[Contents] [Guidelines]


Implementing UAAG 2.0

A guide to understanding and implementing User Agent Accessibility Guidelines 2.0

W3C Working Draft 6 June 2013

This version:
Latest version:
Previous version:
James Allan, Texas School for the Blind and Visually Impaired
Kelly Ford, Microsoft
Kim Patch, Redstart Systems
Jeanne Spellman, W3C/Web Accessibility Initiative

Mobile Accessibility Examples from Implementing UAAG 2.0 provides a filtered view showing how web browsers that follow UAAG benefit people with disabilities using the Web on mobile devices.


This document provides supporting information for the User Agent Accessibility Guidelines (UAAG) 2.0 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.

This document provides explanation of the intent of UAAG 2.0 success criteria, examples of implementation of the guidelines, best practice recommendations and additional resources for the guideline.

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).

Status of this document

May be Superseded

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/.

Working Draft of Implementing UAAG 2.0

This is the W3C Working Draft of 6 June 2013. This draft has CSS classes added to help identify examples of mobile accessibility. It also includes some minor editorial changes.

There are no substantive changes from the 23 May 2013 Working Draft of Implementing UAAG.

Comments on this draft should be sent to public-uaag2-comments@w3.org (Public Archive) by 21 June 2013.

The User Agent Working Group (UAWG) expects to publish UAAG 2.0 as a W3C Recommendation with Implementing UAAG as a supporting Note. Until that time User Agent Accessibility Guidelines 1.0 (UAAG 1.0) [UAAG10] is the stable, referenceable version. This Working Draft does not supersede UAAG 1.0.

Web Accessibility Initiative

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.

No Endorsement

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. The group does not expect this document to become a W3C Recommendation. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

Table of Contents


Definition of User Agent

A user agent is any software that retrieves, renders and facilitates end-user interaction with Web content.

The classic user agent is a browser. A media player, which only performs these functions for time-based media, is also user agent. Web applications and some mobile apps that render web content are also user agents.

For specific advice in determining if software is a user agent, see What Qualifies as a User Agent (Implementing UAAG 2.0). User agents may also include authoring tool features: see Relationship to the Authoring Tool Accessibility Guidelines (ATAG) 2.0. For information on the difference between web applications and content see Relationship to the Web Content Accessibility Guidelines.

What qualifies as a User Agent?

These guidelines employ the following tests to determine if software qualifies as a user agent. UAAG 2.0 divides potential user agents into

If the following three conditions are met, then it is a platform-based application:

  1. It is a standalone application, and
  2. It interprets any W3C-specified language, and
  3. It provides a user interface or interprets a procedural or declarative language that may be used to provide a user interface

If the following two conditions are met then it is an extension or plug-in:

  1. It is launched by, or extends the functionality of a platform-based application, and
  2. Post-launch user interaction is included in, or is within the bounds of the platform-based application
If the following three conditions are met then it is an web-based application:
  1. The user interface is generated by a procedural or declarative language; and
  2. The user interface is embedded in an application that renders web content, and
  3. User interaction is controlled by a procedural or declarative language, or if user interaction does not modify the Document Object Model of its containing document.

The Role of User Agents in Web Authoring

The following is a list of several ways in which user agents are commonly involved in web content authoring and the relationship between UAAG 2.0 and ATAG 2.0.

  1. Preview tool: Authors often preview their work in user agents to test how the content will be appear and operate. ATAG 2.0 includes a special exception when previews are implemented with pre-existing user agents, so there are no additional requirements on user agent developers in this case.
  2. Checking tool: Authors often make use of user agent error panels (e.g. HTML validity, JavaScript errors) during authoring. ATAG 2.0 Part A applies, but may not include additional accessibility requirements beyond the UAAG 2.0 success criteria. If a user agent includes an "accessibility checker", the developer should consult checker implementation guidance in ATAG 2.0 Part B.
  3. Edit modes: Some user agents include a mode where the user can edit and save changes to the web content, modifying the experience of other users. In this mode, the user agent is acting as an authoring tool and all of ATAG 2.0 applies.
  4. Automatic content changes: Some user agents or plug-ins may automatically change retrieved web content before it's rendered. This functionality is not considered an authoring tool because changes are made to the user's own experience, not the experience of other users.
  5. Providing a platform for web-based authoring tools: Many web applications serve as authoring tools and make use of user agent features to deliver functionality (e.g., undo text entry, adjust font size of the authoring tool user interface etc.) User agent developers should consult ATAG 2.0 to understand the ways in which web-based authoring tools can depend on user agent features.

UAAG 2.0 Guidelines

The success criteria and applicability notes in this section are normative. Guideline summaries are informative.

PRINCIPLE 1 - Ensure that the user interface and rendered content are perceivable

Implementing Guideline 1.1 - Provide access to alternative content.

Summary: The user can choose to render any type of alternative content available. (1.1.1). The user can also choose at least one alternative such as alt text to be always displayed (1.1.3), but it's recommended that users also be able to specify a cascade (1.1.5), such as alt text if it's there, otherwise longdesc, otherwise filename, etc. It's recommended that the user can configure the caption text and that text or sign language alternative cannot obscure the video or the controls (1.1.4). The user can configure the size and position of media alternatives (1.1.6).

1.1.1 Render Alternative Content:

For any content element, the user can choose to render any types of recognized alternative content that are present. (Level A)

Note: It is recommended that the user agent allow the user to choose whether the alternative content replaces or supplements the original content element.

  • Intent of Success Criterion 1.1.1:
    Some users with disabilities may find specific images, videos, or other content elements unusable or painful, or that such elements make the page difficult to use because of their size. In these cases they need the ability to either hide the element when it is painful or makes the page difficult to view, and/or get access to alternative content that will be more usable for them than the original element. Users with some disabilities may find a specific content element causes them physical pain (e.g. an image with high contrast) or distress (e.g. an image that triggers post traumatic stress disorder), or that the element's size may make the page difficult to use (because of difficulty scrolling, or shifting gaze, or moving the pointer more than a certain distance). In these cases the user needs to be able to hide that element or replace it with alternative content or a placeholder. Other users may find specific elements are simply unusable (e.g. an image that is too low contrast for the user's vision). In these cases the user needs to be able to access author-provided alternative content (e.g. Alt text or Longdesc) or the very minimum a placeholder (e.g. filename).

    Note: If the user cannot directly select or choose the element in order to perform commands upon it (e.g. if the browser does not support clicking on HTML background images or moving focus to them with the keyboard), the user agent must provide an alternative user interface for this feature.
  • Examples of Success Criterion 1.1.1:
    • Rodney has low vision and finds some images on a web page are painful to look at. He can hide foreground images by right-clicking on them or pressing the Tab key to move focus to them, and then choosing a command from the element's context menu. However, the browser does not let him right-click or navigate to the background image. Therefore it provides a user preference setting to hide all background images or to hide the background image on the current site.

1.1.2 Replace Non-Text Content:

The user can have all recognized non-text content replaced by alternative content, placeholders, or both. (Level A)

Note: At level A, the user agent can specify that an alternative content or placeholder replace the non-text content. At level AA success criterion 1.1.3 requires that the user can specify one format or placeholder to be used. At level AAA success criterion 1.1.5 requires that the user can specify a cascade order of types of alternative content to be used.

  • Intent of Success Criterion 1.1.2:
    Users may wish to hide images for a number of different reasons. Some users with cognitive disabilities may wish to hide images in order to avoid those that would be severely distracting. Some users with visual disabilities may wish to hide images in order to avoid those that are painful (such as those with high contrast). Other users may wish to replace images with alternative content because they are unlikely to be able to visually discern, understand, or otherwise benefit from the images. Some users with impaired motion or dexterity may wish to replace images with smaller alternative content to reduce the amount of scrolling they have to do, while some users with attention deficit disorder may wish to do the same thing in order to keep as much information visible on the screen as possible.
  • Examples of Success Criterion 1.1.2:
    • Tyler has a learning disability and finds images very distracting. He sets a preference in his browser to always display alternative text instead of an image.
    • [mobile] Ben has low vision and needs to use a very large font size to be able to read text. On his mobile device, enlarging the page makes any images so large that they use up too much screen space and require excessive scrolling. He sets a preference to render all images as text (if available) and to reflow the page so that the text flows smoothly with no space for the missing images.
    • Lee has low vision where text is blurred. She finds that the transparency effect that shows detail "bleed through' under the window she is reading makes the text she is trying to read illegible. She sets a preference that hides all background images and transparency effects that the author may have written into a web page or application.
    • James has a reading disability where he needs text to be clear from distractions that are not related to the text. He configures his user agent to not load background images. Then when he navigates to a web page, James gets only the text from the web page without any images interfering with what he is reading.
    • Sasha requires high contrast to be able to discriminate the shape of letters. She always sets a preference in her browser to turn off background images, so that she can see the text clearly without the variations in the background.
    • [mobile] Betty is a low vision user and has difficulty reading text on her mobile device when it is displayed over a background image. Using her user-defined style sheet, she can disable all background images from being rendered in her browser.

1.1.3 Configurable Alternative Content Defaults:

For each type of non-text content, the user can specify a type of alternative content that, if present, will be rendered by default. (Level AA)

  • Intent of Success Criterion 1.1.3:
    Alternative content is wasted if the user agent doesn't render it for users who need it. Default alternative content is a global setting because it is an unreasonable burden for users to change the rendering options every time they visit a new page.
  • Examples of Success Criterion 1.1.3:
    • Sally is blind. In the browser's preferences dialog box, Sally specifies that she wants alt text displayed in place of images, and that the document should reflow to allow the entire alt text to be displayed rather than truncated.
    • Ben has low vision. In the browser's preferences dialog box, he chooses to always display the alternative ("fallback") content for embedded objects, such as a transcript in place of a video.
    • [mobile] Ben has low vision and keeps his mobile phone browser "zoomed" so he can read the text. Because images can become pixelated when enlarged, he prefers the alternative text. In the mobile settings dialog box, he chooses to always display the alternative ("fallback") content for images and to reflow the page without a placeholder for the image. This saves screen space and reduces the amount of scrolling he has to do. .
    • Brin is deaf. She toggles a menu item which turns on the display of all captions for video and audio content.

1.1.4 Display of Alternative Content for Time-Based Media:

For recognized on-screen alternative content for time-based media (e.g. captions, sign language video), the following are all true: (Level AA)

  1. Don't obscure primary media: The user can specify that displaying time-based media alternatives doesn't obscure the primary time-based media; and
  2. Don't obscure controls: The user can specify that the displaying time-based media alternatives doesn't obscure recognized controls for the primary time-based media; and
  3. Use configurable text: The user can configure recognized text within time-based media alternatives (e.g. captions) in conformance with 1.4.1.

Note: Depending on the screen area available, the display of the primary time-based media may need to be reduced in size to meet this requirement.

  • Intent of Success Criterion 1.1.4:
    Users who require or can benefit from alternative media tracks in video or audio may not find that the default or authored position and size of those tracks is usable. Enabling the user to move and scale any displayed alternate media tracks (e.g. captions) allows displayed content to be positioned and sized to meet the needs of the user.
  • Examples of Success Criterion 1.1.4:
    • Justin has low vision and works in a noisy environment that makes it difficult to listen to instructional videos. When he enlarges the text of the captions to a viewable size, they block most of the video image. Justin selects an option that displays the caption track in a separate window, which he positions below the video image so the captions don't block the video image.
    • Jaime is deaf and is taking courses from on online university. She prefers to use ASL if it is available for online media. A course she is taking offers captions and a signing avatar for the recorded lectures. The default size of the avatar window is small, making it difficult to follow the signing. The avatar also overlays a significant part of the lecture video. Jaime drags the avatar out of the video and enlarges it, so that they are side by side and equally sized.
    • [mobile] Jaime is deaf and prefers to always display captions on her mobile phone. She has set her global settings on the phone to turn on closed captions. All videos displayed on the phone will automatically display captions.
    • [mobile] Ben has low vision that becomes worse throughout the day as he becomes more tired. He keeps a floating control on his mobile phone that allows one touch access to his configuration so that he can change the font size. The floating control can be easily moved around the screen so it is not in the way of other controls, and it becomes translucent after it is idle for a few seconds.


1.1.5 Default Rendering of Alternative Content (Enhanced):

For each type of non-text content, the user can specify the cascade order in which to render different types of alternative content when preferred types are not present. (Level AAA)

  • Intent of Success Criterion 1.1.5:
    For a given piece of non-text content the author may provide one or more alternatives. For example, an image may have different versions based on resolution, ‘alt text’ (@alt) or a link to a long description (@longdesc). A video may have bandwidth alternatives, caption files in different languages, and audio descriptions in different languages. Users can choose which item(s) to render by default, and specify the order of the cascade of alternatives to be rendered if the author provided multiple alternatives.
  • Examples of Success Criterion 1.1.5:
    • Mary has a learning disability. She finds looking at images on a webpage very distracting. Mary would like to see all images rendered in the following order: First, for images with long descriptions, render the long description in place of the image. If the long description does not exist, render the ‘alt text’. If neither is available, render the file name. Added functionality would allow Mary to right click (context menu) on an image to list and select the preferred order of available alternatives (thumbnail, original size, full screen, low resolution, high resolution, alt text, long description, file name).
    • Juan is hard of hearing. He always wants to see video on the page. Juan wants to use the Spanish language track and Spanish captions as a default. If these are not available, he wants to see the video with English audio and captions. If no captions are available, Juan wants video with English audio. Added functionality would allow Juan to right click (context menu) on an video to list and select the preferred order of the available alternatives (still image, caption languages, audio languages, audio-description languages).
    • [mobile] Ben has low vision and prefers to display the longer alternative content (@alt or @title) on his desktop browser where his display allows. When using his mobile device, Ben has configured his device to display the shortest alternative content available for non-text content.

1.1.6 Size and Position of Time-Based Media Alternatives:

The user can configure recognized alternative content for time-based media (e.g. captions, sign language video) as follows: (Level AAA)

  1. The user can resize alternative content for time-based media up to the size of the user agent's viewport.
  2. The user can reposition alternative content for time-based media to at least above, below, to the right, to the left, and overlapping the primary time-based media.

Note 1: Depending on the screen area available, the display of the primary time-based media may need to be reduced in size or hidden to meet this requirement.

Note 2: Implementation may involve displaying alternative content for time-based media in a separate viewport, but this is not required.

  • Intent of Success Criterion 1.1.6:
    Users may want to reposition the alternative in close proximity to the most important portion of the main media to reduce the visual scanning distance between them. For example, if the video frequently includes on-screen text near the top of the video then the captions will be easier to read if they are located above the video.
  • Examples of Success Criterion 1.1.6:
    • Maximilian adjusts the position of his captions depending on what he's watching. When watching a sporting event with a dashboard displaying statistics at the top, he positions the captions immediately above the top so the captions are close to the statistics. However, when he watches a movie, he positions the captions so that they overlap the video frame near the bottom. When he watches financial news with a stock ticker along the bottom, he moves the captions to be immediately below the ticker.
    • [mobile] When Tom watches narrow-aspect video on a wide-aspect screen, he moves the window displaying sign language interpretation to the side, allowing the primary video to take up the entire height of the screen without the interpretation getting in the way.
    • [mobile] Raymond has one functioning hand. He positions captions so that they're not covered by the hand he's using to hold his tablet.
    • [mobile] When Tom watches narrow-aspect video on a wide-aspect screen or in landscape mode on his mobile device, he moves the window displaying sign language interpretation to the side, allowing the primary video to take up the entire height of the screen without the interpretation getting in the way.

Implementing Guideline 1.2 - Repair missing content.

Summary: The user can request useful alternative content when the author fails to provide it. For example, showing metadata in place of missing or empty (1.2.1) alt text. The user can ask the browser to predict missing structural information, such as field labels, table headings or section headings (1.2.2).

1.2.1 Support Repair by Assistive Technologies:

If text alternatives for non-text content are missing or empty then both of the following are true: (Level AA)

  1. the user agent does not attempt to repair the text alternatives with text values that are also available to assistive technologies.
  2. the user agent makes metadata related to the non-text content available programmatically (and not via fields reserved for text alternatives).

  • Intent of Success Criterion 1.2.1:
    When alternative content is missing, it is sometimes useful for users to have access to alternative information, such as the filename. Users need to control the flow of this information, because an uncontrolled flow can be distracting and time-consuming. This is particularly important for users who can't use some forms of content (e.g. images) or may need to avoid some forms of content (e.g. animations) and replace them with alternative content.

    Users need to control the flow of the content when this information is added, because truncating the content to fit its container may make the document unusable (e.g. if important information becomes hidden). In other cases, expanding the container will make the document unusable (e.g. when important cues no longer line up correctly).

    Note that repair text is only required for alternative content for images. For example, it would not require the user agent to generate a transcript of audio using speech recognition.
  • Examples of Success Criterion 1.2.1:
    • Ray is blind and counts on alternative text descriptions for images. There is an image in web content that does not have alternative text provided. The browser displays the string '(image canoe.png)', which includes the file name because that is the only available information about the image.
    • Bintu is deaf and relies on captions to replace audio. Bintu selects a caption button for a video she wants to watch, and is informed that no captions exist. The player then analyzes the video soundtrack and provides speech-to-text translation served as captions. Note: this is an advanced example, not a requirement.

1.2.2 Repair Missing Structure:

The user can specify whether or not the user agent should attempt to insert the following types of structural markup on the basis of author-specified presentation attributes (e.g.. position and appearance): (Level AAA)
  1. Labels
  2. Headers (e.g. heading markup, table headers)
  • Intent of Success Criterion 1.2.2:
    When an author neglects to provide labels and/or headers as necessary for accessibility, the user agent can sometimes use heuristics to determine potential labels and/or headers from presentation attributes. Once potential headings and/or labels have been identified, the user agent can proceed (e.g. with communication via platform accessibility services) as if the relationship was defined in the markup. The user can specify whether heuristics should be applied because some users want to experience the content as the author provided it (e.g. to perform evaluations or when heuristics fail).
  • Examples of Success Criterion 1.2.2:
    • Frank uses speech input. When content markup includes a checkbox without a specified label, the user agent detects that a static text component is positioned immediately to the right of the checkbox and no other static text components are nearby. The nearby text is treated as the label. This enables George to toggle the checkbox by speaking its name.
    • Maria uses a screen reader. When a table lacks marked up header rows, the user agent gives her the option to have the first row treated as the table header row.
    • Li uses a scanning keyboard and makes use of the user agent's outline view to more efficiently navigate web pages. The content markup includes instances of static text that differ from surrounding text because they are sentence fragments and styled with a larger font and bold weight. The instances are treated as headings as therefore appear in the outline view, enabling Li to more efficiently navigate to them.

Implementing Guideline 1.3 - Provide highlighting for selection, keyboard focus, enabled elements, visited links.

Summary: The user can visually distinguish selected, focused, and enabled items, and recently visited links (1.3.1), with a choice of highlighting options that at least include foreground and background colors, and border color and thickness (1.3.2).

1.3.1 Highlighted Items:

The user can specify that the following classes be highlighted so that each is uniquely distinguished: (Level A)

  1. selection
  2. active keyboard focus (indicated by focus cursors and/or text cursors)
  3. recognized enabled input elements (distinguished from disabled elements)
  4. elements with alternative content
  5. recently visited links
  • Intent of Success Criterion 1.3.1:
    Users need to be able to easily discover web content they can interact with. One effective way to do this is to highlight enabled elements and links (including recently visited links). Highlighted selection and content focus lets people who use keyboard, gesture and speech input know where they working. On some pages controls may be difficult to discern amid a large amount of other content, or may be styled so the controls are difficult to distinguish from other content. This can be particularly difficult for people with visual impairments, who may not be able to distinguish subtle visual differences. People with some cognitive impairments may have difficulty distinguishing between items with similar or non-standard appearance. Visually distinguishing these items reduces the amount of time or number of commands these groups require to examine a page.

    Note: In addition to these required categories, it is recommended that user agents also allow the user to highlight the active viewport, even when it is a frame or similar within the active window. This makes it much easier for the user to visually locate the active focus.
    Note: Platform conventions will dictate whether or not keyboard focus in an inactive viewport is visually indicated by an inactive cursor.
    Note: the definition of visited and unvisited links is up to the user agent. Visited links may be links visited during the current session or in the browser's history.
  • Examples of Success Criterion 1.3.1:
    • Jerry has low vision. He goes to a website that uses styles to override visited link color. He wants to know what links have yet to be explored. The user agent provides a dialog box for setting overrides to author-selected link colors. Jerry uses the dialog box to override the author styles so visited links are indicated.
    • Jerry goes to a website with styles that remove the content focus outline. The user agent provides a dialog box for setting overrides to the author's focus outline declaration. Jerry uses the dialog box to display the content focus outline so he tell where the focus is on the page.
    • Binh gets easily frustrated when he cannot locate the buttons and links on a page. This happens when buttons and links don't have the standard appearance he's used to. The user agent provides a dialog box for setting overrides to author-selected link colors. Binh turns on the option to have all links appear in bright purple, and buttons drawn with a bright purple border so he can easily scan the page and find the items he's looking for.
    • [mobile] George has limited hand use and uses custom gestures on his mobile phone. He wants a visible focus indicator to know what element on the page has focus so when gestures are used on the mobile phone, he will know what element will be activated.
    • Tinan has repetitive strain injuries and seeks to limit scrolling. The user agent renders distinct visual icons in proximity of content that has short text alternatives, long descriptions, and captions. If the icon forces the text to extend beyond a fixed size container the user agent uses global preference settings to determine whether to expand the container, provide scroll bars, or truncate the content.
    • Aosa is blind. When rendering a Web page using synthesized speech, the user agent generates an audible tone to signify that the word being read is an acronym, and Aosa can press the * key to hear the expansion. When the phrase being read is the Alt text for an image, another tone indicates that Aosa can press + to hear the long description.
    • [mobile] Brin is deaf. The video player she is using has a button displayed beneath the playing video that indicates that captions are available. She clicks the button to toggle the captions on so she can understand the video. [mobile] On her mobile phone, Brin touches a video, which displays the controls including the "display caption" control.

1.3.2 Highlighting Options:

When highlighting classes specified by 1.3.1 Highlighted Items, the user can specify highlighting options that include at least: (Level AA)

  1. foreground colors,
  2. background colors, and
  3. borders (color, style, and thickness)
  • Intent of Success Criterion 1.3.2:
    Low vision users and users with some cognitive disabilities need control over visual properties to meet their individual needs. These include foreground colors, background colors, and visual borders (with the same configurable range as the operating environment's conventional selection utilities)
  • Examples of Success Criterion 1.3.2:
    • Alex has low vision. He sometimes has difficulty distinguishing fields on web forms. The user agent provides a dialog box allowing the user to override any author settings. He chooses to have all form fields displayed with a yellow background and outlined with a thick black border.
    • Marcy has a cognitive disorder that makes it difficult to stay focused on the task she wants to accomplish. The user agent provides a dialog box allowing the user to override any author settings. She chooses to have all form fields displayed with a yellow background and outlined with a thick black border.

Implementing Guideline 1.4 - Provide text configuration.

Summary: The user can control text font, color, and size (1.4.1), including whether all text should be the shown the same size (1.4.2).

1.4.1 Configure Rendered Text:

The user can globally set any or all of the following characteristics of visually rendered text content, overriding any specified by the author or user agent defaults: (Level A)

  1. text scale (the general size of text)
  2. font family
  3. text color (foreground and background)
  4. line spacing
  5. character spacing
  • Intent of Success Criterion 1.4.1:
    Users need to access a wide range of font sizes, styles, colors, and other attributes in order to find the combination that works best for their needs. In providing preferences, it is important to avoid making assumptions. For example, some users may increase font size to make text more legible, while other users may reduce the font size to decrease the need to scroll the content.
  • Examples of Success Criterion 1.4.1:
    • Lee has low vision from albinism and has difficulty with screen resolution and brightness. She chooses to have all text displayed in Palatino font, with white text on a black background, and at least 16-points. The serif Palatino font has character spacing that resolves better for her vision, while the white on black reduces glare and the larger size allows her to distinguish fine detail more clearly.
    • [mobile] Lee has low vision from albinism and has difficulty with screen resolution and brightness. She uses a browser on her mobile phone that supports only 3 font sizes: small, medium, and large. Lee needs to use a font size of 16 pt, which is between the medium and large sizes. The mobile phone settings provide an option to override the 3 font sizes with the operating system font range, so that Lee can select the 16 pt font size she needs.
    • Mike has a reading disability. A website uses a fancy script font for the headings that he cannot understand. He chooses to have all text displayed in a plain font that he can read.
    • [mobile] Ben has low vision. In the mobile settings dialog box, he chooses to large text for font size. All applications on the mobile phone display text in large font.

1.4.2 Preserving Size Distinctions:

The user can specify whether or not distinctions in the size of rendered text are preserved when that text is rescaled (e.g. headers continue to be larger than body text). (Level A)

  • Intent of Success Criterion 1.4.2:
    The relative size of text provides visual cues that help in understanding and navigating web content. Some content may be authored in a way that makes it difficult or impossible to understand when font distinctions were hidden, such as headlines that are in a larger font than body text. It's important that users who need to enlarge or reduce text size be able to preserve these visual cues. It is also important that magnification users who find that text size distinction greatly increases scrolling and fatigue be able to display all text at the same size.
  • Examples of Success Criterion 1.4.2:
    • Lee has low vision. She finds text easiest to read at 16 pt Palatino and chooses to have her browser display body text in the 16 pt Palatino. She needs the headlines to scale proportionally (e.g. 24 pt) in order to preserve headline prominence.
    • Tomas has low vision and uses a screen magnifier. He chooses to have his browser display all text the same size, and sets that size as large as he can without making the letters too tall for his screen. Tomas chooses not to have headings be proportionately larger than normal text because that would make them taller than his screen and so unreadable.

Implementing Guideline 1.5 - Provide volume configuration.

Summary: The user can adjust the volume of each audio track relative to the global volume level (1.5.1).

1.5.1 Global Volume:

The user can adjust the volume of each audio tracksindependently of other tracks, relative to the global volume level set through operating environment mechanisms. (Level A)

  • Intent of Success Criterion 1.5.1:
    User agents can render audio tracks from a variety sources, and in some cases, multiple audio tracks may be present on a single page. Users should be able to globally set the volume of audio tracks, rather than having to adjust the volume of each audio track being played.
  • Examples of Success Criterion 1.5.1:
    • An operating system provides a master audio volume control that applies to all audio tracks rendered within the environment, including the user agent. The user may define a default volume level through a preferences dialog that is retained across sessions.
    • A user encounters a page with two advertisements and one video which begins playback on page load complete. A global mute command, supported via a mute key on the user's keyboard, allows the user to immediately silence the playing audio tracks.

Implementing Guideline 1.6 - Provide synthesized speech configuration.

Summary: If synthesized speech is produced, the user can specify speech rate and volume (1.6.1). It's recommended that users can specify pitch and pitch range (1.6.2), and advanced synthesizer speech characteristics like emphasis (1.6.3) and features like spelling (1.6.4).

1.6.1 Speech Rate, Volume, and Voice:

If synthesized speech is produced, the user can specify the following: (Level A)

  1. speech rate,
  2. speech volume (independently of other sources of audio), and
  3. voice, when more than one voice is available

1.6.2 Speech Pitch and Range:

If synthesized speech is produced, the user can specify the following if offered by the speech synthesizer: (Level AA)

  1. pitch (average frequency of the speaking voice), and
  2. pitch range (variation in average frequency)

Note: Because the technical implementations of text to speech engines vary (e.g. formant-based synthesis, concatenative synthesis), a specific engine may not support varying pitch or pitch range. A user agent will expose the availability of pitch and pitch range control if the currently selected or installed text to speech engine offers this capability.

1.6.3 Advanced Speech Characteristics:

The user can adjust all of the speech characteristics provided by the speech synthesizer. (Level AAA)

  • Intent of Success Criterion 1.6.1, 1.6.2, 1.6.3:
    These success criteria allow users to control speech characteristics so they can perceive and understand the audio information.

    For example, a user may need to increase the volume to a level within the user's range of perception. Or a user may increase the rate of synthesized speech presentation because the user understands it at a rate faster than the default setting of the user agent.

    Success criterion 1.6.1 covers characteristics that users most commonly need to adjust and that are adjustable in most technologies. Success criterion 1.6.2 covers characteristics that are less widely altered and less widely supported.
  • Examples of Success Criterion 1.6.1, 1.6.2, 1.6.3:
    • [mobile] Jamie is blind. He uses a mobile-based web browser to read a web page. He presses a key to increase the rate at which the information is read back. He also uses a mobile browser in a noisy environments such as a crowded subway. With a key press, Jamie quickly increases the volume.
    • Randy has a hearing disability where speech at lower pitches is difficult to hear. He is using an audio browser that reads web pages back to him. He issues a voice command saying "raise pitch" and the overall pitch of the synthetic speech is raised.

1.6.4 Synthesized Speech Features:

If synthesized speech is produced, the following features are provided: (Level AA)

  1. user-defined extensions to the synthesized speech dictionary,
  2. "spell-out", where text is spelled one character at a time, or according to language-dependent pronunciation rules,
  3. at least two ways of speaking numerals: spoken as individual digits and punctuation (e.g. "one two zero three point five" for 1203.5 or "one comma two zero three point five" for 1,203.5), and spoken as full numbers are spoken (e.g. "one thousand, two hundred and three point five" for 1203.5),
  4. at least two ways of speaking punctuation: spoken literally, and with punctuation understood from speech characteristics like pauses.
  • Intent of Success Criterion 1.6.4:
    The synthetic speech presentation of text can be difficult to understand. These success criteria improve understandability by giving the user the ability to adjust the way the speech synthesizer presents text.
  • Examples of Success Criterion 1.6.4:
    • Penny has a reading disabililty. She is using a browser that reads web pages to her so she can review her most recent banking transactions. She has configured her browser to speak currency instead of digits. With this setting she hears a transaction as "Deposit, two hundred fifty five dollars".
    • Penny's speech synthesizer is repeating a phone number. She wishes to copy this number, so she switches to the mode where each digit is spoken as a unique word (e.g. five, five, five, seven, nine).
    • George is blind. His speech synthesizer incorrectly pronounces technical terms employed in his organization. The terms are consistently mispronounced in a way that makes it difficult for George to distinguish them. A dictionary allows George to enter a spelling of the name that causes the synthetic speech to produce the correct pronunciation.

Implementing Guideline 1.7 - Enable Configuration of User Stylesheets.

Summary: The user agent supports user stylesheets (1.7.1) and the user can choose which if any user-supplied (1.7.2) and author-supplied (1.7.3) stylesheets to use. The user agent allows users to save user stylesheets (1.7.4).

1.7.1 Support User Stylesheets:

If the user agent supports a mechanism for author stylesheets, the user agent also provides a mechanism for user stylesheets. (Level A)

1.7.2 Apply User Stylesheets:

If user stylesheets are supported, then the user can enable or disable user stylesheets for: (Level A)

  1. all pages on specified websites, or
  2. all pages

1.7.3 Author Stylesheets:

If the user agent supports a mechanism for author stylesheets, the user can disable the use of author stylesheets on the current page. (Level A)

  • Intent of Success Criterion 1.7.1, 1.7.2 & 1.7.3:
    CSS stylesheets allow users and authors to customize the rendering of web content. Such customization is frequently used to make web content accessible to a wide range of user needs. These success criteria ensure that users can take full advantage of this ability to customize stylesheets. Since different websites may require different style changes to be readable, it is recommended that user agents provide a feature that lets the user specify which stylesheet should be automatically applied to different web pages as they are loaded (e.g. based on a list of domain names or URL templates).
  • Examples of Success Criterion 1.7.1, 1.7.2 & 1.7.3:
    • Tanya has low vision. She finds yellow text on a black background easiest to read. When a website loads, the user agent provides a menu that allows Tanya to select among several stylesheets that the web author has created for the website. Tanya selects the "yellow on black" stylesheet from the menu. The web content is then rendered using this stylesheet.
    • Tanya has changed a website that is normally in full color to yellow text on a black background. When her husband Jeromy sits at her computer to look at the site, he goes to the user agent menu to quickly de-select the user-defined stylesheet that Tanya previously applied to the web page. The website is now rendered in full color.
    • [mobile] Lee has low vision and finds text easiest to read text on her mobile device when it is presented in yellow on a black background. She has configured her browser to override the author stylesheets to always display text in her browser using this color scheme.
    • [mobile] Mattias has ADHD and finds text easiest to read text if text is highlighted in blue as it is being read out loud on his desktop or mobile device. Both the highlight and text color are configurable and override the author stylesheets so text is readable and has sufficient color contrast.

1.7.4 Save Copies of Stylesheets:

The user can save copies of the stylesheets referenced by the current page. This allows the user to edit and load the copies as user stylesheets. (Level AA)

  • Intent of Success Criterion 1.7.4:
    Stylesheets provide for powerful customization of rendered content. Occasionally a user may need to make slight modifications to the author-supplied external stylesheets used on a website to satisfy certain accessibility needs. At other times a web author may have created a stylesheet that a user with a disability finds helpful. The intent of this success criteria is to allow users to easily save the CSS for a website and make needed modifications without having to create full stylesheet of their own and to apply well designed stylesheets to other web pages where they find the stylesheets helpful.
  • Examples of Success Criterion 1.7.4:
    • Mikki browses to a new website and discovers that the Arial 14-point type used for all headlines does not work well with her level of vision. A friend helps Mikki discover that the headlines are created with a CSS stylesheet. They save this stylesheet and study how it is created. Mikki modifies this stylesheet to adjust the headline text to a larger font and a different typeface. She uses the modified stylesheet by applying it as a user style sheet.
    • [mobile] Tanya has low vision. She browses to a new website on her mobile phone and finds that the site is not optimized for mobile devices. She alters the stylesheet to provide better layout and larger fonts. The custom settings for the stylesheet are saved and applied when she returns.

Implementing Guideline 1.8 - Help users to use and orient within windows and viewports.

Summary: The user agent provides programmatic and visual cues to keep the user oriented. These include highlighting the viewport (1.8.1), keeping the focus within the viewport (1.8.2 & 1.8.7), resizing the viewport (1.8.3), providing scrollbar(s) that identify when content is outside the visible region (1.8.4) and which portion is visible (1.8.5), changing the size of graphical content with zoom (1.8.6 & 1.8.12), restoring the focus and point of regard when the user returns to a previously viewed page (1.8.8). Users can set a preference whether new windows or tabs open automatically (1.8.9) or get focus automatically (1.8.10). Additionally, the user can specify that all view ports have the same user interface elements (1.8.11), if and how new viewports open (1.8.9), and whether the new viewport automatically gets focus (1.8.10). The user can mark items in a webpage and use shortcuts to navigate back to marked items. (1.8.13).

1.8.1 Highlight Viewport:

The viewport with the input focus is highlighted and the user can customize attributes of the highlighting mechanism (e.g. shape, size, stroke width, color, blink rate). The viewport can include nested viewports and containers. (Level A)

  • Intent of Success Criterion 1.8.1:
    When a user agent presents content using multiple viewports, users benefit from a clear indication of which viewport has focus. Text foreground and background colors may not provide enough indication of viewport focus for users with low vision. These users need to customize highlighting of viewport frames using color, contrast, and border thickness to provide multiple visual cues.
  • Examples of Success Criterion 1.8.1:
    • Tanya has low vision. Her favorite music website allows her to select which of the top 10 songs are available for listening. Each song is represented by a thumbnail of the album cover – a graphical viewport containing a music player. Tanya uses a keyboard-based screen magnification tool to tab between songs. This highlights the currently selected player with a thick, yellow border against a dark gray background.

1.8.2 Move Viewport to Selection and Focus:

When a viewport's selection or input focus changes, the viewport's content moves as necessary to ensure that the new selection or input focus location is at least partially in the visible portion of the viewport. (Level A)

  • Intent of Success Criterion 1.8.2:
    When content extends horizontally or vertically beyond the visible bounds of its viewport, users must be able to move to one or more selectable elements that may be out of view and to have the selected content automatically move into view. This gives keyboard users and screen magnification users an efficient means to view selected content without having to scroll to locate and view the selection.
  • Examples of Success Criterion 1.8.2:
    • John has low vision and uses a screen magnifier. He is spellchecking his blog, which is contained within a scrollable viewport. The blog text exceeds the vertical size of the viewport. The blogging software provides a command to move to the first, and then any subsequent, unrecognized words. With two unrecognized words in the posting, John ignores the first selected word, and presses the key to move to the next unrecognized word, which is out of view. As the key is pressed, the viewport scrolls to show the selected word.
    • George uses a screen reader. He is showing a sighted colleague how to complete a registration form that's contained within a viewport. The form exceeds the vertical bounds of the viewport, requiring George to scroll vertically to view the complete form content. When George completes each form entry, if the next form is not already visible in the viewport, it scrolls into view.
    • [mobile] Lee typically views web content on her mobile phone at a high level of zoom, frequently positioning elements outside the viewport. When moving between focusable elements, the viewport automatically scrolls to the element currently in focus.

1.8.3 Resize Viewport:

The user can resize viewports within the limits of the display, overriding any values specified by the author. (Level A)

  • Intent of Success Criterion 1.8.3:
    If a viewport contains content that exceeds the dimensions of the viewport, users can increase the size of the viewport – up to the limits of the physical display screen – to allow the full image to be displayed without scrolling. This benefits keyboard users who may find it difficult to scroll content, and users with cognitive or learning disabilities whose understanding of the content is aided by viewing the complete image.
  • Examples of Success Criterion 1.8.3:
    • Perttu has a learning disability. He is studying an organization chart and has difficulty maintaining a mental representation of the organizational linkages for items out of view. In order to facilitate his understanding of the organization, he sizes the viewport to allow the entire chart to be displayed.

1.8.4 Viewport Scrollbars:

When the rendered content extends beyond the viewport dimensions, users can have graphical viewports include scrollbars, overriding any values specified by the author. (Level A)
  • Intent of Success Criterion 1.8.4:
    When rendered content exceeds the bounds of a graphical viewport, horizontal or vertical scrollbars show that not all of the rendered content is currently visible within the viewport and provide a means of navigation to that content. The scrollbars make it clear that the rendered content is not fully visible.
  • Examples of Success Criterion 1.8.4:
    • Tanya has low vision. She is reading a receipe on a website with a fixed size popup window. Tanya has set a preference in her browser to override the author setting and always display scrollbars on content overflow. She increases the font size causing the recipe to exceed the vertical and horizontal dimension of the viewport. The presence of the scrollbar shows her that additional ingredients may be present. She uses the scrollbar to move them into view.
    • [mobile] Terry has memory issues. She configures her mobile computer so that scrollbars are always on so she can instantly see where she is in a document.

1.8.5 Indicate Viewport Position:

The user can determine the viewport's position relative to the full extent of the rendered content. (Level A)

  • Intent of Success Criterion 1.8.5:
    Users who have fine-motor problems that make it difficult to scroll, users who have cognitive issues that make it difficult to orient on the page, and screen reader users, who rely on audio to scan the page, all need to quickly assess the amount of content on the page and where they are located within the content.
  • Examples of Success Criterion 1.8.5:
    • Ally has cognitive issues that make it difficult to orient. She navigates to a lengthy web page and begins paging through the content. A scroll bar indicates her position within the content as she pages and shows that with each paging action only a small portion of the content is rendered.
    • [mobile] Ally has cognitive issues that make it difficult to orient. When looking at a map on her mobile device, she must frequently zoom in to view her current location or destination and zoom out to put the location into the context of the large map.
    • George uses a screenreader to access a lengthy web page. His screen reader speaks the percentage that the page is scrolled, allowing George to know where the cursor is relative to the entire page. .

1.8.6: Zoom:

The user can rescale content within graphical viewports as follows: (Level A)

  1. Zoom in: to 500% or more of the default size; and
  2. Zoom out: to 10% or less of the default size, so the content fits within the height or width of the viewport.
  • Intent of Success Criterion 1.8.6:
    Some users want to be able to magnify content to so it is more legible. Some users  want to be able to shrink content so that more of it is visible onscreen. This can help them understand the structure of the content and their position in  the content, even if text has become too small to read.
  • Examples of Success Criterion 1.8.6:
    • Tanya has low vision. She opens a web application that uses small text fonts, mixed with graphical elements. She tries increasing the text size alone, but the graphical elements remain at their original sizes. She can't interpret the small graphical elements and the text flows improperly. However, when Tanya uses the zoom feature, the graphical elements are legible, and the page flows correctly.
    • [mobile] When Tanya views a web site on her mobile phone, she first scans the website at a very small size to guess where she wants to zoom in first. The zoom feature increases the size of both text and images.
    • Perttu has a learning disability. He is studying an organization chart but has difficulty maintaining a mental representation of the organizational linkages for items out of view. In order to facilitate his understanding of the organization, Perttu zooms out to allow the entire chart to be displayed.
    • [mobile] Ally has cognitive issues that make it difficult to orient. When looking at a map on her mobile device, she must frequently zoom in to view her current location or destination and zoom out to put the location into the context of the larger map.

1.8.7 Maintain point of regard

: The point of regard remains visible and at the same location within the viewport when the viewport is resized, when content is zoomed or scaled, or when content formatting is changed. (Level A)

  • Intent of Success Criterion 1.8.7:
    Users can be confused and disoriented when the area where they are working suddenly shifts outside the visible region of the viewport. When this happens, users may have to expend considerable time and effort to re-navigate back to their previous point of regard. Just as the location in audio does not change when the user increases the volume, the point of regard should not change when the user changes the size of the window or zooms the content.

    The point of regard is the information within the viewport that is visible to the user. When there is focused or selected content inside a viewport, and the viewport is resized, or content is zoomed, scaled, or formatted differently, that content will remain visible in the viewport. Otherwise, the user agent should maintain the same top-left (top-right for text read right-to-left) corner as the initial viewport.

    Note: User agents are encouraged to allow user to override author instructions not to wrap content (e.g., nowrap).
  • Examples of Success Criterion 1.8.7:
    • Jorge has low vision. While viewing a webpage he sees a picture with a caption that is too small to read. He highlights the caption, then uses the browser's zoom feature to increase the size of the content so he can read the caption. Throughout the zooming process the highlighted caption remains in the viewport, allowing Jorge to keep oriented on the caption and begin reading it when the appropriate content size is reached. Later, while reading on a page, Jorge finds some text that's too large to read. The beginning of the large text is at the top of the bowser content area. Jorge uses the zoom feature to make the content smaller. The text is reduced to a comfortable reading size and the beginning of the text remains at the top of the browser window.
    • Melissa has a distraction disorder. She is doing research for school. She scrolls the content so the relevant section heading is the top line of the browser. She resizes the browser so she can see her notes and the browser at the same time. After resizing the browser the heading is still the top line.
    • [mobile] Xu has a reading disability. He is reading a page with footnotes that are too small to read on his mobile device. Xu places the footnote at the top of the browser, and using the increase font-size feature, he increases the font-size of the text on the page. The footnotes stay on the top of the viewport.

1.8.8 Viewport History:

For user agents that implement a viewport history mechanism (e.g. "back" button), the user can return to any state in the viewport history that is allowed by the content, including a restored point of regard, input focus and selection. (Level AA)

1.8.9 Open on Request:

The user can specify whether author content can open new top-level viewports (e.g. windows or tabs). (Level AA)

1.8.10 Do Not Take Focus:

If new top-level viewports (e.g. windows or tabs) are configured to open without explicit user request, the user can specify whether or not top-level viewports take the active keyboard focus when they open. (Level AA)

  • Intent of Success Criteria 1.8.8, 1.8.9 & 1.8.10:
    Unexpected focus and viewport changes can be disorienting for all users, requiring time and effort for the user to orient to the change. These success criteria are intended to allow the user to be in control of when viewport changes happen so the user can orient to the changes in a predictable fashion.
  • Examples of Success Criteria 1.8.8, 1.8.9 & 1.8.10:
    • Justin has an attention deficit disorder. He is studying an online college course and finds a word that he he doesn't know. He follows a link to the definition of the word. After reading the definition, he uses the back button (viewport history) to return. The word remains selected remains the same so he doesn't have to reorient or find it on the page.
    • George uses a screen reader. He visits a web page that ordinarily opens a popup page. George receives an audio alert that additional content is available. He can choose to have this pop-up content open on request.
    • John has low vision and uses a screen magnifier to access his browser. He configures his browser so popup windows do not take focus because the popups can open outside the view of his magnifier.
    • Frank has repetitive strain injuries and uses speech input. He configures his browser so that pop-ups always take focus, so he doesn't have to take multiple steps to locate the window and take the desired action.
    • [mobile] Ray is blind. His mobile device automatically opens location links and calendar dates found on web pages in native apps available on the device. When he returns to the browser, focus on the original link is maintained.

1.8.11 Same UI:

The user can specify that all top-level viewports (e.g. windows or tabs) follow the defined user interface configuration. (Level AA)

  • Intent of Success Criterion 1.8.11:
    Users orient themselves to a browsing environment with a variety of techniques. This success criteria is designed to ensure that the user does not have to learn multiple strategies to use the browsing viewport.
  • Examples of Success Criterion 1.8.11:
    • Robert uses magnification software. After setting up his user agent, he knows that web content begins predictably one inch from the top of the window, so he can configure his magnification software to present content starting at that location.
    • Courtney has difficulty understanding and using complex user interfaces. She has worked with her sister to set up her browser to have only a few of the most common browser controls displayed and she knows to expect them on every browser window.

1.8.12 Reflowing Zoom:

The user can request that when reflowable content in a graphical viewport is rescaled, it is reflowed so that one dimension of the content fits within the height or width of the viewport. (Level AA)

Note: User agents are encouraged to allow users to override author instructions not to wrap content (e.g., nowrap).

  • Intent of Success Criterion 1.8.12:
    It's important that reflowed content remains easily usable. Content is not easily usable if the user has to scroll back and forth to see a single line of text. This is an especially acute issue for users who find it difficult or impossible to use the mouse to scroll and for users who find it difficult to reorient when the content changes. This does not require or prohibit the user agent from providing an option to turn off reflow.
  • Examples of Success Criterion 1.8.12:
    • Frank has repetitive strain injuries and uses speech input. As he's gotten older he sometimes needs to increase the font size to comfortably read text on his computer screen. If the text does not flow properly, he overuses his voice to carry out multiple speech commands, or uses the mouse, which exacerbates his injuries, or simply gives up.
    • [mobile] Frank has repetitive strain injuries and uses speech input. When Frank is using his mobile phone to read a web page, he will zoom in to read a article on a web site. He configures his mobile phone so that the text reflows to always display zoomed content to fit in one column.
    • Maggie has cognitive issues that make it difficult for her to reorient when the computer screen changes. She occasionally zooms in to read small text. She finds it easier to reorient after zooming when at least one dimension of the content fits within the height or width of the viewport.

1.8.13 Webpage Bookmarks:

The user can mark items in a webpage, then use shortcuts to navigate back to marked items. The user can specify whether a navigation mark disappears after a session, or is persistent across sessions. (Level AAA)

  • Intent of Success Criterion 1.8.13:
    This success criterion is crucial for users who have trouble navigating a webpage. People who use speech input, have memory problems, or use small screens may be able to go from one area of a webpage to another area once or twice, but may have trouble frequently repeating the action. The ability to mark areas of the page allows these types of users to navigate more quickly with less fatigue.
  • Examples of Success Criterion 1.8.13:
    • [mobile] Jamie is a quadriplegic who uses speech input. She is a professor who reads long documents online and often finds herself comparing different portions of the same document. It is tedious carrying out multiple scrolling commands by speech every time she needs to change to another portion of the document. She sets several bookmarks instead. This allows her to instantly jump among sections, eliminating the time and effort penalties she usually has to pay for slow scrolling. [mobile] Jamie also uses bookmarks on her mobile phone to cut down on scrolling.
    • Julie has memory problems. She finds it difficult to remember key points from a document she has just read. She uses bookmarks to mark important points she needs to read again. Without the ability to bookmark, she won't remember what she needs to read multiple times in order to do so.
    • George is blind and occasionally travels to unfamiliar places for work. He sometimes uses an iPhone to orient himself within a map of the building he's in. Once he's found a key place on the map – a room where a conference session is held, or the bathroom – he bookmarks it to build a map of useful places. This makes navigation easier the second time around. He sets the marks to be persistent across sessions so next time he visits he won't have to repeat his work.
    • Mary has repetitive strain injuries that make it painful to use a mouse. She is a college professer who uses an elaborate web application to correct papers. After putting a comment in a comment field she has to scroll all the way to the bottom of the document to enter the comment. The bookmarks make even this badly designed application something she can use successfully without hurting herself.

Implementing Guideline 1.9 - Provide alternative views.

Summary: The user can view the source of content (1.9.2), or an outline view of important elements. (1.9.1).

1.9.1 Outline View:

Users can view a navigable outline of rendered content composed of labels for important elements, and can move focus efficiently to these elements in the main viewport. (Level AA)

Note: The important elements depend on the web content technology, but may include headings, table captions, and content sections.

  • Intent of Success Criterion 1.9.1:
    Outline views allow users get a simplified view or overview of a document. They are particularly useful for users with memory or cognitive disabilities, blind users, and users who find it difficult or impossible to use a mouse. A navigable outline views reduce orientation and navigation time and fatigue.
  • Examples of Success Criterion 1.9.1:
    • Frank has repetitive strain injuries and uses speech input. He uses a web browser to read financial information. His browser provides an optional panel displaying a hierarchical list of the headers and tables in the current document. Frank is able to expand or shrink portions of the outline view for faster access to the information he wants.
    • [mobile] George uses a screen reader. He reads long standards documents and uses the headings to navigate quickly so he can compare sections of the standards. George also finds the outline view useful when he is quickly checking a reference on his mobile phone.

1.9.2 Source View:

The user can view all source text that is available to the user agent. (Level AAA)

  • Intent of Success Criterion 1.9.2:
    The source view is the ultimate fallback for a person with disabilities when the browser cannot properly render some content, or when the user cannot take advantage of the content as rendered or using the mechanisms provided.
  • Examples of Success Criterion 1.9.2:
    • [mobile] George uses a screenreader. He visits a web page where the content author failed to provide alt text or a long description for an image he wants to access. As a last resort, George examines the source to see the image's URI, class, and similar attributes. He sees that part of the URI for the image is "home.jpg" and concludes that he can click on that image to return to the home page of the site. [mobile] George also uses the source view feature on his mobile device when he needs to identify an image.
    • Mikki has low vision. She wants to create a user stylesheet for her web-based email program. She examines the source code to identify the CSS class of the email heading. She then creates a user stylesheet that increases the size and contrast of the email headings.

Implementing Guideline 1.10 - Provide element information.

Summary:The user agent presents information about content relationships (e.g. form labels, table headers)(1.10.1), and extended link information (e.g. title, internal vs. external) (1.10.2)

1.10.1 Access Relationships:

The user can access related elements based on the user's position in content (e.g. show the label of a form control, show the headers of a table cell). (Level AA)

  • Intent of Success Criterion 1.10.1:
    Some users have difficulty perceiving, remembering, or understanding the relationships between elements and their descriptions. Certain elements relate to others in a recognizable manner, such as relationships with 'id' attributes and child elements (e.g. Ajax widgets and with form elements). This allows users to better understand these relationships even if the elements are not adjacent on the screen or the DOM.
  • Examples of Success Criterion 1.10.1:
    • John has low vision and uses a screen magnifier to access his browser. When interacting with tables and spreadsheets John has to move the viewport of the magnifier to understand the row and column titles of the cell with which he is interacting. This takes additional time and effort and is therefore frustrating. John switches to a browser that presents the row and column titles when he hovers over a cell - this makes him much more productive at his accounting job.
    • Courtney has a cognitive disability that makes it difficult for her to comprehend complex user interfaces. She is completing an online job application. It is not clear where she should enter her phone number. She mouses over a blank box and sees a tooltip that says "home phone number". She is able to complete the form.

1.10.2 Access to Element Hierarchy:

The user can determine the path of element nodes going from the root element of the element hierarchy to the currently focused or selected element. (Level AAA)

  • Intent of Success Criterion 1.10.2:
    Users who have difficulty working with a web page or document can use user stylesheets or scripts to modify page presentation or interaction so they can gain information or accomplish a task. Stylesheets and scripts may require the user to identify specific elements, element attributes, and element position in the hierarchy. The user agent can facilitate this process by allowing the user to navigate to an element, select it if it's not navigable, and query for element information. If this feature is not provided, the user may be forced to try to find the corresponding element in the source view or entire document tree.
  • Examples of Success Criterion 1.10.2:
    • Jack has low vision. He wants certain content on a web page to be displayed in a larger font, and wants to create a user style sheet that would modify its appearance. He needs to identify the class or ID of the particular element, so he selects the text he's interested in, opens the browser's debug window, which shows him that the selected text is an element with class "story" inside a paragraph inside a DIV with class "Premiere". He then knows the combination of classes and element types to specify in the user style sheet.

PRINCIPLE 2. Ensure that the user interface is operable

Implementing Guideline 2.1 - Ensure full keyboard access.

Summary: Users can operate all functions (2.1.1), and move focus (2.1.2) using just the keyboard. Users can activate important or common features with shortcut keys, (2.1.6), override keyboard shortcuts in content and user interface (2.1.4), escape keyboard traps (2.1.3), specify that selecting an item in a dropdown list or menu not activate that item (2.1.4) and use standard keys for that platform (2.1.5).

2.1.1 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 other input methods in addition to keyboard operation including mouse, touch, gesture and speech. (Level A)

  • Intent of Success Criterion 2.1.1:
    A user has many ways to input information into a computer or device, including mouse, keyboard, gesture, and speech. The keyboard paradigm is the most universal interface for text input ndash; even devices that do not have a keyboard (like mobile phones) support a software interface for them. A user should be able to navigate, read and use all of the web page or application without needing to use a mouse. Some users do not use a mouse. Others can only use a pointing device that uses the keyboard API. It's important that these users be able to interact with enabled components, select content, navigate viewports, configure the user agent, access documentation, install the user agent, and operate user interface controls, all entirely through keyboard input.
    User agents generally support at least three types of keyboard operation:
    1. Direct (e.g. keyboard shortcuts such a "F1" to open the help menu; see checkpoint 11.4 for single-key access requirements)
    2. Sequential (e.g. navigation through cascading menus)
    3. Spatial (e.g. when the keyboard is used to move the pointing device in two-dimensional visual space to manipulate a bitmap image)

    User agents should support direct or sequential keyboard operation for all functionalities. The user agent should offer a combination of keyboard-operable user interface controls (e.g. keyboard operable print menus and settings) and direct keyboard shortcuts (e.g. to print the current page).
  • Examples of Success Criterion 2.1.1:
    • Amal has a medical condition that prevents him from using the mouse. Jeremy finds it difficult or impossible to use a mouse or keyboard and therefore uses speech to control the keyboard. Tanya is blind and uses a screenreader and must be able to accomplish all tasks with the keyboard. Jamie uses a switch device to control the computer. Each of these users must be able to do the following through keyboard alone, speech input alone, or switch device alone:
      • Select content and operate on it. For example, if it is possible to select rendered text with the mouse and make it the content of a new link by pushing a button, these users also need to be able to do so through the keyboard and other supported devices. Other examples include cut, copy, and paste.
      • Set the focus on viewports and on enabled elements.
      • Install, configure, uninstall, and update the user agent software.
      • Amal, Jeremy and Jamie use the graphical user interface menus even though they cannot use the mouse.
      • Fill out forms.
      • Access documentation.
    • Amal is reading a web page where the author used the CSS overflow property to constrain the size of a block of content. Amal's browser provides scroll bars to display text that overflows the container. He uses the keyboard to enter the element and operate the scrollbars to read all the content, he then uses the keyboard to return focus to the main web page. (see 2.1.3 No Keyboard Trap)
    • Tanya needs to use a volume control widget to change the volume on a video she is watching. She use the keyboard to navigate to the widget, uses the arrow keys to increase the volume, then uses the keyboard to navigate to the comments below the video player.
    • Cade has low vision. He can't identify an icon and so he needs to read its alternative text. Mouse users could hover the mouse over the icon and have its alternative text displayed as a pop-up or tooltip, but Cade cannot use a mouse. He uses the keyboard to move focus to the icon. The browser automatically displays the "hover" tooltip, or allows him to press a key to have it displayed.
    • Jeremy is a speech-input user who cannot use his hands to control his computer. It is much easier for him to speak keyboard shortcuts then click on an icon in a new program. He needs to be able to see tooltips to discover keyboard shortcuts without having to use the mouse.
    • [mobile] Karen has muscular dystrophy and cannot easily use the onscreen keyboard to navigate Web pages on her mobile phone. Instead, she uses simple gestures to move between elements on the page. As focus moves from one element to another, there is a visble focus indicator.

2.1.2 Keyboard Focus:

Every viewport has an active or inactive keyboard focus at all times. (Level A)

  • Intent of Success Criterion 2.1.2:
    Both the user and some types of assistive technology need to know what will be affected by any keyboard input, so it's important that they be able to tell which window, viewport, and controls have the keyboard focus at any time. This applies whether window and viewport are active (active keyboard focus) or inactive (inactive keyboard focus). Even when a window is inactive, it can be affected by simulated keyboard input sent by assistive technology tools. Active keyboard focus is indicated to the user by focus cursors and text cursors, as required by Guidelines 1.3, and made available to assistive technology, as required by Success Criterion 4.1.6.
  • Examples of Success Criterion 2.1.2:
    • Amal has a medical condition which prevents him from using the mouse. He launches a web browser and navigates to a web page. Initially the keyboard focus is on the entire document, which is exposed to assistive technology, but there is no visible cursor. When Alan presses the tab key, the focus moves to the first link on the web page, and a cursor in the form of a dotted rectangle appears around that link.
    • Amal launches a web browser and navigates to a web page that has an enabled edit field. The browser places the keyboard focus on the edit field so Amal can immediately start entering text, and its location is shown using a text cursor (usually a vertical line or i-beam). As he types, the text cursor moves to show where the next character will appear. If Amal activates another window, the browser may hide the cursor in the now inactive window, but its location is still available to assistive technology.
    • Raymond has low vision. As the keyboard focus moves from one control to another, or one window to another, his screen enlarger utility detects the focus change and pans its viewport to keep the focus location visible.
    • [mobile] Jeremy is a speech-input user who cannot use his hands to control his tablet. He opens a webpage using a speech command. The webpage has a search field, and normally comes up with the keyboard focus in the search field. Jeremy sees the indicator in the search field and knows he does not have to navigate to the search field before saying a search term.
    • [mobile] Erin has dyslexia which often causes her to confuse directions. She uses gestures to navigate her mobile phone. As focus moves from one element to another, there is a visble focus indicator, which allows her to find the focus easily.

2.1.3 No Keyboard Trap:

If keyboard focus can be moved to a component using a keyboard interface (including nested user agents), then focus can be moved away from that component using only a keyboard interface. If this requires more than unmodified arrow or Tab keys (or standard exit methods like Escape), users are advised of the method for moving focus away. (Level A)

  • Intent of Success Criterion 2.1.3:
    If users can put focus on an element, they can remove focus and move on to the next element. This is often not possible with embedded objects. The user agent needs to provide a way to always return to the previous or next element in the content, or a known location such as the address bar. The user agent also needs to take control back from the embedded object, no matter what it is.
  • Examples of Success Criterion 2.1.3:
    • Ari has repetitive strain injuries that are exacerbated when he uses the mouse. He is using a video hosting site where each page hosts a nested media player. He presses Tab until the focus in on the media player, then presses Enter to activate and put the keyboard focus on it. When he's finished watching the video, he presses Tab to navigate to the comments below the video, but cannot get the focus to leave the video player. He presses Alt+Left to return to the previous page, but that also fails because the video player is consuming those keystrokes. Luckily, Ari knows that Shift+Esc will return focus from a nested user agent, with or without its cooperation. Thus, even a badly behaved nested user agent cannot prevent Ari from getting on with his work.
    • Ari moves the focus to a toolbar extension that does not relinquish control back to the user agent. He presses Alt-D to move the focus to the address bar.
    • Mary is a blind user who does not use the mouse. She moves the focus to an embedded scripted application that was poorly programmed. She presses a documented key combination –  Alt+N – to override the scripting and move the focus to the next element in the content.
    • Katan cannot use the mouse and has trouble with short-term memory. He is using a virtual machine. The escape sequence is Shift+Ctrl+Escape. Every time Katan opens the program, it briefly shows the escape sequence near the top right corner of the screen.  The virtual machine also has an Exit option in its menu system. The Escape keystrokes are also indicated on the menu.

2.1.4 Separate Selection from Activation:

The user can specify that focus and selection can be moved without causing further changes in focus, selection, or the state of controls (including activation), by either the user agent or author content. (Level A)

  • Intent of Success Criterion 2.1.4:
    People do not expect side effects when moving the keyboard focus regardless of whether the side effect is caused by the user agent or author content. If users fail to notice side effects, they could end up doing something disastrous. This is especially likely for users of assistive technology who cannot see changes happening elsewhere on the screen. Users may also find it confusing or disorienting if the effect causes unexpected focus movement or changes in context. If the user agent does implement side effects to keyboard navigation, it is recommended that it provide a user preference setting to disable them. However, in some cases it may be more appropriate to provide a separate navigation mechanism that avoids side effects, such as allowing the user to hold down the Ctrl key while navigating to avoid changing selection or choice. Note: It may not be possible for the user agent to detect or prevent side effects implemented by scripts in the content, but the user agent is required to prevent side effects that are under its control.
  • Examples of Success Criterion 2.1.4:
    • Murray uses a screen magnifier that allows him to see the element with the focus and a small area around it. He explores a dialog box by repeatedly pressing the Tab key to move to, and read each control in succession. He uses the arrow keys to navigate through a dropdown menu. When he moves the focus to the first option he goes to that page. He wants to navigate to the third selection, but can't get there. Fortunately, the platform also has a convention that holding down the Ctrl key while navigating that moves the focus without changing selection or option choice. Murray uses this while exploring. His web browser implements its own form controls and navigation mechanisms rather than using the platform's infrastructure, but also implements this Ctrl-key mechanism for users like Murray.
    • [mobile] Ari uses Voiceover on his iPhone to navigate a webpage. He selects an item and is able to activate the element using gestures. This requires sufficient screen real estate to perform gestures without changing focus.

2.1.5 Follow Text Keyboard Conventions:

The user agent follows keyboard conventions for the operating environment. (Level A)

  • Intent of Success Criterion 2.1.5:
    Keyboard users rely on the user agent to provide keyboard support that is full-featured and consistent among applications. Following platform conventions for keyboard access helps ensure that the functions that people rely on are not accidentally omitted. In addition, making these inputs consistent within and across programs greatly reduces learning curve, cognitive load, and errors. User agents are encouraged to add keyboard commands when the commands provide additional features or benefit for users. User agents should avoid omitting the standard commands, or assigning them to different keys.
  • Examples of Success Criterion 2.1.5:
    • Jack is blind and uses a screenreader. He edits blog posts in his browser's text area control, and can use the same keys for navigation, editing , and formatting that he's used to using in other applications on the platform (e.g. arrow keys, commands to move to the beginning and end of the line, cut, copy, paste, ctrl-b for bolding).
    • Jack's user agent uses a custom tree control showing a hierarchical outline view of the document headings. He can navigate within that control using the same keys as work in the native tree controls used in other applications (e.g. up, down, left and right arrow keys, and navigating directly to entries by typing the beginning of their text).
    • Jack puts his browser into a caret browsing mode so he can move the text cursor through the text on the page. The browser supports the same keys for navigation and editing as are used in other applications.

2.1.6 Efficient Keyboard Access:

The user agent user interface includes mechanisms to make keyboard access more efficient than sequential keyboard access. (Level A)

  • Intent of Success Criterion 2.1.6:
    Efficient keyboard navigation is especially important for people who cannot easily use a mouse, are quickly fatigued, or find it difficult to memorize the menu structure for sequential navigation. This is important in all types of user agent environments.
    • In a browser: A browser provides keyboard shortcuts for its menu functions as well as access keys in the design of its menus and dialog boxes. The choice of shortcut keys follows platform conventions where applicable (e.g. for open document, save document, cut, copy, paste).
    • In a mobile environment: A social networking application on a mobile device has only a very few keyboard shortcuts available on its targeted devices. These few keyboard shortcuts are used for the most commonly accessed functions of the application (e.g. home, list of friends).
    • In a media player: A embedded media player provides shortcut keys for commonly used functions (e.g. pause and play).
  • Examples of Success Criterion 2.1.6:
    • Jack is blind and uses a screenreader. He opens his browser to write his email. He uses a shortcut to start a new message. He uses the same CTRL-N command he uses in his desktop email application.
    • Jean has a medical condition that makes it difficult to visualize complex visual structures like dropdown menus. She is writing a new blog entry and discovers that her blogging application has updated and all the menus have changed. She cannot find the menu option to format the text, but is pleased to find that CTRL-B still works to bold the text she wants.
    • [mobile] George is blind and uses the gestures on his mobile device to move focus to the top of the page, return to the previous web page and activate links.

Implementing Guideline 2.2 - Provide sequential navigation

Summary: Users can use the keyboard to navigate sequentially (2.2.3) to all the operable elements (2.2.1) in the viewport as well as between viewports (2.2.2). Users can optionally disable wrapping or request a signal when wrapping occurs (2.2.4).

2.2.1 Sequential Navigation Between Elements :

The user can move the keyboard focus backwards and forwards through all recognized enabled elements in the current viewport. (Level A)

2.2.2 Sequential Navigation Between Viewports:

The user can move the keyboard focus backwards and forwards between viewports, without having to sequentially navigate all the elements in a viewport. (Level A)

2.2.3 Default Navigation Order:

If the author has not specified a navigation order, the default sequential navigation order is the document order. (Level A)

2.2.4 Options for Wrapping in Navigation

The user can prevent sequential navigation from wrapping the focus at the beginning or end of a document, and can request notification when such wrapping occurs. (Level AA)

Implementing Guideline 2.3 - Provide direct navigation and activation

Summary: Users can navigate directly (e.g. keyboard shortcuts) to important elements (2.3.1) with the option of immediate activation of the operable elements (2.3.3). Display commands with the elements to make it easier for users to discover the commands (2.3.2 & 2.3.4). The user can remap and save direct commands (2.3.5).

2.3.1 Direct Navigation to Important Elements:

The user can navigate directly to any important elements (e.g. structural or operable) in rendered content. (Level AA)

2.3.2 Present Direct Commands from Rendered Content (enhanced):

The user can have any recognized direct commands in rendered content (e.g. accesskey, landmark) be presented with their associated elements (e.g. Alt+R to reply to a web email). (Level AA)

2.3.3 Direct activation of Enabled Elements:

The user can move directly to and activate any enabled element in rendered content. (Level A)

2.3.4 Present Direct Commands in User Interface:

The user can have any direct commands in the user agent user interface (e.g. keyboard shortcuts) be presented with their associated user interface controls (e.g. "Ctrl+S" displayed on the "Save" menu item and toolbar button). (Level AA)

2.3.5 Customize Keyboard Commands:

The user can override any keyboard shortcut including recognized author supplied shortcuts (e.g. accesskeys) and user agent user interface controls, except for conventional bindings for the operating environment (e.g. arrow keys for navigating within menus). The rebinding options must include single-key and key-plus-modifier keys if available in the operating environment. The user must be able to save these settings beyond the current session. (Level AA)

Implementing Guideline 2.4 - Provide text search.

Summary: Users can search rendered content (2.4.1) forward or backward (2.4.2) and can have the matched content highlighted in the viewport (2.4.3). The user is notified if there is no match (2.4.4). Users can also search by case and for text within alternative content (2.4.5).

2.4.1 Text Search:

The user can perform a search within rendered content (e.g. not hidden with a style), including rendered text alternatives and rendered generated content, for any sequence of printing characters from the document character set. (Level A)

  • Intent of Success Criterion 2.4.1:
    The find or text search function in a user agent allows the user to easily locate desired information in rendered content. People who read or navigate slowly or with difficulty due to a disability rely more heavily on the ability to search for text, rather than scanning or reading an entire document to find it. The ability to search alternative content allows screen reader users to find content they heard on their speaker. Users with hearing impairments use Text Search as an efficient method of jumping to specific points in a video. Users who find it difficult to use the mouse or keyboard and have to limit their physical operations will save movements using search.
  • Examples of Success Criterion 2.4.1:
    • Marvin has a dexterity impairment. He needs to move efficiently to specific text in the document.  The user agent provides a local search function that is available using speech commands. Marvin says "find box," a text box with a search button appears. He speaks the word he is looking for, and says "enter", which executes the search function.
    • Betty, who has low vision, is attempting to create a user stylesheet for a site. She need to know the 'class' attribute value for navigation headers. Betty gets the source view of the current page and searches for the specific phrase used in a navigation list to find the class associated with  the navigation element
    • Joe, a user with a distraction disorder, is taking an online exam. He is working on the 6th question when he realizes he wrote something wrong in the essay on question 2. He uses the search function in the browser to find the text in error inside the textarea of question 2.
    • Sam is a screen reader user. He has images off and the alternative content for images  is revealed. He wants to send the flow chart image on the page to a collegue. Sam searches for the word "flowchart" that he heard spoken as part of the 'alt' text for the image. He then uses the context menu to select the address of the image and sends it to a colleague.
    • Agnes is deaf. She is watching a video with captions turned on. Agnes uses the search function to seach through the captions and jump to the point in the video where the search term is located in the time line.
    • Greta has a reading impairment. She is trying to efficiently locate some information in a large, detailed graphic. She is using a browser with native support for SVG. When Greta searches for a term, text within the SVG is searched along with the HTML content.

2.4.2 Find Direction:

The user can search forward or backward in rendered content. (Level A)

  • Intent of Success Criterion 2.4.2:
    People who read slowly or with difficulty due to a disability rely more heavily on the ability to search for the text they're looking for, rather than scanning or reading an entire document to find it. Local find in a user agent allows the user to easily locate desired information in rendered content. The ability to search for alternative text content allows screen reader users to find content they heard on their speaker. Users with hearing impairment use text search as an efficient method of jumping to specific points in a video.
  • Examples of Success Criterion 2.4.2:
    • A user has been reading through a web page and wants to quickly locate a phrase previously read. When opening the browser's page search feature, the user has options to search forward and backward from the current location. If the search reaches an endpoint in the document, the user is notified that the search has wrapped around, such as with an alert box or other indication.

2.4.3 Match Found:

When a search operation produces a match, the matched content is highlighted, the viewport is scrolled if necessary so that the matched content is within its visible area, and the user can search from the location of the match. (Level A)

  • Intent of Success Criterion 2.4.3:
    It is important for the user to easily recognize that a search term has been found and that the term is revealed to the user in context. The user agent moves the viewport to include the found term and the term is highlighted in some fashion.The point of regard is the found element in the viewport. Any subsequent searches on the same term or other navigation tasks (e.g tabbing to the next anchor) begin from this point.
  • Examples of Success Criterion 2.4.3:
    • Jules is low vision and uses a magnified screen. She frequently searches for terms that appear multiple times in a document that contains a lot of repetition. It is important that the viewport moves and if necessary her screen scrolls after each search so she can easily track where she is in the document.

2.4.4 Alert on Wrap or No Match:

The user can be notified when there is no match to a search operation. The user can be notified when the search continues from the beginning or end of content. (Level A)

  • Intent of Success Criterion 2.4.4:
    It is important for users to get clear, timely feedback so they don't waste time waiting or, worse, issue a command based on a wrong assumption. It is important during a search that users are informed when there is no match or that the search has reached the beginning of the document.
  • Examples of Success Criterion 2.4.4:
    • Dennis uses a screen reader. As soon as he gets a message that there is no match he goes on to search for something else, however, if he does not get a message he wastes time retrying the search to make sure the entire document has been searched.

2.4.5 Search alternative content:

The user can perform text searches within textual alternative content (e.g. text alternatives for non-text content, captions) even when the textual alternative content is not rendered onscreen. (Level AA)

  • Intent of Success Criterion 2.4.5:
    Authors frequently provide alternative content to meet web content accessibility guidelines. Users with disabilities may experience this as part of the content. The purpose of this success criteria is to ensure that text search allows users to locate this content, even if it is not visibly rendered.
  • Examples of Success Criterion 2.4.5:
    • Rhonda typically browses the web with images turned off so she sees alternative text rendered in place of images. She visits a favorite website on a friend's computer and wants to find a link to her favorite artist's photo gallery. She searches for the artist's name on her friend's computer. The alt text is not displayed, but the artist's image is highlighted because her 'text search' command has associated the alt text with the image.
    • Dennis remembers a phrase in a captioned training movie that he wants to replay. He goes to the web page with the embedded movie. He types in the phrase in the "Find" box and the user agent moves to the point in the movie where the phrase is found.

Implementing Guideline 2.5 - Provide structural navigation.

Summary: Users can view (2.5.1), navigate (2.5.2), and configure the elements used in navigating (2.5.3) content hierarchy.

2.5.1 Location in Hierarchy:

When the user agent is presenting hierarchical information, but the hierarchy is not reflected in a standardized fashion in the DOM or platform accessibility services, the user can view the path of nodes leading from the root of the hierarchy to a specified element. (Level AA) .

2.5.2 Navigate by structural element:

The user agent provides at least the following types of structural navigation, where the structure types exist:(Level AA)

  1. by heading
  2. within tables

2.5.3 Configure Elements for Structural Navigation:

The user can configure sets of important elements (including element types) for structured navigation and hierarchical/outline view. (Level AAA)

Implementing Guideline 2.6 - Provide access to event handlers

Summary:Users can interact with web content by mouse, keyboard, voice input, gesture, or a combination of input methods. Users can discover what event handlers (e.g. onmouseover) are available at the element and activate an element's events individually (2.6.1).

2.6.1 Access to input methods:

The user can discover recognized input methods explicitly associated with an element, and activate those methods in a modality independent manner. (Level AA)

  • Intent of Success Criterion 2.6.1:
    Users interacting with a web browser may use one or more input technologies including keyboard, mouse, speech, touch, and gesture. Sometimes a web page is scripted so that it assumes and requires an input method that is not available to the user, such as handling drag events for a user relying solely on the keyboard. In those cases, the user needs to determine what methods are available and activate that element with a modality independent method.

    In addition, any one input method should not hold back another. For instance, people who don't use a mouse shouldn't have to map their input methods to the same steps a mouse user would take. The user agent can constrain steps such as not allowing a mouseup before a mousedown.
  • Examples of Success Criterion 2.6.1:
    • Jeremy cannot use a mouse. He needs to activate a flyout menu that appears when he hovers the mouse over a button. He navigates to the button and pulls up its context menu, which includes an "Inputs" submenu that lists the available input methods (e.g. events that were registered for this element: click, double-click, swipe left, and hover). Then he chooses the "Hover" command.
    • Ken is a speech input user. In order to get his work done in a reasonable amount of time and without overtaxing his voice he uses a single speech command phrase to move the mouse up, left and click.
    • Karen cannot use a mouse. She clicks a single key to activate both events for link that has an onmousedown and an onmouseup event link.
    • [mobile] Ingrid has low vision. When navigating a page with a smartphone, she can chooose a bluetooth keyboard or gestures to operate all of the controls within the page.

Implementing Guideline 2.7 - Configure and store preference settings

Summary: Users can restore preference settings to default (2.7.2), and accessibility settings persist between sessions (2.7.1). Users can manage multiple sets of preference settings (2.7.3), and adjust preference setting outside the user interface so the current user interface does not prevent access (2.7.4). It's also recommended that groups of settings can be transported to compatible systems (2.7.5).

2.7.1 Persistent Accessibility Settings:

User agent accessibility preference settings persist between sessions. (Level A)

  • Intent of Success Criterion 2.7.1:
    When a user has customized settings within the user agent to maximize accessibility, customization is saved between browsing sessions. The user can automatically use those settings in subsequent browsing sessions.
  • Examples of Success Criterion 2.7.1:
    • Lynn has moderately low vision. She sets the default zoom level, font size, and colors to make pages easier for her to read. Because those settings are persistent, she doesn't have to manually restore her settings every time she starts the browser.
    • Brian has to adjust settings in his browser to make it fully compatible with his speech input system. It's difficult for him to adjust these settings, since he can't fully operate the browser until it's complete. Once his browser is configured this way, he relies on it staying in that configuration even if he upgrades the browser or restarts his system.
    • [mobile] Betty has low vision. She customizes her mobile browser's color and font settings to make text much easier to read. Her browser incorporates a cloud-based profile so she can retain her settings across her browsing sessions and her desktop and tablet browsers.

2.7.2 Restore all to default:

The user can restore all preference settings to default values. (Level A)

  • Intent of Success Criterion 2.7.2:
    For some users, it may be difficult to easily recall all modified settings. Others may find it difficult to navigate to each modified setting, especially if a particular setting impacts their ability to do so. Users who customize settings may find that their chosen settings are not suitable and decide to restore these settings to default values. This success criteria allows a user to easily restore all preference settings to default values using a single function or action.
  • Examples of Success Criterion 2.7.2:
    • Ron is blind. He accidentally changes a browser setting that makes his browser incompatible with his screen reader, preventing him from changing it back. He restarts his browser using a command line option that starts in the default configuration. From there he can adjust the setting that caused him problems.
    • [mobile] Kathy has repetive stress injuries which makes it painful to experiment with settings. She accidently turns on a zoom feature on her smartphone and cannot figure out how to turn it off. She gestures to navigate to the preferences menus and selects a command to reset preferences to default.

2.7.3 Multiple Sets of Preference Settings:

The user can save and retrieve multiple sets of user agent preference settings. (Level AA)

  • Intent of Success Criterion 2.7.3:
    Some users may need to change their setting preferences under circumstances such as varying levels of user fatigue, changes in environmental noise, or changing lighting conditions. Providing an easy method for saving and switching between sets of preferences helps the user complete intended tasks.
  • Examples of Success Criterion 2.7.3:
    • [mobile] Hiroki has low vision. When he is carrying his tablet computer he operates it with the built-in touchscreen. When at his desk he links it to a Bluetooth keyboard and mouse, and redirects the display to a large computer monitor. The browser allows him to quickly switch between different configurations for different environments.
    • Davy has moderately low vision and must adjust the contrast of media to different levels for day and night. Because this requires a multiple steps, he has two user profiles, one for each environment.
    • Aaron has repetitive strain injury. He usually uses a keyboard and mouse, but when his repetitive strain injury is bothering him he prefers to use the keyboard and avoid using the mouse as much as possible. At those times he users his browser's user preference profiles to load a different configuration that’s optimized for the keyboard.

2.7.4 Change preference settings outside the user interface:

The user can adjust any preference settings required to meet the User Agent Accessibility Guidelines (UAAG) 2.0 from outside the user agent user interface. (Level AA)

  • Intent of Success Criterion 2.7.4:
    Users with disabilities may not be able to use a user agent in a particular configuration. This can occur during setup when default settings don't meet their needs, or after someone changes an option. If users cannot change the settings from the user interface, they need a way to adjust or reset those options from outside the user agent. The user agent can accomplish this in multiple including including detecting and implementing the platform accessibility settings, providing an external file to modify, providing access to settings from a separate utility program, providing accessibility options in the installation program, or providing command-line switches to change the user agent's behavior.

    Note: User agents are encouraged to allow all user preferences to be adjusted.
  • Examples of Success Criterion 2.7.4:
    • Aosa is blind. Her web browser is incompatible with her screen reader unless she changes one of the browser's advanced settings. Because she cannot activate and use the appropriate dialog box until the setting is changed, she needs to start the browser using a dedicated command-line switch that changes the behavior.
    • Bintu is deaf and enjoys watching captioned videos. Since different video players may not have accessible settings, she sets her browser to always display captions, knowing the video player will respect the browser's request to display captions. In this way the options in one user agent (the embedded video player) are set outside its user interface by being set in another program (the hosting browser).
    • Sasha requires high contrast to be able to discriminate the shape of letters. She has set the accessibility preferences on her computer to use high contrast mode. When she launches her browser, it detects that she is using high contrast and adjusts the font and color settings for its user interface to reflect those settings.
    • Justin has an attention deficit disorder. He is setting up his new e-book reader and is interrupted while setting the default font colors, then finds he accidentally set his background and font color to white on white. He cannot read the settings screen to recover his default settings, so he exits the reader and follows the instructions on the vendor's website to edit the "settings.ini" file to adjust the colors. He then restarts the reader with the corrected color settings.
    • [mobile] Jan is easily confused by new interfaces. Using the screen reader capabilities on her mobile phone she changes the interface of the updated browser, then can't figure out how to undo them. She uses an app from the browser developer to reset the browser settings to default.

2.7.5 Portable Preference Settings:

The user can transfer all compatible user agent preference settings between computers. (Level AAA)

  • Intent of Success Criterion 2.7.5:
    Configuring a user agent may be a complex and time-consuming task. Some users hire assistive technology professional trainers to do their system setup. Users who have spent time customizing accessibility preferences to meet their requirements need to migrate preference setting to other compatible devices. Schools and universities also need to maintain accessibility settings across multiple machines.
  • Examples of Success Criterion 2.7.5:
    • Lori is a rehabilitation specialist who works with clients to customize electronics and assistive technology to their needs. She sets up a new system for Ray, and saves a backup of the accessibility setting for Ray and for herself. She keeps electronic backups of her clients' configurations that she can quickly email to them if they lose their settings.
    • Ray is blind and uses a screenreader on his desktop and a voice application on his phone. He sets up web-based email application accessibility preferences on his phone. The preferences are automatically reflected in the desktop version of that web-based email application.
    • Trisha is a 4th grader with low vision. When she changes classrooms, she carries a USB stick containing her accessibility settings so she and her teachers do not have to use class time customizing her computer.
    • [mobile] Betty is a low vision user and has a highly customized color palette defined in her browser. She saves her customizations to a cloud-based storage service, so her preferences can be transferred to the other desktop and mobile browsers that she uses.

Implementing Guideline 2.8 - Customize display of GUI controls

Summary: It's recommended that users can add, remove and configure the position of graphical user agent controls and restore them to their default settings (2.8.1).

2.8.1 Customize display of controls representing user interface commands, functions, and extensions:

The user can customize which user agent commands, functions, and extensions are displayed within the user agent's user interface as follows:(Level AA)

  1. Show: The user can choose to display any controls available within the user agent user interface, including user-installed extensions. It is acceptable to limit the total number of controls that are displayed onscreen.
  2. Simplify: The user can simplify the default user interface by choosing to display only commands essential for basic operation (e.g. by hiding some control).
  3. Reposition: The user can choose to reposition individual controls within containers (e.g. Toolbars or tool palettes), as well as reposition the containers themselves to facilitate physical access (e.g. To minimize hand travel on touch screens, or to facilitate preferred hand access on handheld mobile devices).
  4. Assign Activation Keystrokes or Gestures: The user can choose to view, assign or change default keystrokes or gestures used to activate controls.
  5. Reset: The user has the option to reset the containers and controls to their original configuration.
  • Intent of Success Criterion 2.8.1:
    The user needs to control which user interface elements are visible and usable, where elements are visually located on the screen, and where elements fall in the navigation order. In some cases adjusting whether an element is visible and usable may involve installing or uninstalling a component — or merely showingor hiding it — depending on the user agent and the specific component. This can reduce keystrokes, bring buttons into view that are hidden by default or otherwise allow the user to interact with the user agent in a more efficient fashion. Users with dexterity impairments or mobility impairments may have problems making the large movements required to select between non-adjacent controls which they need to use frequently. Similarly, users with low vision may have to move their magnified view-port excessively to see frequently used controls. Enabling these controls to be situated together removes some of the strain faced by these users, and increases productivity as task completion times are decreased.
  • Examples of Success Criterion 2.8.1:
    • Martin accesses the computer by pressing keys with a stick held in his mouth. He gets around the user agent with taps on the tab and arrow keys. The button for printing a web page is the last button on a toolbar. This button requires six presses of a right arrow key. This is the only button Martin uses on the toolbar. Using a preferences dialog, Martin is able to configure this toolbar to only show the Print button, reducing the number of time he must press with his mouthstick.
    • [mobile] Laura has one hand. When she holds her mobile phone in her left hand, she must use her thumb to press the controls. She configures her mobile apps so that the toolbars are at the left side or the bottom, so she can reach them.
    • Caraway has a repetitive strain injury. She uses speech input. The speech program automatically clicks toolbar items that she speaks. In programs she uses a lot she removes toolbars that she doesn't use in order to reduce the probably that the speech program will interpret text input as a toolbar command and click something Caraway does not intend.
    • Zelda has a brain injury that leaves her easily confused. She reorders the toolbars in her web-based word processing and layout programs so that the text color and highlight color icons are in the same order and she can rely on habit to click the correct button no matter what program she is in. Without this ability to reorder she finds herself constantly clicking the wrong button because they are configured differently by default in the different programs.
    • Devon is easily distracted. In programs he uses frequently, he removes toolbars he does not use in order to cut down on distractions.
    • Sally has memory issues that make it difficult to memorize keyboard shortcuts. She has aligned the keyboard shortcuts in several programs so she doesn't have to memorize as many shortcuts. She reminds herself of keyboard shortcuts by hitting a key that gives her a list of keyboard shortcuts in the current program.
    • [mobile] Linda has rheumatoid arthritis and finds it difficult to perform the pinch gesture that's commonly used to zoom on mobile phones. She changes the default gesture for zooming to a gesture she can more easily do. Linda's left hand is less damaged than her right hand. She moves a common control from the right side of the screen to the left side of the screen to make it easier to access with her left hand.
    • [mobile] Jennifer is blind. She sometimes configures apps on her friend Linda's mobile phone. When Jennifer picks up Linda's mobile phone, she turns on the built-in voice application so she so she can quickly find her way around Linda's phone. When Jennifer is done, she changes the controls back to Linda's original settings..


Implementing Guideline 2.9 - Allow time-independent interaction.

Summary: Users can extend the time limit for user input when such limits are controllable by the user agent (2.9.1); by default, the user agent shows the progress of content in the process of downloading (2.9.2).

2.9.1 Adjustable Timing:

Where time limits for user input are recognized and controllable by the user agent, the user can extend the time limits. (Level A)

  • Intent of Success Criterion 2.9.1:
    People who use assistive technology and those who require more time to read, understand, or act upon content (e.g. individuals with reading disabilities or non-native readers of the presented language) should be able to extend or override any content or author imposed presentation or interaction time limits.
  • Examples of Success Criterion 2.9.1:
    • Lee has low vision and uses a screen magnifier. She goes to a news organization website with a home page region that cycles featured stories every 3 seconds. Lee requires more than three seconds to read the news item and select it. Lee uses a global setting to freeze all timed events. She uses another keyboard command to resume the timed presentation.
    • Jennifer is blind and uses a screen reader. She is logged into a financial services website and is reading the site's detailed privacy policy. The site terminate sessions that have been inactive for 5 minutes. A prompt appears warning that Jennifer will be logged off. Jennifer selects an option in her browser that automatically responds to those prompts.

2.9.2 Retrieval Progress:

By default, the user agent shows the progress of content retrieval. (Level A)

Implementing Guideline 2.10 - Help users avoid flashing that could cause seizures.

Summary: To help users avoid seizures, the default configuration prevents the browser user interface and rendered content from flashing more than three times a second above a luminescence or color threshold (2.10.1), or does not flash at all (2.10.2).

2.10.1 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)

  • Intent of Success Criterion 2.10.1:
    Seizures due to photosensitivity can occur when there is a rapid series of general flashing, or a red flash. A potentially harmful flash occurs when there is a pair of significantly opposing changes in luminance. A transition to or from a saturated red is potentially harmful irrespective of luminance.
  • Examples of Success Criterion 2.10.1:
    • Jamie has photosensitive epilepsy. He checks a game website that has just added a flashing red icon to advertise their newest product. Because his browser's default configuration protects him from harmful flashing, the potentially harmful flashing does not occur on his machine.
    • Jamie visits a weather web site that uses flashing to indicate a tornado warning. In order to avoid triggering seizures, the flashing is limited to fewer than three times per second, and, to be extra cautious, it is not red.

2.10.2 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)

  • Intent of Success Criterion 2.10.2:
  • Seizures due to photosensitivity can occur when there is a rapid series of general flashing, or a red flash. People who are particularly senstive to flashing can be harmed by any level of flashing. 2.10.2 has the same effect as 2.10.1, going further to ensure that more sensitive users can traverse the Web without potentially harmful effects.
  • Examples of Success Criterion 2.10.2:
    • Alfred has photosensitive epilepsy and is particularly sensitive to flashes. He checks a game website that has just added a flashing red icon to advertise their newest product. His browser's default configuration protects him from all flashing, so the potentially harmful flashing does not occur on his machine.

Implementing Guideline 2.11 - Provide control of content that may reduce accessibility.

Summary: The user can present placeholders for time-based media (2.11.1) and executable regions (2.11.2), or block all executable content (2.11.3); adjust playback (2.11.4), stop/pause/resume (2.11.5), navigate, (2.11.6) and specify tracks for prerecorded time-based media (2.11.8); and adjust contrast and brightness of visual time-based media (2.11.9).

Applicability Notes:

Guideline 2.11 and its success criteria only apply to images, animations, video, audio, etc. that the user agent can recognize.

2.11.1 Time-Based Media Load-Only:

The user can override the play on load of recognized time-based media content such that the content is not played until explicit user request. (Level A)

2.11.2 Execution Placeholder:

The user can 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)

2.11.3 Execution Toggle:

The user can turn on/off the execution of executable content that would not normally be contained within a particular area (e.g. Javascript). (Level A)

2.11.4 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)

  1. The user can adjust the playback rate of the time-based media tracks to between 50% and 250% of real time.
  2. Speech whose playback rate has been adjusted by the user maintains pitch in order to limit degradation of the speech quality.
  3. Audio and video tracks remain synchronized across this required range of playback rates.
  4. The user agent provides a function that resets the playback rate to normal (100%).

2.11.5 Stop/Pause/Resume Time-Based Media:

The user can stop, pause, and resume rendered audio and animation content (including video, animated images, and changing text) that last three or more seconds at their default playback rate. (Level A)

2.11.6 Navigate Time-Based Media:

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)

2.11.7 Semantic Navigation of Time-Based Media:

The user can navigate by semantic structure within the time-based media, such as by chapters or scenes present in the media (Level AA).

2.11.8 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, overriding global default settings, such as captions or audio descriptions. (Level AA)

2.11.9 Video Contrast and Brightness:

Users can adjust the contrast and brightness of visual time-based media. (Level AAA)

Implementing Guideline 2.12 - Other Input Devices

Summary: For all input devices supported by the platform, the user agents should let the user perform all functions aside from entering text (2.12.2), and enter text with any platform-provided features (2.12.1). If possible, it is also encouraged to let the user enter text even if the platform does not provide such a feature (2.12.3).

2.12.1 Support Platform Text Input Devices:

If the platform supports text input using an input device, the user agent is compatible with this functionality. (Level A)

2.12.2 Operation With Any Device:

If an input device is supported by the platform, all user agent functionality other than text input can be operated using that device. (Level AA)

2.12.3 Text Input With Any Device:

If an input device is supported by the platform, all user agent functionality including text input can be operated using that device. (Level AAA)

PRINCIPLE 3: Ensure that the user interface is understandable

Implementing Guideline 3.1 - Help users avoid unnecessary messages.

Summary: Users can turn off non-essential messages from the author or user-agent.

3.1.1 Reduce Interruptions:

The user can avoid or defer recognized non-essential or low priority messages and updating/changing information in the user agent user interface and rendered content.(Level AA)

  • Intent of Success Criterion 3.1.1:
    It's important that users be able to avoid unnecessary messages. Messages designed to inform the user can be a burden to users for whom pressing keys is time-consuming, tiring, or painful. Similarly, users with some cognitive impairments find it difficult to deal with constant distractions caused by updating visual or audio information, and would prefer to hide unnecessary updates.
  • Examples of Success Criterion 3.1.1:
    • Randall has repetitive strain injuries. He finds pop-up messages difficult. Randall has set the option to receive updates only on request. This way, he can request updates when he has a friend helping him, so that if the update changes the way his computer behaves, he can get help to adjust the computer settings or roll the update back.
    • Shirley has a cognitive disability and is distracted by the page flicker. A web page has a stock market ticker that is coded as having a WAI-ARIA low priority level, so she changes the browser's preference setting to indicate that regions with low priority level should not be automatically updated.

Implementing Guideline 3.2 - Help users avoid and correct mistakes.

Summary: Users can have form submissions require confirmation (3.2.1), go back after navigating (3.2.2), and have their text checked for spelling errors (3.2.3).

3.2.1 Form Submission:

The user can specify whether or not recognized form submissions must be confirmed. (Level AA)

  • Intent of Success Criterion 3.2.1:
    Users need to be protected against accidentally submitting a form. Some assistive technologies use the Enter key to advance to the next field. If the form is designed to submit on Enter, the user can unknowingly "submit on Enter" function.
  • Examples of Success Criterion 3.2.1:
    • Marka is blind and uses a screenreader. When she installs a web browser she selects an option to disable form submission on Enter. This allows her to complete forms from the banking website knowing that the form won't be submitted until she selects the submit button.
    • Ryan uses a mouse but his hand tremor makes him more likely to accidentally miss his intended target. Cancel and Submit (or OK) buttons are often next to each other, and Ryan has found that submitting a form inappropriately can cause serious complications, so he sets a browser option to always request confirmation of form submissions. As a result, when he clicks on a submit button the browser presents a message box asking "Are you sure you want to submit this form?" with larger, well-spaced buttons for Submit and Cancel.

3.2.2 Back Button

: The user can reverse recognized navigation between web addresses (e.g. standard "back button" functionality). (Level AA)

  • Intent of Success Criterion 3.2.2:
    Retracing a navigation step is important for users with cognitive issues that involve memory and attention. This is also important for users whose means of input is not 100% accurate, such as speech input users or users with fine motor challenges. It is also beneficial for users for whom navigation is time consuming, tiring, or painful, because it allows them to avoid having to re-enter long URLs.
  • Examples of Success Criterion 3.2.2:
    • Joe is a quadraplegic who is using speech input in a relatively noisy room. The program hears an especially loud word from across the room and interprets it as Joe saying "Enter" to click a selected link. Joe says "Go Back" to go back to the page he was on.
    • Mike's head injury leaves him easily distracted. He is in the middle of a search when the phone rings. When he comes back he says "Go Back" to go back to the original search page so he can reorient himself.
    • Ellen had a head injury that affects her short-term memory. She clicks on a link, and is interrupted by a colleague. When she goes back to her task she has forgotten what she was originally doing. It's important that she be able to retrace her steps to reorient herself.
    • Etta has moderately low vision and doesn't use assistive technoogy. She occasionally clicks on the wrong link. When she does so, she clicks the Back button in order to get back to where she had been.

3.2.3 Provide spell checking functionality:

User agents provide spell checking functionality for text created inside the user agent. (Level AA)

  • Intent of Success Criterion 3.2.3:
    Users with various disabilities benefit from spell checkers. The ability to check spelling is particularly important for users with disabilities such as dyslexia that significantly increase the likelihood of misspelled words. Spellcheckers also alert blind and low vision users to errors in text entry.
  • Examples of Success Criterion 3.2.3:
    • Amanda is dyslexic and frequently spells words incorrectly. She is able to correct words when alerted to the errors. She navigates to her web-based email application and composes a new message. The user agent alerts her to spelling errors as she is typing and she quickly corrects the mistakes and sends an error-free message.

3.2.4 Text Entry Undo:

The user can reverse recognized text entry actions prior to submission. (Level A)

Note: Submission can be triggered in many different ways, such as clicking a submit button, typing a key in a control with an onkeypress event, or by a script responding to a timer.

  • Intent of Success Criterion 3.2.4:
    Users who are blind, have visual impairments, or have cognitive disabilities may have difficulty determining the location of the keyboard focus. This puts them at risk of entering text in an undesired window or location. Users with mobility problems may have difficulty selecting a form field and may not notice an incorrect selection until they have entered text information.  These users need to be able to reverse a text entry ("Undo") prior to submission.
  • Examples of Success Criterion 3.2.4:
    • Billie is a paraplegic who uses speech input. When she is working from the main office, she is in a noisy location that can interfere with her speech input.  She is writing a blog entry and is almost finished when her speech input software incorrectly interprets some background noise as a "select all" command. This causes her to overwrite her entire blog entry with the next phrase she utters. She then uses the "undo" command to reverse the text entry and restore her blog entry.
    • George is blind and uses a screenreader.  He is entering financial information into his banking billpaying account.  He types the first few letters of the payee from a long list. When George reviews the selection prior to pressing "submit", he hears that he had selected the wrong payee. George uses the "undo" command and selects the correct payee.

3.2.5 Settings Change Confirmation:

If the user agent provides mechanisms for changing its user interface settings, it either allows the user to reverse the setting changes, or the user can require user confirmation to proceed. (Level A)

  • Intent of Success Criterion 3.2.5:
    The description of some user interface settings can be confusing to less technical users. Settings changes can also have unintended consequences. In addition, some disabilities make it more likely that a user can make an unintended selection on a preference screen.  Users need to be able to reverse changes to the user interface.
  • Examples of Success Criterion 3.2.5:
    • [mobile] Davy has moderately low vision. He is adjusting the contrast of the background on his mobile phone when he accidentally selects a white background with the previously selected white text. This causes all the icon labels to disappear.  He can see a highlighted rectangle on the screen that usually contains the word "undo" when he makes a change on his phone. He selects that box and the dark background returns, so he can now read the text.  He then changes the background to a color with sufficient contrast for comfortable reading.

Implementing Guideline 3.3 - Document the user agent user interface including accessibility features.

Summary: User documentation is available in an accessible format (3.3.1), it includes accessibility features (3.3.2), delineates differences between versions (3.3.3), provides a centralized views of conformance UAAG2.0 (3.3.4), and is available as context sensitive help in the UA (3.3.5).

3.3.1 Accessible documentation:

The product documentation is available in a format that meets success criteria of WCAG 2.0 Level "A" or greater. (Level A)

  • Intent of Success Criterion 3.3.1:
    People with disabilities need documentation in a format that is accessible. If provided as Web content, it must at least conform to WCAG 2.0 Level "A." If the document is not provided as Web content, it must be in conformance to a published accessibility benchmark.
  • Examples of Success Criterion 3.3.1:
    • Randall has repetitive strain injuries. His injuries make it painful to sit at the computer for long periods of time. When exploring a new program, he will often print out the documentation to read while away from his desk.This allows him to be more efficient, and learn new programs without having to spend as much computer time.
    • Lee has low vision. When she upgrades her user agent, she wants to see if any features she relies on have changed. She opens the HTML help documentation and pleased to see that the documentation is using her preferred settings.

3.3.2 Document Accessibility Features:

All features of the user agent that meet User Agent Accessibility Guidelines 2.0 success criteria are documented. (Level A)

  • Intent of Success Criterion 3.3.2:
    People that use the accessibility features of the user agent user interface need easy descriptions of how to use and configure the features. These descriptions can be provided in the documentation or user interface of the user agent or by the underlying platform, if the feature is a service of that platform.
  • Examples of Success Criterion 3.3.2:
    • Lee has low vision. When she installs a new user agent, she checks the accessibility documentation to see if the features she needs are available. She finds section entitled "Browser Features Supporting Accessibility", which provides a detailed description of user agent features that provide accessibility, describes how they function, and lists any supported third party assistive technologies that may be supported or required.
    • Lee is exploring the menus of her user agent and finds a feature named "Use My Style Sheet". She clicks "help" to learn that this feature allows custom CSS stylesheets to be created to help make web content more accessible.
    • [mobile] Neta has a repetitive strain injury. She relies on gestures and shortcuts to complete tasks. Using a specialized command, she pulls up a list of all the gesture commands available including descriptions.

3.3.3 Changes Between Versions:

Changes to features that meet UAAG 2.0 success criteria since the previous user agent release are documented. (Level AA)

  • Intent of Success Criterion 3.3.3:
    Users need to be informed about accessibility features implemented in new versions of the user agent.
  • Examples of Success Criterion 3.3.3:
    • Martha goes to an app store on her computer and installs an update for her web browser. After it installs, she sees a welcome page describing the new features in this release. One of the welcome page links is titled "What's New For Accessibility". Following this link, Martha reads about the accessibility improvements and discovers a feature that allows her to have tooltips displayed for elements when she is using caret browsing. The text also informs Martha that this feature is off by default and that she should go to accessibility settings to turn it on.

3.3.4 Centralized View:

There is a dedicated section of the documentation that presents a view of all features of the user agent necessary to meet the requirements of User Agent Accessibility Guidelines 2.0. (Level AAA)

  • Intent of Success Criterion 3.3.4:
    Users need to know about accessibility features and how to operate them. A centralized view of accessibility features makes it easier for people with disabilities and people who are evaluating software to quickly become familiar with the features such as keyboard shortcuts, how to zoom the viewport, and where to find accessibility configuration settings. Nested user agents or addons may provide separate centralized documentation. It is also useful to document accessibility features in context (such as displaying keyboard shortcuts next to their menu command).
  • Examples of Success Criterion 3.3.4:
    • [mobile] Bob is blind and uses a screen reader that is part of his phone's operating system. He downloads a new web browser on his mobile phone. The browser's online help includes a section on accessiblity that point him to pages on non-visual access, such as interaction with screen readers, helpful hints such as an explanation of the screen layout, and a list of supported touch gestures.
    • Marissa is assessing new user agents for clients who are blind. The first thing she does in looking at each user agent is to turn to the section in the documentation (local or online) that details accessibility features. This gives her a quick overview of the accessibility features across different products.

Implementing Guideline 3.4 - The user agent must behave in a predictable fashion.

Summary: Users can prevent non-requested focus changes (3.4.1).

3.4.1 Avoid unpredictable focus

The user can prevent focus changes that are not a result of explicit user request. (Level A)

  • Intent of Success Criterion 3.4.1:
    Users need to know that navigation in a web page is going to start in a predictable location and move in a predictable fashion. If a page moves the initial focus to somewhere other than the beginning of the page, the user may skip over content without realizing it. If the focus moves and remains unnoticed, users can make unintentional changes, such as entering data in an incorrect field. Focus changes can cause a window to scroll unexpectedly, confusing users. This is particularly problematic for users who can only see a small portion of the document, because they must use more effort to determine where the cursor has moved. Such users also are more likely to continue typing, not immediately realizing that the context has changed. Users who find navigation time consuming, tiring, or painful (including those using screen readers or with impaired dexterity) may also need more steps to return to the area where they want to work. While it may improve accessibility for some users on some pages to have the page to set focus to specific link or field when the page loads, it can also be detrimental for some users, and therefore users need to control of this behavior.
  • Examples of Success Criterion 3.4.1:
    • Jerome has repetitive strain injuries. He tries to limit the number of keyboard and mouse entrys he makes each day, because it is painful. He loads a page that has its default focus in a search box. Jerome wants to read the content of the page, rather than search. This requires him to make additional clicks to get to the content of the page. He intends to use this page frequently, so he adjusts his browser's settings to disable the automatic focus change to prevent the extra clicking in the future.
    • Jessica uses a screen enlarger. She loads a page that contains instructions followed by a form. If the page automatically moves the keyboard focus to the form, she may not realize there were instructions. To avoid this problem, she sets an option to prevent default focus changes.
    • James uses speech recognition. He speaks his credit card number by saying several digits followed by speaking "tab". He needs to know ahead of time whether it is necessary to include the "tab" command in the phrase.
    • Joey is blind and uses a screenreder. She is filling in a Web form that asks for her phone number using three separate fields. When she types the three digits of her area code into the first field, the browser automatically moves the focus to the second field. Because Joey does not realize that the focus has moved for her, she presses the Tab key to move it manually, not realizing that this now puts the focus on the third field rather than the second. To avoid this problem, Joey goes to her browser's Preferences dialog box and checks the option that prevents focus changes that she has not explicitly requested.
    • Justine has trouble using a mouse. She uses a keyboard macro in her web email program to execute a command to start a new message and put a block of text in the new message. The focus moves without her control, causing the macro to execute in the Inbox instead of the Compose window. With the Inbox in focus several single-key shortcuts execute, changing the column sorting and deleting several messages.

PRINCIPLE 4: Facilitate programmatic access

Implementing Guideline 4.1 - Facilitate programmatic access to assistive technology

Summary: Be compatible with assistive technologies by supporting platform standards (4.1.1), including providing information about all menus, buttons, dialogs, etc. (4.1.2, 4.1.6), access to DOMs (4.1.4), and access to structural relationships and meanings, such as what text or image labels a control or serves as a heading (4.1.5). Where something can't be made accessible, provide an accessible alternative version, such as a standard window in place of a customized window (4.1.3). Make sure that that programmatic exchanges are quick and responsive (4.1.7).

4.1.1 Platform Accessibility Services:

The user agent supports relevant platform accessibility services. (Level A)

4.1.2 Name, Role, State, Value, Description:

For all user interface components including user interface, rendered content, generated content, and alternative content, the user agent makes available the name, role, state, value, and description via platform accessibility services. (Level A)

4.1.3 Accessible Alternative:

If a component of the user agent user interface cannot be exposed through platform accessibility services, then the user agent provides an equivalent alternative that is exposed through the platform accessibility service. (Level A)

4.1.4 Programmatic Availability of DOMs:

If the user agent implements one or more DOMs, they must be made programmatically available to assistive technologies. (Level A)

4.1.5 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)

4.1.6 Expose Accessible Properties:

If any of the following properties are supported by the platform accessibility services, make the properties available to the accessibility platform architecture: (Level A)

  1. the bounding dimensions and coordinates of onscreen elements
  2. font family of text
  3. font size of text
  4. foreground color of text
  5. background color of text.
  6. change state/value notifications
  7. selection
  8. highlighting
  9. input device focus
  10. direct keyboard commands
  11. underline of menu items (keyboard command/shortcuts)

4.1.7 Timely Communication:

For APIs implemented to satisfy the requirements of UAAG 2.0, ensure that programmatic exchanges proceed at a rate such that users do not perceive a delay. (Level A)

PRINCIPLE 5: Comply with applicable specifications and conventions

Implementing Guideline 5.1 - Comply with applicable specifications and conventions.

Summary: When the browser's menus, buttons, dialogs, etc. are authored in HTML or similar standards, they need to meet W3C's Web Content Accessibility Guidelines.

5.1.1 WCAG Compliant:

Web-based user agent user interfaces meet the WCAG 2.0 success criteria: Level A to meet WCAG 2.0 Level A success criteria; Level AA to meet WCAG 2.0 Level A and AA success criteria; Level AAA to meet all WCAG 2.0 success criteria. (Level AAA)

Note: This success criterion 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).

  • Intent of Success Criterion 5.1.1:
    User agent user interfaces that are web based must meet the same accessibility guidelines as web content. The Web Content Accessibility Guidelines (WCAG) 2.0 are an internationally accepted guideline for accessible web content.
  • Examples of Success Criterion 5.1.1:
    • Lee has low vision. She needs to customize the appearance of her web based media player. WCAG 2.0 success criteria 2.7.1 requires that a user agent enable a user to change settings that impact accessibility. Her web-based media player enables her to change accessibility settings to display high contrast captions.

5.1.2 Implement accessibility features of content specs:

Implement and cite in the conformance claim the accessibility features of content specifications. Accessibility features are those that are either (Level A):

  1. Identified as such in the specification or
  2. Allow authors to satisfy a requirement of WCAG
  • Intent of Success Criterion 5.1.2:
    Most content specifications include features important to users with disabilities. Users may find it difficult or impossible to use a product that fails to support those features. Users should be able to easily discover detailed information about the user agent's adherence to accessibility standards, including those related to content such as HTML and WAI-ARIA, and should be able to do so without installing and testing the accessibility features. This will allow users to make informed decisions about whether or not they will be able to use, and therefore should install, a new product or version of that product.
  • Examples of Success Criterion 5.1.2:
    • Jordy is blind and uses a screenreader. He often uses a website that is coded with WAI-ARIA to identify the functions of custom controls. He is downloading a new version of a web browser. If the browser doesn't support WAI-ARIA and expose that information to assistive technology, the website would be unusable. Before he installs the new browser, Jordy makes sure it fully supports WAI-ARIA. He determines this by reading product documentation and UAAG conformance claims posted on the web.

5.1.3 Implement Accessibility Features of platform:

If the user agent contains non-web-based user interfaces, then those user interfaces follow user interface accessibility guidelines for the platform. (Level A)

5.1.4 Handle Unrendered Technologies:

If the user agent does not render a technology, the user can choose a way to handle content in that technology (e.g. by launching another application or by saving it to disk). (Level A)

  • Intent of Success Criterion 5.1.4:
    Users with disabilities may have fewer options in terms of how they access information. A given piece of Information may be available in a format that the user agent cannot render. The user agent needs to let the user access that content through alternate means, such as invoking a third-party renderer or saving the file to the user's hard drive.
  • Examples of Success Criterion 5.1.4:
    • Tracy has low vision. She finds it much more convenient to access her bank statement electronically than on paper, even though the electronic version is in a TIFF image, a format that her browser cannot render. In this case, the browser lets her save the image to her hard drive so she can open it in another program.

5.1.5 Alternative content handlers:

The user can select content elements and have them rendered in alternative viewers. (Level AA)

  • Intent of Success Criterion 5.1.5:
    When accessing media or specialized content (e.g. MathML) on the Web, users with disabilities can have a richer or more accessible experience using a third-party application, plug-in, or extension, rather than using the browser's built-in facilities. Users need to be able to enable or activate a browser plug-in or extension to interact with the content. Alternately, they may elect to save that content to disk and launch it in a third-party application. If streaming video cannot be saved to disk, the browser launches the external viewer, passing it the URI to the online video.
  • Examples of Success Criterion 5.1.5:
    • George is blind. His browser supports the VIDEO tag and adds its own play and pause controls, but George prefers to view the video content in a third-party application that provides much more sophisticated navigation controls such as bookmarks, skip-forward and backwards, and the ability to speed playback without increasing pitch of the audio track. In the browser, he right-clicks on the video to display a context menu, and from that chooses "Open in…", and then chooses his preferred video player. The browser launches the player to show that video file.
    • Jukka is blind and uses a screenreader. He is a scientist whose uses mathematical models. Many of the journals he reads online use MathML to display equations. Jukka finds the native support for MathML accessibility in his web browser to be generally compatible with his screen reader, but it can become unreliable for extremely complex equations. In those cases, Jukka selects an alternate rendering plugin to make the MathML understandable to his screen reader.

5.1.6 Enable Reporting of User Agent Accessibility Faults:

The user agent provides a mechanism for users to report user agent accessibility issues.(Level AAA)

  • Intent of Success Criterion 5.1.6:
    People who use assistive technologies such as screen readers may find that a technology isn't fully compatible with a web browser, or that the browser doesn't accessibly render content authored in compliance with WCAG. This causes information loss and inconvenience. When this happens, users benefit from being able to easily file a report with the user agent vendor to report the incompatibility, similar the way users can file bug reports or provide feedback.
  • Examples of Success Criterion 5.1.6:
    • Alice is a visually impaired college student who frequently uses a refreshable braille display with her Web browser. She experiences difficulty with a drop-down list boxes because the text is only partially rendered on her braille display. When Alice notices this incompatibility, she navigates to the feedback section of her browser. After providing some basic information (such as AT software and computer hardware used), Alice describes the problem and submits the report to the browser vendor.
    • Fred has low vision and uses screen magnification software to enlarge displayed information and alter color contrast. While reading content on a website in compliance with WCAG, Fred discovers that the scroll bars are not visible and he cannot scroll further down the page. Unable to read the information he needs, Fred selects the Feedback option from his browser's Tools menu, and is presented with a dialog where he can select which information to transmit to the browser vendor. He includes the current URI of the page he is trying to view, system information including OS and screen magnifier version, and enters a description of the problem he is having. Though not required, Fred chooses to provide his email address so that the vendor may contact him for further details or to provide a workaround.

Applicability Note:

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.


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.

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:

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.


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.

a · b · c · d · e · f · g · h · i · j · k · l · m · n · o · p · q · r · s · t · u · v · w · x · y · z

accelerator key
see keyboard command
To carry out the behaviors associated with an enabled element in the rendered content or a component of the user agent user interface.
active input focus
see focus
active selection
see focus
alternative content
Content ot placeholder that can be used in place of default content that may not be universally accessible. Alternative content fulfills the same purpose as the original content. Examples include text alternatives for non-text content, captions for audio, audio descriptions for video, sign language for audio, media alternatives for time-based media. See WCAG for more information.
alternative content stack
A set of alternative content items. The items may be mutually exclusive (e.g. regular contrast graphic vs. high contrast graphic) or non-exclusive (e.g. caption track that can play at the same time as a sound track).
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), (conventional input/output/device API)
An application programming interface (API) defines how communication may take place between applications.
assistive technology
An assistive technology:
  1. relies on services (such as retrieving Web resources and parsing markup) provided by one or more other "host" user agents. Assistive technologies communicate data and messages with host user agents by using and monitoring APIs.
  2. 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:

Beyond UAAG 2.0, assistive technologies consist of software or hardware that has been specifically designed to assist people with disabilities in carrying out daily activities. These technologies include wheelchairs, reading machines, devices for grasping, text telephones, and vibrating pagers. For example, the following very general definition of "assistive technology device" comes from the (U.S.) Assistive Technology Act of 1998 [AT1998]:

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.

The technology of sound reproduction. Audio can be created synthetically (including speech synthesis), streamed from a live source (such as a radio broadcast), or recorded from real world sounds.
audio description - (described video, video description or descriptive narration)
An equivalent alternative 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. In extended audio description, the video is paused so that there is time to add additional description.
The people who have worked either alone or collaboratively to create the content (e.g. content authors, designers, programmers, publishers, testers).
author styles
See Style properties
background images
Images that are rendered on the base background.
base background
The background of the content as a whole, such that no content may be layered behind it. In graphics applications the base background is often referred to as the canvas.
blinking text
Text whose visual rendering alternates between visible and invisible at any rate of change.
captions (caption)
An equivalent alternative 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 are captions that are always rendered with a visual track; they cannot be turned off. Closed captions are 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 in UAAG 2.0. For instance, a "table caption" is a title for the table, often positioned graphically above or below the table. In UAAG 2.0, the intended meaning of "caption" will be clear from context.
collated text transcript
A collated text transcript is a text equivalent of a movie or other animation. It is the combination of the text transcript of the audio track and the text equivalent of the visual track. For example, a collated text transcript typically includes segments of spoken dialogue interspersed with text descriptions of the key visual elements of a presentation (actions, body language, graphics, and scene changes). See also the definitions of text transcript and audio description. Collated text transcripts are essential for people who are deaf-blind.
command, direct command, direct navigation command, direct activation command, sequential navigation command , spacial (directional) command, structural navigation command
direct commands apply to a specified item (e.g., button) or action (e.g. save function), regardless of the current focus location
direct navigation commands move focus to a specified item
direct activation commands activate the specified item (and may also move focus to it) or action
sequential navigation commands (sometimes called logical or linear navigation commands) 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, etc.)
structural navigation commands move forwards, backwards, up and down a hierarchy
spatial commands (sometimes called directional commands), require the user to be cognizant of the spatial arrangement of items on the screen:
content (web content), empty content, reflowable 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 [adapted from WCAG 2.0]

empty content (which may be alternative content) is either a null value or an empty string (e.g. 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).

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

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.
see focus
see properties
direct command, direct navigation command, direct activation command, linear navigation command , spacial (directional) command, structural navigation command
see command
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.
document character set
The internal representation of data in the source content by a user agent.
document object, (Document Object Model, DOM)
The Document Object Model is 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. This is an overview of DOM-related materials here at W3C and around the web: http://www.w3.org/DOM/#what.
document source, (text source, source text)
Text the user agent renders upon user request to view the source of specific viewport content (e.g. selected content, frame, page).
Any information that supports the use of a user agent. This information may be found, for example, in manuals, installation instructions, the help system, and tutorials. Documentation may be distributed (e.g. as files installed as part of the installation, some parts may be delivered on CD-ROM, others on the Web). See guideline 5.3 for information about documentation.
element, element type
UAAG 2.0 uses the terms "element" and "element type" primarily in the sense employed by the XML 1.0 specification ([XML], section 3): an element type is a syntactic construct of a document type definition (DTD) for its application. 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).
empty content
see content
enabled element, disabled 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. A disabled element is a potentially enabled element that is not currently available for activation (e.g. a "grayed out" menu item).
equivalent alternative
Acceptable substitute content that a user may not be able to access. An equivalent alternative fulfills essentially the same function or purpose as the original content upon presentation:
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.
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 considered an explicit user request.
focus (active input focus, active selection, cursor, focus cursor, focusable element, highlight, inactive input focus, inactive selection, input focus, keyboard focus, pointer, pointing device focus, selection, split focus, text cursor)

Hierarchical Summary of some focus terms

active input focus
The input focus location in the active viewport. The active focus is in the active viewport, while the inactive input focus is the inactive viewport. The active input focus is usually visibly indicated. In UAAG 2.0 "active input focus" generally refers to the active keyboard input focus.
active selection
The selection that will currently be affected by a user command, as opposed to selections in other viewports, called inactive selections, which would not currently be affected by a user command.
see support
Visual indicator showing where keyboard input will occur. There are two types of cursors: focus cursor (e.g. the dotted line around a button) and text cursor (e.g. the flashing vertical bar in a text field, also called a 'caret'). Cursors are active when in the active viewport, and inactive when in an inactive viewport.
focus cursor
Indicator that highlights a user interface element to show that it has keyboard focus, e.g. a dotted line around a button, or brightened title bar on a window. There are two types of cursors: focus cursor (e.g. the dotted line around a button) and text cursor (e.g. the flashing vertical bar in a text field).
focusable element
Any element capable of having input focus, e.g. 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.
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 ("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.
inactive input focus
An input focus location in an inactive viewport such as a background window or pane. The inactive input focus location will become the active input focus location when input focus returns to that viewport. An inactive input focus may or may not be visibly indicated.
inactive selection
A selection that does not have the input focus and thus does not take input events.
input focus
The place where input will occur if a viewport is active. Examples include keyboard focus and pointing device focus. Input focus can also be active (in the active viewport) or inactive (in an inactive viewport).
keyboard focus
The screen location where keyboard input will occur if a viewport is active. Keyboard focus can be active (in the active viewport) or inactive (in an inactive viewport). See keyboard interface definition for types of keyboards included and what constitutes a keyboard.
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. [from ATAG 2.0]
Visual 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 touch screens are used, the "pointing device" is a combination of the touch screen and the user's finger or stylus. On most systems there is no pointer (on-screen visual indication) associated with this type of pointing device.
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.
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.
split focus
A state when the user could be confused because the input focus is separated from something it is usually linked to, such as being at a different place than the selection or similar highlighting, or has been scrolled outside of the visible portion of the viewport.
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).
globally, global configuration
a global 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.
Information (e.g. text, colors, graphics, images, and animations) rendered for visual consumption.
highlight, highlighted, highlighting
see focus
Pictorial content that is static (i.e. not moving or changing). See also the definition of animation.
see support
important elements
This specification intentionally does not identify which "important elements" must be navigable because this will vary by specification. What constitutes "efficient navigation" may depend on a number of factors as well, including the "shape" of content (e.g. sequential navigation of long lists is not efficient) and desired granularity (e.g. among tables, then among the cells of a given table). Refer to the Implementing document [Implementing UAAG 2.0] for information about identifying and navigating important elements.
inactive input focus
see focus
inactive selection
see focus
informative (non-normative)
see normative
input configuration
The set of bindings between user agent functionalities and user interface input mechanisms (e.g. menus, buttons, keyboard keys, and voice commands). The default input configuration is the set of bindings the user finds after installation of the software. Input configurations may be affected by author-specified bindings (e.g. through the accesskey attribute of HTML 4 [HTML4]).
input focus
see focus
keyboard (keyboard emulator, keyboard interface)
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 Independence Principle). 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 command (keyboard binding, keyboard shortcuts, 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 Independence Principle). 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.
keyboard focus
see focus
natural language
Natural language is spoken, written, or signed human language such as French, Japanese, and American Sign Language. On the Web, the natural language of content may be specified by markup or HTTP headers. Some examples include the 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.
see command
non-text content (non-text element, non-text equivalent)
see text
normative, informative (non-normative) [WCAG 2.0, ATAG 2.0]
What is identified as "normative" is required for conformance (noting that one may conform in a variety of well-defined ways to UAAG 2.0). What is identified as "informative" (or, "non-normative") is never required for conformance.
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).
operating system (OS)
Software that supports a computer'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.
In UAAG 2.0, the term "override" means that 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).
A placeholder is 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. Placeholders appear in the alternative content stack.
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, MacOS, 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 MacOSX applications, Gnome Accessibility Toolkit API for Gnome applications, Java Access for Java applications). On some platforms it may be conventional to enhance communication further via implementing a DOM.
plug-in [ATAG 2.0]
A plug-in is a program that runs as part of the user agent and that is not part of content. Users generally choose to include or exclude plug-ins from their user agents.
point of regard
The point of regard is 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. The stability of the point of regard is addressed by success criterion 1.8.7
see focus
pointing device focus
see focus
A profile is 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.
prompt [ATAG 2.0]
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 ([CSS2], section 3). A reference to "styles" in UAAG 2.0 means a set of style-related properties. The value given to a property by a user agent at installation is the property's default value.
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.
relative time units
Relative time units define 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, rendered text
Rendered content is the part of content that the user agent makes available to the user's senses of sight and hearing (and only those senses for the purposes of UAAG 2.0). Any content that causes an effect that may be perceived through these senses constitutes rendered content. This includes text characters, images, stylesheets, scripts, and any other content that, once processed, may be perceived through sight and hearing.
The term "rendered text" refers to text content that is rendered in a way that communicates information about the characters themselves, whether visually or as synthesized speech.
In the context of UAAG 2.0, invisible content is content that is not rendered but that may influence the graphical rendering (i.e. layout) of other content. Similarly, silent content is content that is not rendered but that may influence the audio rendering of other content. Neither invisible nor silent content is considered rendered content.
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:

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 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].

In UAAG 2.0, the term "script" almost always refers to a scripting (programming) language used to create dynamic Web content. However, in guidelines referring to the written (natural) language of content, the term "script" is used as in Unicode [UNICODE] to mean "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, current selection
see focus
style properties, user agent default styles, author styles, user styles
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 stylesheets).
user styles: Style property values that are set by the user (e.g., via user agent interface settings, user stylesheets).
style sheet, user style sheet, author 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 is what allows author stylesheets to be toggled or substituted, and user stylesheets 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.
support, implement, conform
Support, implement, and conform all refer to what a developer has designed a user agent to do, but they represent different degrees of specificity. A user agent "supports" general classes of objects, such as "images" or "Japanese." A user agent "implements" a specification (e.g. the PNG and SVG image format specifications or a particular scripting language), or an API (e.g. the DOM API) when it has been programmed to follow all or part of a specification. A user agent "conforms to" a specification when it implements the specification and satisfies its conformance criteria.
The act of time-coordinating two or more presentation components (e.g. a visual track with captions, or several tracks in a multimedia presentation). For Web content developers, 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) [WCAG 2.0, ATAG 2.0]
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 (text content, non-text content, text element, non-text element, text equivalent, non-text equivalent )
Text used by itself refers to a sequence of characters from a markup language's document character set. Refer to the "Character Model for the World Wide Web" [CHARMOD] for more information about text and characters. Note: UAAG 2.0 makes use of other terms that include the word "text" that have highly specialized meanings: collated text transcript, non-text content, text content, non-text element, text element, text equivalent, and text transcript.

Atext element adds text characters to either content or the user interface. Both in the Web Content Accessibility Guidelines 2.0 [WCAG20] and in UAAG 2.0, text elements are presumed to produce text that can be understood when rendered visually, as synthesized speech, or as Braille. Such text elements benefit at least these three groups of users:

  1. visually-displayed text benefits users who are deaf and adept in reading visually-displayed text;
  2. synthesized speech benefits users who are blind and adept in use of synthesized speech;
  3. braille benefits users who are blind, and possibly deaf-blind, and adept at reading braille.

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.

text decoration
Any stylistic effect that the user agent may apply to visually rendered text that does not affect the layout of the document (i.e. does not require reformatting when applied or removed). Text decoration mechanisms include underline, overline, and strike-through.
text format
Any media object given an Internet media type of "text" (e.g. "text/plain", "text/html", or "text/*") as defined in RFC 2046 [RFC2046], section 4.1, or any media object identified by Internet media type to be an XML document (as defined in [XML], section 2) or SGML application. Refer, for example, to Internet media types defined in "XML Media Types" [RFC3023].
text transcript
A text equivalent 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). See also the definitions of captions and collated text transcripts.
defining a common time scale for all components of a time-based media presentation. For example, a media-player will expose a single timebase for a presentation composed of individual video and audio tracks, for instance allowing users or technology to query or alter the playback rate and position.
track (audio track or visual track)
Content rendered as sound through an audio viewport. The audio track may be all or part of the audio portion presentation (e.g. each instrument may have a track, or each stereo channel may have a track). Also see definition of visual track
A collection of commonly used controls presented in a region that can be configured or navigated separately from other regions. Such containers may be docked or free-floating, permanent or transient, integral to the application or addons. Variations are often called toolbars, palettes, panels, or inspectors.
user agent
A user agent is any software that retrieves, renders and facilitates end user interaction with Web content. @@ED Note: this following definition text is still under discussion. If the software only performs these functions for time-based media, then the software is typically referred to as a *media player*, otherwise, the more general designation *browser* is used. UAAG 2.0 identifies several user agent architectures:

stand-alone, non-web-based, browser: These user agents 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, IE, Chrome, Opera).

embedded user agent: These user agents "plug-in" to stand-alone user agents in order to rendering and facilitate end-user interaction for content types (e.g., multimedia), that the stand-alone user agent is not able to (e.g. Quicktime, Acrobat Reader, Shockwave). Embedded user agents establish direct connections with the platform (e.g. communication via platform accessibility services)

web-based user agent: These user agents operate by (a) transforming the web content into a technology that the stand-alone (or embedded) user agent can render and (b) injecting the user agent's own user interface functionality into the content to be rendered. (e.g. Gmail, Facebook, Skype)

web view component, mobile app: These user agents are used to package a constrained set of web content into non-web-based applications, especially on mobile platforms. If the finished application retrieves, renders and facilitates end-user interaction with web content, then the application is a user agent. If the finished application only renders non web content, then the application is not a user agent for the purposes of UAAG 2.0 conformance.

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 to *modify the user agent's own user interface * (e.g. add a headings view).
user agent default styles
User agent default styles are style property values applied in the absence of any author or user styles. Some markup languages specify a default rendering for content in that markup language; others do not. For example, XML 1.0 [XML] does not specify default styles for XML documents. HTML 4 [HTML4] does not specify default styles for HTML documents, but the CSS 2 [CSS2] specification suggests a sample default style sheet for HTML 4 based on current practice.
user interface, user interface control
For the purposes of UAAG 2.0, user interface includes both:
  1. the user agent user interface, i.e. the controls (e.g. menus, buttons, prompts, and other components for input and output) and mechanisms (e.g. selection and focus) provided by the user agent ("out of the box") that are not created by content.
  2. the "content user interface," i.e. the enabled elements that are part of content, such as form controls, links, and applets.
The document distinguishes them only where required for clarity. For more information, see the section on requirements for content, for user agent features, or both @@.

The term "user interface control" refers to a component of the user agent user interface or the content user interface, distinguished where necessary.

user styles
User styles are style property values that come from user interface settings, user stylesheets, or other user interactions.
see properties
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, such as:
The part of an onscreen view that the user agent is currently presenting onscreen to the user, such that the user can attend to any part of it without further action (e.g. scrolling). There may be multiple viewports on to the same 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). A container can hold multiple viewports at the same nesting level. When the viewport is smaller in extent than the content it is presenting, user agents typically provide mechanisms to bring the occluded content into the viewport (e.g., scrollbars).
A visual-only presentation is content consisting exclusively of one or more visual tracks presented concurrently or in series. A silent movie is an example of a visual-only presentation.
visual track
A visual object is 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
From "Introduction and Overview of W3C Speech Interface Framework" [VOICEBROWSER]: "A voice browser is 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."
web resource
Anything that can be identified by a Uniform Resource Identifier (URI).

Appendix B: How to refer to UAAG 2.0 from other documents

This section is informative.

There are two recommended ways to refer to the "User Agent Accessibility Guidelines 2.0" (and to W3C documents in general):

  1. References to a specific version of "User Agent Accessibility Guidelines 2.0." For example, use the "this version" URI to refer to the current document:
  2. References to the latest version of "User Agent Accessibility Guidelines 2.0." Use the "latest version" URI to refer to the most recently published document in the series:

In almost all cases, references (either by name or by link) should be to a specific version of the document. W3C will make every effort to make UAAG 2.0 indefinitely available at its original address in its original form. The top of UAAG 2.0 includes the relevant catalog metadata for specific references (including title, publication date, "this version" URI, editors' names, and copyright information).

An XHTML 1.0 paragraph including a reference to this specific document might be written:

<cite><a href="http://www.w3.org/TR/2010/WD-UAAG20-20100617/">
"User Agent Accessibility Guidelines 2.0,"</a></cite>
J. Allan, K. Ford, J. Spellman, eds.,
W3C Recommendation, http://www.w3.org/TR/ATAG20/.
The <a href="http://www.w3.org/TR/ATAG20/">latest version</a> of this document is available at http://www.w3.org/TR/ATAG20/.</p>

For very general references to this document (where stability of content and anchors is not required), it may be appropriate to refer to the latest version of this document. Other sections of this document explain how to build a conformance claim.

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.

"Cascading Style Sheets (CSS1) Level 1 Specification," B. Bos, H. Wium Lie, eds., 17 December 1996, revised 11 January 1999. This W3C Recommendation is http://www.w3.org/TR/1999/REC-CSS1-19990111.
"Cascading Style Sheets, level 2 (CSS2) Specification," B. Bos, H. Wium Lie, C. Lilley, and I. Jacobs, eds., 12 May 1998. This W3C Recommendation is http://www.w3.org/TR/1998/REC-CSS2-19980512/.
"Document Object Model (DOM) Level 2 Core Specification," A. Le Hors, P. Le Hégaret, L. Wood, G. Nicol, J. Robie, M. Champion, S. Byrne, eds., 13 November 2000. This W3C Recommendation is http://www.w3.org/TR/2000/REC-DOM-Level-2-Core-20001113/.
"Document Object Model (DOM) Level 2 Style Specification," V. Apparao, P. Le Hégaret, C. Wilson, eds., 13 November 2000. This W3C Recommendation is http://www.w3.org/TR/2000/REC-DOM-Level-2-Style-20001113/.
"XML Information Set," J. Cowan and R. Tobin, eds., 24 October 2001. This W3C Recommendation is http://www.w3.org/TR/2001/REC-xml-infoset-20011024/.
"Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types," N. Freed, N. Borenstein, November 1996.
"Web Content Accessibility Guidelines 1.0," W. Chisholm, G. Vanderheiden, and I. Jacobs, eds., 5 May 1999. This W3C Recommendation is http://www.w3.org/TR/1999/WAI-WEBCONTENT-19990505/.
"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.
The Assistive Technology Act of 1998.
"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/.
"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/.
"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/.
"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/.
"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/.
"Hypertext Transfer Protocol — HTTP/1.1," J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee, June 1999.
"XML Media Types," M. Murata, S. St. Laurent, D. Kohn, January 2001.
"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/.
"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/.
"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/.
"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/.
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.
Information about UAAG 1.0 conformance icons and their usage is available at http://www.w3.org/WAI/UAAG10-Conformance.
An appendix to UAAG 2.0 provides a summary of the goals and structure of User Agent Accessibility Guidelines 1.0.
"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/.
The Unicode Consortium. The Unicode Standard, Version 6.1.0, (Mountain View, CA: The Unicode Consortium, 2012. ISBN 978-1-936213-02-3)
"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.
"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/.
"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.
"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.
"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/
"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.
"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.
"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/.
"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/.
"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:

Previous Editor:
Jan Richards, Inclusive Design Institute, OCAD University

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

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.

Appendix E: Alternative Content

These are the elements and attributes that present 'alternative content' relevant to Guideline 3.

@@ Editors' Note: This needs update and permanent links as HTML5 goes to rec. Get listings of alternative content for other technologies. Think about better format for presenting it.