
reals; U+0211D
rect; U+025AD
reg; U+000AE ®
rfisht; U+0297D
rfloor; U+0230B
rfr; U+1D52F 𝔯
rhard; U+021C1
rharu; U+021C0
rharul; U+0296C
rho; U+003C1 ρ
rhov; U+003F1 ϱ
rightarrow; U+02192
rightarrowtail; U+021A3
rightharpoondown; U+021C1
rightharpoonup; U+021C0
rightleftarrows; U+021C4
rightleftharpoons; U+021CC
rightrightarrows; U+021C9
rightsquigarrow; U+0219D
rightthreetimes; U+022CC
ring; U+002DA ˚
risingdotseq; U+02253
rlarr; U+021C4
rlhar; U+021CC
rlm; U+0200F
rmoust; U+023B1
rmoustache; U+023B1
rnmid; U+02AEE
roang; U+027ED
roarr; U+021FE
robrk; U+027E7
ropar; U+02986
ropf; U+1D563 𝕣
roplus; U+02A2E
rotimes; U+02A35
rpar; U+00029 )
rpargt; U+02994
rppolint; U+02A12
rrarr; U+021C9
rsaquo; U+0203A
rscr; U+1D4C7 𝓇
rsh; U+021B1
rsqb; U+0005D ]
rsquo; U+02019
rsquor; U+02019
rthree; U+022CC
rtimes; U+022CA
rtri; U+025B9
rtrie; U+022B5
rtrif; U+025B8
rtriltri; U+029CE
ruluhar; U+02968
rx; U+0211E
sacute; U+0015B ś
sbquo; U+0201A
sc; U+0227B
scE; U+02AB4
scap; U+02AB8
scaron; U+00161 š
sccue; U+0227D
sce; U+02AB0
scedil; U+0015F ş
scirc; U+0015D ŝ
scnE; U+02AB6
scnap; U+02ABA
scnsim; U+022E9
scpolint; U+02A13
scsim; U+0227F
scy; U+00441 с
sdot; U+022C5
sdotb; U+022A1
sdote; U+02A66
seArr; U+021D8
searhk; U+02925
searr; U+02198
searrow; U+02198
sect; U+000A7 §
semi; U+0003B ;
seswar; U+02929
setminus; U+02216
setmn; U+02216
sext; U+02736
sfr; U+1D530 𝔰
sfrown; U+02322
sharp; U+0266F
shchcy; U+00449 щ
shcy; U+00448 ш
shortmid; U+02223
shortparallel; U+02225
shy; U+000AD ­
sigma; U+003C3 σ
sigmaf; U+003C2 ς
sigmav; U+003C2 ς
sim; U+0223C
simdot; U+02A6A
sime; U+02243
simeq; U+02243
simg; U+02A9E
simgE; U+02AA0
siml; U+02A9D
simlE; U+02A9F
simne; U+02246
simplus; U+02A24
simrarr; U+02972
slarr; U+02190
smallsetminus; U+02216
smashp; U+02A33
smeparsl; U+029E4
smid; U+02223
smile; U+02323
smt; U+02AAA
smte; U+02AAC
smtes; U+02AAC U+0FE00 ⪬︀
softcy; U+0044C ь
sol; U+0002F /
solb; U+029C4
solbar; U+0233F
sopf; U+1D564 𝕤
spades; U+02660
spadesuit; U+02660
spar; U+02225
sqcap; U+02293
sqcaps; U+02293 U+0FE00 ⊓︀
sqcup; U+02294
sqcups; U+02294 U+0FE00 ⊔︀
sqsub; U+0228F
sqsube; U+02291
sqsubset; U+0228F
sqsubseteq; U+02291
sqsup; U+02290
sqsupe; U+02292
sqsupset; U+02290
sqsupseteq; U+02292
squ; U+025A1
square; U+025A1
squarf; U+025AA
squf; U+025AA
srarr; U+02192
sscr; U+1D4C8 𝓈
ssetmn; U+02216
ssmile; U+02323
sstarf; U+022C6
star; U+02606
starf; U+02605
straightepsilon; U+003F5 ϵ
straightphi; U+003D5 ϕ
strns; U+000AF ¯
sub; U+02282
subE; U+02AC5
subdot; U+02ABD
sube; U+02286
subedot; U+02AC3
submult; U+02AC1
subnE; U+02ACB
subne; U+0228A
subplus; U+02ABF ⪿
subrarr; U+02979
subset; U+02282
subseteq; U+02286
subseteqq; U+02AC5
subsetneq; U+0228A
subsetneqq; U+02ACB
subsim; U+02AC7
subsub; U+02AD5
subsup; U+02AD3
succ; U+0227B
succapprox; U+02AB8
succcurlyeq; U+0227D
succeq; U+02AB0
succnapprox; U+02ABA
succneqq; U+02AB6
succnsim; U+022E9
succsim; U+0227F
sum; U+02211
sung; U+0266A
sup; U+02283
sup1; U+000B9 ¹
sup2; U+000B2 ²
sup3; U+000B3 ³
supE; U+02AC6
supdot; U+02ABE
supdsub; U+02AD8
supe; U+02287
supedot; U+02AC4
suphsol; U+027C9
suphsub; U+02AD7
suplarr; U+0297B
supmult; U+02AC2
supnE; U+02ACC
supne; U+0228B
supplus; U+02AC0
supset; U+02283
supseteq; U+02287
supseteqq; U+02AC6
supsetneq; U+0228B
supsetneqq; U+02ACC
supsim; U+02AC8
supsub; U+02AD4
supsup; U+02AD6
swArr; U+021D9
swarhk; U+02926
swarr; U+02199
swarrow; U+02199
swnwar; U+0292A
szlig; U+000DF ß
target; U+02316
tau; U+003C4 τ
tbrk; U+023B4
tcaron; U+00165 ť
tcedil; U+00163 ţ
tcy; U+00442 т
tdot; U+020DB ◌⃛
telrec; U+02315
tfr; U+1D531 𝔱
there4; U+02234
therefore; U+02234
theta; U+003B8 θ
thetasym; U+003D1 ϑ
thetav; U+003D1 ϑ
thickapprox; U+02248
thicksim; U+0223C
thinsp; U+02009
thkap; U+02248
thksim; U+0223C
thorn; U+000FE þ
tilde; U+002DC ˜
times; U+000D7 ×
timesb; U+022A0
timesbar; U+02A31
timesd; U+02A30
tint; U+0222D
toea; U+02928
top; U+022A4
topbot; U+02336
topcir; U+02AF1
topf; U+1D565 𝕥
topfork; U+02ADA
tosa; U+02929
tprime; U+02034
trade; U+02122
triangle; U+025B5
triangledown; U+025BF
triangleleft; U+025C3
trianglelefteq; U+022B4
triangleq; U+0225C
triangleright; U+025B9
trianglerighteq; U+022B5
tridot; U+025EC
trie; U+0225C
triminus; U+02A3A
triplus; U+02A39
trisb; U+029CD
tritime; U+02A3B
trpezium; U+023E2
tscr; U+1D4C9 𝓉
tscy; U+00446 ц
tshcy; U+0045B ћ
tstrok; U+00167 ŧ
twixt; U+0226C
twoheadleftarrow; U+0219E
twoheadrightarrow; U+021A0
uArr; U+021D1
uHar; U+02963
uacute; U+000FA ú
uarr; U+02191
ubrcy; U+0045E ў
ubreve; U+0016D ŭ
ucirc; U+000FB û
ucy; U+00443 у
udarr; U+021C5
udblac; U+00171 ű
udhar; U+0296E
ufisht; U+0297E
ufr; U+1D532 𝔲
ugrave; U+000F9 ù
uharl; U+021BF
uharr; U+021BE
uhblk; U+02580
ulcorn; U+0231C
ulcorner; U+0231C
ulcrop; U+0230F
ultri; U+025F8
umacr; U+0016B ū
uml; U+000A8 ¨
uogon; U+00173 ų
uopf; U+1D566 𝕦
uparrow; U+02191
updownarrow; U+02195
upharpoonleft; U+021BF
upharpoonright; U+021BE
uplus; U+0228E
upsi; U+003C5 υ
upsih; U+003D2 ϒ
upsilon; U+003C5 υ
upuparrows; U+021C8
urcorn; U+0231D
urcorner; U+0231D
urcrop; U+0230E
uring; U+0016F ů
urtri; U+025F9
uscr; U+1D4CA 𝓊
utdot; U+022F0
utilde; U+00169 ũ
utri; U+025B5
utrif; U+025B4
uuarr; U+021C8
uuml; U+000FC ü
uwangle; U+029A7
vArr; U+021D5
vBar; U+02AE8
vBarv; U+02AE9
vDash; U+022A8
vangrt; U+0299C
varepsilon; U+003F5 ϵ
varkappa; U+003F0 ϰ
varnothing; U+02205
varphi; U+003D5 ϕ
varpi; U+003D6 ϖ
varpropto; U+0221D
varr; U+02195
varrho; U+003F1 ϱ
varsigma; U+003C2 ς
varsubsetneq; U+0228A U+0FE00 ⊊︀
varsubsetneqq; U+02ACB U+0FE00 ⫋︀
varsupsetneq; U+0228B U+0FE00 ⊋︀
varsupsetneqq; U+02ACC U+0FE00 ⫌︀
vartheta; U+003D1 ϑ
vartriangleleft; U+022B2
vartriangleright; U+022B3
vcy; U+00432 в
vdash; U+022A2
vee; U+02228
veebar; U+022BB
veeeq; U+0225A
vellip; U+022EE
verbar; U+0007C |
vert; U+0007C |
vfr; U+1D533 𝔳
vltri; U+022B2
vnsub; U+02282 U+020D2 ⊂⃒
vnsup; U+02283 U+020D2 ⊃⃒
vopf; U+1D567 𝕧
vprop; U+0221D
vrtri; U+022B3
vscr; U+1D4CB 𝓋
vsubnE; U+02ACB U+0FE00 ⫋︀
vsubne; U+0228A U+0FE00 ⊊︀
vsupnE; U+02ACC U+0FE00 ⫌︀
vsupne; U+0228B U+0FE00 ⊋︀
vzigzag; U+0299A
wcirc; U+00175 ŵ
wedbar; U+02A5F
wedge; U+02227
wedgeq; U+02259
weierp; U+02118
wfr; U+1D534 𝔴
wopf; U+1D568 𝕨
wp; U+02118
wr; U+02240
wreath; U+02240
wscr; U+1D4CC 𝓌
xcap; U+022C2
xcirc; U+025EF
xcup; U+022C3
xdtri; U+025BD
xfr; U+1D535 𝔵
xhArr; U+027FA
xharr; U+027F7
xi; U+003BE ξ
xlArr; U+027F8
xlarr; U+027F5
xmap; U+027FC
xnis; U+022FB
xodot; U+02A00
xopf; U+1D569 𝕩
xoplus; U+02A01
xotime; U+02A02
xrArr; U+027F9
xrarr; U+027F6
xscr; U+1D4CD 𝓍
xsqcup; U+02A06
xuplus; U+02A04
xutri; U+025B3
xvee; U+022C1
xwedge; U+022C0
yacute; U+000FD ý
yacy; U+0044F я
ycirc; U+00177 ŷ
ycy; U+0044B ы
yen; U+000A5 ¥
yfr; U+1D536 𝔶
yicy; U+00457 ї
yopf; U+1D56A 𝕪
yscr; U+1D4CE 𝓎
yucy; U+0044E ю
yuml; U+000FF ÿ
zacute; U+0017A ź
zcaron; U+0017E ž
zcy; U+00437 з
zdot; U+0017C ż
zeetrf; U+02128
zeta; U+003B6 ζ
zfr; U+1D537 𝔷
zhcy; U+00436 ж
zigrarr; U+021DD
zopf; U+1D56B 𝕫
zscr; U+1D4CF 𝓏
zwj; U+0200D
zwnj; U+0200C

The glyphs displayed above are non-normative. Refer to the Unicode specifications for formal definitions of the characters listed above.

9 The XHTML syntax

This section only describes the rules for XML resources. Rules for text/html resources are discussed in the section above entitled "The HTML syntax".

The syntax for using HTML with XML, whether in XHTML documents or embedded in other XML documents, is defined in the XML and Namespaces in XML specifications. [XML] [XMLNS]

This specification does not define any syntax-level requirements beyond those defined for XML proper.

XML documents may contain a DOCTYPE if desired, but this is not required to conform to this specification. This specification does not define a public or system identifier, nor provide a format DTD.

According to the XML specification, XML processors are not guaranteed to process the external DTD subset referenced in the DOCTYPE. This means, for example, that using entity references for characters in XHTML documents is unsafe if they are defined in an external file (except for &lt;, &gt;, &amp;, &quot; and &apos;).

10 Obsolete features

10.1 Obsolete but conforming features

Features listed in this section will trigger warnings in conformance checkers.

Authors should not specify an http-equiv attribute in the Content Language state on a meta element. The lang attribute should be used instead.

Authors should not specify a border attribute on an img element. If the attribute is present, its value must be the string "0". CSS should be used instead.

Authors should not specify a language attribute on a script element. If the attribute is present, its value must be an ASCII case-insensitive match for the string "JavaScript" and either the type attribute must be omitted or its value must be an ASCII case-insensitive match for the string "text/javascript". The attribute should be entirely omitted instead (with the value "JavaScript", it has no effect), or replaced with use of the type attribute.

Authors should not specify the name attribute on a elements. If the attribute is present, its value must not be the empty string and must neither be equal to the value of any of the IDs in the element's home subtree other than the element's own ID, if any, nor be equal to the value of any of the other name attributes on a elements in the element's home subtree. If this attribute is present and the element has an ID, then the attribute's value must be equal to the element's ID. In earlier versions of the language, this attribute was intended as a way to specify possible targets for fragment identifiers in URLs. The id attribute should be used instead.

In the HTML syntax, specifying a DOCTYPE that is an obsolete permitted DOCTYPE will also trigger a warning.

The summary attribute, defined in the table section, will also trigger a warning.

10.2 Non-conforming features

Elements in the following list are entirely obsolete, and must not be used by authors:

applet

Use embed or object instead.

acronym

Use abbr instead.

bgsound

Use audio instead.

dir

Use ul instead.

frame
frameset
noframes

Either use iframe and CSS instead, or use server-side includes to generate complete pages with the various invariant parts merged in.

isindex

Use an explicit form and text field combination instead.

listing
xmp

Use pre and code instead.

nextid

Use GUIDs instead.

noembed

Use object instead of embed when fallback is necessary.

plaintext

Use the "text/plain" MIME type instead.

rb

Providing the ruby base directly inside the ruby element is sufficient; the rb element is unnecessary. Omit it altogether.

strike

Use del instead if the element is marking an edit, otherwise use s instead.

basefont
big
blink
center
font
marquee
multicol
nobr
spacer
tt
u

Use appropriate elements and/or CSS instead.

Where the tt element would have been used for marking up keyboard input, consider the kbd element; for variables, consider the var element; for computer code, consider the code element; and for computer output, consider the samp element.

Similarly, if the u element is being used to indicate emphasis, consider using the em element; if it is being used for marking up keywords, consider the b element; and if it is being used for highlighting text for reference purposes, consider the mark element.

See also the text-level semantics usage summary for more suggestions with examples.


The following attributes are obsolete (though the elements are still part of the language), and must not be used by authors:

charset on a elements
charset on link elements

Use an HTTP Content-Type header on the linked resource instead.

coords on a elements
shape on a elements

Use area instead of a for image maps.

methods on a elements
methods on link elements

Use the HTTP OPTIONS feature instead.

name on a elements (except as noted in the previous section)
name on embed elements
name on img elements
name on option elements

Use the id attribute instead.

rev on a elements
rev on link elements

Use the rel attribute instead, with an opposite term. (For example, instead of rev="made", use rel="author".)

urn on a elements
urn on link elements

Specify the preferred persistent identifier using the href attribute instead.

nohref on area elements

Omitting the href attribute is sufficient; the nohref attribute is unnecessary. Omit it altogether.

profile on head elements

When used for declaring which meta terms are used in the document, unnecessary; omit it altogether, and register the names.

When used for triggering specific user agent behaviors: use a link element instead.

version on html elements

Unnecessary. Omit it altogether.

usemap on input elements

Use img instead of input for image maps.

longdesc on iframe elements
longdesc on img elements

Use a regular a element to link to the description, or (in the case of images) use an image map to provide a link from the image to the image's description.

lowsrc on img elements

Use a progressive JPEG image (given in the src attribute), instead of using two separate images.

target on link elements

Unnecessary. Omit it altogether.

scheme on meta elements

Use only one scheme per field, or make the scheme declaration part of the value.

archive on object elements
classid on object elements
code on object elements
codebase on object elements
codetype on object elements

Use the data and type attributes to invoke plugins. To set parameters with these names in particular, the param element can be used.

declare on object elements

Repeat the object element completely each time the resource is to be reused.

standby on object elements

Optimize the linked resource so that it loads quickly or, at least, incrementally.

type on param elements
valuetype on param elements

Use the name and value attributes without declaring value types.

language on script elements (except as noted in the previous section)

Use the type attribute instead.

event on script elements
for on script elements

Use DOM Events mechanisms to register event listeners. [DOMEVENTS]

datapagesize on table elements

Unnecessary. Omit it altogether.

abbr on td and th elements

Use text that begins in an unambiguous and terse manner, and include any more elaborate text after that. The title attribute can also be useful in including more detailed text, so that the cell's contents can be made terse.

axis on td and th elements

Use the scope attribute on the relevant th.

datasrc on a, applet, button, div, frame, iframe, img, input, label, legend, marquee, object, option, select, span, table, and textarea elements
datafld on a, applet, button, div, fieldset, frame, iframe, img, input, label, legend, marquee, object, param, select, span, and textarea elements
dataformatas on button, div, input, label, legend, marquee, object, option, select, span, and table elements

Use script and a mechanism such as XMLHttpRequest to populate the page dynamically. [XHR]

alink on body elements
bgcolor on body elements
link on body elements
marginbottom on body elements
marginheight on body elements
marginleft on body elements
marginright on body elements
margintop on body elements
marginwidth on body elements
text on body elements
vlink on body elements
clear on br elements
align on caption elements
align on col elements
char on col elements
charoff on col elements
valign on col elements
width on col elements
align on div elements
compact on dl elements
align on embed elements
hspace on embed elements
vspace on embed elements
align on hr elements
color on hr elements
noshade on hr elements
size on hr elements
width on hr elements
align on h1h6 elements
align on iframe elements
allowtransparency on iframe elements
frameborder on iframe elements
hspace on iframe elements
marginheight on iframe elements
marginwidth on iframe elements
scrolling on iframe elements
vspace on iframe elements
align on input elements
hspace on input elements
vspace on input elements
align on img elements
border on img elements (except as noted in the previous section)
hspace on img elements
vspace on img elements
align on legend elements
type on li elements
compact on menu elements
align on object elements
border on object elements
hspace on object elements
vspace on object elements
compact on ol elements
align on p elements
width on pre elements
align on table elements
bgcolor on table elements
border on table elements
cellpadding on table elements
cellspacing on table elements
frame on table elements
rules on table elements
width on table elements
align on tbody, thead, and tfoot elements
char on tbody, thead, and tfoot elements
charoff on tbody, thead, and tfoot elements
valign on tbody, thead, and tfoot elements
align on td and th elements
bgcolor on td and th elements
char on td and th elements
charoff on td and th elements
height on td and th elements
nowrap on td and th elements
valign on td and th elements
width on td and th elements
align on tr elements
bgcolor on tr elements
char on tr elements
charoff on tr elements
valign on tr elements
compact on ul elements
type on ul elements
background on body, table, thead, tbody, tfoot, tr, td, and th elements

Use CSS instead.

11 IANA considerations

11.1 text/html

This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.

Type name:
text
Subtype name:
html
Required parameters:
No required parameters
Optional parameters:
charset

The charset parameter may be provided to definitively specify the document's character encoding, overriding any character encoding declarations in the document. The parameter's value must be the name of the character encoding used to serialize the file, must be a valid character encoding name, and must be an ASCII case-insensitive match for the preferred MIME name for that encoding. [IANACHARSET]

Encoding considerations:
See the section on character encoding declarations.
Security considerations:

Entire novels have been written about the security considerations that apply to HTML documents. Many are listed in this document, to which the reader is referred for more details. Some general concerns bear mentioning here, however:

HTML is scripted language, and has a large number of APIs (some of which are described in this document). Script can expose the user to potential risks of information leakage, credential leakage, cross-site scripting attacks, cross-site request forgeries, and a host of other problems. While the designs in this specification are intended to be safe if implemented correctly, a full implementation is a massive undertaking and, as with any software, user agents are likely to have security bugs.

Even without scripting, there are specific features in HTML which, for historical reasons, are required for broad compatibility with legacy content but that expose the user to unfortunate security problems. In particular, the img element can be used in conjunction with some other features as a way to effect a port scan from the user's location on the Internet. This can expose local network topologies that the attacker would otherwise not be able to determine.

HTML relies on a compartmentalization scheme sometimes known as the same-origin policy. An origin in most cases consists of all the pages served from the same host, on the same port, using the same protocol.

It is critical, therefore, to ensure that any untrusted content that forms part of a site be hosted on a different origin than any sensitive content on that site. Untrusted content can easily spoof any other page on the same origin, read data from that origin, cause scripts in that origin to execute, submit forms to and from that origin even if they are protected from cross-site request forgery attacks by unique tokens, and make use of any third-party resources exposed to or rights granted to that origin.

Interoperability considerations:
Rules for processing both conforming and non-conforming content are defined in this specification.
Published specification:
This document is the relevant specification. Labeling a resource with the text/html type asserts that the resource is an HTML document using the HTML syntax.
Applications that use this media type:
Web browsers, tools for processing Web content, HTML authoring tools, search engines, validators.
Additional information:
Magic number(s):
No sequence of bytes can uniquely identify an HTML document. More information on detecting HTML documents is available in the Media Type Sniffing specification. [MIMESNIFF]
File extension(s):
"html" and "htm" are commonly, but certainly not exclusively, used as the extension for HTML documents.
Macintosh file type code(s):
TEXT
Person & email address to contact for further information:
Ian Hickson <ian@hixie.ch>
Intended usage:
Common
Restrictions on usage:
No restrictions apply.
Author:
Ian Hickson <ian@hixie.ch>
Change controller:
W3C

Fragment identifiers used with text/html resources refer to the indicated part of the document.

11.2 text/html-sandboxed

This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.

Type name:
text
Subtype name:
html-sandboxed
Required parameters:
No required parameters
Optional parameters:
Same as for text/html
Encoding considerations:
Same as for text/html
Security considerations:

The purpose of the text/html-sandboxed MIME type is to provide a way for content providers to indicate that they want the file to be interpreted in a manner that does not give the file's contents access to the rest of the site. This is achieved by assigning the Document objects generated from resources labeled as text/html-sandboxed unique origins.

To avoid having legacy user agents treating resources labeled as text/html-sandboxed as regular text/html files, authors should avoid using the .html or .htm extensions for resources labeled as text/html-sandboxed.

Furthermore, since the text/html-sandboxed MIME type impacts the origin security model, authors should be careful to prevent tampering with the MIME type labeling mechanism itself when documents are labeled as text/html-sandboxed. If an attacker can cause a file to be served as text/html instead of text/html-sandboxed, then the sandboxing will not take effect and a cross-site scripting attack will become possible.

Beyond this, the type is identical to text/html, and the same considerations apply.

Interoperability considerations:
Same as for text/html
Published specification:
This document is the relevant specification. Labeling a resource with the text/html-sandboxed type asserts that the resource is an HTML document using the HTML syntax.
Applications that use this media type:
Same as for text/html
Additional information:
Magic number(s):
Documents labeled as text/html-sandboxed are heuristically indistinguishable from those labeled as text/html.
File extension(s):
"sandboxed"
Macintosh file type code(s):
TEXT
Person & email address to contact for further information:
Ian Hickson <ian@hixie.ch>
Intended usage:
Common
Restrictions on usage:
No restrictions apply.
Author:
Ian Hickson <ian@hixie.ch>
Change controller:
W3C

Fragment identifiers used with text/html-sandboxed resources refer to the indicated part of the document.

11.3 application/xhtml+xml

This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.

Type name:
application
Subtype name:
xhtml+xml
Required parameters:
Same as for application/xml [RFC3023]
Optional parameters:
Same as for application/xml [RFC3023]
Encoding considerations:
Same as for application/xml [RFC3023]
Security considerations:
Same as for application/xml [RFC3023]
Interoperability considerations:
Same as for application/xml [RFC3023]
Published specification:
Labeling a resource with the application/xhtml+xml type asserts that the resource is an XML document that likely has a root element from the HTML namespace. As such, the relevant specifications are the XML specification, the Namespaces in XML specification, and this specification. [XML] [XMLNS]
Applications that use this media type:
Same as for application/xml [RFC3023]
Additional information:
Magic number(s):
Same as for application/xml [RFC3023]
File extension(s):
"xhtml" and "xht" are sometimes used as extensions for XML resources that have a root element from the HTML namespace.
Macintosh file type code(s):
TEXT
Person & email address to contact for further information:
Ian Hickson <ian@hixie.ch>
Intended usage:
Common
Restrictions on usage:
No restrictions apply.
Author:
Ian Hickson <ian@hixie.ch>
Change controller:
W3C

Fragment identifiers used with application/xhtml+xml resources have the same semantics as with any XML MIME type. [RFC3023]

11.4 text/cache-manifest

This registration is for community review and will be submitted to the IESG for review, approval, and registration with IANA.

Type name:
text
Subtype name:
cache-manifest
Required parameters:
No parameters
Optional parameters:
No parameters
Encoding considerations:
Always UTF-8.
Security considerations:

Cache manifests themselves pose no immediate risk unless sensitive information is included within the manifest. Implementations, however, are required to follow specific rules when populating a cache based on a cache manifest, to ensure that certain origin-based restrictions are honored. Failure to correctly implement these rules can result in information leakage, cross-site scripting attacks, and the like.

Interoperability considerations:
Rules for processing both conforming and non-conforming content are defined in this specification.
Published specification:
This document is the relevant specification.
Applications that use this media type:
Web browsers.
Additional information:
Magic number(s):
Cache manifests begin with the string "CACHE MANIFEST", followed by either a U+0020 SPACE character, a U+0009 CHARACTER TABULATION (tab) character, a U+000A LINE FEED (LF) character, or a U+000D CARRIAGE RETURN (CR) character.
File extension(s):
"manifest"
Macintosh file type code(s):
No specific Macintosh file type codes are recommended for this type.
Person & email address to contact for further information:
Ian Hickson <ian@hixie.ch>
Intended usage:
Common
Restrictions on usage:
No restrictions apply.
Author:
Ian Hickson <ian@hixie.ch>
Change controller:
W3C

Fragment identifiers have no meaning with text/cache-manifest resources.

Index

Elements

This section is non-normative.

List of elements
Element Description Categories Parents Children Attributes Interface
a Hyperlink flow; phrasing*; interactive phrasing transparent* globals; href; target; rel; media; hreflang; type HTMLAnchorElement
abbr Abbreviation flow; phrasing phrasing phrasing globals HTMLElement
address Contact information for a page or section flow; formatBlock candidate flow flow* globals HTMLElement
area Hyperlink or dead area on an image map flow; phrasing phrasing* empty globals; alt; coords; shape; href; target; rel; media; hreflang; type HTMLAreaElement
article Self-contained syndicatable or reusable composition flow; sectioning; formatBlock candidate flow flow globals HTMLElement
aside Sidebar for tangentially related content flow; sectioning; formatBlock candidate flow flow globals HTMLElement
audio Audio player flow; phrasing; embedded; interactive phrasing source*; transparent* globals; src; preload; autoplay; loop; controls HTMLAudioElement
b Keywords flow; phrasing phrasing phrasing globals HTMLElement
base Base URL and default target browsing context for hyperlinks and forms metadata head empty globals; href; target HTMLBaseElement
bdi Text directionality isolation flow; phrasing phrasing phrasing globals HTMLElement
bdo Text directionality formatting flow; phrasing phrasing phrasing globals HTMLElement
blockquote A section quoted from another source flow; sectioning root; formatBlock candidate flow flow globals; cite HTMLQuoteElement
body Document body sectioning root html flow globals; onafterprint; onbeforeprint; onbeforeunload; onblur; onerror; onfocus; onhashchange; onload; onmessage; onoffline; ononline; onpagehide; onpageshow; onpopstate; onredo; onresize; onscroll; onstorage; onundo; onunload HTMLBodyElement
br Line break, e.g. in poem or postal address flow; phrasing phrasing empty globals HTMLBRElement
button Button control flow; phrasing; interactive; listed; labelable; submittable; form-associated phrasing phrasing* globals; autofocus; disabled; form; formaction; formenctype; formmethod; formnovalidate; formtarget; name; type; value HTMLButtonElement
canvas Scriptable bitmap canvas flow; phrasing; embedded phrasing transparent globals; width; height HTMLCanvasElement
caption Table caption none table flow* globals HTMLTableCaptionElement
cite Title of a work flow; phrasing phrasing phrasing globals HTMLElement
code Computer code flow; phrasing phrasing phrasing globals HTMLElement
col Table column none colgroup empty globals; span HTMLTableColElement
colgroup Group of columns in a table none table col globals; span HTMLTableColElement
command Menu command metadata; flow; phrasing head; phrasing empty globals; type; label; icon; disabled; checked; radiogroup HTMLCommandElement
datalist Container for options for combo box control flow; phrasing phrasing phrasing; option globals HTMLDataListElement
dd Content for corresponding dt element(s) none dl flow globals HTMLElement
del A removal from the document flow; phrasing* phrasing transparent globals; cite; datetime HTMLModElement
details Disclosure control for hiding details flow; sectioning root; interactive flow summary*; flow globals; open HTMLDetailsElement
dfn Defining instance flow; phrasing phrasing phrasing* globals HTMLElement
div Generic flow container flow; formatBlock candidate flow flow globals HTMLDivElement
dl Association list consisting of zero or more name-value groups flow flow dt*; dd* globals HTMLDListElement
dt Legend for corresponding dd element(s) none dl phrasing globals HTMLElement
em Stress emphasis flow; phrasing phrasing phrasing globals HTMLElement
embed Plugin flow; phrasing; embedded; interactive phrasing empty globals; src; type; width; height; any* HTMLEmbedElement
fieldset Group of form controls flow; sectioning root; listed; form-associated flow legend*; flow globals; disabled; form; name HTMLFieldSetElement
figcaption Caption for figure none figure flow globals HTMLElement
figure Figure with optional caption flow; sectioning root flow figcaption*; flow globals HTMLElement
footer Footer for a page or section flow; formatBlock candidate flow flow* globals HTMLElement
form User-submittable form flow flow flow* globals; accept-charset; action; autocomplete; enctype; method; name; novalidate; target HTMLFormElement
h1, h2, h3, h4, h5, h6 Section heading flow; heading; formatBlock candidate hgroup; flow phrasing globals HTMLHeadingElement
head Container for document metadata none html metadata content* globals HTMLHeadElement
header Introductory or navigational aids for a page or section flow; formatBlock candidate flow flow* globals HTMLElement
hgroup heading group flow; heading; formatBlock candidate flow One or more h1, h2, h3, h4, h5, and/or h6 globals HTMLElement
hr Thematic break flow flow empty globals HTMLHRElement
html Root element none none* head*; body* globals; manifest HTMLHtmlElement
i Alternate voice flow; phrasing phrasing phrasing globals HTMLElement
iframe Nested browsing context flow; phrasing; embedded; interactive phrasing text* globals; src; srcdoc; name; sandbox; seamless; width; height HTMLIFrameElement
img Image flow; phrasing; embedded; interactive* phrasing empty globals; alt; src; usemap; ismap; width; height HTMLImageElement
input Form control flow; phrasing; interactive*; listed; labelable; submittable; resettable; form-associated phrasing empty globals; accept; alt; autocomplete; autofocus; checked; dirname; disabled; form; formaction; formenctype; formmethod; formnovalidate; formtarget; height; list; max; maxlength; min; multiple; name; pattern; placeholder; readonly; required; size; src; step; type; value; width HTMLInputElement
ins An addition to the document flow; phrasing* phrasing transparent globals; cite; datetime HTMLModElement
kbd User input flow; phrasing phrasing phrasing globals HTMLElement
keygen Cryptographic key-pair generator form control flow; phrasing; interactive; listed; labelable; submittable; resettable; form-associated phrasing empty globals; autofocus; challenge; disabled; form; keytype; name HTMLKeygenElement
label Caption for a form control flow; phrasing; interactive; form-associated phrasing phrasing* globals; form; for HTMLLabelElement
legend Caption for fieldset none fieldset phrasing globals HTMLLegendElement
li List item none ol; ul; menu flow globals; value* HTMLLIElement
link Link metadata metadata; flow*; phrasing* head; noscript*; phrasing* empty globals; href; rel; media; hreflang; type; sizes HTMLLinkElement
map Image map flow; phrasing* phrasing transparent; area* globals; name HTMLMapElement
mark Highlight flow; phrasing phrasing phrasing globals HTMLElement
menu Menu of commands flow; interactive* flow li*; flow globals; type; label HTMLMenuElement
meta Text metadata metadata; flow*; phrasing* head; noscript*; phrasing* empty globals; name; http-equiv; content; charset HTMLMetaElement
meter Gauge flow; phrasing; labelable; form-associated phrasing phrasing* globals; value; min; max; low; high; optimum; form HTMLMeterElement
nav Section with navigational links flow; sectioning; formatBlock candidate flow flow globals HTMLElement
noscript Fallback content for script metadata; flow; phrasing head*; phrasing* varies* globals HTMLElement
object Image, nested browsing context, or plugin flow; phrasing; embedded; interactive*; listed; submittable; form-associated phrasing param*; transparent globals; data; type; name; usemap; form; width; height HTMLObjectElement
ol Ordered list flow flow li globals; reversed; start HTMLOListElement
optgroup Group of options in a list box none select option globals; disabled; label HTMLOptGroupElement
option Option in a list box or combo box control none select; datalist; optgroup text globals; disabled; label; selected; value HTMLOptionElement
output Calculated output value flow; phrasing; listed; labelable; resettable; form-associated phrasing phrasing globals; for; form; name HTMLOutputElement
p Paragraph flow; formatBlock candidate flow phrasing globals HTMLParagraphElement
param Parameter for object none object empty globals; name; value HTMLParamElement
pre Block of preformatted text flow; formatBlock candidate flow phrasing globals HTMLPreElement
progress Progress bar flow; phrasing; labelable; form-associated phrasing phrasing* globals; value; max; form HTMLProgressElement
q Quotation flow; phrasing phrasing phrasing globals; cite HTMLQuoteElement
rp Parenthesis for ruby annotation text none ruby phrasing globals HTMLElement
rt Ruby annotation text none ruby phrasing globals HTMLElement
ruby Ruby annotation(s) flow; phrasing phrasing phrasing; rt element; rp element* globals HTMLElement
s Inaccurate text flow; phrasing phrasing phrasing globals HTMLElement
samp Computer output flow; phrasing phrasing phrasing globals HTMLElement
script Embedded script metadata; flow; phrasing head; phrasing script, data, or script documentation* globals; src; async; defer; type; charset HTMLScriptElement
section Generic document or application section flow; sectioning; formatBlock candidate flow flow globals HTMLElement
select List box control flow; phrasing; interactive; listed; labelable; submittable; resettable; form-associated phrasing option, optgroup globals; autofocus; disabled; form; multiple; name; required; size HTMLSelectElement
small Side comment flow; phrasing phrasing phrasing globals HTMLElement
source Media source for video or audio none video; audio empty globals; src; type; media HTMLSourceElement
span Generic phrasing container flow; phrasing phrasing phrasing globals HTMLSpanElement
strong Importance flow; phrasing phrasing phrasing globals HTMLElement
style Embedded styling information metadata; flow head; noscript*; flow* varies* globals; media; type; scoped HTMLStyleElement
sub Subscript flow; phrasing phrasing phrasing globals HTMLElement
summary Caption for details none details phrasing globals HTMLElement
sup Superscript flow; phrasing phrasing phrasing globals HTMLElement
table Table flow flow caption*; colgroup*; thead*; tbody*; tfoot*; tr* globals; summary HTMLTableElement
tbody Group of rows in a table none table tr globals HTMLTableSectionElement
td Table cell sectioning root tr flow globals; colspan; rowspan; headers HTMLTableDataCellElement
textarea Multiline text field flow; phrasing; interactive; listed; labelable; submittable; resettable; form-associated phrasing text globals; autofocus; cols; disabled; form; maxlength; name; placeholder; readonly; required; rows; wrap HTMLTextAreaElement
tfoot Group of footer rows in a table none table tr globals HTMLTableSectionElement
th Table header cell none tr phrasing globals; colspan; rowspan; headers; scope HTMLTableHeaderCellElement
thead Group of heading rows in a table none table tr globals HTMLTableSectionElement
time Date and/or time flow; phrasing phrasing phrasing* globals; datetime; pubdate HTMLTimeElement
title Document title metadata head text globals HTMLTitleElement
tr Table row none table; thead; tbody; tfoot th*; td globals HTMLTableRowElement
track Timed text track none audio; video empty globals; default; kind; label; src; srclang HTMLTrackElement
ul List flow flow li globals HTMLUListElement
var Variable flow; phrasing phrasing phrasing globals HTMLElement
video Video player flow; phrasing; embedded; interactive phrasing source*; transparent* globals; src; poster; preload; autoplay; loop; controls; width; height HTMLVideoElement
wbr Line breaking opportunity flow; phrasing phrasing empty globals HTMLElement

An asterisk (*) in a cell indicates that the actual rules are more complicated than indicated in the table above.

Element content categories

This section is non-normative.

List of element content categories
Category Elements Elements with exceptions
Metadata content base; command; link; meta; noscript; script; style; title
Flow content a; abbr; address; article; aside; audio; b; bdi; bdo; blockquote; br; button; canvas; cite; code; command; datalist; del; details; dfn; div; dl; em; embed; fieldset; figure; footer; form; h1; h2; h3; h4; h5; h6; header; hgroup; hr; i; iframe; img; input; ins; kbd; keygen; label; map; mark; math; menu; meter; nav; noscript; object; ol; output; p; pre; progress; q; ruby; s; samp; script; section; select; small; span; strong; sub; sup; svg; table; textarea; time; ul; var; video; wbr; Text area (if it is a descendant of a map element); style (if the scoped attribute is present)
Sectioning content article; aside; nav; section
Heading content h1; h2; h3; h4; h5; h6; hgroup
Phrasing content abbr; audio; b; bdi; bdo; br; button; canvas; cite; code; command; datalist; dfn; em; embed; i; iframe; img; input; kbd; keygen; label; mark; math; meter; noscript; object; output; progress; q; ruby; s; samp; script; select; small; span; strong; sub; sup; svg; textarea; time; var; video; wbr; Text a (if it contains only phrasing content); area (if it is a descendant of a map element); del (if it contains only phrasing content); ins (if it contains only phrasing content); map (if it contains only phrasing content)
Embedded content audio canvas embed iframe img math object svg video
Interactive content a; button; details; embed; iframe; keygen; label; select; textarea; audio (if the controls attribute is present); img (if the usemap attribute is present); input (if the type attribute is not in the Hidden state); menu (if the type attribute is in the toolbar state); object (if the usemap attribute is present); video (if the controls attribute is present)
Sectioning roots blockquote; body; details; fieldset; figure; td
Form-associated elements button; fieldset; input; keygen; label; meter; object; output; progress; select; textarea
Listed elements button; fieldset; input; keygen; object; output; select; textarea
Labelable elements button; input; keygen; meter; output; progress; select; textarea
Submittable elements button; input; keygen; object; select; textarea
Resettable elements input; keygen; output; select; textarea
formatBlock candidates section; nav; article; aside; h1; h2; h3; h4; h5; h6; hgroup; header; footer; address; p; pre; blockquote; div

Attributes

This section is non-normative.

List of attributes (excluding event handler content attributes)
Attribute Element(s) Description Value
accept input Hint for expected file type in file upload controls Set of comma-separated tokens* consisting of valid MIME types with no parameters or audio/*, video/*, or image/*
accept-charset form Character encodings to use for form submission Ordered set of unique space-separated tokens, ASCII case-insensitive, consisting of preferred MIME names of ASCII-compatible character encodings*
accesskey HTML elements Keyboard shortcut to activate or focus element Ordered set of unique space-separated tokens, case-sensitive, consisting of one Unicode code point in length
action form URL to use for form submission Valid URL potentially surrounded by spaces
alt area; img; input Replacement text for use when images are not available Text*
async script Execute script asynchronously Boolean attribute
autocomplete form; input Prevent the user agent from providing autocompletions for the form control(s) "on"; "off"
autofocus button; input; keygen; select; textarea Automatically focus the form control when the page is loaded Boolean attribute
autoplay audio; video Hint that the media resource can be started automatically when the page is loaded Boolean attribute
challenge keygen String to package with the generated and signed public key Text
charset meta Character encoding declaration Preferred MIME name of an encoding*
charset script Character encoding of the external script resource Preferred MIME name of an encoding*
checked command; input Whether the command or control is checked Boolean attribute
cite blockquote; del; ins; q Link to the source of the quotation or more information about the edit Valid URL potentially surrounded by spaces
class HTML elements Classes to which the element belongs Set of space-separated tokens
cols textarea Maximum number of characters per line Valid non-negative integer greater than zero
colspan td; th Number of columns that the cell is to span Valid non-negative integer greater than zero
content meta Value of the element Text*
contenteditable HTML elements Whether the element is editable "true"; "false"
contextmenu HTML elements The element's context menu ID*
controls audio; video Show user agent controls Boolean attribute
coords area Coordinates for the shape to be created in an image map Valid list of integers*
data object Address of the resource Valid non-empty URL potentially surrounded by spaces
datetime del; ins Date and (optionally) time of the change Valid date string with optional time
datetime time Value of the element Valid date or time string*
default track Enable the track if no other text track is more suitable. Boolean attribute
defer script Defer script execution Boolean attribute
dir HTML elements The text directionality of the element "ltr"; "rtl"
dirname input; textarea Name of form field to use for sending the element's directionality in form submission Text*
disabled button; command; fieldset; input; keygen; optgroup; option; select; textarea Whether the form control is disabled Boolean attribute
draggable HTML elements Whether the element is draggable "true"; "false"
dropzone HTML elements Accepted item types for drag-and-drop Unordered set of unique space-separated tokens, ASCII case-insensitive, consisting of accepted types and drag feedback*
enctype form Form data set encoding type to use for form submission "application/x-www-form-urlencoded"; "multipart/form-data"; "text/plain"
for label Associate the label with form control ID*
for output Specifies controls from which the output was calculated Unordered set of unique space-separated tokens, case-sensitive, consisting of IDs*
form button; fieldset; input; keygen; label; meter; object; output; progress; select; textarea Associates the control with a form element ID*
formaction button; input URL to use for form submission Valid URL potentially surrounded by spaces
formenctype button; input Form data set encoding type to use for form submission "application/x-www-form-urlencoded"; "multipart/form-data"; "text/plain"
formmethod button; input HTTP method to use for form submission "GET"; "POST"
formnovalidate button; input Bypass form control validation for form submission Boolean attribute
formtarget button; input Browsing context for form submission Valid browsing context name or keyword
headers td; th The header cells for this cell Unordered set of unique space-separated tokens, case-sensitive, consisting of IDs*
height canvas; embed; iframe; img; input; object; video Vertical dimension Valid non-negative integer
hidden HTML elements Whether the element is relevant Boolean attribute
high meter Low limit of high range Valid floating point number*
href a; area Address of the hyperlink Valid URL potentially surrounded by spaces
href link Address of the hyperlink Valid non-empty URL potentially surrounded by spaces
href base Document base URL Valid URL potentially surrounded by spaces
hreflang a; area; link Language of the linked resource Valid BCP 47 language tag
http-equiv meta Pragma directive Text*
icon command Icon for the command Valid non-empty URL potentially surrounded by spaces
id HTML elements The element's ID Text*
ismap img Whether the image is a server-side image map Boolean attribute
keytype keygen The type of cryptographic key to generate Text*
kind track The type of text track "subtitles"; "captions"; "descriptions"; "chapters"; "metadata"
label command; menu; optgroup; option; track User-visible label Text
lang HTML elements Language of the element Valid BCP 47 language tag or the empty string
list input List of autocomplete options ID*
loop audio; video Whether to loop the media resource Boolean attribute
low meter High limit of low range Valid floating point number*
manifest html Application cache manifest Valid non-empty URL potentially surrounded by spaces
max input Maximum value varies*
max meter; progress Upper bound of range Valid floating point number*
maxlength input; textarea Maximum length of value Valid non-negative integer
media a; area; link; source; style Applicable media Valid media query
method form HTTP method to use for form submission "GET"; "POST"
min input Minimum value varies*
min meter Lower bound of range Valid floating point number*
multiple input; select Whether to allow multiple values Boolean attribute
name button; fieldset; input; keygen; output; select; textarea Name of form control to use for form submission and in the form.elements API Text*
name form Name of form to use in the document.forms API Text*
name iframe; object Name of nested browsing context Valid browsing context name or keyword
name map Name of image map to reference from the usemap attribute Text*
name meta Metadata name Text*
name param Name of parameter Text
novalidate form Bypass form control validation for form submission Boolean attribute
open details Whether the details are visible Boolean attribute
optimum meter Optimum value in gauge Valid floating point number*
pattern input Pattern to be matched by the form control's value Regular expression matching the JavaScript Pattern production
placeholder input; textarea User-visible label to be placed within the form control Text*
poster video Poster frame to show prior to video playback Valid non-empty URL potentially surrounded by spaces
preload audio; video Hints how much buffering the media resource will likely need "none"; "metadata"; "auto"
pubdate time Whether the element's value represents a publication time for the nearest article or body Boolean attribute
radiogroup command Name of group of commands to treat as a radio button group Text
readonly input; textarea Whether to allow the value to be edited by the user Boolean attribute
rel a; area; link Relationship between the document containing the hyperlink and the destination resource Set of space-separated tokens*
required input; select; textarea Whether the control is required for form submission Boolean attribute
reversed ol Number the list backwards Boolean attribute
rows textarea Number of lines to show Valid non-negative integer greater than zero
rowspan td; th Number of rows that the cell is to span Valid non-negative integer
sandbox iframe Security rules for nested content Unordered set of unique space-separated tokens, ASCII case-insensitive, consisting of "allow-same-origin", "allow-forms", and "allow-scripts"
spellcheck HTML elements Whether the element is to have its spelling and grammar checked "true"; "false"
scope th Specifies which cells the header cell applies to "row"; "col"; "rowgroup"; "colgroup"
scoped style Whether the styles apply to the entire document or just the parent subtree Boolean attribute
seamless iframe Whether to apply the document's styles to the nested content Boolean attribute
selected option Whether the option is selected by default Boolean attribute
shape area The kind of shape to be created in an image map "circle"; "default"; "poly"; "rect"
size input; select Size of the control Valid non-negative integer greater than zero
sizes link Sizes of the icons (for rel="icon") Unordered set of unique space-separated tokens, ASCII case-insensitive, consisting of sizes*
span col; colgroup Number of columns spanned by the element Valid non-negative integer greater than zero
src audio; embed; iframe; img; input; script; source; track; video Address of the resource Valid non-empty URL potentially surrounded by spaces
srcdoc iframe A document to render in the iframe The source of an iframe srcdoc document*
srclang track Language of the text track Valid BCP 47 language tag
start ol Ordinal value of the first item Valid integer
step input Granularity to be matched by the form control's value Valid floating point number greater than zero, or "any"
style HTML elements Presentational and formatting instructions CSS declarations*
summary table Explanatory text for complex tables for users of screen readers Text*
tabindex HTML elements Whether the element is focusable, and the relative order of the element for the purposes of sequential focus navigation Valid integer
target a; area Browsing context for hyperlink navigation Valid browsing context name or keyword
target base Default browsing context for hyperlink navigation and form submission Valid browsing context name or keyword
target form Browsing context for form submission Valid browsing context name or keyword
title HTML elements Advisory information for the element Text
title abbr; dfn Full term or expansion of abbreviation Text
title command Hint describing the command Text
title link Title of the link Text
title link; style Alternative style sheet set name Text
type a; area; link Hint for the type of the referenced resource Valid MIME type
type button Type of button "submit"; "reset"; "button"
type button; input Type of form control input type keyword
type command Type of command "command"; "checkbox"; "radio"
type embed; object; script; source; style Type of embedded resource Valid MIME type
type menu Type of menu "context"; "toolbar"
usemap img; object Name of image map to use Valid hash-name reference*
value button; option Value to be used for form submission Text
value input Value of the form control varies*
value li Ordinal value of the list item Valid integer
value meter; progress Current value of the element Valid floating point number
value param Value of parameter Text
width canvas; embed; iframe; img; input; object; video Horizontal dimension Valid non-negative integer
wrap textarea How the value of the form control is to be wrapped for form submission "soft"; "hard"

An asterisk (*) in a cell indicates that the actual rules are more complicated than indicated in the table above.


List of event handler content attributes
Attribute Element(s) Description Value
onabort HTML elements abort event handler Event handler content attribute
onafterprint body afterprint event handler for Window object Event handler content attribute
onbeforeprint body beforeprint event handler for Window object Event handler content attribute
onbeforeunload body beforeunload event handler for Window object Event handler content attribute
onblur body blur event handler for Window object Event handler content attribute
onblur HTML elements blur event handler Event handler content attribute
oncanplay HTML elements canplay event handler Event handler content attribute
oncanplaythrough HTML elements canplaythrough event handler Event handler content attribute
onchange HTML elements change event handler Event handler content attribute
onclick HTML elements click event handler Event handler content attribute
oncontextmenu HTML elements contextmenu event handler Event handler content attribute
oncuechange HTML elements cuechange event handler Event handler content attribute
ondblclick HTML elements dblclick event handler Event handler content attribute
ondrag HTML elements drag event handler Event handler content attribute
ondragend HTML elements dragend event handler Event handler content attribute
ondragenter HTML elements dragenter event handler Event handler content attribute
ondragleave HTML elements dragleave event handler Event handler content attribute
ondragover HTML elements dragover event handler Event handler content attribute
ondragstart HTML elements dragstart event handler Event handler content attribute
ondrop HTML elements drop event handler Event handler content attribute
ondurationchange HTML elements durationchange event handler Event handler content attribute
onemptied HTML elements emptied event handler Event handler content attribute
onended HTML elements ended event handler Event handler content attribute
onerror body error event handler for Window object, and handler for script error notifications Event handler content attribute
onerror HTML elements error event handler Event handler content attribute
onfocus body focus event handler for Window object Event handler content attribute
onfocus HTML elements focus event handler Event handler content attribute
onformchange HTML elements formchange event handler Event handler content attribute
onforminput HTML elements forminput event handler Event handler content attribute
onhashchange body hashchange event handler for Window object Event handler content attribute
oninput HTML elements input event handler Event handler content attribute
oninvalid HTML elements invalid event handler Event handler content attribute
onkeydown HTML elements keydown event handler Event handler content attribute
onkeypress HTML elements keypress event handler Event handler content attribute
onkeyup HTML elements keyup event handler Event handler content attribute
onload body load event handler for Window object Event handler content attribute
onload HTML elements load event handler Event handler content attribute
onloadeddata HTML elements loadeddata event handler Event handler content attribute
onloadedmetadata HTML elements loadedmetadata event handler Event handler content attribute
onloadstart HTML elements loadstart event handler Event handler content attribute
onmessage body message event handler for Window object Event handler content attribute
onmousedown HTML elements mousedown event handler Event handler content attribute
onmousemove HTML elements mousemove event handler Event handler content attribute
onmouseout HTML elements mouseout event handler Event handler content attribute
onmouseover HTML elements mouseover event handler Event handler content attribute
onmouseup HTML elements mouseup event handler Event handler content attribute
onmousewheel HTML elements mousewheel event handler Event handler content attribute
onoffline body offline event handler for Window object Event handler content attribute
ononline body online event handler for Window object Event handler content attribute
onpagehide body pagehide event handler for Window object Event handler content attribute
onpageshow body pageshow event handler for Window object Event handler content attribute
onpause HTML elements pause event handler Event handler content attribute
onplay HTML elements play event handler Event handler content attribute
onplaying HTML elements playing event handler Event handler content attribute
onpopstate body popstate event handler for Window object Event handler content attribute
onprogress HTML elements progress event handler Event handler content attribute
onratechange HTML elements ratechange event handler Event handler content attribute
onreadystatechange HTML elements readystatechange event handler Event handler content attribute
onredo body redo event handler for Window object Event handler content attribute
onreset HTML elements reset event handler Event handler content attribute
onresize body resize event handler for Window object Event handler content attribute
onscroll body scroll event handler for Window object Event handler content attribute
onscroll HTML elements scroll event handler Event handler content attribute
onseeked HTML elements seeked event handler Event handler content attribute
onseeking HTML elements seeking event handler Event handler content attribute
onselect HTML elements select event handler Event handler content attribute
onshow HTML elements show event handler Event handler content attribute
onstalled HTML elements stalled event handler Event handler content attribute
onstorage body storage event handler for Window object Event handler content attribute
onsubmit HTML elements submit event handler Event handler content attribute
onsuspend HTML elements suspend event handler Event handler content attribute
ontimeupdate HTML elements timeupdate event handler Event handler content attribute
onundo body undo event handler for Window object Event handler content attribute
onunload body unload event handler for Window object Event handler content attribute
onvolumechange HTML elements volumechange event handler Event handler content attribute
onwaiting HTML elements waiting event handler Event handler content attribute

Interfaces

This section is non-normative.

List of interfaces for elements
Element(s) Interface(s)
a HTMLAnchorElement : HTMLElement
abbr HTMLElement
address HTMLElement
area HTMLAreaElement : HTMLElement
article HTMLElement
aside HTMLElement
audio HTMLAudioElement : HTMLMediaElement : HTMLElement
b HTMLElement
base HTMLBaseElement : HTMLElement
bdi HTMLElement
bdo HTMLElement
blockquote HTMLQuoteElement : HTMLElement
body HTMLBodyElement : HTMLElement
br HTMLBRElement : HTMLElement
button HTMLButtonElement : HTMLElement
canvas HTMLCanvasElement : HTMLElement
caption HTMLTableCaptionElement : HTMLElement
cite HTMLElement
code HTMLElement
col HTMLTableSectionElement : HTMLElement
colgroup HTMLTableColElement : HTMLElement
command HTMLCommandElement : HTMLElement
datalist HTMLDataListElement : HTMLElement
dd HTMLElement
del HTMLModElement : HTMLElement
details HTMLDetailsElement : HTMLElement
div HTMLDivElement : HTMLElement
dl HTMLDListElement : HTMLElement
dt HTMLElement
em HTMLElement
embed HTMLEmbedElement : HTMLElement
fieldset HTMLFieldSetElement : HTMLElement
figcaption HTMLElement
figure HTMLElement
footer HTMLElement
form HTMLFormElement : HTMLElement
head HTMLHeadElement : HTMLElement
h1 HTMLHeadingElement : HTMLElement
h2 HTMLHeadingElement : HTMLElement
h3 HTMLHeadingElement : HTMLElement
h4 HTMLHeadingElement : HTMLElement
h5 HTMLHeadingElement : HTMLElement
h6 HTMLHeadingElement : HTMLElement
header HTMLElement
hgroup HTMLElement
hr HTMLHRElement : HTMLElement
html HTMLHtmlElement : HTMLElement
i HTMLElement
iframe HTMLIFrameElement : HTMLElement
img HTMLImageElement : HTMLElement
input HTMLInputElement : HTMLElement
ins HTMLModElement : HTMLElement
kbd HTMLElement
keygen HTMLKeygenElement : HTMLElement
label HTMLLabelElement : HTMLElement
legend HTMLLegendElement : HTMLElement
li HTMLLIElement : HTMLElement
link HTMLLinkElement : HTMLElement
map HTMLMapElement : HTMLElement
mark HTMLElement
meter HTMLMeterElement : HTMLElement
nav HTMLElement
noscript HTMLElement
object HTMLObjectElement : HTMLElement
ol HTMLOListElement : HTMLElement
optgroup HTMLOptGroupElement : HTMLElement
option HTMLOptionElement : HTMLElement
output HTMLOutputElement : HTMLElement
p HTMLParagraphElement : HTMLElement
param HTMLParamElement : HTMLElement
pre HTMLPreElement : HTMLElement
progress HTMLProgressElement : HTMLElement
q HTMLElement
rp HTMLElement
rt HTMLElement
ruby HTMLElement
s HTMLElement
samp HTMLElement
section HTMLElement
select HTMLSelectElement : HTMLElement
small HTMLElement
source HTMLSourceElement : HTMLElement
span HTMLSpanElement : HTMLElement
strong HTMLElement
style HTMLStyleElement : HTMLElement
sub HTMLElement
summary HTMLElement
sup HTMLElement
table HTMLTableElement : HTMLElement
tbody HTMLTableSectionElement : HTMLElement
td HTMLTableDataCellElement : HTMLTableCellElement : HTMLElement
textarea HTMLTextAreaElement : HTMLElement
tfoot HTMLTableSectionElement : HTMLElement
th HTMLTableHeaderCellElement : HTMLTableCellElement : HTMLElement
thead HTMLTableSectionElement : HTMLElement
time HTMLTimeElement : HTMLElement
title HTMLTitleElement : HTMLElement
tr HTMLTableRowElement : HTMLElement
track HTMLTrackElement : HTMLElement
ul HTMLUListElement : HTMLElement
var HTMLElement
video HTMLVideoElement : HTMLMediaElement : HTMLElement
wbr HTMLElement

Events

This section is non-normative.

List of events
Event Interface Description
DOMContentLoaded Event Fired at the Document once it and its scripts have loaded, without waiting for other subresources
abort Event Fired at the Window when the download was aborted by the user
afterprint Event Fired at the Window after printing
beforeprint Event Fired at the Window before printing
beforeunload BeforeUnloadEvent Fired at the Window when the page is about to be unloaded, in case the page would like to show a warning prompt
blur Event Fired at nodes losing focus
change Event Fired at controls when the user commits a value change
click Event Fired at an element before its activation behavior is run
contextmenu Event Fired at elements when the user requests their context menu
error Event Fired at elements when network and script errors occur
focus Event Fired at nodes gaining focus
formchange Event Fired at form controls when the user commits a value change to a control on the form
forminput Event Fired at form controls when the user changes the value of a control on the form
hashchange HashChangeEvent Fired at the Window when the fragment identifier part of the document's current address changes
input Event Fired at controls when the user changes the value
invalid Event Fired at controls during form validation if they do not satisfy their constraints
load Event Fired at the Window when the document has finished loading; fired at an element containing a resource (e.g. img, embed) when its resource has finished loading
message MessageEvent Fired at an object when the object receives a message
offline Event Fired at the Window when the network connections fails
online Event Fired at the Window when the network connections returns
pagehide PageTransitionEvent Fired at the Window when the page's entry in the session history stops being the current entry
pageshow PageTransitionEvent Fired at the Window when the page's entry in the session history becomes the current entry
popstate PopStateEvent Fired at the Window when the user navigates the session history
readystatechange Event Fired at the Document when it finishes parsing and again when all its subresources have finished loading
reset Event Fired at a form element when it is reset
show Event Fired at a menu element when it is shown as a context menu
submit Event Fired at a form element when it is submitted
unload Event Fired at the Window object when the page is going away

See also media element events, application cache events, and drag-and-drop events.

References

All references are normative unless marked "Non-normative".

[ABNF]
Augmented BNF for Syntax Specifications: ABNF, D. Crocker, P. Overell. IETF.
[ABOUT]
The 'about' URI scheme, J. Holsten, L. Hunt. IETF.
[ARIA]
Accessible Rich Internet Applications (WAI-ARIA), J. Craig, M. Cooper, L. Pappas, R. Schwerdtfeger, L. Seeman. W3C.
[ARIAIMPL]
WAI-ARIA 1.0 User Agent Implementation Guide, A. Snow-Weaver, M. Cooper. W3C.
[ATAG]
(Non-normative) Authoring Tool Accessibility Guidelines (ATAG) 2.0, J. Richards, J. Spellman, J. Treviranus. W3C.
[ATOM]
(Non-normative) The Atom Syndication Format, M. Nottingham, R. Sayre. IETF.
[BCP47]
Tags for Identifying Languages; Matching of Language Tags, A. Phillips, M. Davis. IETF.
[BECSS]
Behavioral Extensions to CSS, I. Hickson. W3C.
[BIDI]
UAX #9: Unicode Bidirectional Algorithm, M. Davis. Unicode Consortium.
[BOCU1]
(Non-normative) UTN #6: BOCU-1: MIME-Compatible Unicode Compression, M. Scherer, M. Davis. Unicode Consortium.
[CESU8]
(Non-normative) UTR #26: Compatibility Encoding Scheme For UTF-16: 8-BIT (CESU-8), T. Phipps. Unicode Consortium.
[CHARMOD]
(Non-normative) Character Model for the World Wide Web 1.0: Fundamentals, M. Dürst, F. Yergeau, R. Ishida, M. Wolf, T. Texin. W3C.
[COMPUTABLE]
(Non-normative) On computable numbers, with an application to the Entscheidungsproblem, A. Turing. In Proceedings of the London Mathematical Society, series 2, volume 42, pages 230-265. London Mathematical Society, 1937.
[COOKIES]
HTTP State Management Mechanism, A. Barth. IETF.
[CORS]
Cross-Origin Resource Sharing, A. van Kesteren. W3C.
[CP51932]
CP51932, Y. Naruse. IANA.
[CSS]
Cascading Style Sheets Level 2 Revision 1, B. Bos, T. Çelik, I. Hickson, H. Lie. W3C.
[CSSATTR]
CSS Styling Attribute Syntax, E. Etemad. W3C.
[CSSCOLOR]
CSS Color Module Level 3, T. Çelik, C. Lilley, L. Baron. W3C.
[CSSOM]
Cascading Style Sheets Object Model (CSSOM), A. van Kesteren. W3C.
[CSSOMVIEW]
CSSOM View Module, A. van Kesteren. W3C.
[CSSRUBY]
CSS3 Ruby Module, R. Ishida. W3C.
[CSSUI]
CSS3 Basic User Interface Module, T. Çelik. W3C.
[CSSVALUES]
CSS3 Values and Units, H. Lie, C. Lilley. W3C.
[DOMCORE]
Document Object Model (DOM) Level 3 Core Specification, A. Le Hors, P. Le Hegaret, L. Wood, G. Nicol, J. Robie, M. Champion, S. Byrnes. W3C.
[DOMEVENTS]
Document Object Model (DOM) Level 3 Events Specification, D. Schepers. W3C.
[DOMRANGE]
Document Object Model (DOM) Level 2 Traversal and Range Specification, J. Kesselman, J. Robie, M. Champion, P. Sharpe, V. Apparao, L. Wood. W3C.
[ECMA262]
ECMAScript Language Specification. ECMA.
[ECMA357]
(Non-normative) ECMAScript for XML (E4X) Specification. ECMA.
[EUCKR]
Hangul Unix Environment. Korea Industrial Standards Association. Ref. No. KS C 5861-1992.
[EUCJP]
Definition and Notes of Japanese EUC. UI-OSF-USLP. In English in the abridged translation of the UI-OSF Application Platform Profile for Japanese Environment, Appendix C.
[FILEAPI]
File API, A. Ranganathan. W3C.
[GBK]
Chinese Internal Code Specification. Chinese IT Standardization Technical Committee.
[GRAPHICS]
(Non-normative) Computer Graphics: Principles and Practice in C, Second Edition, J. Foley, A. van Dam, S. Feiner, J. Hughes. Addison-Wesley. ISBN 0-201-84840-6.
[GREGORIAN]
(Non-normative) Inter Gravissimas, A. Lilius, C. Clavius. Gregory XIII Papal Bulls, February 1582.
[HTMLDIFF]
(Non-normative) HTML5 differences from HTML4, A. van Kesteren. W3C.
[HTTP]
Hypertext Transfer Protocol — HTTP/1.1, R. Fielding, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee. IETF.
[IANACHARSET]
Character Sets. IANA.
[IANAPERMHEADERS]
Permanent Message Header Field Names. IANA.
[ISO8601]
ISO8601: Data elements and interchange formats — Information interchange — Representation of dates and times. ISO.
[ISO885911]
ISO-8859-11: Information technology — 8-bit single-byte coded graphic character sets — Part 11: Latin/Thai alphabet. ISO.
[JSURL]
The 'javascript' resource identifier scheme, B. Höhrmann. IETF.
[MAILTO]
The mailto URL scheme, P. Hoffman, L. Masinter, J. Zawinski. IETF.
[MATHML]
Mathematical Markup Language (MathML), D. Carlisle, P. Ion, R. Miner, N. Poppelier. W3C.
[MIMESNIFF]
Media Type Sniffing, A. Barth, I. Hickson. IETF.
[MQ]
Media Queries, H. Lie, T. Çelik, D. Glazman, A. van Kesteren. W3C.
[NPAPI]
(Non-normative) Gecko Plugin API Reference. Mozilla.
[OPENSEARCH]
Autodiscovery in HTML/XHTML. In OpenSearch 1.1 Draft 4, Section 4.6.2. OpenSearch.org.
[ORIGIN]
The HTTP Origin Header, A. Barth, C. Jackson, I. Hickson. IETF.
[PINGBACK]
Pingback 1.0, S. Langridge, I. Hickson.
[PNG]
Portable Network Graphics (PNG) Specification, D. Duce. W3C.
[POLYGLOT]
(Non-normative) Polyglot Markup: HTML-Compatible XHTML Documents, E. Graff. W3C.
[PPUTF8]
(Non-normative) The Properties and Promises of UTF-8, M. Dürst. University of Zürich. In Proceedings of the 11th International Unicode Conference.
[PROGRESS]
Progress Events, C. McCathieNevile. W3C.
[PSL]
Public Suffix List. Mozilla Foundation.
[RFC1034]
Domain Names - Concepts and Facilities, P. Mockapetris. IETF, November 1987.
[RFC1345]
Character Mnemonics and Character Sets, K. Simonsen. IETF.
[RFC1468]
Japanese Character Encoding for Internet Messages, J. Murai, M. Crispin, E. van der Poel. IETF.
[RFC1554]
ISO-2022-JP-2: Multilingual Extension of ISO-2022-JP, M. Ohta, K. Handa. IETF.
[RFC1557]
Korean Character Encoding for Internet Messages, U. Choi, K. Chon, H. Park. IETF.
[RFC1842]
ASCII Printable Characters-Based Chinese Character Encoding for Internet Messages, Y. Wei, Y. Zhang, J. Li, J. Ding, Y. Jiang. IETF.
[RFC1922]
Chinese Character Encoding for Internet Messages, HF. Zhu, DY. Hu, ZG. Wang, TC. Kao, WCH. Chang, M. Crispin. IETF.
[RFC2046]
Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types, N. Freed, N. Borenstein. IETF.
[RFC2119]
Key words for use in RFCs to Indicate Requirement Levels, S. Bradner. IETF.
[RFC2237]
Japanese Character Encoding for Internet Messages, K. Tamaru. IETF.
[RFC2313]
PKCS #1: RSA Encryption, B. Kaliski. IETF.
[RFC2318]
The text/css Media Type, H. Lie, B. Bos, C. Lilley. IETF.
[RFC2388]
Returning Values from Forms: multipart/form-data, L. Masinter. IETF.
[RFC2397]
The "data" URL scheme, L. Masinter. IETF.
[RFC2425]
A MIME Content-Type for Directory Information, T. Howes, M. Smith, F. Dawson. IETF.
[RFC2426]
vCard MIME Directory Profile, F. Dawson, T. Howes. IETF.
[RFC2483]
URI Resolution Services Necessary for URN Resolution, M. Mealling, R. Daniel. IETF.
[RFC2781]
UTF-16, an encoding of ISO 10646, P. Hoffman, F. Yergeau. IETF.
[RFC2646]
The Text/Plain Format Parameter, R. Gellens. IETF.
[RFC3023]
XML Media Types, M. Murata, S. St. Laurent, D. Kohn. IETF.
[RFC3279]
Algorithms and Identifiers for the Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile, W. Polk, R. Housley, L. Bassham. IETF.
[RFC3490]
Internationalizing Domain Names in Applications (IDNA), P. Faltstrom, P. Hoffman, A. Costello. IETF.
[RFC3629]
UTF-8, a transformation format of ISO 10646, F. Yergeau. IETF.
[RFC3986]
Uniform Resource Identifier (URI): Generic Syntax, T. Berners-Lee, R. Fielding, L. Masinter. IETF.
[RFC3987]
Internationalized Resource Identifiers (IRIs), M. Dürst, M. Suignard. IETF.
[RFC4281]
The Codecs Parameter for "Bucket" Media Types, R. Gellens, D. Singer, P. Frojdh. IETF.
[RFC4329]
(Non-normative) Scripting Media Types, B. Höhrmann. IETF.
[RFC4648]
The Base16, Base32, and Base64 Data Encodings, S. Josefsson. IETF.
[RFC5280]
Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile, D. Cooper, S. Santesson, S. Farrell, S. Boeyen, R. Housley, W. Polk. IETF.
[RFC5322]
Internet Message Format, P. Resnick. IETF.
[RFC5724]
URI Scheme for Global System for Mobile Communications (GSM) Short Message Service (SMS), E. Wilde, A. Vaha-Sipila. IETF.
[SCSU]
(Non-normative) UTR #6: A Standard Compression Scheme For Unicode, M. Wolf, K. Whistler, C. Wicksteed, M. Davis, A. Freytag, M. Scherer. Unicode Consortium.
[SELECTORS]
Selectors, T. Çelik, E. Etemad, D. Glazman, I. Hickson, P. Linss, J. Williams. W3C.
[SHIFTJIS]
JIS X0208: 7-bit and 8-bit double byte coded KANJI sets for information interchange. Japanese Industrial Standards Committee.
[SRGB]
IEC 61966-2-1: Multimedia systems and equipment — Colour measurement and management — Part 2-1: Colour management — Default RGB colour space — sRGB. IEC.
[SVG]
Scalable Vector Graphics (SVG) Tiny 1.2 Specification, O. Andersson, R. Berjon, E. Dahlström, A. Emmons, J. Ferraiolo, A. Grasso, V. Hardy, S. Hayman, D. Jackson, C. Lilley, C. McCormack, A. Neumann, C. Northway, A. Quint, N. Ramani, D. Schepers, A. Shellshear. W3C.
[TIS620]
UDC 681.3.04:003.62. Thai Industrial Standards Institute, Ministry of Industry, Royal Thai Government. ISBN 974-606-153-4.
[UAAG]
(Non-normative) Web Content Accessibility Guidelines (UAAG) 2.0, J. Allan, K. Ford, J. Richards, J. Spellman. W3C.
[UNICODE]
The Unicode Standard. Unicode Consortium.
[UNIVCHARDET]
(Non-normative) A composite approach to language/encoding detection, S. Li, K. Momoi. Netscape. In Proceedings of the 19th International Unicode Conference.
[UTF7]
UTF-7: A Mail-Safe Transformation Format of Unicode, D. Goldsmith, M. Davis. IETF.
[UTF8DET]
(Non-normative) Multilingual form encoding, M. Dürst. W3C.
[UTR36]
(Non-normative) UTR #36: Unicode Security Considerations, M. Davis, M. Suignard. Unicode Consortium.
[WCAG]
(Non-normative) Web Content Accessibility Guidelines (WCAG) 2.0, B. Caldwell, M. Cooper, L. Reid, G. Vanderheiden. W3C.
[WEBIDL]
Web IDL, C. McCormack. W3C.
Web Linking, M. Nottingham. IETF.
[WEBSOCKET]
The WebSocket API, I. Hickson. W3C.
[WEBSTORAGE]
Web Storage, I. Hickson. W3C.
[WEBWORKERS]
Web Workers, I. Hickson. W3C.
[WHATWGWIKI]
The WHATWG Wiki. WHATWG.
[WIN1252]
Windows 1252. Microsoft.
[WIN1254]
Windows 1254. Microsoft.
[WIN31J]
Windows Codepage 932. Microsoft.
[WIN874]
Windows 874. Microsoft.
[WIN949]
Windows Codepage 949. Microsoft.
[X690]
Recommendation X.690 — Information Technology — ASN.1 Encoding Rules — Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER), and Distinguished Encoding Rules (DER). International Telecommunication Union.
[XHR]
XMLHttpRequest, A. van Kesteren. W3C.
[XML]
Extensible Markup Language, T. Bray, J. Paoli, C. Sperberg-McQueen, E. Maler, F. Yergeau. W3C.
[XMLBASE]
XML Base, J. Marsh, R. Tobin. W3C.
[XMLNS]
Namespaces in XML, T. Bray, D. Hollander, A. Layman, R. Tobin. W3C.
[XPATH10]
XML Path Language (XPath) Version 1.0, J. Clark, S. DeRose. W3C.
[XSLT10]
XSL Transformations (XSLT) Version 1.0, J. Clark. W3C.

Acknowledgements

ISSUE-139 (ack-microdata) blocks progress to Last Call

Thanks to Aankhen, Aaron Boodman, Aaron Leventhal, Adam Barth, Adam de Boor, Adam Hepton, Adam Roben, Addison Phillips, Adele Peterson, Adrian Bateman, Adrian Sutton, Agustín Fernández, Ajai Tirumali, Akatsuki Kitamura, Alan Plum, Alastair Campbell, Alejandro G. Castro, Alex Bishop, Alex Nicolaou, Alex Rousskov, Alexander J. Vincent, Alexey Feldgendler, Алексей Проскуряков (Alexey Proskuryakov), Alexis Deveria, Allan Clements, Amos Jeffries, Anders Carlsson, Andreas, Andreas Kling, Andrei Popescu, André E. Veltstra, Andrew Clover, Andrew Gove, Andrew Grieve, Andrew Oakley, Andrew Sidwell, Andrew Smith, Andrew W. Hagen, Andrey V. Lukyanov, Andy Heydon, Andy Palay, Anne van Kesteren, Anthony Boyd, Anthony Bryan, Anthony Hickson, Anthony Ricaud, Antti Koivisto, Arne Thomassen, Aron Spohr, Arphen Lin, Aryeh Gregor, Asbjørn Ulsberg, Ashley Sheridan, Atsushi Takayama, Aurelien Levy, Ave Wrigley, Ben Boyle, Ben Godfrey, Ben Lerner, Ben Leslie, Ben Meadowcroft, Ben Millard, Benjamin Carl Wiley Sittler, Benjamin Hawkes-Lewis, Bert Bos, Bijan Parsia, Bil Corry, Bill Mason, Bill McCoy, Billy Wong, Bjartur Thorlacius, Björn Höhrmann, Blake Frantz, Boris Zbarsky, Brad Fults, Brad Neuberg, Brad Spencer, Brady Eidson, Brendan Eich, Brenton Simpson, Brett Wilson, Brett Zamir, Brian Campbell, Brian Korver, Brian Kuhn, Brian Ryner, Brian Smith, Brian Wilson, Bryan Sullivan, Bruce D'Arcus, Bruce Lawson, Bruce Miller, C. Williams, Cameron McCormack, Cao Yipeng, Carlos Gabriel Cardona, Carlos Perelló Marín, Chao Cai, 윤석찬 (Channy Yun), Charl van Niekerk, Charles Iliya Krempeaux, Charles McCathieNevile, Chris Apers, Chris Cressman, Chris Evans, Chris Morris, Chris Pearce, Christian Biesinger, Christian Johansen, Christian Schmidt, Christopher Aillon, Chriswa, Clark Buehler, Cole Robison, Colin Fine, Collin Jackson, Corprew Reed, Craig Cockburn, Csaba Gabor, Csaba Marton, Cynthia Shelly, Daniel Barclay, Daniel Bratell, Daniel Brooks, Daniel Brumbaugh Keeney, Daniel Cheng, Daniel Davis, Daniel Glazman, Daniel Peng, Daniel Schattenkirchner, Daniel Spång, Daniel Steinberg, Danny Sullivan, Darin Adler, Darin Fisher, Darxus, Dave Camp, Dave Hodder, Dave Lampton, Dave Singer, Dave Townsend, David Baron, David Bloom, David Bruant, David Carlisle, David E. Cleary, David Egan Evans, David Flanagan, David Gerard, David Håsäther, David Hyatt, David I. Lehn, David John Burrowes, David Matja, David Remahl, David Smith, David Woolley, DeWitt Clinton, Dean Edridge, Dean Edwards, Debi Orton, Derek Featherstone, Devdatta, Dimitri Glazkov, Dimitry Golubovsky, Dirk Pranke, Divya Manian, Dmitry Titov, dolphinling, Dominique Hazaël-Massieux, Don Brutzman, Doron Rosenberg, Doug Kramer, Doug Simpkinson, Drew Wilson, Edmund Lai, Eduard Pascual, Eduardo Vela, Edward O'Connor, Edward Welbourne, Edward Z. Yang, Eira Monstad, Eitan Adler, Eliot Graff, Elizabeth Castro, Elliott Sprehn, Elliotte Harold, Eric Carlson, Eric Law, Eric Rescorla, Eric Semling, Erik Arvidsson, Erik Rose, Evan Martin, Evan Prodromou, Evert, fantasai, Felix Sasaki, Francesco Schwarz, Francis Brosnan Blazquez, Franck 'Shift' Quélain, Frank Barchard, 鵜飼文敏 (Fumitoshi Ukai), Futomi Hatano, Gavin Carothers, Gareth Rees, Garrett Smith, Geoffrey Garen, Sam Sneddon, George Lund, Gianmarco Armellin, Giovanni Campagna, Glenn Adams, Graham Klyne, Greg Botten, Greg Houston, Greg Wilkins, Gregg Tavares, Gregory J. Rosmaita, Grey, Guilherme Johansson Tramontina, Gytis Jakutonis, Håkon Wium Lie, Hallvord Reiar Michaelsen Steen, Hans S. Tømmerhalt, Hans Stimer, Henri Sivonen, Henrik Lied, Henry Mason, Hugh Winkler, Ian Bicking, Ian Davis, Ignacio Javier, Ivan Enderlin, Ivo Emanuel Gonçalves, J. King, Jacques Distler, James Craig, James Graham, James Justin Harrell, James M Snell, James Perrett, James Robinson, Jamie Lokier, Jan-Klaas Kollhof, Jason Kersey, Jason Lustig, Jason White, Jasper Bryant-Greene, Jatinder Mann, Jed Hartman, Jeff Balogh, Jeff Cutsinger, Jeff Schiller, Jeff Walden, Jeffrey Zeldman, 胡慧鋒 (Jennifer Braithwaite), Jens Bannmann, Jens Fendler, Jens Lindström, Jens Meiert, Jeremy Keith, Jeremy Orlow, Jeroen van der Meer, Jian Li, Jim Jewett, Jim Ley, Jim Meehan, Jjgod Jiang, João Eiras, Joe Clark, Joe Gregorio, Joel Spolsky, Johan Herland, John Boyer, John Bussjaeger, John Carpenter, John Fallows, John Foliot, John Harding, John Keiser, John Snyders, John-Mark Bell, Johnny Stenback, Jon Ferraiolo, Jon Gibbins, Jon Perlow, Jonas Sicking, Jonathan Cook, Jonathan Rees, Jonathan Worent, Jonny Axelsson, Jorgen Horstink, Jorunn Danielsen Newth, Joseph Kesselman, Joseph Pecoraro, Josh Aas, Josh Levenberg, Joshua Randall, Jukka K. Korpela, Jules Clément-Ripoche, Julian Reschke, Jürgen Jeka, Justin Lebar, Justin Schuh, Justin Sinclair, Kai Hendry, Kartikaya Gupta, Kathy Walton, Kelly Norton, Kevin Benson, Kornél Pál, Kornel Lesinski, Kristof Zelechovski, Krzysztof Maczyński, 黒澤剛志 (Kurosawa Takeshi), Kyle Hofmann, Léonard Bouchet, Lachlan Hunt, Larry Masinter, Larry Page, Lars Gunther, Lars Solberg, Laura Carlson, Laura Granka, Laura L. Carlson, Laura Wisewell, Laurens Holst, Lee Kowalkowski, Leif Halvard Silli, Lenny Domnitser, Leons Petrazickis, Lobotom Dysmon, Logan, Loune, Luke Kenneth Casson Leighton, Maciej Stachowiak, Magnus Kristiansen, Maik Merten, Malcolm Rowe, Mark Birbeck, Mark Miller, Mark Nottingham, Mark Pilgrim, Mark Rowe, Mark Schenk, Mark Wilton-Jones, Martijn Wargers, Martin Atkins, Martin Dürst, Martin Honnen, Martin Janecke, Martin Kutschker, Martin Nilsson, Martin Thomson, Masataka Yakura, Mathieu Henri, Matias Larsson, Matt Schmidt, Matt Wright, Matthew Gregan, Matthew Mastracci, Matthew Raymond, Matthew Thomas, Mattias Waldau, Max Romantschuk, Menno van Slooten, Micah Dubinko, Michael 'Ratt' Iannarelli, Michael A. Nachbaur, Michael A. Puls II, Michael Carter, Michael Daskalov, Michael Enright, Michael Gratton, Michael Nordman, Michael Powers, Michael Rakowski, Michael(tm) Smith, Michal Zalewski, Michel Fortin, Michelangelo De Simone, Michiel van der Blonk, Mihai Şucan, Mihai Parparita, Mike Brown, Mike Dierken, Mike Dixon, Mike Schinkel, Mike Shaver, Mikko Rantalainen, Mohamed Zergaoui, Mounir Lamouri, Ms2ger, NARUSE Yui, Neil Deakin, Neil Rashbrook, Neil Soiffer, Nicholas Shanks, Nicholas Stimpson, Nicholas Zakas, Nickolay Ponomarev, Nicolas Gallagher, Noah Mendelsohn, Noah Slater, NoozNooz42, Ojan Vafai, Olaf Hoffmann, Olav Junker Kjær, Oldřich Vetešník, Oli Studholme, Oliver Hunt, Oliver Rigby, Olivier Gendrin, Olli Pettay, oSand, Patrick H. Lauke, Paul Norman, Per-Erik Brodin, Perry Smith, Peter Beverloo, Peter Karlsson, Peter Kasting, Peter Stark, Peter-Paul Koch, Phil Pickering, Philip Jägenstedt, Philip Taylor, Philip TAYLOR, Prateek Rungta, Pravir Gupta, Rachid Finge, Rajas Moonka, Ralf Stoltze, Ralph Giles, Raphael Champeimont, Remco, Remy Sharp, Rene Saarsoo, Rene Stach, Ric Hardacre, Rich Doughty, Richard Ishida, Rigo Wenning, Rikkert Koppes, Rimantas Liubertas, Riona Macnamara, Rob Ennals, Rob Jellinghaus, Robert Blaut, Robert Collins, Robert O'Callahan, Robert Sayre, Robin Berjon, Rodger Combs, Roland Steiner, Roman Ivanov, Roy Fielding, Ruud Steltenpool, Ryan King, Ryosuke Niwa, S. Mike Dierken, Salvatore Loreto, Sam Dutton, Sam Kuper, Sam Ruby, Sam Weinig, Sander van Lambalgen, Sarven Capadisli, Scott González, Scott Hess, Sean Fraser, Sean Hayes, Sean Hogan, Sean Knapp, Sebastian Markbåge, Sebastian Schnitzenbaumer, Seth Call, Shanti Rao, Shaun Inman, Shiki Okasaka, Sierk Bornemann, Sigbjørn Vik, Silvia Pfeiffer, Simon Montagu, Simon Pieters, Simon Spiegel, skeww, Stanton McCandlish, Stefan Haustein, Stefan Santesson, Steffen Meschkat, Stephen Ma, Steve Faulkner, Steve Runyon, Steven Bennett, Steven Garrity, Steven Tate, Stewart Brodie, Stuart Ballard, Stuart Parmenter, Subramanian Peruvemba, Sunava Dutta, Susan Borgrink, Susan Lesch, Sylvain Pasche, T. J. Crowder, Tab Atkins, Tantek Çelik, 田村健人 (TAMURA Kent), Ted Mielczarek, Terrence Wood, Thomas Broyer, Thomas Koetter, Thomas O'Connor, Tim Altman, Tim Johansson, Toby Inkster, Todd Moody, Tom Baker, Tom Pike, Tommy Thorsen, Travis Leithead, Tyler Close, Vladimir Katardjiev, Vladimir Vukićević, voracity, Wakaba, Wayne Carr, Wayne Pollock, Wellington Fernando de Macedo, Weston Ruter, Will Levine, William Swanson, Wladimir Palant, Wojciech Mach, Wolfram Kriesing, Yang Chen, Ye-Kui Wang, Yehuda Katz, Yi-An Huang, Yngve Nysaeter Pettersen, Yuzo Fujishima, Zhenbin Xu, Zoltan Herczeg, and Øistein E. Andersen, for their useful comments, both large and small, that have led to changes to this specification over the years.

Thanks also to everyone who has ever posted about HTML to their blogs, public mailing lists, or forums, including all the contributors to the various W3C HTML WG lists and the various WHATWG lists.

Special thanks to Richard Williamson for creating the first implementation of canvas in Safari, from which the canvas feature was designed.

Special thanks also to the Microsoft employees who first implemented the event-based drag-and-drop mechanism, contenteditable, and other features first widely deployed by the Windows Internet Explorer browser.

Thanks to the participants of the microdata usability study for allowing us to use their mistakes as a guide for designing the microdata feature.

Thanks to the many sources that provided inspiration for the examples used in the specification.

Thanks also to the Microsoft blogging community for some ideas, to the attendees of the W3C Workshop on Web Applications and Compound Documents for inspiration, to the #mrt crew, the #mrt.no crew, and the #whatwg crew, and to Pillar and Hedral for their ideas and support.