HTML 5 differences from HTML 4

Abstract

HTML 5 defines the fifth major revision of the core language of the World Wide Web, HTML. "HTML 5 differences from HTML 4" describes the differences between HTML 4 and HTML 5 and provides some of the rationale for the changes. This document may not provide accurate information as the HTML 5 specification is still actively in development. When in doubt, always check the HTML 5 specification itself. [HTML5]

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 latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This is the 23 April 2009 W3C Working Draft produced by the HTML Working Group, part of the HTML Activity. The Working Group intends to publish this document as a Working Group Note to accompany the HTML 5 specification. The appropriate forum for comments is public-html-comments@w3.org, a mailing list with a public archive.

Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

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 Introduction
  • 1.1 Open Issues
  • 1.2 Backwards Compatible
  • 1.3 Development Model
  • 1.4 Impact on Web Architecture
• 2 Syntax
  • 2.1 Character Encoding
  • 2.2 The DOCTYPE
  • 2.3 MathML and SVG
  • 2.4 Miscellaneous
• 3 Language
  • 3.1 New Elements
  • 3.2 New Attributes
  • 3.3 Changed Elements
  • 3.4 Absent Elements
  • 3.5 Absent Attributes
• 4 APIs
  • 4.1 Extensions to HTMLDocument
  • 4.2 Extensions to HTMLElement
• 5 HTML 5 Changelogs
  • 5.1 Changes since 12 February 2009
  • 5.2 Changes from 10 June 2008 to 12 February 2009
  • 5.3 Changes from 22 January 2008 to 10 June 2008
• Acknowledgments
• References

1 Introduction

HTML has been in continuous evolution since it was introduced to the Internet in the early 1990's. Some features were introduced in specifications; others were introduced in software releases. In some respects, implementations and author practices have converged with each other and with specifications and standards, but in other ways, they continue to diverge.

HTML 4 became a W3C Recommendation in 1997. While it continues to serve as a rough guide to many of the core features of HTML, it does not provide enough information to build implementations that interoperate with each other and, more importantly, with a critical mass of deployed content. The same goes for XHTML 1, which defines an XML serialization for HTML 4, and DOM Level 2 HTML, which defines JavaScript APIs for both HTML and XHTML. HTML 5 will replace these documents. [DOM2HTML] [HTML4] [XHTML1]

The HTML 5 draft reflects an effort, started in 2004, to study contemporary HTML implementations and deployed content. The draft:

1. Defines a single language called HTML 5 which can be written in HTML syntax and in XML syntax.
2. Defines detailed processing models to foster interoperable implementations.
3. Improves markup for documents.
4. Introduces markup and APIs for emerging idioms, such as Web applications.

1.1 Open Issues

HTML 5 is still a draft. The contents of HTML 5, as well as the contents of this document which depend on HTML 5, are still being discussed on the HTML Working Group and WHATWG mailing lists. The open issues include (this list is not exhaustive):

• De facto semantic definitions for some formerly presentational elements.
• Details of accessibility and media-independence features, such as the longdesc, alt and summary attributes.

1.2 Backwards Compatible

HTML 5 is defined in a way that it is backwards compatible with the way user agents handle deployed content. To keep the authoring language relatively simple for authors several elements and attributes are not included as outlined in the other sections of this document, such as presentational elements that are better dealt with using CSS.

User agents, however, will always have to support these older elements and attributes and this is why the specification clearly separates requirements for authors and user agents. This means that authors cannot use the isindex or the plaintext element, but user agents are required to support them in a way that is compatible with how these elements need to behave for compatibility with deployed content.

Since HTML 5 has separate conformance requirements for authors and user agents there is no longer a need for marking features "deprecated".

1.3 Development Model

The HTML 5 specification will not be considered finished before there are at least two complete implementations of the specification. This is a different approach than previous versions of HTML had. The goal is to ensure that the specification is implementable and usable by designers and developers once it is finished.

2 Syntax

HTML 5 defines an HTML syntax that is compatible with HTML 4 and XHTML 1 documents published on the Web, but is not compatible with the more esoteric SGML features of HTML 4, such as the NET syntax (i.e. <em/content/). Documents using the HTML syntax must be served with the text/html media type.

HTML 5 also defines detailed parsing rules (including "error handling") for this syntax which are largely compatible with popular implementations. User agents must use these rules for resources that have the text/html media type. Here is an example document that conforms to the HTML syntax:

<!doctype html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>Example document</title>
  </head>
  <body>
    <p>Example paragraph</p>
  </body>
</html>

The other syntax that can be used for HTML 5 is XML. This syntax is compatible with XHTML 1 documents and implementations. Documents using this syntax need to be served with an XML media type and elements need to be put in the http://www.w3.org/1999/xhtml namespace following the rules set forth by the XML specifications. [XML]

Below is an example document that conforms to the XML syntax of HTML 5. Note that XML documents must have an XML media type such as application/xhtml+xml or application/xml.

<?xml version="1.0" encoding="UTF-8"?>
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <title>Example document</title>
  </head>
  <body>
    <p>Example paragraph</p>
  </body>
</html>

2.1 Character Encoding

For the HTML syntax of HTML 5 authors have three means of setting the character encoding:

• At the transport level. By using the HTTP Content-Type header for instance.
• Using a Unicode Byte Order Mark (BOM) character at the start of the file. This character provides a signature for the encoding used.
• Using a meta element with a charset attribute that specifies the encoding within the first 512 bytes of the document. E.g. <meta charset="UTF-8"> could be used to specify the UTF-8 encoding. This replaces the need for <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> although that syntax is still allowed.

For the XML syntax, authors have to use the rules as set forth in the XML specifications to set the character encoding.

2.2 The DOCTYPE

The HTML syntax of HTML 5 requires a DOCTYPE to be specified to ensure that the browser renders the page in standards mode. The DOCTYPE has no other purpose and is therefore optional for XML. Documents with an XML media type are always handled in standards mode. [DOCTYPE]

The DOCTYPE declaration is <!DOCTYPE html> and is case-insensitive in the HTML syntax. DOCTYPEs from earlier versions of HTML were longer because the HTML language was SGML-based and therefore required a reference to a DTD. With HTML 5 this is no longer the case and the DOCTYPE is only needed to enable standards mode for documents written using the HTML syntax. Browsers already do this for <!DOCTYPE html>.

2.3 MathML and SVG

The HTML syntax of HTML 5 allows for MathML and SVG elements to be used inside a document. E.g. a very simple document using some of the minimal syntax features could look like:

<!doctype html>
<title>SVG in text/html</title>
<p>
 A green circle:
 <svg> <circle r="50" cx="50" cy="50" fill="green"/> </svg>
</p>

More complex combinations are also possible. E.g. with the SVG foreignObject element you could nest MathML, HTML, or both inside an SVG fragment that is itself inside HTML.

2.4 Miscellaneous

There are a few other syntax changes worthy of mentioning:

• HTML now has native support for IRIs, though they can only be fully used if the document encoding is UTF-8 or UTF-16.
• The lang attribute takes the empty string in addition to a valid language identifier, just like xml:lang does in XML.

3 Language

This section is split up in several subsections to more clearly illustrate the various differences there are between HTML 4 and HTML 5.

3.1 New Elements

The following elements have been introduced for better structure:

• section represents a generic document or application section. It can be used together with the h1, h2, h3, h4, h5, and h6 elements to indicate the document structure.

• article represents an independent piece of content of a document, such as a blog entry or newspaper article.

• aside represents a piece of content that is only slightly related to the rest of the page.

• header represents the header of a section.

• footer represents a footer for a section and can contain information about the author, copyright information, et cetera.

• nav represents a section of the document intended for navigation.

• dialog can be used to mark up a conversation like this:

  <dialog>
   <dt> Costello
   <dd> Look, you gotta first baseman?
   <dt> Abbott
   <dd> Certainly.
   <dt> Costello
   <dd> Who's playing first?
   <dt> Abbott
   <dd> That's right.
   <dt> Costello
   <dd> When you pay off the first baseman every month, who gets the money?
   <dt> Abbott
   <dd> Every dollar of it. 
  </dialog>

• figure can be used to associate a caption together with some embedded content, such as a graphic or video:

  <figure>
   <video src="ogg"></video>
   <legend>Example</legend>
  </figure>

Then there are several other new elements:

• audio and video for multimedia content. Both provide an API so application authors can script their own user interface, but there is also a way to trigger a user interface provided by the user agent. source elements are used together with these elements if there are multiple streams available of different types.

• embed is used for plugin content.

• mark represents a run of marked text.

• meter represents a measurement, such as disk usage.

• progress represents a completion of a task, such as downloading or when performing a series of expensive operations.

• time represents a date and/or time.

• canvas is used for rendering dynamic bitmap graphics on the fly, such as graphs or games.

• command represents a command the user can invoke.

• datagrid represents an interactive representation of a tree, list or tabular data.

• details represents additional information or controls which the user can obtain on demand.

• datalist together with the a new list attribute for input is used to make comboboxes:

  <input list="browsers">
  <datalist id="browsers">
   <option value="Safari">
   <option value="Internet Explorer">
   <option value="Opera">
   <option value="Firefox">
  </datalist>

• keygen represents control for key pair generation.

• bb represents a user agent command that the user can invoke.

• output represents some type of output, such as from a calculation done through scripting.

• ruby, rt and rp allow for marking up ruby annotations.

The input element's type attribute now has the following new values:

• datetime
• datetime-local
• date
• month
• week
• time
• number
• range
• email
• url
• search
• color

The idea of these new types is that the user agent can provide the user interface, such as a calendar date picker or integration with the user's address book, and submit a defined format to the server. It gives the user a better experience as his input is checked before sending it to the server meaning there is less time to wait for feedback.

3.2 New Attributes

HTML 5 has introduced several new attributes to various elements that were already part of HTML 4:

• The a and area elements now have a media attribute for consistency with the link element. It is purely advisory.

• The a and area elements have a new attribute called ping that specifies a space-separated list of URLs which have to be pinged when the hyperlink is followed. Currently user tracking is mostly done through redirects. This attribute allows the user agent to inform users which URLs are going to be pinged as well as giving privacy-conscious users a way to turn it off.

• The area element, for consistency with the a and link elements, now also has the hreflang and rel attributes.

• The base element can now have a target attribute as well, mainly for consistency with the a element. (This is already widely supported.) Also, the target attribute for the a and area elements is no longer deprecated, as it is useful in Web applications, e.g. in conjunction with iframe.

• The value attribute for the li element is no longer deprecated as it is not presentational. The same goes for the start attribute of the ol element.

• The meta element has a charset attribute now as this was already widely supported and provides a nice way to specify the character encoding for the document.

• A new autofocus attribute can be specified on the input (except when the type attribute is hidden), select, textarea and button elements. It provides a declarative way to focus a form control during page load. Using this feature should enhance the user experience as the user can turn it off if he does not like it, for instance.

• A new placeholder attribute can be specified on the input and textarea elements.

• The new form attribute for input, output, select, textarea, button and fieldset elements allows for controls to be associated with a form. I.e. these elements can now be placed anywhere on a page, not just as descendants of the form element.

• The new required attribute applies to input (except when the type attribute is hidden, image or some button type such as submit) and textarea. It indicates that the user has to fill in a value in order to submit the form.

• The fieldset element now allows the disabled attribute disabling all its contents when specified.

• The input element has several new attributes to specify constraints: autocomplete, min, max, multiple, pattern and step. As mentioned before it also has a new list attribute which can be used together with the datalist and select element.

• The form element has a novalidate attribute that can be used to disable form validation submission (i.e. the form can always be submitted).

• The input and button elements have formaction, formenctype, formmethod, formnovalidate, and formtarget as new attributes. If present, they override the action, enctype, method, novalidate, and target attributes on the form element.

• The menu element has two new attributes: type and label. They allow the element to transform into a menu as found in typical user interfaces as well as providing for context menus in conjunction with the global contextmenu attribute.

• The style element has a new scoped attribute which can be used to enable scoped style sheets. Style rules within such a style element only apply to the local tree.

• The script element has a new attribute called async that influences script loading and execution.

• The html element has a new attribute called manifest that points to an application cache manifest used in conjunction with the API for offline Web applications.

• The link element has a new attribute called sizes. It can be used in conjunction with the icon relationship (set through the rel attribute) to indicate the size of the referenced icon.

• The ol element has a new attribute called reversed to indicate that the list order is descending when present.

• The iframe element has two new attributes called seamless and sandbox which allow for sandboxing content, e.g. blog comments.

Several attributes from HTML 4 now apply to all elements. These are called global attributes: class, dir, id, lang, style, tabindex and title.

There are also several new global attributes:

• The contenteditable attribute indicates that the element is an editable area. The user can change the contents of the element and manipulate the markup.
• The contextmenu attribute can be used to point to a context menu provided by the author.
• The data-* collection of author-defined attributes. Authors can define any attribute they want as long as they prefix it with data- to avoid clashes with future versions of HTML. The only requirement on these attributes is that they are not used for user agent extensions.
• The draggable attribute can be used together with the new drag & drop API.
• The hidden attribute indicates that an element is not yet, or is no longer, relevant.
• The spellcheck attribute allows for hinting whether content can be checked for spelling or not.

HTML 5 also makes all event handler attributes from HTML 4 that take the form onevent-name global attributes and adds several new event handler attributes for new events it defines, such as the onmessage attribute which can be used together with the new eventsource element and the cross-document messaging API.

3.3 Changed Elements

These elements have slightly modified meanings in HTML 5 to better reflect how they are used on the Web or to make them more useful:

• The a element without an href attribute now represents a "placeholder link". It can also contain flow content rather than being restricted to phrase content.

• The address element is now scoped by the new concept of sectioning.

• The b element now 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 emboldened.

• The hr element now represents a paragraph-level thematic break.

• The i element now 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. Usage varies widely by language.

• For the label element the browser should no longer move focus from the label to the control unless such behavior is standard for the underlying platform user interface.

• The menu element is redefined to be useful for toolbars and context menus.

• The small element now represents small print (for side comments and legal print).

• The strong element now represents importance rather than strong emphasis.

3.4 Absent Elements

The elements in this section are not to be used by authors. User agents will still have to support them and various sections in HTML 5 define how. E.g. the obsolete isindex element is handled by the parser section.

The following elements are not in HTML 5 because their effect is purely presentational and their function is better handled by CSS:

• basefont
• big
• center
• font
• s
• strike
• tt
• u

The following elements are not in HTML 5 because their usage affected usability and accessibility for the end user in a negative way:

• frame
• frameset
• noframes

The following elements are not included because they have not been used often, created confusion, or their function can be handled by other elements:

• acronym is not included because it has created a lot of confusion. Authors are to use abbr for abbreviations.
• applet has been obsoleted in favor of object.
• isindex usage can be replaced by usage of form controls.
• dir has been obsoleted in favor of ul.

Finally the noscript is only conforming in the HTML syntax. It is not included in the XML syntax as its usage relies on an HTML parser.

3.5 Absent Attributes

Some attributes from HTML 4 are no longer allowed in HTML 5. If they need to have any impact on user agents for compatibility reasons it is defined how they should work in those scenarios.

• accesskey attribute on a, area, button, input, label, legend and textarea.
• rev and charset attributes on link and a.
• shape and coords attributes on a.
• longdesc attribute on img and iframe.
• target attribute on link.
• nohref attribute on area.
• profile attribute on head.
• version attribute on html.
• name attribute on img and a (use id instead).
• scheme attribute on meta.
• archive, classid, codebase, codetype, declare and standby attributes on object.
• valuetype and type attributes on param.
• language attribute on script.
• summary attribute on table.
• axis and abbr attributes on td and th.
• scope attribute on td.

In addition, HTML 5 has none of the presentational attributes that were in HTML 4 as their functions are better handled by CSS:

• align attribute on caption, iframe, img, input, object, legend, table, hr, div, h1, h2, h3, h4, h5, h6, p, col, colgroup, tbody, td, tfoot, th, thead and tr.
• alink, link, text and vlink attributes on body.
• background attribute on body.
• bgcolor attribute on table, tr, td, th and body.
• border attribute on table, img and object.
• cellpadding and cellspacing attributes on table.
• char and charoff attributes on col, colgroup, tbody, td, tfoot, th, thead and tr.
• clear attribute on br.
• compact attribute on dl, menu, ol and ul.
• frame attribute on table.
• frameborder attribute on iframe.
• height attribute on td and th.
• hspace and vspace attributes on img and object.
• marginheight and marginwidth attributes on iframe.
• noshade attribute on hr.
• nowrap attribute on td and th.
• rules attribute on table.
• scrolling attribute on iframe.
• size attribute on hr.
• type attribute on li, ol and ul.
• valign attribute on col, colgroup, tbody, td, tfoot, th, thead and tr.
• width attribute on hr, table, td, th, col, colgroup and pre.

4 APIs

HTML 5 introduces a number of APIs that help in creating Web applications. These can be used together with the new elements introduced for applications:

• 2D drawing API which can be used with the new canvas element.
• API for playing of video and audio which can be used with the new video and audio elements.
• An API that enables offline Web applications.
• An API that allows a Web application to register itself for certain protocols or media types.
• Editing API in combination with a new global contenteditable attribute.
• Drag & drop API in combination with a draggable attribute.
• API that exposes the history and allows pages to add to it to prevent breaking the back button.
• Cross-document messaging.

4.1 Extensions to HTMLDocument

HTML 5 has extended the HTMLDocument interface from DOM Level 2 HTML in a number of ways. The interface is now implemented on all objects implementing the Document interface so it stays meaningful in a compound document context. It also has several noteworthy new members:

• getElementsByClassName() to select elements by their class name. The way this method is defined will allow it to work for any content with class attributes and a Document object such as SVG and MathML.

• innerHTML as an easy way to parse and serialize an HTML or XML document. This attribute was previously only available on HTMLElement in Web browsers and not part of any standard.

• activeElement and hasFocus to determine which element is currently focused and whether the Document has focus respectively.

• getSelection() which returns an object that represents the current selection(s).

• designMode and execCommand() which are mostly used for editing of documents.

4.2 Extensions to HTMLElement

The HTMLElement interface has also gained several extensions in HTML 5:

• getElementsByClassName() which is basically a scoped version of the one found on HTMLDocument.

• innerHTML as found in Web browsers today. It is also defined to work in XML context (when it is used in an XML document).

• classList is a convenient accessor for className. The object it returns exposes methods, has(), add(), remove() and toggle(), for manipulating the element's classes. The a, area and link elements have a similar attribute called relList that provides the same functionality for the rel attribute.

5 HTML 5 Changelogs

The changelogs in this section indicate what has been changed between publications of the HTML 5 drafts. Rationale for changes can be found in the public-html@w3.org and whatwg@whatwg.org mailing list archives and to some extent in the This Week in HTML 5 series of blog posts. Many editorial and minor technical changes are not included in these changelogs. I.e. implementors are strongly encouraged to follow the development of the main specification on a frequent basis so they become aware of all changes that affect them early on.

The changes in the changelogs are in rough chronological order to ease editing this document.

5.1 Changes since 12 February 2009

• A new global attribute called spellcheck has been added.
• Defined that ECMAScript this in the global object returns a WindowProxy object rather than the Window object.
• The value DOM attribute for input elements in the File Upload state is now defined.
• Definition of designMode was changed to be more in line with legacy implementations.
• The drawImage() method of the 2D drawing API can now take a video element as well.
• The way media elements load resources has been changed.
• document.domain is now IPv6-compatible.
• The video element gained an autobuffer boolean attribute that serves as a hint.
• You are now allowed to specify the meta element with a charset attribute in XML documents if the value of that attribute matches the encoding of the document. (Note that it does not specify the value, it is just a talisman.)
• The bufferingRate and bufferingThrottled members of media elements have been removed.
• The media element resource selection algorithm is now asynchronous.
• The postMessage() API now takes an array of MessagePort objects rather than just one.
• The second argument of the add() method on the select element and the options member of the select element is now optional.
• The action, enctype, method, novalidate, and target attributes on input and button elements have been renamed to formaction, formenctype, formmethod, formnovalidate, and formtarget.
• A "storage mutex" concept has been added to deal with separate pages trying to change a storage object (document.cookie and localStorage) at the same time. The Navigator gained a getStorageUpdates() method to allow it to be explicitly released.
• A syntax for SVG similar to MathML is now defined so that SVG can be included in text/html resources.
• The placeholder attribute has been added to the textarea element.
• Added a keygen element for key pair generation.
• The datagrid element was revised to make the API more asynchronous and allow for unloaded parts of the grid.

In addition, several parts of HTML 5 have been taken out and will be further developed by the Web Applications Working Group as standalone specifications:

• Web Sockets
• Server-Sent Events
• Web Storage (the persistent storage and database storage features)

5.2 Changes from 10 June 2008 to 12 February 2009

• The data member of ImageData objects has been changed from an array to a CanvasPixelArray object.
• Shadows are now required from implementations of the canvas element and its API.
• Security model for canvas is clarified.
• Various changes to the processing model of canvas have been made in response to implementation and author feedback. E.g. clarifying what happens when NaN and Infinity are passed and fixing the definitions of arc() and arcTo().
• innerHTML in XML was slightly changed to improve round-tripping.
• The toDataURL() method on the canvas element now supports setting a quality level when the media type argument is image/jpeg.
• The poster attribute of the video element now affects its intrinsic dimensions.
• The behavior of the type attribute of the link element has been clarified.
• Sniffing is now allowed for link when the expected type is an image.
• A section on URLs is introduced dealing with how URL values are to be interpreted and what exactly authors are required to do. Every feature of the specification that uses URLs has been reworded to take the new URL section into account.
• It is now explicit that the href attribute of the base element does not depend on xml:base.
• It is now defined what the behavior should be when the base URL changes.
• URL decomposition DOM attributes are now more aligned with Internet Explorer.
• The xmlns attribute with the value http://www.w3.org/1999/xhtml is now allowed on all HTML elements.
• data-* attributes and custom attributes on the embed element now have to match the XML Name production and cannot contain a colon.
• Web Socket API is introduced for bidirectional communication with a server. It is currently limited to text messages.
• The default value of volume on media elements is now 1.0 rather than 0.5.
• event-source was renamed to eventsource because no other HTML element uses a hyphen.
• A message channel API has been introduced augmenting postMessage().
• A new element named bb has been added. It represents a user agent command that the user can invoke.
• The addCueRange() method on media elements has been modified to take an identifier which is exposed in the callbacks.
• It is now defined how to mutate a DOM into an infoset.
• The parent attribute of the Window object is now defined.
• The embed element is defined to do extension sniffing for compatibilty with servers that deliver Flash as text/plain. (This is marked as an issue in the specification to figure out if there is a better way to make this work.)
• The embed can now be used without its src attribute.
• getElementsByClassName() is defined to be ASCII case-insensitive in quirks mode for consistency with CSS.
• In HTML documents localName no longer returns the node name in uppercase.
• data-* attributes are defined to be always lowercase.
• The opener attribute of the Window object is not to be present when the page was opened from a link with target="_blank" and rel="noreferrer".
• The top attribute of the Window object is now defined.
• The a element now allows nested flow content, but not nested interactive content.
• It is now defined what the header element means to document summaries and table of contents.
• What it means to fetch a resource is now defined.
• Patterns are now required for the canvas element.
• The autosubmit attribute has been removed from the menu element.
• Support for outerHTML and insertAdjacentHTML() has been added.
• xml:lang is now allowed in HTML when lang is also specified and they have the same value. In XML lang is allowed if xml:lang is also specified and they have the same value.
• The frameElement attribute of the Window object is now defined.
• An event loop and task queue is now defined detailing script execution and events. All features have been updated to be defined in terms of this mechanism.
• If the alt attribute is omitted a title attribute, an enclosing figure element with a legend element descendant, or an enclosing section with an associated heading must be present.
• The irrelevant attribute has been renamed to hidden.
• The definitionURL attribute of MathML is now properly supported. Previously it would have ended up being all lowercase during parsing.
• User agents must treat US-ASCII as Windows-1252 for compatibility reasons.
• An alternative syntax for the DOCTYPE is allowed for compatibility with some XML tools.
• Data templates have been removed (consisted of the datatemplate, rule and nest elements).
• The media elements now support just a single loop attribute.
• The load() method on media elements has been redefined as asynchronous. It also tries out files in turn now rather than just looking at the type attribute of the source element.
• A new member called canPlayType() has been added to the media elements.
• The totalBytes and bufferedBytes attributes have been removed from the media elements.
• The Location object gained a resolveURL() method.
• The q element has changed again. Punctation is to be provided by the user agent again.
• Various changes were made to the HTML parser algorithm to be more in line with the behavior Web sites require.
• The unload and beforeunload events are now defined.
• The IDL blocks in the specification have been revamped to be in line with the upcoming Web IDL specification.
• Table headers can now have headers. User agents are required to support a headers attribute pointing to a td or th element, but authors are required to only let them point to th elements.
• Interested parties can now register new http-equiv values.
• When the meta element has a charset attribute it must occur within the first 512 bytes.
• The StorageEvent object now has a storageArea attribute.
• It is now defined how HTML is to be used within the SVG foreignObject element.
• The notification API has been dropped.
• How [[Get]] works for the HTMLDocument and Window objects is now defined.
• The Window object gained the locationbar, menubar, personalbar, scrollbars, statusbar and toolbar attributes giving information about the user interface.
• The application cache section has been significantly revised and updated.
• document.domain now relies on the Public Suffix List. [PSL]
• A non-normative rendering section has been added that describes user agent rendering rules for both obsolete and conforming elements.
• A normative section has been added that defines when certain selectors as defined in the Selectors and the CSS3 Basic User Interface Module match HTML elements. [SELECTORS] [CSS-UI]

Web Forms 2.0, previously a standalone specification, has been fully integrated into HTML 5 since last publication. The following changes were made to the forms chapter:

• Support for XML submission has been removed.
• Support for form filling has been removed.
• Support for filling of the select and datalist elements through the data attribute has been removed.
• Support for associating a field with multiple forms has been removed. A field can still be associated with a form it is not nested in through the form attribute.
• The dispatchFormInput() and dispatchFormChange() methods have been removed.
• Repetition templates have been removed.
• The inputmode attribute has been removed.
• The input element in the File Upload state no longer supports the min and max attributes.
• The allow attribute on input elements in the File Upload state is no longer authoritative.
• The pattern and accept attributes for textarea have been removed.
• RFC 3106 is no longer explicitly supported.
• The submit() method now just submits, it no longer ensures the form controls are valid.
• The input element in the Range state now defaults to the middle, rather than the minimum value.
• The size attribute on the input element is now conforming (rather than deprecated).
• object elements now partake in form submission.
• The type attribute of the input element gained the values color and search.
• The input element gained a multiple attribute which allows for either multiple e-mails or multiple files to be uploaded depending on the value of the type attribute.
• The input, button and form elements now have a novalidate attribute to indicate that the form fields should not be required to have valid values upon submission.
• When the label element contains an input it may still have a for attribute as long as it points to the input element it contains.
• The input element now has an indeterminate DOM attribute.
• The input element gained a placeholder attribute.

5.3 Changes from 22 January 2008 to 10 June 2008

• Implementation and authoring details around the ping attribute have changed.
• <meta http-equiv=content-type> is now a conforming way to set the character encoding.
• API for the canvas element has been cleaned up. Text support has been added.
• globalStorage is now restricted to the same-origin policy and renamed to localStorage. Related event dispatching has been clarified.
• postMessage() API changed. Only the origin of the message is exposed, no longer the URL. It also requires a second argument that indicates the origin of the target document.
• Drag and drop API has got clarification. The dataTransfer object now has a types attribute indicating the type of data being transferred.
• The m element is now called mark.
• Server-sent events has changed and gotten clarification. It uses a new format so that older implementations are not broken.
• The figure element no longer requires a caption.
• The ol element has a new reversed attribute.
• Character encoding detection has changed in response to feedback.
• Various changes have been made to the HTML parser section in response to implementation feedback.
• Various changes to the editing section have been made, including adding queryCommandEnabled() and related methods.
• The headers attribute has been added for td elements.
• The table element has a new createTBody() method.
• MathML support has been added to the HTML parser section. (SVG support is still awaiting input from the SVG WG.)
• Author-defined attributes have been added. Authors can add attributes to elements in the form of data-name and can access these through the DOM using dataset[name] on the element in question.
• The q element has changed to require punctation inside rather than having the browser render it.
• The target attribute can now have the value _blank.
• The showModalDialog API has been added.
• The document.domain API has been defined.
• The source element now has a new pixelratio attribute useful for videos that have some kind encoding error.
• bufferedBytes, totalBytes and bufferingThrottled DOM attributes have been added to the video element.
• Media begin event has been renamed to loadstart for consistency with the Progress Events specification.
• charset attribute has been added to script.
• The iframe element has gained the sandbox and seamless attributes which provide sandboxing functionality.
• The ruby, rt and rp elements have been added to support ruby annotation.
• A showNotification() method has been added to show notification messages to the user.
• Support for beforeprint and afterprint events has been added.

Acknowledgments

The editor would like to thank Ben Millard, Cameron McCormack, Charles McCathieNevile, Dan Connolly, David Håsäther, Frank Ellermann, Henri Sivonen, James Graham, Jens Meiert, Jürgen Jeka, Maciej Stachowiak, Mark Pilgrim, Martijn Wargers, Martyn Haigh, Masataka Yakura, Michael Smith, Olivier Gendrin, Øistein E. Andersen, Philip Taylor and Simon Pieters for their contributions to this document as well as to all the people who have contributed to HTML 5 over the years for improving the Web!

References

[CSS-UI]

CSS3 Basic User Interface Module, T. Çelik, editor. W3C, May 2004.

[DOCTYPE]

Activating Browser Modes with Doctype, H. Sivonen, January 2008.

[DOM2HTML]

Document Object Model (DOM) Level 2 HTML Specification, J. Stenback, P. Le Hégaret, A. Le Hors, editors. W3C, January 2003.

[HTML4]

HTML 4.01 Specification, D. Raggett, A. Le Hors, I. Jacobs, editors. W3C, December 1999.

[HTML5]

HTML 5, I. Hickson, D. Hyatt, editors. W3C, February 2009.

HTML 5 (editor's draft), I. Hickson, editor. WHATWG, 2009.

HTML 5 (editors' draft), I. Hickson, D. Hyatt, editors. W3C, 2009.

[PSL]

Public Suffix List, Mozilla Foundation, 2007.

[SELECTORS]

Selectors, D. Glazman, T. Çelik, I. Hickson, editors. W3C, December 2005.

[XHTML1]

XHTML™ 1.1 - Module-based XHTML (Second Edition), S. McCarron, M. Ishikawa, editors. W3C, February 2007.

[XML]

Extensible Markup Language (XML) 1.0 (Fifth Edition), T. Bray, J. Paoli, C. Sperberg-McQueen, E. Maler, F. Yergeau, editors. W3C, November 2008.

Namespaces in XML 1.0 (Second Edition), T. Bray, D. Hollander, A. Layman, R. Tobin, editors. W3C, August 2006.