[contents] [implementing]
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This document provides guidelines for designing user agents that lower barriers to Web accessibility for people with disabilities. User agents include browsers and other types of software that retrieve and render Web content. A user agent that conforms to these guidelines will promote accessibility through its own user interface and through other internal facilities, including its ability to communicate with other technologies (especially assistive technologies). Furthermore, all users, not just users with disabilities, should find conforming user agents to be more usable.
In addition to helping developers of browsers and media players, this document will also benefit developers of assistive technologies because it explains what types of information and control an assistive technology may expect from a conforming user agent. Technologies not addressed directly by this document (e.g., technologies for braille rendering) will be essential to ensuring Web access for some users with disabilities.
The "User Agent Accessibility Guidelines 2.0" (UAAG 2.0) is part of a series of accessibility guidelines published by the W3C Web Accessibility Initiative (WAI).
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 document is the internal working draft used by the UAWG and is updated continuously and without notice. This document has no formal standing within W3C. Please consult the group's home page and the W3C technical reports index for information about the latest publications by this group.
This document has been produced as part of the W3C Web Accessibility Initiative (WAI). The goals of the User Agent Working Group (UAWG) are discussed in the Working Group charter. The UAWG is part of the WAI Technical Activity.
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.
This section is informative.
A user agent is any software that retrieves and presents Web content for end users. Examples include Web browsers, media players, plug-ins, and other programs including assistive technologies, that help in retrieving, rendering and interacting with Web content. This document specifies requirements that, if satisfied by user agent developers, will lower barriers to accessibility.
Accessibility involves a wide range of disabilities, including visual, auditory, physical, speech, cognitive, language, learning, neurological disabilities, and disabilities related to ageing. This document emphasizes the goal of ensuring that users, including users with disabilities, have control over their environment for accessing the Web. Key methods for achieving that goal include:
Some users may have more than one disability, and the needs of different disabilities may contradict. Thus, many of the requirements in this document involve configuration as one way to ensure that a functionality designed to improve accessibility for one user does not interfere with accessibility for another. A default user agent setting may be useful for one user but interfere with accessibility for another, therefore this document prefers configuration requirements rather than requirements for default settings. For some content, a feature required by this document may be ineffective or cause content to be less accessible, making it imperative that the user be able to turn off the feature. To avoid overwhelming users with an abundance of configuration options, this document includes requirements that promote ease of configuration and documentation of accessibility features.
This document also acknowledges the importance of author preferences, however, requirements are included to override certain author preferences when the user would not otherwise be able to access that content.
Some of the requirements of this document may have security implications, such as communication through APIs, and allowing programmatic read and write access to content and user interface control. This document assumes that features required by this document will be built on top of an underlying security architecture. Consequently, unless permitted explicitly in a success criterion, this document grants no conformance exemptions based on security issues.
The UAWG expects that software which satisfies the requirements of this document will be more flexible, manageable, extensible, and beneficial to all users.
In order to meet the varying needs of the different audiences using UAAG, several layers of guidance are provided including overall principles, general guidelines, testable success criteria, and a rich collection of sufficient techniques and resource links.
Principles - At the top are five principles that provide the foundation for accessible user agents. Three of the principles are congruent to Web Content Accessibility Guidelines (WCAG) 2.0: perceivable, operable, understandable. Two principles have been added which are specific to user agents: follows specifications and programmatic access.
Guidelines - Under the principles are guidelines. The guidelines provide the basic goals that authors should work toward in order to make user agents more accessible to users with different disabilities. The guidelines are not testable, but provide the framework and overall objectives to help authors understand the success criteria and better implement the techniques.
Success Criteria - For each guideline, testable success criteria are provided to allow UAAG 2.0 to be used where requirements and conformance testing are necessary such as in design specification, purchasing, regulation, and contractual agreements. In order to meet the needs of different groups and different situations, three levels of conformance are defined: A (lowest), AA, and AAA (highest). Additional information on UAAG levels can be found in the section on Conformance.
All of these layers of guidance (principles, guidelines, and success criteria) work together to provide guidance on how to make user agents more accessible. Developers are encouraged to view and apply all layers that they are able to, including the advisory techniques, in order to best address the needs of the widest possible range of users.
Note that even user agents that conform at the highest level (AAA) will not be accessible to individuals with all types, degrees, or combinations of disability, particularly in the cognitive, language, and learning areas. Developers are encouraged to consider the full range of techniques, including the advisory techniques, as well as to seek relevant advice about current best practice to ensure that their user agent is accessible, as far as possible, to this community.
A separate document, entitled "Implementing User Agent Accessibility Guidelines 2.0" (the "Implementing document" from here on) provides suggestions and examples of how each success criteria might be satisfied. It also includes references to other accessibility resources (such as platform-specific software accessibility guidelines) that provide additional information on how a user agent may satisfy each success criteria. The techniques in the Implementing document are informative examples only, and other strategies may be used or required to satisfy the success criteria. The UAWG expects to update the Implementing document more frequently than the current guidelines. Developers, W3C Working Groups, users, and others are encouraged to contribute examples and resources.
Web accessibility depends not only on accessible user agents, but also on the availability of accessible content, a factor that is greatly influenced by the accessibility of authoring tools. For an overview of how these components of Web development and interaction work together, see:
User Agents may claim conformance to UAAG 2.0 at one of three conformance levels. The level achieved depends on the level of the success criteria that have been satisfied. The conformance levels are:
A user agent is any software that retrieves, renders and facilitates end user interaction with Web content.
1.1.1 Non-Web-Based Accessible (Level A): Non-Web-based user agent user interfaces comply with and cite the "Level A" requirements of standards or operating environment conventions that benefit accessibility. The "Level A" requirements are those that are functionally equivalent to WCAG Level A success criteria. (Level A)
1.1.2 Non-Web-Based Accessible (Level AA): Non-Web-based user agent user interfaces comply with and cite the "Level AA" requirements of standards or operating environment conventions that benefit accessibility. The "Level AA" requirements are those that are functionally equivalent to WCAG Level AA success criteria. (Level AA)
1.1.3 Non-Web-Based Accessible (Level AAA): Non-Web-based user agent user interfaces comply with and cite the "Level AAA" requirements of standards or operating environment conventions that benefit accessibility. The "Level AAA" requirements are those that are functionally equivalent to WCAG Level AAA success criteria. (Level AAA)
This guideline does not apply to Web-based user agent user interfaces, but does includes any parts of Web-based user agents that are non-Web-based @@DEFINE@@ (e.g., client-side file uploaders).
1.2.1 Web-Based Accessible (Level A): User agent user interfaces that are rendered using Web standard technologies conform to WCAG Level "A". (Level A)
1.2.2 Web-Based Accessible (Level AA): User agent user interfaces that are rendered using Web standard technologies conform to WCAG Level "AA". (Level AA)
1.2.3 Web-Based Accessible (Level AAA): User agent user interfaces that are rendered using Web standard technologies conform to WCAG Level "AAA". (Level AAA)
This guideline does not apply to non-Web-based user agent user interfaces, but does include any parts of non-Web-based user agents that are Web-based(e.g., help systems).
1.3.1 Accessibility Features: Implement and cite in the conformance claim the accessibility features of a technology specification. Accessibility features are those that are either (Level A):
1.4.1 Follow Specifications: Render content according to the technology specification. This includes any accessibility features of the technology (see Guideline 1.3). (Level A)
1.4.2 Handle Unrendered Technologies: If the user agent does not render a technology, it allows the user to choose a way to handle content in that technology (e.g., by launching another application or by saving it to disk). (Level A)
When a rendering requirement of another specification contradicts a requirement of UAAG 2.0, the user agent may disregard the rendering requirement of the other specification and still satisfy this guideline.
2.1.1 Platform Accessibility Architecture: Support an platform accessibility architecture relevant to the operating environment. (Level A)
2.1.2 Name, Role, State, Value, Description: 2.1.2 Name, Role, State, Value, Description: For all user interface components including the user interface, rendered content, and alternative content, make available the name, role, state, value, and description via an platform accessibility architecture. (Level A)
2.1.3 Accessible Alternative: If a feature is not supported by the accessibility architecture(s), provide an equivalent feature that does support the accessibility architecture(s). Document the equivalent feature in the conformance claim. (Level A)
2.1.4 Programmatic Availability of DOMs: If the user agent implements one or more DOMs, they must be made programmatically available to assistive technologies. (Level A)
2.1.5 Write Access: If the user can modify the state or value of a piece of content through the user interface (e.g., by checking a box or editing a text area), the same degree of write access is available programmatically. (Level A)
2.1.6 Properties: If any of the following properties are supported by the accessibility platform architecture, make the properties available to the accessibility platform architecture: (Level A)
2.1.7 Timely Communication: For APIs (for non-web-based user agents) implemented to satisfy the requirements of this document, ensure that programmatic exchanges proceed at a rate such that users do not perceive a delay. (Level A).
3.1.1 Identify Presence of Alternative Content The user has the ability to have indicators rendered along with rendered elements that have alternative content (e.g. visual icons rendered in proximity of content which has short text alternatives, long descriptions, or captions). In cases where the alternative content has different dimensions than the original content, the user has the option to specify how the layout/reflow of the document should be handled. (Level A).
3.1.2 Configurable Default Rendering: The user has a global option to specify which types of alternative content by default and, in cases where the alternative content has different dimensions than the original content, how the layout/reflow of the document should be handled. (Level A)
3.1.3 Browse and Render: The user can browse the alternatives, switch between them, and render them according to the following (Level A):
3.1.4 Rendering Alternative (Enhanced): Provide the user with the global option to configure a cascade of types of alternatives to render by default, in case a preferred type is unavailable. If the alternative content has a different height or width, then the user agent will reflow the viewport. (Level AA)
3.3.1 Access Relationships: Provide access to explicitly-defined relationships based on the user's position in content (e.g., show form control's label, show label's form control, show a cell's table headers, etc.). (Level A)
3.3.2 Location in Hierarchy: For content in a hierarchy (e.g., tree node, nested frame), the user can view the path of nodes leading from the root to the content. (Level AA)
Editors' Note: Success Criteria from 3.3 have been moved to 4.9
3.3.3 Retrieval Progress: Show the progress of content retrieval. (Level A)
3.4.1 Repair Missing Alternatives: The user has the option of receiving generated repair text when the user agent recognizes that the author has not provided alternative content required by the technology specification (e.g., short text alternative for an image). (Level A)
3.4.2 Repair Empty Alternatives: The user has the option of receiving generated repair text when the user agent recognizes that the author has provided empty alternative content. for an enabled element. (Level AA)
3.5.1 Highlighted items: The user has the option to highlight the following classes of information so that each is uniquely distinguished. (Level A):
3.5.2 Highlighting options: The highlighting options (with the same configurable range as the operating environment's conventional selection utilities) include at least (Level A):
3.6.1 Configure Text: The user can globally set the following characteristics of visually rendered text content, overriding any specified by the author or user agent defaults (Level A):
3.6.2 Preserve Distinctions: When rendered text is rescaled, distinctions in the size of rendered text are preserved (e.g., headers continue to be larger than body text). (Level A)
3.6.3 Option Range: The range of options for each text characteristic includes at least (Level A):
3.7.1 Global Volume: The user can globally set volume of all audio tracks it renders (including a "mute" setting) through available operating environment mechanisms. (Level A)
3.7.2 Speech Volume: The user agent allows the user to adjust the volume of all audio tracks it renders, independent or relative to the volume level at the operating environment.
3.8.1 Speech Rate and Volume: The user can set both of the following synthesized speech characteristics, overriding any values specified by the author (Level A):
3.8.2 Speech Pitch and Range: The user can set all of the following synthesized speech characteristics, overriding any values specified by the author (Level AA):
3.8.3 Advanced Speech Characteristics: The user can set all of the speech characteristics offered by the speech synthesizer, according to the full range of values available, overriding any values specified by the author. (Level AAA)
3.8.4 Speech Features: The following speech features are provided (Level AA):
3.9.1 Author Style Sheets: If the author has supplied one or more style sheets, the user has the following options (Level A):
3.9.2 User Style Sheets: If the user has supplied one or more style sheets, the user has the following options (Level A):
3.10.1 Highlight Viewport: The viewport with the current focus is highlighted (including any frame that takes current focus) using a highlight mechanism that does not rely on rendered text foreground and background colors alone (e.g., a thick outline). (Level A)
3.10.2 Move Viewport to Selection: When a viewport's selection changes, the viewport moves as necessary to ensure that the new selection is at least partially in the viewport. (Level A)
3.10.3 Move Viewport to Focus: When a viewport's content focus changes, the viewport moves as necessary to ensure that the new content focus is at least partially in the viewport. (Level A)
3.10.4 Resizable: The user has the option to make graphical viewports resizable, within the limits of the display, overriding any values specified by the author. (Level A)
3.10.5 Scrollbars: Graphical viewports include scrollbars if the rendered content (including after user preferences have been applied) extends beyond the viewport dimensions, overriding any values specified by the author. (Level A)
3.10.6 Viewport History: If the user agent maintains a viewport history mechanism (e.g., via the "back button") that stores previous "viable" states (i.e., that have not been negated by the content, user agent settings or user agent extensions), it maintains information about the point of regard and it restores the saved values when the user returns to a state in the history. (Level A)
3.10.7 Open on Request: The user has the option of having "top-level"viewports (e.g., windows) only open on explicit user request. In this mode, instead of opening a viewport automatically, notify the user and allow the user to open it with an explicit request (e.g., by confirming a prompt or following a link generated by the user agent). (Level AA)
3.10.8 Do Not Take Focus: When configured to allow "top-level" viewports to open without explicit user request, the user has the option that if a "top-level" viewport opens, neither its content focus nor its user interface focus automatically becomes the current focus. (Level AA)
3.10.9 Stay on Top: The user has the option of having the viewport with the current focus remain "on top" of all other viewports with which it overlaps. (Level AA)
3.10.10 Close Viewport: The user can close any "top-level" viewport. (Level AA)
3.10.11 Same UI: The user has the option of having all "top-level" viewports follow the same user interface configuration as the current or spawning viewpor. (Level AA)
3.10.12 Indicate Viewport Position: Indicate the viewport's position relative to rendered content (e.g., the proportion along an audio or video timeline, the proportion of a Web page before the current position ). (Level AAA)
3.11.1 Content Focus: At least one content focus is provided for each viewport (including frames), where enabled elements are part of the rendered content. (Level A)
3.11.2 Current Focus: The user can make the content focus of each viewport the current focus. (Level A)
3.11.3 User Interface Focus: A user interface focus is provided. (Level A)
3.11.4 Extensions Focusable: The user interface focus can navigate within extensions to the user interface. (Level A)
3.11.5 Hand-Off Focus: The user agent programmatically notifies any nested user agent(s) (e.g., plug-ins) when focus moves to them. (Level A)
3.11.6 Retrieve Focus: At any time, the user agent is able to retrieve focus from a nested viewport (including nested viewports that are user agents). (Level A)
3.11.7 Return Focus: Embedded user agents are responsible for notifying embedding user agent that focus should move back to it. (Level A)
3.11.8 Bi-Directional: The user can move the content focus forward or backward to any enabled element in the viewport. (Level A)
3.11.9 Sequential Navigation: If the author has not specified a navigation order, the default is sequential navigation, in document order. (Level A)
3.11.10 Only on User Request: The user has the option of having the content focus of a viewport only change on explicit user request. (Level A)
3.11.11 On Focus: The user has the option of ensuring that moving the content focus to or from an enabled element does not cause the user agent to take any further action. (Level A)
3.12.1 Text View: For content authored in text formats, a view of the text source is provided. (Level A)
3.12.2 Outline View: An "outline" view of rendered content is provided, composed of labels for important structural elements (e.g., heading text, table titles, form titles, and other labels that are part of the content). (Level AA)
Note: What constitutes a label is defined by each markup
language specification. For example, in HTML, a heading
(H1
-H6
) is a label for the section that follows it,
a CAPTION
is a label for a table, and the title
attribute is a label for its element.
3.12.3 Configure Set of Important Elements: The user has the option to configure the set of important elements for the "outline" view, including by element type (e.g., headers). (Level AAA)
3.13.1 Basic Link Information: The following information is provided for each link (Level A):
3.13.2 Extended Link Information: The following information is provided for each link (Level AAA):
4.1.1 Keyboard Operation: All functionality can be operated via the keyboard using sequential or direct keyboard commands that do not require specific timings for individual keystrokes, except where the underlying function requires input that depends on the path of the user's movement and not just the endpoints (e.g., free hand drawing). This does not forbid and should not discourage providing mouse input or other input methods in addition to keyboard operation. (Level A)
4.1.2 Keystroke Precedence: The user has the option to specify that keystrokes be processed in the following order: user agent user interface, user agent extensions, content keystroke operations administered by the user agent (e.g., access keys), and executable content (e.g., key press events in scripts, etc.). (Level A)
4.1.3 No Keyboard Trap (Minimum): The user agent prevents keyboard traps as follows (Level A):
4.1.4 Separate Selection from Activation: The user has the option to have selection separate from activation (e.g., navigating through a set of radio buttons without changing which is the active/selected option). (Level A)
4.1.5 Standard Text Area Navigation Conventions: Views that render text support the standard text area conventions for the operating environment, including, but not necessarily limited to: character keys, backspace/delete, insert, "arrow" key navigation (e.g., "caret" browsing), page up/page down, navigate to start/end, navigate by paragraph, shift-to-select mechanism, etc. (Level A)
4.1.6 Present Direct Commands in Rendered Content: The user has the option to have any recognized direct commands (e.g. accesskey) in rendered content be presented with their associated elements (e.g. "[Ctrl+t]" displayed after a link whose accesskey value is "t", or an audio browser reading the value or label of a form control followed by "accesskey control plus t"). (Level A)
4.1.7 Present Direct Commands in User Interface: The user has the option to have any direct commands (e.g. keyboard shortcuts) in the user agent user interface be presented with their associated user interface controls (e.g. "Ctrl+S" displayed on the "Save" menu item and toolbar button). (Level AA)
4.1.8 Keyboard Navigation: The user can use the keyboard to navigate from group to group of focusable items and to traverse forwards and backwards all of the focusable items within each group. Groups include, but are not limited to, toolbars, panels, and user agent extensions. (Level AA)
4.1.9 Important Command Functions: Important command functions (e.g. related to navigation, display, content, information management, etc.) are available using a single or sequence of keystrokes or key combinations. (Level AA)
4.1.10 Override of UI Keyboard Commands: The user can override any keyboard shortcut binding for the user agent user interface except for conventional bindings for the operating environment (e.g., for access to help). The rebinding options must include single-key and key-plus-modifier keys if available in the operating environment. (Level AA)
4.1.11 User Override of Accesskeys: The user can override any recognized author supplied content keybinding (i.e. access key). The user must have an option to save the override of user interface keyboard shortcuts so that the rebinding persists beyond the current session. (Level AA)
4.1.12 Specify preferred keystrokes: The user can override any keyboard shortcut including recognized author supplied shortcuts (e.g accesskeys) and user interface controls, except for conventional bindings for the operating environment (e.g., for access to help). (Level AA)
4.2.1 List event handlers: The user can, through keyboard input alone, have presented the list of input device event handlers explicitly associated with the content focus element. (Level A)
4.2.2 Activate any event handler: The user can, through keyboard input alone, activate any input device event handlers explicitly associated with the content focus element. (Level A)
4.2.3 Activate all event handlers: The user can, through keyboard input alone, simultaneously activate all input device event handlers explicitly associated with the content focus element. (Level A)
4.3.1 Timing Adjustable: Where time limits for user input are recognized and controllable by the user agent, an option is provided to extend the time limit. (Level A)
4.4.1 Three Flashes or Below Threshold: In its default configuration, the user agent does not display any user interface components or recognized content that flashes more than three times in any one second period, unless the flash is below the general flash and red flash thresholds. (Level A)
4.4.2 Three Flashes: In its default configuration, the user agent does not display any user interface components or recognized content that flashes more than three times in any one second period (regardless of whether not the flash is below the general flash and red flash thresholds). (Level AAA) [WCAG 2.0]
4.5.1 Change Preference Settings The user has the option to change settings that impact accessibility. (Level A)
4.5.2 Persistent Accessibility Settings: User agent accessibility preference settings persist between sessions. (Level A)
4.5.3 Multiple Sets of Preference Settings: The user can save and retrieve multiple sets of user agent preference settings. (Level AA)
4.5.4 Portable Preference Settings:The user can transfer preference settings across locations onto a compatible system. (Level AAA)
4.5.5 Preferences Wizard: A wizard helps the user to configure (at least) the accessibility-related user agent preferences. (Level AAA)
4.5.6 Restore all to default. The user can restore all preference settings to their default values. (Level A)
4.5.7 Restore related preferences to default. The user can restore groups of related preference settings to their default values (e.g. reset keyboard shortcuts, reset colors and sizes of rendered content, etc.). (Level AA)
4.5.8 Change preference setting outside the UI: The user can adjust preference settings from outside the user agent user interface. (Level AA)
4.6.1 Find:The user can perform a search within rendered content (e.g., not hidden with a style), including text alternatives, for any sequence of characters from the document character set set. (Level A)
4.6.2 Find Direction: The user has the option of searching forward or backward from the focused location in content. The user will be notified of changes in search direction; and when the search reaches the upper or lower extent of the content based on the search direction. (Level A)
4.6.3 Match Found: When there is a match, the user is alerted and the viewport moves so that the matched text content is at least partially within it. The user can search for the next instance of the text from the location of the match.
4.6.4 Alert on No Match: The user is notified when there is no match or after the last match in content (i.e., prior to starting the search over from the beginning of content). (Level A)
4.6.5 Advanced Find: The user agent provides an accessible advanced search facility, with a case sensitive and case-insensitive search option, and the ability for the user to perform a search within all content (including hidden content and captioning) for text and text alternatives, for any sequence of characters from the document character set. (Level AA)
4.7.1 Structured Navigation: Forward and backward sequential navigation over important (structural) elements in rendered content is provided. (Level A)
4.7.2 Direct navigation: direct movement to important (structural and operable) elements in rendered content is provided. (Level A).
4.7.3 Direct activation: direct movement to and activation of any operable elements in rendered content is provided. (Level AA)
4.7.4 Configure Set of Important Elements: The user has the option to configure the set of important elements for structured navigation, including by element type (e.g., headers, list items, images). (Level AAA) @@Editor's note: Review the definition of "important elements" @@
4.7.5 Discover navigation and activation keystrokes: Direct navigation and activation keystrokes are discoverable both programmatically and via perceivable labels. (Level A)
4.7.2OLD @@Editor's note: Review the definition of "important elements" @@
Note: For example, allow the user to navigate only paragraphs, or only headings and paragraphs, or to suppress and restore navigation bars, or to navigate within and among tables and table cells
4.8.1 Configure Position: For graphical user agent user interfaces with toolbars, the user can add, remove and configure the position of user agent user interface controls on those toolbars from a pre-defined set of controls. (Level AAA)
4.8.2 Restore Default Toolbars: The user can restore the default toolbar configuration. (Level AAA)
4.9.1 Background Image Toggle: The user has the global option to hide/show background images. (Level A)
4.9.2 Time-Based Media Load-Only: The user has the option to load time-based media content @@DEFINE@@ such that the first frame is displayed (if video), but the content is not played until explicit user request. (Level A)
4.9.3 Execution Placeholder: The user has the option to render a placeholder instead of executable content that would normally be contained within an on-screen area (e.g., Applet, Flash), until explicit user request to execute. (Level A)
4.9.4 Execution Toggle: The user has the option to turn on/off the execution of executable content that would not normally be contained within a particular area (e.g., Javascript). (Level A)
4.9.5 Playback Rate Adjustment for Prerecorded Content: The user can adjust the playback rate of prerecorded time-based media content, such that all of the following are true (Level A):
4.9.6 Stop/Pause/Resume Multimedia: The user can stop, pause, and resume rendered audio and animation content (including video and animated images) that last three or more seconds at their default playback rate. (Level A)
4.9.6 Navigate Multimedia:The user can navigate along the timebase using a continuous scale, and by relative time units within rendered audio and animations (including video and animated images) that last three or more seconds at their default playback rate. (Level A)
4.9.7 Semantic Navigation of Time-Based Media. The user can navigate by semantic structure within the time-based media, such as by chapters or scenes, if present in the media (AA).
4.9.8 Track Enable/Disable of Time-Based Media. During time-based media playback, the user can determine which tracks are available and select or deselect tracks. These selections may override global default settings for captions, audio descriptions, etc.
4.9.9 Sizing Playback Viewport: User has the ability to adjust the size of the time-based media up to the full height or width of the containing viewport, with the ability to preserve aspect ratio and to adjust the size of the playback viewport to avoid cropping, within the scaling limitations imposed by the media itself. (Level AA)
4.9.10 Scale and position alternative media tracks. User has ability to scale and position alternative media tracks independent of base video. (Level AAA)
4.9.1113 Adjust Playback Contrast and Brightness. User has ability to control the contrast and brightness of the content within the playback viewport.
The guideline only applies to images, animations, video, audio, etc. that the user agent can recognize.
If the browser is playing the video natively, then there is only 1 user agent. Then it falls on the browser to meet the UAAG spec.
If author uses windows media player inside the video element, the browser needs to map its native controls to the embedded wmp controls, and provide access to all the controls.
User needs to be able to define rendering parameters of playback at rendertime.
5.1.1 Option to Ignore: The user has the option to turn off rendering of non-essential or low priority text messages or updating/changing information in the content based on priority properties defined by the author (e.g., ignoring updating content marked "polite" ). (Level AA)
5.2.1 Form Submission:The user has the ability to set a global option disable any form submission made by a control that is not the submit control (e.g. forms that submit when Enter is pressed). Should login be an exception? (Level AA)
5.3.1 Accessible Format: At least one version of the documentation is either (Level A):
5.3.2 Document Accessibility Features: All user agent features that benefit accessibility @@DEFINE - as specified in the conformance claim@@ are documented. (Level A)
5.3.3 Changes Between Versions: Changes to features that affect accessibility since the previous version of the user agent are documented. (Level AA)
5.3.4 Centralized View: There is a centralized view of all features of the user agent that benefit accessibility, in a dedicated section of the documentation. (Level AA)
5.3.5 Context Sensitive Help: There is context-sensitive help on all user agent features that benefit accessibility. (Level AAA)
5.3.6 Appropriate Language If characteristics of your user agent involve producing an end user experience such as speech, you need to react appropriately to language changes.
5.4.1 Control default focus: A user agent provides a mechanism for setting global configuration of whether web pages can set default focus.
5.4.2 Unpredictable focus: Don't move the focus without telling the user. Provide a global option to block uninitiated focus changes.
Missing: Greater ease in interpreting security messaging. Should be cross-referenced with the security working group.
This section is normative.
Conformance means that the user agent satisfies the success criteria defined in the guidelines section. This conformance section describes conformance and lists the conformance requirements.
In order for a Web page to conform to UAAG 2.0, one of the following levels of conformance is met in full.
Note 1: Although conformance can only be achieved at the stated levels, developers are encouraged to report (in their claim) any progress toward meeting success criteria from all levels beyond the achieved level of conformance.
If a conformance claim is made, then the conformance claim must meet the following conditions and include the following information (user agents can conform to UAAG 2.0 without making a claim):
A description of how the UAAG 2.0 success criteria were met where this may not be obvious.
Developers of user agents that do not yet conform fully to a particular UAAG 2.0 conformance level are encouraged to publish a statement on progress towards conformance. This statement would be the same as a conformance claim except that this statement would specify an UAAG 2.0 conformance level that is being progressed towards, rather than one already satisfied, and report the progress on success criteria not yet met. The author of a "Progress Towards Conformance" Statement is solely responsible for the accuracy of their statement. Developers are encouraged to provide expected timelines for meeting outstanding success criteria within the Statement.
Neither W3C, WAI, nor UAWG take any responsibility for any aspect or result of any UAAG 2.0 conformance claim that has not been published under the authority of the W3C, WAI, or UAWG.
This glossary is normative.
Examples of assistive technologies that are important in the context of this document include the following:
Any item, piece of equipment, or product system, whether acquired commercially, modified, or customized, that is used to increase, maintain, or improve functional capabilities of individuals with disabilities.
empty
content (which may be alternative content) is
either a null value or an empty string (i.e., one that is zero
characters long). For instance, in HTML, alt=""
sets the
value of the alt
attribute to the empty string. In some
markup languages, an element may have empty content (e.g., the
HR
element in HTML).
Some examples of explicit user requests include when the user selects "New viewport," responds "yes" to a prompt in the user agent's user interface, configures the user agent to behave in a certain way, or changes the selection or focus with the keyboard or pointing device.
Note: Users can make errors when interacting with the user agent. For example, a user may inadvertently respond "yes" to a prompt instead of "no." In this document, this type of error is still considered an explicit user request.
User interface mechanisms may resemble content focus, but do not satisfy all of the properties. For example, designers of word processing software often implement a "caret" that indicates the current location of text input or editing. The caret may have state and may respond to input device events, but it does not enable users to activate the behaviors associated with enabled elements.
The user interface focus shares the properties of the content focus except that, rather than designating pieces of content, it designates zero or one control of the user agent user interface that has associated behaviors (e.g., a radio button, text box, or menu).
On the screen, the user agent may highlight the content focus in a variety of ways, including through colors, fonts, graphics, and magnification. The user agent may also highlight the content focus when rendered as synthesized speech, for example through changes in speech prosody. The dimensions of the rendered content focus may exceed those of the viewport.
In this document, each viewport is expected to have at most one content focus and at most one user interface focus. This document includes requirements for content focus only, for user interface focus only, and for both. When a requirement refers to both, the term "focus" is used.
When several viewports coexist, at most one viewport's content focus or user interface focus responds to input events; this is called the current focus.
accesskey
attribute of HTML 4 [HTML4]).lang
attribute in HTML 4 ([HTML4] section 8.1), the xml:lang
attribute in XML 1.0 ([XML], section 2.12), the hreflang
attribute for links in HTML 4 ([HTML4],
section 12.1.5), the HTTP Content-Language header ([RFC2616], section 14.12)
and the Accept-Language request header ([RFC2616], section 14.4).
See also the definition of script.H1
element, so a user agent that implements HTML
can recognize that content as a heading. If the author creates a
heading using a visual effect alone (e.g., just by increasing the font
size), then the author has encoded the heading in a manner that does
not allow the user agent to recognize it as a heading.
Some requirements of this document depend on content roles, content relationships, timing relationships, and other information supplied by the author. These requirements only apply when the author has encoded that information in a manner that the user agent can recognize. See the section on conformance for more information about applicability.
In practice, user agents will rely heavily on information that the author has encoded in a markup language or style sheet language. On the other hand, behaviors, style, meaning encoded in a script, and markup in an unfamiliar XML namespace may not be recognized by the user agent as easily or at all. The Techniques document [UAAG10-TECHS] lists some markup known to affect accessibility that user agents can recognize.
This document does not require user agents to include repair content in the document object. Repair content inserted in the document object should conform to the Web Content Accessibility Guidelines 1.0 [WCAG10]. For more information about repair techniques for Web content and software, refer to "Techniques for Authoring Tool Accessibility Guidelines 1.0" [ATAG10-TECHS].
On the screen, the selection may be highlighted in a variety of ways, including through colors, fonts, graphics, and magnification. The selection may also be highlighted when rendered as synthesized speech, for example through changes in speech prosody. The dimensions of the rendered selection may exceed those of the viewport.
The selection may be used for a variety of purposes, including for cut and paste operations, to designate a specific element in a document for the purposes of a query, and as an indication of point of regard.
The selection has state, i.e., it may be "set," programmatically or through the user interface.
In this document, each viewport is expected to have at most one selection. When several viewports coexist, at most one viewport's selection responds to input events; this is called the current selection.
Note: Some user agents may also implement a selection for designating a range of information in the user agent user interface. The current document only includes requirements for a content selection mechanism.
The expression "sequential navigation" refers to navigation through an ordered set of items (e.g., the enabled elements in a document, a sequence of lines or pages, or a sequence of menu options). Sequential navigation implies that the user cannot skip directly from one member of the set to another, in contrast to direct or structured navigation. Users with blindness or some users with a physical disability may navigate content sequentially (e.g., by navigating through links, one by one, in a graphical viewport with or without the aid of an assistive technology). Sequential navigation is important to users who cannot scan rendered content visually for context and also benefits users unfamiliar with content. The increments of sequential navigation may be determined by a number of factors, including element type (e.g., links only), content structure (e.g., navigation from heading to heading), and the current navigation context (e.g., having navigated to a table, allow navigation among the table cells).
Users with serial access to content or who navigate sequentially may require more time to access content than users who use direct or structured navigation.
A text element may consist of both text and non-text data. For instance, a text element may contain markup for style (e.g., font size or color), structure (e.g., heading levels), and other semantics. The essential function of the text element should be retained even if style information happens to be lost in rendering.
A user agent may have to process a text element in order to have access to the text characters. For instance, a text element may consist of markup, it may be encrypted or compressed, or it may include embedded text in a binary format (e.g., JPEG).
"Text content" is content that is composed of one or more text elements. A "text equivalent" (whether in content or the user interface) is an equivalent composed of one or more text elements. Authors generally provide text equivalents for content by using the alternative content mechanisms of a specification.
A "non-text element" is an element (in content or the user interface) that does not have the qualities of a text element. "Non-text content" is composed of one or more non-text elements. A "non-text equivalent" (whether in content or the user interface) is an equivalent composed of one or more non-text elements.
The term "user interface control" refers to a component of the user agent user interface or the content user interface, distinguished where necessary.
Graphical and tactile viewports have two spatial dimensions. A viewport may also have temporal dimensions, for instance when audio, speech, animations, and movies are rendered. When the dimensions (spatial or temporal) of rendered content exceed the dimensions of the viewport, the user agent provides mechanisms such as scroll bars and advance and rewind controls so that the user can access the rendered content "outside" the viewport. Examples include: when the user can only view a portion of a large document through a small graphical viewport, or when audio content has already been played.
When several viewports coexist, only one has the current focus at a given moment. This viewport is highlighted to make it stand out.
User agents may render the same content in a variety of ways; each
rendering is called a view. For instance, a user agent may
allow users to view an entire document or just a list of the document's
headers. These are two different views of the document.
"top-level" viewports are
viewports that are not contained within other user agent viewports.
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This section is informative.
For the latest version of any W3C specification please consult the list of W3C Technical Reports at http://www.w3.org/TR/. Some documents listed below may have been superseded since the publication of this document.
Note: In this document, bracketed labels such as "[WCAG20]" link to the corresponding entries in this section. These labels are also identified as references through markup.
This document would not have been possible without the work of those who contributed to UAAG 1.0.
This publication has been funded in part with Federal funds from the U.S. Department of Education, National Institute on Disability and Rehabilitation Research (NIDRR) under contract number ED05CO0039. The content of this publication does not necessarily reflect the views or policies of the U.S. Department of Education, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.
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