[contents] [implementing]

User Agent Accessibility Guidelines (UAAG) 2.0

W3C Editors' Draft 10 April 2014

This version:

http://www.w3.org/WAI/UA/2014/ED-UAAG20-20140410/

Latest version:

http://www.w3.org/TR/UAAG20/

Previous version:

http://www.w3.org/WAI/UA/2014/ED-UAAG20-20140403/

Latest Editor's Draft:

http://www.w3.org/WAI/UA/UAAG20/

Editors:

James Allan, Texas School for the Blind and Visually Impaired

Kelly Ford, Microsoft

Kim Patch, Redstart Systems

Jeanne Spellman, W3C/Web Accessibility Initiative

Copyright © 2014 W3C^® (MIT, ERCIM, Keio, Beihang), All Rights Reserved. W3C liability, trademark and document use rules apply.

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Introduction

UAAG 2.0 Guidelines

UAAG 2.0 Conformance Applicability Notes:

1. Recognized Content Only: UAAG 2.0 success criteria only apply to web content and its behaviors that can be recognized by user agents.
2. Optional Settings: Throughout UAAG 2.0, all required behaviors may be provided as optional preference settings unless a success criterion explicitly says otherwise. For example, if a success criteria requires high contrast between foreground text and its background, the user agent may also provide choices with low contrast. A required behavior does not need to be the default option unless the success criteria explicitly says otherwise.
3. RFC 2119 language not used: UAAG 2.0 does not use RFC 2119 language (must, may, should) because these are guidelines and not interoperable specifications. These words in UAAG 2.0 don't have the same sense as they do in RFC 2119.
4. Simultaneous satisfaction of success criteria: Users can access all behaviors required by UAAG 2.0 at the same time (e.g. when the user resizes the viewport per 1.8.9, content is reflowed per 1.8.6), except where those behaviors are mutually exclusive.
5. Vertical layout languages: When user agents render vertical layout languages (e.g. Mongolian, Han), success criteria normally relating to horizontal rendering should be applied to vertical rendering instead.
6. Extensions: Success criteria can be met by a user agent alone or in conjunction with extensions and add-ons, as long as those are available to users. See Components of UAAG 2.0 Conformance Claims.
7. Relationship with operating system or platform: The user agent does not need to implement every behavior itself. A required behavior may be provided by the platform, user agent, user agent extensions, or potentially other layers. All are acceptable, as long as they are enumerated in the conformance claim.

Conformance

This section is normative.

Conformance means that the user agent satisfies the success criteria defined in the guidelines section. This section lists requirements for conformance and conformance claims.

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.

• Level A: For level A conformance (the minimum level of conformance), the user agent satisfies all the Level A success criteria.
• Level AA: For level AA conformance, the user agent satisfies all level A and level AA Success Criteria.
• Level AAA: For level AAA conformance, the user agent satisfies all level A, level AA and level AAA Success Criteria.

Note: 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.

Conformance Claims

User agents can conform to UAAG 2.0 without making a claim. If a conformance claim is made, the conformance claim must meet the following conditions and include the following information:

Conditions on Conformance Claims

If a conformance claim is made, the conformance claim must meet the following conditions:

• At least one version of the conformance claim must be published on the web as a document meeting level "A" of WCAG 2.0. A suggested metadata description for this document is "UAAG 2.0 Conformance Claim".
• Whenever the claimed conformance level is published (e.g. product information website), the URI for the on-line published version of the conformance claim must be included.
• The existence of a conformance claim does not imply that the W3C has reviewed the claim or assured its validity.
• There are no restrictions on who can make a claim.
• Claimants are solely responsible for the accuracy of their claims.
• Claimants are encouraged to claim conformance to the most recent version of the User Agent Accessibility Guidelines Recommendation.

Components of UAAG 2.0 Conformance Claims

1. Claimant name and affiliation
2. Claimant contact information
3. Date of the claim
4. Conformance level satisfied
5. User agent information:
   1. Name and manufacturer
   2. Version number or version range
   3. Required patches or updates, human language of the user interface and documentation
   4. Configuration changes to the user agent that are needed to meet the success criteria (e.g. ignore author foreground/background color, turn on Carat Browsing)
   5. Plugins or extensions (including version numbers) needed to meet the success criteria (e.g. mouseless browsing)
6. Platform: Provide relevant information about the software and/or hardware platform(s) that the user agent relies on for conformance. This information may include:
   1. Name and manufacturer
   2. Version of key software components (e.g. operating system, other software environment)
   3. Hardware requirements (e.g. audio output enabled, minimum screen size: 2", bluetooth keyboard attached)
   4. Operating system(s) (e.g. Windows, Android, iOS, GNOME)
   5. Other software environment (Java, Eclipse)
   6. Host web browser when the conforming user agent is web-based (e.g. JW Player on Firefox)
   7. Configuration changes to the platform that are needed to meet the success criteria (e.g. turn on Sticky Keys, use High Contrast Mode)
7. Platform Limitations: If the platform (hardware or operating system) does not support a capability necessary for a given UAAG 2.0 success criterion, list the success criterion and the feature (e.g. a mobile operating system does not support platform accessibility services, therefore the user agent cannot meet success criterion 4.1.2). For these listed technologies, the user agent can claim that the success criteria do not apply.
8. Web Content Technologies: List the web content technologies rendered by the user agent that are included in the claim. If there are any web content technologies rendered by the user agent that are excluded from the conformance claim, list these separately. Examples of web content technologies include web markup languages such HTML, XML, CSS, SVG, and MathML, image formats such as PNG, JPG and GIF, scripting languages such as JavaScript/EcmaScript, specific video codecs, and proprietary document formats.
9. Declarations: For each success criterion, provide a declaration of either
   1. whether or not the success criterion has been satisfied; or
   2. declaration that the success criterion is not applicable and a rationale for why not

Limited Conformance for Extensions

This option may be used for a user agent extension or plug-in with limited functionality that wishes to claim UAAG 2.0 conformance. An extension or plugin can claim conformance for a specific success criterion or a narrow range of success criteria as stated in the claim. All other success criteria may be denoted as Not Applicable. The add-in must not cause the combined user agent (hosting user agent plus installed extension or plug-in) to fail any success criteria that the hosting user agent would otherwise pass.

Optional Components of an UAAG 2.0 Conformance Claim

A description of how the UAAG 2.0 success criteria were met where this may not be obvious.

Disclaimer

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.

Appendix A: Glossary

This glossary is normative.

activate

To carry out the behaviors associated with an enabled element in the rendered content or a component of the user agent user interface.

alternative content

Web content that user agents can programmatically determine is usable in place of other content that some people are not able to access. Alternative content fulfills essentially the same function or purpose as the original content. There are several general types of alternative content:

• text alternative for non-text content: Text that is programmatically associated with non-text content or referred to from text that is programmatically associated with non-text content. For example, an image of a chart might have two text alternatives: a short text alternative and a described-by relationship to a nearby paragraph that more fully describes the content of the chart.
• alternative for time-based media: Web content that serves the same function or purpose as one or more tracks in a time-based media presentation. This includes alternatives for audio such as captions and sign language interpretation, and alternatives for video such as audio descriptions and extended audio descriptions. Another form of time-based media alternative is a correctly sequenced text description of time-based visual and auditory information that also is capable of achieving the outcomes of any interactivity in the time-based presentation.
• text alternatives for text content: Text that is programmatically associated with certain types of text content to provide expanded information. For example, an abbreviation (or acronym) may provide an expansion of the shortened word or initialized words (<abbr title="User Agent Accessibility Guidelines">UAAG</abbr>).
• media alternative for text: Media that presents no more information than is already presented in text (directly or via text alternatives). A media alternative for text is provided for people who benefit from alternate representations of text. Media alternatives for text may be audio-only, video-only (including sign-language video), or audio-video.
  

Note: According to WCAG 2.0, alternative content may or may not be programmatically determinable (e.g., a short description for an image might appear in the image's description attribute or within text near the image). However, UAAG 2.0 adds the programmatically available condition because this is the only type of alternative content that user agents can recognize.

animation

Graphical content rendered to automatically change over time, giving the user a visual perception of movement. Examples include video, animated images, scrolling text, programmatic animation (e.g. moving or replacing rendered objects).

application programming interface (API)

A mechanism that defines how communication may take place between applications.

assistive technology

For the purpose of UAAG 2.0 conformance, assistive technology meets the following criteria:

1. Relies on services (such as retrieving web resources and parsing markup) provided by one or more host user agents.
2. Communicates data and messages with host user agents by monitoring and using APIs.
3. Provides services beyond those offered by the host user agents to meet the requirements of users with disabilities. Additional services include alternative renderings (e.g. as synthesized speech or magnified content), alternative input methods (e.g. voice), additional navigation or orientation mechanisms, and content transformations (e.g. to make tables more accessible).

Examples of assistive technologies that are important in the context of UAAG 2.0 include the following:

• Screen magnifiers, which are used by people with visual disabilities to enlarge and change colors on the screen to improve the visual readability of rendered text and images.
• Screen readers, which are used by people who are blind or have reading disabilities to read textual information through synthesized speech or braille displays.
• Voice recognition software, which is used by some people who have physical disabilities to simulate the keyboard and mouse.
• Alternative keyboards, which are used by some people with physical disabilities to simulate the keyboard and mouse.
• Alternative pointing devices, which are used by some people with physical disabilities to simulate mouse pointing and button activations.

audio

The technology of sound transmission. Audio can be created synthetically (including speech synthesis), streamed from a live source (e.g. a radio broadcast), or recorded from real world sounds. There may be multiple audio tracks in a presentation.

audio description

A type of alternative content that takes the form of narration added to the audio to describe important visual details that cannot be understood from the main soundtrack alone. Audio description of video provides information about actions, characters, scene changes, on-screen text, and other visual content. In standard audio description, narration is added during existing pauses in dialogue.

• extended audio description: An audio description in which the video is sometimes paused so that there is time to add additional description.

audio track

All or part of the audio portion of a presentation (e.g. each instrument may have a track, or each stereo channel may have a track).

author

A person who works alone or collaboratively to create content (e.g. content author, designer, programmer, publisher, tester).

available printing devices

Printing devices that are identified as available to applications via the platform.

captions

A type of alternative content that takes the form of text presented and synchronized with time-based media to provide not only the speech, but also non-speech information conveyed through sound, including meaningful sound effects and identification of speakers. In some countries, the term "subtitle" is used to refer to dialogue only and "captions" is used as the term for dialogue plus sounds and speaker identification. In other countries, "subtitle" (or its translation) is used to refer to both.

• open captions: Captions that are always rendered with a visual track; they cannot be turned off.
• closed captions: Captions that may be turned on and off. The captions requirements of UAAG 2.0 assume that the user agent can recognize the captions as such.

Note: Other terms that include the word "caption" may have different meanings. For instance, a "table caption" is a title for a table, often positioned graphically above or below the table.

commands

Actions made by users to control the user agent. These include:

• direct commands: Commands that apply to a specified item (e.g. button) or action (e.g. save function), regardless of the current focus location:
  • direct navigation commands: Commands that move focus to a specified item.
  • direct activation commands: Commands that activate the specified item (and may also move focus to it) or action.
• sequential navigation commands (sometimes called "logical navigation commands" or "linear navigation commands"): Commands that move focus forwards and backwards through a list of items. The element list being navigated may be the list of all elements or just a subset (e.g. the list of headers, the list of links).
• spatial commands (sometimes called "directional commands"): Commands that require the user to be aware of the spatial arrangement of items on the screen:
  • spatial navigation commands: Commands that move from one item to another based on direction on the screen.
  • spatial manipulation commands: Commands that resize or reposition an item on the screen.
• structural navigation commands: Commands that move forwards, backwards, up and down a hierarchy.

content (web content)

Information and sensory experience to be communicated to the user by means of a user agent, including code or markup that defines the content's structure, presentation, and interactions.

continuous scale

When interacting with a time-based media presentation, a continuous scale allows user (or programmatic) action to set the active playback position to any time point on the presentation timeline. The granularity of the positioning is determined by the smallest resolvable time unit in the media timebase.

default

see properties

disabled element

see element

document character set

The internal representation of data in the source content by a user agent.

document object, Document Object Model (DOM)

A platform- and language-neutral interface that allows programs and scripts to dynamically access and update the content, structure and style of documents. The document can be further processed and the results of that processing can be incorporated back into the presented page. Overview of DOM-related materials: http://www.w3.org/DOM/#what.

documentation

Any information that supports the use of a user agent. This information may be provided electronically or otherwise and includes help, manuals, installation instructions, tutorials, etc. Documentation may be accessed in various ways (e.g. as files included in the installation, available on the web).
Note: The level of technical detail in documentation for users should match the technical level of the feature. For example, user documentation for a browser's zoom function should not refer users to the source code repository for that browser.

element, element type

Primarily, a syntactic construct of a document type definition (DTD) for its application. This is the sense employed by the XML 1.0 specification ([XML], section 3). This sense is also relevant to structures defined by XML schemas. UAAG 2.0 also uses the term "element" more generally to mean a type of content (such as video or sound) or a logical construct (such as a header or list).

• enabled element: An element with associated behaviors that can be activated through the user interface or through an API. The set of elements that a user agent enables is generally derived from, but is not limited to, the set of elements defined by implemented markup languages.
• disabled element: A potentially enabled element that is not currently available for activation (e.g. a "grayed out" menu item).

events and scripting, event handler, event type

User agents often perform a task when an event having a particular "event type" occurs, including a user interface event, a change to content, loading of content, or a request from the operating environment. Some markup languages allow authors to specify that a script, called an event handler, be executed when an event of a given type occurs. An event handler is explicitly associated with an element through scripting, markup or the DOM.

enabled element

see element

explicit user request

An interaction by the user through the user agent user interface, the focus, or the selection. User requests are made, for example, through user agent user interface controls and keyboard commands. 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." This type of error is still considered an explicit user request.

extended audio description

see audio description

focus, input focus

The location where input will occur if a viewport is active. Examples include:

• keyboard focus: The screen location where keyboard input will occur if a viewport is active.
• pointing device focus: The screen location where pointer input will occur if a viewport is active. There can be multiple pointing device foci for example when using a screen sharing utility there is typically one for the user's physical mouse and one for the remote mouse.

The active input focus is in the active viewport. The inactive input focus is in the inactive viewport. Focus is typically indicated by a focus cursor.

focus cursor

Visual indicator that highlights a user interface element to show that it has input focus (e.g. the dotted line around a button, outline around a pane, or brightened title bar on a window).

• keyboard focus cursor: Indicator showing the enabled element with current input focus where focus has been moved by the keyboard (e.g. the dotted line around a button).
• text cursor: Indicator showing where keyboard input will occur in text (e.g. the flashing vertical bar in a text field, also called a caret).
• pointer: Indicator showing where pointing device input will occur. The indicator can be moved with a pointing device or emulator such as a mouse, pen tablet, keyboard-based mouse emulator, speech-based mouse commands, or 3-D wand. A pointing device click typically moves the input focus to the pointer location. The indicator may change to reflect different states. When touchscreens are used, the "pointing device" is a combination of the touchscreen and the user's finger or stylus. On most touchscreen systems there is no pointer (on-screen visual indication).

Cursors are active when in the active viewport, and inactive when in an inactive viewport.

focusable element

Any element capable of having input focus (e.g. a link, text box, or menu item). In order to be accessible and fully usable, every focusable element should take keyboard focus, and ideally would also take pointer focus.

globally, global configuration

A setting is one that applies to the entire user agent or all content being rendered by it, rather than to a specific feature within the user agent or a specific document being viewed.

graphical

Information (e.g. text, colors, graphics, images, or animations) rendered for visual consumption.

highlight, highlighted, highlighting

Emphasis indicated through the user interface. For example, user agents highlight content that is selected, focused, or matched by a search operation. Graphical highlight mechanisms include dotted boxes, changed colors or fonts, underlining, adjacent icons, magnification, and reverse video. Synthesized speech highlight mechanisms include alterations of voice pitch and volume ( i.e. speech prosody). User interface items may also be highlighted, for example a specific set of foreground and background colors for the title bar of the active window. Content that is highlighted may or may not be a selection.

image

Pictorial content that is static (i.e. not moving or changing). Also see animation.

informative (non-normative)

see normative

keyboard

The letter, symbol and command keys or key indicators that allow a user to control a computing device. Assistive technologies have traditionally relied on the keyboard interface as a universal, or modality independent interface. In this document references to keyboard include keyboard emulators and keyboard interfaces that make use of the keyboard's role as a modality independent interface (see Modality Independent Controls). Keyboard emulators and interfaces may be used on devices which do not have a physical keyboard, such as mobile devices based on touchscreen input.

keyboard interface

Keyboard interfaces are programmatic services provided by many platforms that allow operation in a device independent manner. A keyboard interface can allow keystroke input even if particular devices do not contain a hardware keyboard (e.g. a touchscreen-controlled device can have a keyboard interface built into its operating system to support onscreen keyboards as well as external keyboards that may be connected).
Note: Keyboard-operated mouse emulators, such as MouseKeys, do not qualify as operation through a keyboard interface because these emulators use pointing device interfaces, not keyboard interfaces.

keyboard command (keyboard binding, keyboard shortcuts, accesskey, access key, accelerator keys, direct keyboard command)

A key or set of keys that are tied to a particular UI control or application function, allowing the user to navigate to or activate the control or function without traversing any intervening controls (e.g. CTRL+"S" to save a document). It is sometimes useful to distinguish keyboard commands that are associated with controls that are rendered in the current context (e.g. ALT+"D" to move focus to the address bar) from those that may be able to activate program functionality that is not associated with any currently rendered controls (e.g. "F1" to open the Help system). Keyboard commands can be triggered using a physical keyboard or keyboard emulator (e.g. on-screen keyboard or speech recognition). (See Modality Independent Controls). Sequential keyboard commands require multiple keystrokes to carry out an action (e.g. a series of Tab or arrow presses followed by Enter, or a sequence like ALT-F, V to drop down a File menu and choose Print Preview).

non-text content (non-text element, non-text equivalent)

see text

normative, informative (non-normative)

Required (or not required) for conformance. Abilities identified as "normative" are required for conformance (noting that one may conform in a variety of well-defined ways to UAAG 2.0). Abilities identified as "informative" (or, "non-normative") are never required for conformance.

notify

To make the user aware of events or status changes. Notifications can occur within the user agent user interface (e.g. a status bar) or within the content display. Notifications may be passive and not require user acknowledgment, or they may be presented in the form of a prompt requesting a user response (e.g. a confirmation dialog).

obscure

To render a visual element in the same screen space as a second visual element in a way that prevents the second visual element from being visually perceived.
Note: The use of transparent backgrounds for the overlaying visual element (e.g., video captions) is an acceptable technique for reducing obscuration, if space is available.

operating environment

The software environment that governs the user agent's operation, whether it is an operating system or a programming language environment such as Java.

operating system (OS)

Software that supports a device's basic functions, such as scheduling tasks, executing applications, and managing hardware and peripherals.
Note: Many operating systems mediate communication between executing applications and assistive technology via a platform accessibility service.

override

When one configuration or behavior preference prevails over another. Generally, the requirements of UAAG 2.0 involve user preferences prevailing over author preferences and user agent default settings and behaviors. Preferences may be multi-valued in general (e.g. the user prefers blue over red or yellow), and include the special case of two values (e.g. turn on or off blinking text content).

placeholder

Content generated by the user agent to replace author-supplied content. A placeholder may be generated as the result of a user preference (e.g. to not render images) or as repair content (e.g. when an image cannot be found). A placeholder can be any type of content, including text, images, and audio cues. A placeholder should identify the technology of the replaced object.

platform

The software and hardware environment(s) within which the user agent operates. Platforms provide a consistent operational environment. There may be layers of software in an hardware architecture and each layer may be considered a platform. Non-web-based platforms include desktop operating system (e.g. Linux, Mac OS, Windows, etc.), mobile operating systems (e.g. Android, Blackberry, iOS, Windows Phone, etc.), and cross-OS environments (e.g. Java). Web-based platforms are other user agents. User agents may employ server-based processing, such as web content transformations, text-to-speech production, etc.
Note 1: A user agent may include functionality hosted on multiple platforms (e.g. a browser running on the desktop may include server-based pre-processing and web-based documentation).
Note 2: Accessibility guidelines for developers exist for many platforms.

platform accessibility service

A programmatic interface that is engineered to enhance communication between mainstream software applications and assistive technologies (e.g. MSAA, UI Automation, and IAccessible2 for Windows applications, AXAPI for Mac OSX applications, Gnome Accessibility Toolkit API for GNOME applications, Java Access for Java applications). On some platforms it may be conventional to enhance communication further by implementing a DOM.

plug-in

see user agent

point of regard

The position in rendered content that the user is presumed to be viewing. The dimensions of the point of regard may vary. For example,it may be a two-dimensional area (e.g. content rendered through a two-dimensional graphical viewport), or a point (e.g. a moment during an audio rendering or a cursor position in a graphical rendering), or a range of text (e.g. focused text), or a two-dimensional area (e.g. content rendered through a two-dimensional graphical viewport). The point of regard is almost always within the viewport, but it may exceed the spatial or temporal dimensions of the viewport (see the definition of rendered content for more information about viewport dimensions). The point of regard may also refer to a particular moment in time for content that changes over time (e.g. an audio-only presentation). User agents may determine the point of regard in a number of ways, including based on viewport position in content, keyboard focus, and selection.

pointer

see focus cursor

profile

A named and persistent representation of user preferences that may be used to configure a user agent. Preferences include input configurations, style preferences, and natural language preferences. In operating environments with distinct user accounts, profiles enable users to reconfigure software quickly when they log on. Users may share their profiles with one another. Platform-independent profiles are useful for those who use the same user agent on different devices.

programmatically available

Information that is encoded in a way that allows different software, including assistive technologies, to extract and use the information relying on published, supported mechanisms, such as, platform accessibility services, APIs, or the document object models (DOM). For web-based user interfaces, this means ensuring that the user agent can pass on the information (e.g. through the use of WAI-ARIA). Something is programmatically available if the entity presenting the information does so in a way that is explicit and unambiguous, in a way that can be understood without reverse-engineering or complex (and thus potentially fallible) heuristics, and only relying on methods that are published, and officially supported by the developers of the software being evaluated.

prompt

Any user agent-initiated request for a decision or piece of information from a user.

properties, values, and defaults

A user agent renders a document by applying formatting algorithms and style information to the document's elements. Formatting depends on a number of factors, including where the document is rendered (e.g. on screen, on paper, through loudspeakers, on a braille display, on a mobile device). Style information (e.g. fonts, colors, synthesized speech prosody) may come from the elements themselves (e.g. certain font and phrase elements in HTML), from stylesheets, or from user agent settings. For the purposes of these guidelines, each formatting or style option is governed by a property and each property may take one value from a set of legal values. Generally in UAAG 2.0, the term "property" has the meaning defined in CSS 2.1 Conformance ([CSS21], ). A reference to "styles" in UAAG 2.0 means a set of style-related properties.

• default value: The value given to a property by a user agent at installation.

recognize

Authors encode information in many ways, including in markup languages, style sheet languages, scripting languages, and protocols. When the information is encoded in a manner that allows the user agent to process it with certainty, the user agent can "recognize" the information. For instance, HTML allows authors to specify a heading with the 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 UAAG 2.0 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. User agents will rely heavily on information that the author has encoded in a markup language or style sheet language. 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.

reflowable content

Web content that can be arbitrarily wrapped over multiple lines. The primary exceptions to reflowable content are graphics and video.

relative time units

Time intervals for navigating media relative to the current point (e.g. move forward 30 seconds). When interacting with a time-based media presentation, a user may find it beneficial to move forward or backward via a time interval relative to their current position. For example, a user may find a concept unclear in a video lecture and elect to skip back 30 seconds from the current position to review what had been described. Relative time units may be preset by the user agent, configurable by the user, and/or automatically calculated based upon media duration (e.g. jump 5 seconds in a 30-second clip, or 5 minutes in a 60-minute clip). Relative time units are distinct from absolute time values such as the 2 minute mark, the half-way point, or the end.

rendered content

The presentation generated by the user agent based on the author supplied code. This includes text characters, images, stylesheets, scripts, and any other content that, once processed, may be perceived.

• rendered text: Text content that is rendered in a way that communicates information about the characters themselves, whether visually or as synthesized speech.

repair content, repair text

Content generated by the user agent to correct an error condition. "Repair text" refers to the text portion of repair content. Error conditions that may lead to the generation of repair content include:

• Erroneous or incomplete content (e.g. ill-formed markup, invalid markup, or missing alternative content that is required by format specification);
• Missing resources for handling or rendering content (e.g. the user agent lacks a font family to display some characters, or the user agent does not implement a particular scripting language).

Note: UAAG 2.0 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 2.0 [WCAG20]. For more information about repair techniques for web content and software, refer to "Techniques for Authoring Tool Accessibility Guidelines 1.0" [ATAG10-TECHS].

script

Instructions to create dynamic web content that are written in a programming (scripting) language. In guidelines referring to the written (natural) language of content, as referenced in Unicode [UNICODE]), script can also refer to "a collection of symbols used to represent textual information in one or more writing systems". Information encoded in (programming) scripts may be difficult for a user agent to recognize. For instance, a user agent is not expected to recognize that, when executed, a script will calculate a factorial. The user agent will be able to recognize some information in a script by virtue of implementing the scripting language or a known program library (e.g. the user agent is expected to recognize when a script will open a viewport or retrieve a resource from the web).

selection

A user agent mechanism for identifying a (possibly empty) range of content that will be the implicit source or target for subsequent operations. 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 (e.g. the matched results of a search may be automatically selected). The selection should be highlighted in a distinctive manner. On the screen, the selection may be highlighted in a variety of ways, including through colors, fonts, graphics, and magnification. When rendered using synthesized speech, the selection may be highlighted through changes in pitch, speed, or prosody.

source text

Text that the user agent renders upon user request to view the source of specific viewport content (e.g. selected content, frame, page).

style properties

Properties whose values determine the presentation (e.g. font, color, size, location, padding, volume, synthesized speech prosody) of content elements as they are rendered (e.g. onscreen, via loudspeaker, via braille display) by user agents. Style properties can have several origins:

• user agent default styles: The default style property values applied in the absence of any author or user styles. Some web content technologies specify a default rendering; others do not.
• author styles: Style property values that are set by the author as part of the content (e.g. in-line styles, author style sheets).
• user styles: Style property values that are set by the user (e.g. via user agent interface settings, user style sheets).

style sheet

A mechanism for communicating style property settings for web content, in which the style property settings are separable from other content resources. This separation allows author style sheets to be toggled or substituted, and user style sheets defined to apply to more than one resource. Style sheet web content technologies include Cascading Style Sheets (CSS) and Extensible Stylesheet Language (XSL).

• user style sheet: Stylesheets specified by the user, resulting in user styles.
• author style sheet: Style sheets specified by the author, resulting in author styles.

synchronize

The act of time-coordinating two or more presentation components (e.g. a visual track with captions, several tracks in a multimedia presentation). For authors, the requirement to synchronize means to provide the data that will permit sensible time-coordinated rendering by a user agent. For example, web content developers can ensure that the segments of caption text are neither too long nor too short, and that they map to segments of the visual track that are appropriate in length. For user agent developers, the requirement to synchronize means to present the content in a sensible time-coordinated fashion under a wide range of circumstances including technology constraints (e.g. small text-only displays), user limitations (e.g. slow reading speeds, large font sizes, high need for review or repeat functions), and content that is sub-optimal in terms of accessibility.

technology (web content technology)

A mechanism for encoding instructions to be rendered, played or executed by user agents. Web content technologies may include markup languages, data formats, or programming languages that authors may use alone or in combination to create end-user experiences that range from static web pages to multimedia presentations to dynamic web applications. Some common examples of web content technologies include HTML, CSS, SVG, PNG, PDF, Flash, and JavaScript.

text

A sequence of characters that are programmatically available, where the sequence is expressing something in human language.

• non-text content: Any content that is not a sequence of characters that can be programmatically determined or where the sequence is not expressing something in human language Note: This includes ASCII Art (which is a pattern of characters), emoticons, leetspeak (which uses character substitution), and images representing text.
• blocks of text: More than one sentence of text [ based on WCAG definition: blocks of text]

text transcript

A type of alternative content that takes the form of text equivalents of audio information (e.g. an audio-only presentation or the audio track of a movie or other animation). A text transcript provides text for both spoken words and non-spoken sounds such as sound effects. Text transcripts make audio information accessible to people who have hearing disabilities and to people who cannot play the audio. Text transcripts are usually created by hand but may be generated on the fly (e.g. by voice-to-text converters).

top-level viewport

see viewport

user agent

Any software that retrieves, renders and facilitates end user interaction with web content. UAAG 2.0 identifies four user agent architectures:

• platform-based user agent, non-web-based user agent: User agents that run on non-web platforms (operating systems and cross-OS platforms, such as Java) and perform content retrieval, rendering and end-user interaction facilitation themselves (e.g. Firefox, Internet Explorer, Chrome, Opera, Windows Media Player, QuickTime Pro, RealPlayer).
• embedded user agent, plug-in: User agents that "plug-in" to other user agents or applications (e.g. media player plug-in for a web browser, web view component). Embedded user agents may establish direct connections with the platform (e.g. communication via platform accessibility services).
• web-based user agent: User agents that have user interfaces that are implemented using web content technologies and are accessed by users via a user agent. web-based user agents transform content into web content technologies that the host user agent can render (e.g. Google Docs, Bing Translator, Yahoo Mail).

Note: Many web applications retrieve, render and facilitate interaction with very limited data sets (e.g. online ticket booking). In such cases, WCAG 2.0, without UAAG 2.0, may be appropriate for assessing the application's accessibility.
Examples of software that are generally considered user agents under UAAG 2.0:

• Desktop web browsers (e.g. Internet Explorer, Firefox, Chrome, Safari, Opera)
• Mobile web browsers (e.g. Firefox, Chrome, Safari, Android Browser, Opera Mini, Atomic Web, Puffin)
• Browser plug-ins (e.g. QuickTime Plug-in for Firefox, Acrobat Reader Plug-in for Internet Explorer, Shockwave Plug-in for Chrome)
• Web view components (e.g. Webkit Webview component, Web Tools Platform Plug-in for Eclipse, UIWebView for iOS)
• Authoring tools that render the web content being edited (e.g. Word, Dreamweaver, HTML-Kit)

Examples of software that are not considered user agents under UAAG 2.0 (in all cases, WCAG 2.0 still applies if the software is web-based):

• Operating environments or software bundles that include platform-based user agents (e.g. Windows, OS X, KDE, iOS), though the included user agents themselves are covered by UAAG 2.0.
• General-purpose platforms or toolkits that don't use web technologies, even though they may be used by user agents for other purposes (e.g. GNOME, KDE, .NET Framework/CLR).
• Narrow-purpose platform-based or web applications (e.g. online ticket booking applications).
• Authoring tools that only display a source view of the web content being edited (e.g. Notepad, Vim).

user agent extension (add-in)

Software installed into a user agent that adds one or more additional features that modify the behavior of the user agent. Two common capabilities for user agent extensions are the ability to:

• modify the content before the user agent renders it (e.g. to add highlights if certain types of alternative content are present), and
• modify the user agent's own user interface (e.g. add a headings view).

user interface

For the purposes of UAAG 2.0, the user interface includes both:

• user agent user interface: The controls (e.g. menus, buttons, prompts, native audio/video player controls, and other components for input and output) and mechanisms (e.g. selection and focus) provided by the user agent that are not created on the basis of the author-supplied content. The user agent user interface may include extensions that become part of the user agent user interface (e.g. toolbars, additional menus).
• content user interface: The user interface that emerges from the user agent rendering of the author-supplied content. It includes all rendered content (e.g. text, headings, enabled elements, disabled elements, author-supplied audio/video controls).
  Note: There may be a mix of recognized and unrecognized user interface controls depending on the author-supplied content.

This document distinguishes user agent user interface and content user interface only where required for clarity.

user interface control

A component of the user agent user interface or the content user interface, distinguished where necessary.

video

The technology of moving pictures or images. Video can be made up of animated or photographic images, or both.

view

A user interface function that lets users interact with web content. UAAG 2.0 recognizes a variety of approaches to presenting the content in a view, including:

• rendered view: A view where content is presented such that it is rendered, played or executed. There are two sub-types:
  • In conventionally rendered views the content is rendered, played or executed according to the web content technology specification. This is the default view of most user agents.
  • In unconventionally rendered views the content is rendered quite differently than specified in the technology specification (e.g. rendering an audio file as a graphical wavefront).
• source view: A view where the web content is presented without being rendered, played or executed. The source view may be plain text (i.e. "View Source") or it may include some other organization (e.g. presenting the markup in a tree).
• outline view: A view where only a subset of the rendered content is presented, usually composed of labels or placeholders for important structural elements. The important structural elements will depend on the web content technology, but may include headings, table captions, and content sections.

Note: A view can be visual, audio, or tactile.

viewport

A mechanism for presenting only part of a visual or tactile view to the user via a screen or tactile display. There may be multiple viewports on to the same underlying view (e.g. when a split-screen is used to present the top and bottom of a document simultaneously) and viewports may be nested (e.g. a scrolling frame located within a larger document). When the viewport is smaller than the view it is presenting, some of the view will not be presented. Mechanisms are typically provided to move the view or the viewport such that all of the view can be brought into the viewport (e.g. scrollbars).

Note: In UAAG 1.0 viewports were defined as having a temporal dimension. In UAAG 2.0, this is not the case. Since audio content is inherently time-based, audio viewports are excluded.

• top-level viewport: A viewport that is not contained within another viewport of a platform-based user agent. Web-based user agents are always displayed inside another viewport, and therefore are never top-level viewports. A popular browser implementation is to provide a window that includes some user agent user interface elements (e.g., menus) and a series of tabbed panels, each of which contains additional user agent user interface elements (e.g., address bar, bookmarks, back/forward buttons) and a top-level viewport for rendering a view of the addressed web resource.

viewport dimensions

The onscreen size of a viewport, or the temporal duration of a viewport displaying time-based media. 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 (e.g. 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).

visual-only

Content consisting exclusively of one or more visual tracks presented concurrently or in series (e.g. a silent movie is an example of a visual-only presentation).

visual track

Content rendered through a graphical viewport. Visual objects include graphics, text, and visual portions of movies and other animations. A visual track is a visual object that is intended as a whole or partial presentation. A visual track does not necessarily correspond to a single physical object or software object.

voice browser

A device (hardware and software) that interprets voice markup languages to generate voice output, interpret voice input, and possibly accept and produce other modalities of input and output. Definition from "Introduction and Overview of W3C Speech Interface Framework" [VOICEBROWSER].

web resource

Anything that can be identified by a Uniform Resource Identifier (URI).

Appendix C: References

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 UAAG 2.0.

Note: In UAAG 2.0, bracketed labels such as "[WCAG20]" link to the corresponding entries in this section. These labels are also identified as references through markup.

[ATAG10]

"Authoring Tool Accessibility Guidelines 1.0," J. Treviranus, C. McCathieNevile, I. Jacobs, and J. Richards, eds., 3 February 2000. This W3C Recommendation is http://www.w3.org/TR/2000/REC-ATAG10-20000203/.

[ATAG10-TECHS]

"Techniques for Authoring Tool Accessibility Guidelines 1.0," J. Treviranus, C. McCathieNevile, J. Richards, eds., 29 Oct 2002. This W3C Note is http://www.w3.org/TR/2002/NOTE-ATAG10-TECHS-20021029/.

[CHARMOD]

"Character Model for the World Wide Web," M. Dürst and F. Yergeau, eds., 30 April 2002. This W3C Working Draft is http://www.w3.org/TR/2002/WD-charmod-20020430/. The latest version is available at http://www.w3.org/TR/charmod/.

[CSS21]

"Cascading Style Sheets Level 2 Revision 1 (CSS 2.1) Specification," B. Bos, T. Celik, I. Hickson, H. Lie, eds., 07 June 2011. This W3C Recommendation is http://www.w3.org/TR/2011/REC-CSS2-20110607/.

[DOM2HTML]

"Document Object Model (DOM) Level 2 HTML Specification," J. Stenback, P. Le Hégaret, A. Le Hors, eds., 8 November 2002. This W3C Proposed Recommendation is http://www.w3.org/TR/2002/PR-DOM-Level-2-HTML-20021108/. The latest version is available at http://www.w3.org/TR/DOM-Level-2-HTML/.

[HTML4]

"HTML 4.01 Recommendation," D. Raggett, A. Le Hors, and I. Jacobs, eds., 24 December 1999. This W3C Recommendation is http://www.w3.org/TR/1999/REC-html401-19991224/.

[RFC2616]

"Hypertext Transfer Protocol — HTTP/1.1," J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee, June 1999.

[RFC3023]

"XML Media Types," M. Murata, S. St. Laurent, D. Kohn, January 2001.

[SMIL]

"Synchronized Multimedia Integration Language (SMIL) 1.0 Specification," P. Hoschka, ed., 15 June 1998. This W3C Recommendation is http://www.w3.org/TR/1998/REC-smil-19980615/.

[SMIL20]

"Synchronized Multimedia Integration Language (SMIL 2.0) Specification," J. Ayars, et al., eds., 7 August 2001. This W3C Recommendation is http://www.w3.org/TR/2001/REC-smil20-20010807/.

[SVG]

"Scalable Vector Graphics (SVG) 1.0 Specification," J. Ferraiolo, ed., 4 September 2001. This W3C Recommendation is http://www.w3.org/TR/2001/REC-SVG-20010904/.

[UAAG10]

"User Agent Accessibility Guidelines 1.0," I. Jacobs, J. Gunderson, E. Hansen, eds.17 December 2002. This W3C Recommendation is available at http://www.w3.org/TR/2002/REC-UAAG10-20021217/.

[UAAG10-CHECKLIST]

An appendix to UAAG 2.0 lists all of the checkpoints, sorted by priority. The checklist is available in either tabular form or list form.

[UAAG10-ICONS]

Information about UAAG 1.0 conformance icons and their usage is available at http://www.w3.org/WAI/UAAG10-Conformance.

[UAAG10-SUMMARY]

An appendix to UAAG 2.0 provides a summary of the goals and structure of User Agent Accessibility Guidelines 1.0.

[UAAG10-TECHS]

"Techniques for User Agent Accessibility Guidelines 1.0," I. Jacobs, J. Gunderson, E. Hansen, eds. The latest draft of the techniques document is available at http://www.w3.org/TR/UAAG10-TECHS/.

[UNICODE]

The Unicode Consortium. The Unicode Standard, Version 6.1.0, (Mountain View, CA: The Unicode Consortium, 2012. ISBN 978-1-936213-02-3)
http://www.unicode.org/versions/Unicode6.1.0/

[VOICEBROWSER]

"Introduction and Overview of W3C Speech Interface Framework," J. Larson, 4 December 2000. This W3C Working Draft is http://www.w3.org/TR/2000/WD-voice-intro-20001204/. The latest version is available at http://www.w3.org/TR/voice-intro/. UAAG 2.0 includes references to additional W3C specifications about voice browser technology.

[W3CPROCESS]

"World Wide Web Consortium Process Document," I. Jacobs ed. The 19 July 2001 version of the Process Document is http://www.w3.org/Consortium/Process-20010719/. The latest version is available at http://www.w3.org/Consortium/Process/.

[WCAG20]

"Web Content Accessibility Guidelines (WCAG) 2.0" B. Caldwell, M. Cooper, L. Guarino Reid, G. Vanderheiden, eds., 8 December 2008. This W3C Recommendation is http://www.w3.org/TR/2008/REC-WCAG20-20081211/. The latest version is available at http://www.w3.org/TR/WCAG20/. Additional format-specific techniques documents are available from this Recommendation.

[WCAG20-TECHS]

"Techniques for Web Content Accessibility Guidelines 2.0," B. Caldwell, M. Cooper, L. Guarino Reid, G. Vanderheiden, eds., 8 December 2008. This W3C Note is http://www.w3.org/TR/2010/NOTE-WCAG20-TECHS-20101014/. The latest version is available at http://www.w3.org/TR/WCAG20-TECHS/. Additional format-specific techniques documents are available from this Note.

[WCAG-EM]

"Website Accessibility Conformance Evaluation Methodology (WCAG-EM) 1.0" E. Velleman, S. Abou-Zahra, eds., 26 February 2013. This is an informative draft of a Working Group Note. The latest version is available at http://www.w3.org/TR/WCAG-EM/

[WEBCHAR]

"Web Characterization Terminology and Definitions Sheet," B. Lavoie, H. F. Nielsen, eds., 24 May 1999. This is a W3C Working Draft that defines some terms to establish a common understanding about key Web concepts. This W3C Working Draft is http://www.w3.org/1999/05/WCA-terms/01.

[XAG10]

"XML Accessibility Guidelines 1.0," D. Dardailler, S. Palmer, C. McCathieNevile, eds., 3 October 2001. This W3C Working Draft is http://www.w3.org/TR/2002/WD-xag-20021003. The latest version is available at http://www.w3.org/TR/xag.

[XML]

"Extensible Markup Language (XML) 1.0 (Second Edition)," T. Bray, J. Paoli, C.M. Sperberg-McQueen, eds., 6 October 2000. This W3C Recommendation is http://www.w3.org/TR/2000/REC-xml-20001006.

[XHTML10]

"XHTML[tm] 1.0: The Extensible HyperText Markup Language," S. Pemberton, et al., 26 January 2000. This W3C Recommendation is http://www.w3.org/TR/2000/REC-xhtml1-20000126/.

[XMLDSIG]

"XML-Signature Syntax and Processing," D. Eastlake, J. Reagle, D. Solo, eds., 12 February 2002. This W3C Recommendation is http://www.w3.org/TR/2002/REC-xmldsig-core-20020212/.

[XMLENC]

"XML Encryption Syntax and Processing," D. Eastlake, J. Reagle, eds., 10 December 2002. This W3C Recommendation is http://www.w3.org/TR/2002/REC-xmlenc-core-20021210/.

Appendix D: Acknowledgments

Participants active in the UAWG prior publication:

• Jim Allan (Co-Chair, Texas School for the Blind and Visually Impaired)
• Kelly Ford (Co-Chair, Microsoft)
• Mark Hakkinen (Educational Testing Service)
• Eric Hansen (Educational Testing Service)
• Simon Harper (University of Manchester)
• Greg Lowney (Invited Expert)
• Kimberly Patch (Invited Expert)
• Jan Richards ( Inclusive Design Institute, OCAD University)
• Jeanne Spellman (W3C Staff Contact)

Previous Editor:

Jan Richards, Inclusive Design Institute, OCAD University

Additional Contributors of Mobile Examples

• Kathy Walhbin
• Mark Sadecki

Other previously active UAWG participants and other contributors to UAAG 2.0:

• Judy Brewer (W3C)
• Alan Cantor (Invited Expert)
• Wayne Dick (Invited Expert)
• Bim Egan (Royal National Institute of Blind People)
• Sean Hayes (Microsoft)
• Dean Hudson (Apple)
• Patrick Lauke (Opera Software)
• Cathy Laws (IBM)
• Peter Parente (IBM)
• David Poehlman (Invited Expert)
• Simon Pieters (Opera Software)
• Henny Swan (Opera Software)
• Gregory Rosmaita (Invited Expert)
• David Tseng (Apple)

UAAG 2.0 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 ED-OSE-10-C-0067. 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.