[contents]

Web Content Accessibility Guidelines 2.0

Editor's Draft May-September 2007

This version:
http://www.w3.org/WAI/GL/WCAG20/WD-WCAG20-20070730/
Latest version:
http://www.w3.org/TR/WCAG20/
Previous version:
http://www.w3.org/TR/2007/WD-WCAG20-20070517/
Editors:
Ben Caldwell, Trace R&D Center, University of Wisconsin-Madison
Michael Cooper, W3C
Loretta Guarino Reid, Google, Inc.
Gregg Vanderheiden, Trace R&D Center, University of Wisconsin-Madison
Previous Editors:
Wendy Chisholm (until July 2006 while at W3C)
John Slatin (until June 2006 while at Accessibility Institute, University of Texas at Austin)
Jason White (until June 2005 while at University of Melbourne)

This document is also available in these non-normative formats:


Abstract

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

WCAG 2.0 success criteria are written as testable statements that are not technology-specific. Guidance about satisfying the success criteria in specific technologies as well as general information about interpreting the success criteria are provided in separate documents. An Overview of Web Content Accessibility Guidelines (WCAG) 2.0 Last Call Documents is also available.

Until WCAG 2.0 advances to W3C Recommendation, the current and referenceable document is Web Content Accessibility Guidelines 1.0 [WCAG10], published as a W3C Recommendation May 1999.

Status of this Document

This document is the internal working draft used by the WCAG WG and is updated continuously and without notice. This document has no formal standing within W3C. Please consult the group's home page and the W3C technical reports index for information about the latest publications by this group.

This draft includes revisions that have been made since the 17 May 2007 Working Draft was published. Please refer to the latest public version of WCAG 2.0 for information about the status of WCAG 2.0 as well as information about submitting comments to the working group.

History of Changes to WCAG 2.0 Working Drafts


Table of Contents

Appendices


Introduction

This section is informative.

Web Content Accessibility Guidelines (WCAG) 2.0 defines how to make Web content more accessible to people with disabilities, and older people with changing abilities due to aging. Accessibility involves a wide range of disabilities, including visual, auditory, physical, speech, cognitive, language, learning, and neurological disabilities. These guidelines also often make content more usable in general. Although these guidelines cover a wide range of issues, they are not able to address the needs of people with all types, degrees and combinations of disabilities.

WCAG 2.0 is developed through the W3C process in cooperation with individuals and organizations around the world, with a goal of providing a shared standard for Web content accessibility that meets the needs of individuals, organizations, and governments internationally. WCAG 2.0 builds on WCAG 1.0 [WCAG10] and is designed to apply broadly to different Web technologies now and in the future, and to be testable with a combination of automated testing and human evaluation. For an introduction to WCAG, see the Web Content Accessibility Guidelines (WCAG) Overview.

Web accessibility depends not only on accessible content, but also on accessible Web browsers and other user agents. Authoring tools also have an important role in Web accessibility. For an overview of how these components of Web development and interaction work together, see:

WCAG 2.0 Layers of Guidance

The individuals and organizations that use WCAG vary widely and include Webmasters, policy makers, purchasing agents, teachers, and students. In order to meet the varying needs several layers of guidance are provided including overall principles, general guidelines, testable success criteria and a rich collection of sufficient techniques, advisory techniques and documented failures with examples, resource links and code.

  • Principles - At the top are four principles that provide the foundation for Web accessibility: perceivable, operable, understandable, and robust. See also Understanding the Four Principles of Accessibility.

  • Guidelines - Under the principles are guidelines. The 12 guidelines provide the basic goals that authors should work toward in order to make content more accessible to users with different disabilities. These guidelines are not testable but provide the framework and overall objectives to help authors understand the success criteria and better implement the techniques.

  • Success Criteria - For each guideline, testable success criteria are provided to allow WCAG 2.0 to be used in design specification, purchasing, regulation, contractual agreements, etc. where requirements and testing for conformance are necessary. In order to meet the needs of different groups and different situations, three levels of conformance are defined: A (lowest), AA, AAA (highest). (Additional information on WCAG levels can be found in Understanding Levels of Conformance.)

  • Sufficient and Advisory Techniques - For each of the guidelines and success criteria in the WCAG 2.0 document itself, the working group has also documented a wide variety of techniques. The techniques fall into two categories: those that are sufficient for meeting the success criteria and those that are “advisory” and go beyond what is required by the individual success criteria and allow authors to better address the guidelines. See also Sufficient and Advisory Techniques.

All of these layers of guidance (guidelines, success criteria, and sufficient and advisory techniques) work together to provide guidance on how to make content more accessible. Authors are encouraged to view and apply all layers that they are able to, including the advisory techniques, in order to best address the needs of the widest possible range of users.

Note that even content that conforms at the highest level (AAA) will not be accessible to individuals with all types, degrees, or combinations of disability particularly in the cognitive language and learning areas. Authors are encouraged to consider the full range of techniques, including the advisory techniques, as well as to seek relevant advice about current best practice to ensure that Web content is accessible, as far as possible, to this community.

WCAG 2.0 Supporting Documents

The WCAG 2.0 document itself is designed to meet the needs of those who need a stable, referenceable technical standard. For different needs and different types of users, W3C WAI provides additional material. These include:

  1. WCAG 2.0 Quick Reference - A concise list that includes all of the guidelines, success criteria, and techniques for authors to use as they are developing and evaluating Web content.

  2. Understanding WCAG 2.0 - A guide to understanding and implementing WCAG 2.0. There is a short "Understanding" document for each guideline and success criterion in WCAG 2.0 as well as key topics.

  3. Techniques for WCAG 2.0 - A collection of techniques and known failures, each in a separate document, that includes a description, examples, code and tests.

See Overview of WCAG 2.0 Documents for a description of the WCAG 2.0 supporting material, including education resources related to WCAG 2.0.

Important Terms in WCAG 2.0

WCAG 2.0 includes three important terms that are different from WCAG 1.0.

Web Page

It is important to note that, in this standard, the term "Web page" includes much more than static HTML pages. It also includes the increasingly dynamic Web pages that are emerging on the Web, including "pages" that can present entire virtual interactive communities. For example, the term "Web page" includes an immersive interactive movie-like experience that you find at a single URL. For more information, see Understanding "Web Page".

Programmatically Determined

Several success criteria require that content (or certain aspects of content) can be "programmatically determined." This means that the content is delivered in such a way that user agents, including assistive technologies, can extract and present this information to users in different modalities. For more information, see Understanding Programmatically Determined.

Accessibility Supported

An accessibility supported technology is a Web technology (HTML, CSS, etc.) that will work with assistive technologies (AT) and the accessibility features of browsers and other user agents. Only Web technologies or features of the technologies, that are "accessibility supported" can be used to conform to WCAG 2.0 success criteria. Technologies that are not accessibilty supported (do not work with AT etc.) can be used, but cannot be used to conform to any success criterion.

The requirements for "accessibility support" are provided in the Conformance section of these guidelines. For more information, see Understanding accessibility support in Understanding WCAG 2.0.

WCAG 2.0 Guidelines

This section is normative.

Principle 1: Perceivable - Information and user interface components must be presentable to users in ways they can perceive

Guideline 1.1 Text Alternatives: Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language Understanding Guideline 1.1

1.1.1 Non-text Content: All non-text content has a text alternative that presents equivalent information, except for the situations listed below. (Level A) How to Meet 1.1.1 Understanding 1.1.1

  • Controls, Input: If it is a control or accepts user input, then it has a name that describes its purpose. (See also Guideline 4.1.)

  • Media, Test, Sensory: If it is (1) synchronized media, (2) live audio-only or live video-only content, (3) a test or exercise that must be presented in non-text format, (4) primarily intended to create a specific sensory experience, then text alternatives at least provide descriptive identification of the non-text content, or (5) a media alternative to text that is clearly labeled as such. (For synchronized media, see also Guideline 1.2.)

    Note: Prerecorded audio-only and video-only files would be covered under [Success Criterion 1.1.1], which requires text alternatives that present equivalent information.

  • CAPTCHA: If it is to confirm that content is being accessed by a person rather than a computer, then text alternatives that identify and describe the purpose of the non-text content are provided, and alternative forms of CAPTCHA using output modes for different types of sensory perception are provided to accommodate different disabilities.

  • Decoration, Formatting, Invisible: If it is pure decoration, or used only for visual formatting, or if it is not presented to users, then it is implemented in a way that it can be ignored by assistive technology.

1.1.2 Live Audio-only: All live audio-only content has a text alternative (Level AAA) How to Meet 1.1.2 Understanding 1.1.2

Guideline 1.2 Synchronized Media: Provide synchronized alternatives for synchronized media Understanding Guideline 1.2

1.2.1 Captions (Prerecorded): Captions are provided for prerecorded synchronized media, except if the synchronized media is an alternative to text and is clearly labeled as such. (Level A) How to Meet 1.2.1 Understanding 1.2.1

1.2.2 Audio Description or Full Text Alternative: Audio description of video, or a full text alternative for synchronized media including any interaction , is provided for prerecorded synchronized media. (Level A) How to Meet 1.2.2 Understanding 1.2.2

Note: For 1.2.2, 1.2.4, and 1.2.7, if all of the information in the video track is already provided in the audio track, no audio description is necessary.

1.2.3 Captions (Live): Captions are provided for live synchronized media. (Level AA) How to Meet 1.2.3 Understanding 1.2.3

Note: If synchronized media is completely computer generated, it is not live and is subject to the requirements for prerecorded synchronized media in WCAG 2.0.

1.2.4 Audio Description: Audio description of video is provided for prerecorded synchronized media. (Level AA) How to Meet 1.2.4 Understanding 1.2.4

1.2.6 Audio Description (Extended): Extended audio description of video is provided for prerecorded synchronized media. (Level AAA) How to Meet 1.2.6 Understanding 1.2.6

1.2.7 Full Text Alternative: A full text alternative for synchronized media including any interaction is provided for all prerecorded synchronized media, except if the synchronized media is an alternative to text and is clearly labeled as such. (Level AAA) How to Meet 1.2.7 Understanding 1.2.7

Guideline 1.3 Adaptable: Create content that can be presented in different ways (for example simpler layout ) without losing information or structure Understanding Guideline 1.3

1.3.1 Info and Relationships: Information and relationships conveyed through presentation can be programmatically determined or are available in text. (Level A) How to Meet 1.3.1 Understanding 1.3.1

1.3.2 Meaningful Sequence: When the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined and sequential navigation of interactive components is consistent with that sequence. (Level A) How to Meet 1.3.2 Understanding 1.3.2

1.3.3 Sensory Characteristics: Instructions provided for understanding and operating content do not rely solely on sensory characteristics of components such as shape, size, visual location, orientation or sound. (Level A) How to Meet 1.3.3 Understanding 1.3.3

Guideline 1.4 Distinguishable: Make it easier for users to see and hear content including separating foreground from background Understanding Guideline 1.4

1.4.1 Use of Color: Color must not be used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element. (Level A) How to Meet 1.4.1 Understanding 1.4.1

Note: This success criterion addresses color perception specifically. Other forms of perception are covered in Guideline 1.3.

1.4.2 Audio Control: If any audio on a Web page plays automatically for more than 3 seconds, either a mechanism is available to pause or stop the audio, or a mechanism is available to control audio volume which can be set to be a different level from the system volume level . (Level A) How to Meet 1.4.2 Understanding 1.4.2

Note: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether used to meet other success criteria or not) must meet this success criterion. See conformance requirement 5.

1.4.3 Contrast (Minimum): Text and images of text have a contrast ratio of at least 5:1, and large-scale text and images of text have a contrast ratio of at least 3:1, except for the following: (Level AA) How to Meet 1.4.3 Understanding 1.4.3

  • Inactive User Interface: If text content is part of an inactive user interface component, then no minimum contrast requirement applies.

  • Decoration or Incidental: If text content is pure decoration, or is incidental text in an image, then no minimum contrast requirement applies.

  • Invisible: If text is not visible to anyone, then no minimum contrast requirement applies.

Note: Success Criteria 1.4.3 and 1.4.5 can be met via a contrast control available on or from the page.

1.4.4 Resize text: Text (but not images of text) can be resized without assistive technology up to 200 percent and down to 50 percent without loss of content or functionality. (Level AA) How to Meet 1.4.4 Understanding 1.4.4

1.4.5 Contrast (Enhanced): Text and images of text have a contrast ratio of at least 7:1, and large-scale text or images of text have a contrast ratio of at least 5:1, except for the following: (Level AAA) How to Meet 1.4.5 Understanding 1.4.5

  • Inactive User Interface: If text content is part of an inactive user interface component, then no minimum contrast requirement applies.

  • Decoration or Incidental: If text content is pure decoration, or is incidental text in an image, then no minimum contrast requirement applies.

  • Invisible: If text is not visible to anyone, then no minimum contrast requirement applies.

Note: Success Criteria 1.4.3 and 1.4.5 can be met via a contrast control available on or from the page.

1.4.6 Low or No Background Audio: Audio content that is not an audio CAPTCHA and that contains speech in the foreground does not contain background sounds, background sounds can be turned off, or background sounds are at least 20 decibels lower than the foreground speech content, with the exception of occasional sound effects. (Level AAA) How to Meet 1.4.6 Understanding 1.4.6

Note: Background sound that meets this requirement will be approximately one quarter as loud as the foreground speech content.

1.4.7 Resize and Wrap: Text (but not images of text) can be resized without assistive technology up to 200 percent and down to 50 percent without loss of content or functionality and in a way that does not require the user to scroll horizontally. (Level AAA) How to Meet 1.4.7 Understanding 1.4.7

Principle 2: Operable - User interface components and navigation must be operable

Guideline 2.1 Keyboard Accessible: Make all functionality available from a keyboard Understanding Guideline 2.1

2.1.1 Keyboard: All functionality of the content is operable through a keyboard interface without requiring 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. (Level A) How to Meet 2.1.1 Understanding 2.1.1

Note 1: This exception relates to the underlying function, not the input technique. For example, if using handwriting to enter text, the input technique (handwriting) requires path dependent input but the underlying function (text input) does not.

Note 2: This does not forbid and should not discourage providing mouse input or other input methods in addition to keyboard operation.

2.1.2 Keyboard (No Exception): All functionality of the content is operable through a keyboard interface without requiring specific timings for individual keystrokes. (Level AAA) How to Meet 2.1.2 Understanding 2.1.2

Guideline 2.2 Enough Time: Provide users with disabilities enough time to read and use content Understanding Guideline 2.2

2.2.1 Timing Adjustable: For each time limit that is set by the content, at least one of the following is true: (Level A) How to Meet 2.2.1 Understanding 2.2.1

  • Turn off: the user is allowed to turn off the time limit before encountering it; or

  • Adjust: the user is allowed to adjust the time limit before encountering it over a wide range that is at least ten times the length of the default setting; or

  • Extend: the user is warned before time expires and given at least 20 seconds to extend the time limit with a simple action (for example, "press the space bar "), and the user is allowed to extend the time limit at least ten times; or

  • Real-time Exception: the time limit is a required part of a real-time event (for example, an auction), and no alternative to the time limit is possible; or

  • Essential Exception: the time limit can not be extended without invalidating the activity.

  • 20 Hour Exception: the time limit is longer than 20 hours.

Note: This provision acts to ensure that changes in content or context as a result of a time-out will not occur unexpectedly, preventing users from completing tasks. While exceptions to success criterion 2.2.1 where timing is essential exist, guideline 2.2 in general limits changes in content for no reason. This provisions should be considered in conjunction with provision 3.2.1 which puts limits on changes of content or context as a result of user action.

2.2.2 Pausing: Moving, blinking, scrolling, or auto-updating information on a Web page that lasts for more than three seconds can be paused by the user unless the movement, blinking, scrolling, or auto-updating is part of an activity where the changes are essential. Moving or blinking content that is pure decoration can be stopped or hidden by the user. (Level AA) How to Meet 2.2.2 Understanding 2.2.2

Note 1: For requirements related to flickering or flashing content, refer to Guideline 2.3.

Note 2: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether used to meet other success criteria or not) must meet this success criterion. See conformance requirement 5.

Note 3: Content that is updated from a process, real-time or remote stream is not required to preserve or present information that is generated or received between the initiation of the pause and resuming presentation, as this may not be technically possible, and in many situations could be misleading to do so.

2.2.3 No Timing: Timing is not an essential part of the event or activity presented by the content, except for non-interactive synchronized media and real-time events. (Level AAA) How to Meet 2.2.3 Understanding 2.2.3

2.2.4 Interruptions: Interruptions can be postponed or suppressed by the user, except interruptions involving an emergency. (Level AAA) How to Meet 2.2.4 Understanding 2.2.4

2.2.5 Re-authenticating: When an authenticated session expires, the user can continue the activity without loss of data after re-authenticating. (Level AAA) How to Meet 2.2.5 Understanding 2.2.5

Guideline 2.3 Seizures: Do not design content in a way that is known to cause seizures Understanding Guideline 2.3

2.3.1 Three Flashes or Below Threshold: Web pages do not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds. (Level A) How to Meet 2.3.1 Understanding 2.3.1

Note: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether used to meet other success criteria or not) must meet this success criterion. See conformance requirement 5.

2.3.2 Three Flashes: Web pages do not contain anything that flashes more than three times in any one second period. (Level AAA) How to Meet 2.3.2 Understanding 2.3.2

Guideline 2.4 Navigable: Provide ways to help users with disabilities navigate, find content and determine where they are Understanding Guideline 2.4

Principle 3: Understandable - Information and the operation of user interface must be understandable

Guideline 3.1 Readable: Make text content readable and understandable Understanding Guideline 3.1

3.1.1 Language of Page: The default human language of each Web page within the content can be programmatically determined. (Level A) How to Meet 3.1.1 Understanding 3.1.1

3.1.2 Language of Parts: The human language of each passage or phrase in the content can be programmatically determined. (Level AA) How to Meet 3.1.2 Understanding 3.1.2

Note: This requirement does not apply to individual words. It also does not apply to proper names, to technical terms or to phrases that have become part of the language of the context in which they are used.

3.1.3 Unusual Words: A mechanism is available for identifying specific definitions of words or phrases used in an unusual or restricted way, including idioms and jargon. (Level AAA) How to Meet 3.1.3 Understanding 3.1.3

3.1.4 Abbreviations: A mechanism for finding the expanded form or meaning of abbreviations is available. (Level AAA) How to Meet 3.1.4 Understanding 3.1.4

3.1.5 Reading Level: When text requires reading ability more advanced than the lower secondary education level, supplemental content or a version that does not require reading ability more advanced than the lower secondary education level is available. (Level AAA) How to Meet 3.1.5 Understanding 3.1.5

3.1.6 Pronunciation: A mechanism is available for identifying specific pronunciation of words where meaning is ambiguous without knowing the pronunciation. (Level AAA) How to Meet 3.1.6 Understanding 3.1.6

Guideline 3.2 Predictable: Make Web pages appear and operate in predictable ways Understanding Guideline 3.2

3.2.1 On Focus: When any component receives focus, it does not initiate a change of context. (Level A) How to Meet 3.2.1 Understanding 3.2.1

3.2.2 On Input: Changing the setting of any user interface component does not automatically cause a change of context unless the user has been advised of the behavior before using the component. (Level A) How to Meet 3.2.2 Understanding 3.2.2

3.2.3 Consistent Navigation: Navigational mechanisms that are repeated on multiple Web pages within a set of Web pages occur in the same relative order each time they are repeated, unless a change is initiated by the user. (Level AA) How to Meet 3.2.3 Understanding 3.2.3

3.2.4 Consistent Identification: Components that have the same functionality within a set of Web pages are identified consistently. (Level AA) How to Meet 3.2.4 Understanding 3.2.4

3.2.5 Change on Request: Changes of context are initiated only by user request or a mechanism is available to turn off such changes . (Level AAA) How to Meet 3.2.5 Understanding 3.2.5

Guideline 3.3 Input Assistance: Help users avoid and correct mistakes Understanding Guideline 3.3

3.3.1 Error Identification: If an input error is detected, the item that is in error is identified and the error is described to the user in text. (Level A) How to Meet 3.3.1 Understanding 3.3.1

3.3.2 Labels or Instructions: Labels or instructions are provided when content requires user input. (Level A) How to Meet 3.3.2 Understanding 3.3.2

3.3.3 Error Suggestion: If an input error is detected and suggestions for correction are known, then the suggestions are provided to the user, unless it would jeopardize the security or purpose of the content. (Level AA) How to Meet 3.3.3 Understanding 3.3.3

3.3.4 Error Prevention (Legal, Financial, Data): For Web pages that cause legal commitments or financial transactions for the user to occur, that modify or delete user-controllable data in data storage systems, or that submit user test responses, at least one of the following is true: (Level AA) How to Meet 3.3.4 Understanding 3.3.4

  1. Reversible: Submissions are reversible.

  2. Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them .

  3. Confirmed: A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission .

3.3.5 Help: Context-sensitive help is available. (Level AAA) How to Meet 3.3.5 Understanding 3.3.5

3.3.6 Error Prevention (All): For Web pages that require the user to submit information, at least one of the following is true: (Level AAA) How to Meet 3.3.6 Understanding 3.3.6

  1. Reversible: Submissions are reversible.

  2. Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them .

  3. Confirmed: A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission .

Principle 4: Robust - Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies

Guideline 4.1 Compatible: Maximize compatibility with current and future user agents, including assistive technologies Understanding Guideline 4.1

4.1.1 Parsing: Content implemented using markup languages has elements with complete start and end tags, except as allowed by their specifications, are nested according to their specifications and any IDs are unique . (Level A) How to Meet 4.1.1 Understanding 4.1.1

Note: Start and end tags that are missing a critical character in their formation, such as a closing angle bracket or a mismatched attribute value quotation mark are not complete.

4.1.2 Name, Role, Value: For all user interface components, the name and role can be programmatically determined; states, properties, and values that can be set by the user can be programmatically determined and programmatically set; and notification of changes to these items is available to user agents, including assistive technologies. (Level A) How to Meet 4.1.2 Understanding 4.1.2

Note: This success criterion is primarily for Web authors who develop or script their own user interface controls. For example, standard HTML controls already meet this provision when used according to specification.

Conformance

This section is normative.

This section lists requirements for conformance to WCAG 2.0 as well as information about how to make optional conformance claims. It also explains what it means for Web content technologies to be accessibility-supported, since only accessibility-supported content can be relied on for conformance.

Conformance Requirements

In order to conform to WCAG 2.0, all of the following conformance requirements must be satisfied for each Web page:

1.) Conformance Level: One of the following levels of conformance is met in full.

  • Level A: For Level A conformance (the minimum level of conformance), the Web page satisfies all the Level A success criteria, or a conforming alternate version is provided.

  • Level AA: For Level AA conformance, the Web page satisfies all the Level A and Level AA success criteria, or a Level AA conforming alternate version is provided.

  • Level AAA: For Level AAA conformance, the Web page satisfies all the Level A, Level AA and Level AAA success criteria, or a Level AAA conforming alternate version is provided.

Note: Although conformance can only be achieved at the stated levels, authors are encouraged to satisfy and report progress toward meeting success criteria from all levels beyond the achieved level of conformance.

2.) Full pages: Conformance is for full Web page(s) only, and cannot be achieved if part of a Web page is excluded.

Note: For the purpose of determining conformance, a conforming alternative to part of a page's content is considered part of the page when the alternative content is obtainable directly from the page.

3.) Accessibility-Supported Technologies Only: Only accessibility-supported Web technologies are relied upon to satisfy the success criteria. Any information or functionality that is implemented in technologies that are not accessibility supported must also be available via technologies that are accessibility supported. (See Understanding accessibility support.)

4.) Complete processes: When a series of Web pages present sequential steps that need to be completed in order to accomplish an activity, all Web pages in the series conform at a particular level. (Conformance is not possible at any level if all pages in the sequence do not conform at that level.)

Example: An online store has a series of pages that are used to select and purchase products. All pages in the series from start to finish (checkout) must conform in order for any page that is part of the sequence to conform.

5.) Non-Interference: If Web technologies that are not accessibility supported are used on a page, or accessibility-supported technologies are used in a non-conforming way, then they do not block the ability of users to access the rest of the page. Specifically, the Web page as a whole continues to meet the conformance requirements under all of the following conditions:

  1. when any (non accessibility-supported) technology is turned on in a user agent, and

  2. when it is turned off in a user agent, and

  3. when it is not supported by a user agent

Note: The following success criteria all apply to full pages including technologies that are not accessibility supported or relied upon to meet the other success criterion because they deal with things that could interfere with overall use of the page: 1.4.2 - Audio Control, 2.1.1 - Keyboard, 2.3.1 - Three Flashes or Below Threshold, and 2.2.2 - Pausing

Note: If pages can not conform (for example, conformance test pages or example pages) they can not be included in the scope of conformance or conformance claim.

For more information, see Understanding Conformance Requirements.

Conformance claims (optional)

Conformance is defined only for Web pages. However, a conformance claim may be made to cover one page, a series of pages, or multiple related Web pages.

Required components of a conformance claim

Conformance claims are not required. Authors can conform to WCAG 2.0 without making a claim. However, if a conformance claim is made, then the conformance claim must include the following information:

  1. Date of the claim

  2. Guidelines title, version and URI "Web Content Accessibility Guidelines 2.0 at {URI of final document}"

  3. Conformance level satisfied: (Level A, AA or AAA)

  4. A concise description of the Web pagessuch as a list of URIs for which the claim is made, including whether subdomains are included in the claim.

    Note 1: The Web pages may be described by list or by an expression which describes all of the URIs included in the claim.

    Note 2: Web-based products that do not have a URI prior to installation on the customer's Web site may have a statement that the product would conform when installed.

  5. A list of accessibility-supported technologies that includes all of the Web content technologies relied upon .

    Note: When citing technologies that have multiple versions, the version(s) supported must be specified.

Optional components of a conformance claim

In addition to the required components of a conformance claim above, consider providing additional information to assist users. Recommended additional information includes:

  1. A list of success criteria beyond the level of conformance claimed that have been met. This information should be provided in a form that consumers can use, preferably machine-readable metadata.

  2. A list of the specific technologies that are "used but not relied upon ."

  3. A list of user agents, including assistive technologies, that were used to test the content.

  4. Information about any additional steps taken that go beyond the success criteria to enhance accessibility.

  5. A machine-readable metadata version of the list of specific technologies that are relied upon.

  6. A machine-readable metadata version of the conformance claim.

Statement of partial conformance

Sometimes, Web pages are created that will later have additional content added to them. For example, an email program, a blog, an article that allows users to add comments to the bottom, or applications supporting user contributed content. Another example would be a page composed of content aggregated from multiple contributors, such as in portals and news sites. Sometimes, the content from the other sources is automatically inserted into the page over time.

In both of these cases, it is not possible to know at the time of original posting what the content of the pages will be. Two options are available:

  1. A determination of conformance can be made based on best knowledge. If a page of this type is monitored and kept conforming (non-conforming content is immediately removed or made conforming) then a determination or claim of conformance can be made since, except for except for errors in externally contributed content which are corrected or removed immediately, the page conforms. No conformance claim should be made if it is not possible to monitor or correct non-conforming content;

    OR

  2. A "statement of partial conformance" is made, that the page does not conform, but could conform if certain parts were removed. The form of that statement would be, "This page would conform to WCAG 2.0 at level X if the following parts from uncontrolled sources were removed." In addition, the following would also be true of the non-conforming content. The content that is excluded in the statement of partial conformance:

    1. cannot be content that is under the author's control

    2. must be described in a way that that users can identify (e.g. they can't be described as "all parts that we do not control" unless they are clearly marked as such.)

Appendix A: Glossary

This section is normative.

abbreviation

shortened form of a word, phrase, or name

Note: This includes initialisms and acronyms where:

  1. initialisms are shortened forms of a name or phrase made from the initial letters of words or syllables contained in that name or phrase

    Note 1: Not defined in all languages.

    Example 1: SNCF is a French initialism that contains the initial letters of the Société Nationale des Chemins de Fer, the French national railroad.

    Example 2: ESP is an initialism for extrasensory perception.

  2. acronyms are abbreviated forms made from the initial letters or parts of other words (in a name or phrase) which may be pronounced as a word

    Example: NOAA is an acronym made from the initial letters of the National Oceanic and Atmospheric Administration in the United States.

accessibility supported

supported by users' assistive technologies as well as the accessibility features in browsers and other user agents

To qualify as an accessibility-supported Web content technology (or feature of a technology), both of the following must be true for a Web content technology (or feature):

  1. The Web content technology must be supported by users' assistive technology (AT). This means that the technology has been tested for interoperability with users' assistive technology in the human language(s) of the content,

    AND

  2. The Web content technology must have accessibility-supported user agents that are available to users. This means that at least one of the following is true:

    1. The technology is supported natively in widely-distributed user agents that are also accessibility supported (such as HTML and CSS);

      OR

    2. The technology is supported in a widely-distributed plug-in that is also accessibility supported;

      OR

    3. The content is available in a closed environment, such as a university or corporate network, where the user agent required by the technology and used by the organization is also accessibility supported;

      OR

    4. The user agent(s) that support the technology are accessibility supported and are available for download or purchase in a way that:

      1. does not cost a person with a disability any more than a person without a disability and

      2. is as easy to find and obtain for a person with a disability as it is for a person without disabilities.

Note 1: The WCAG Working group and the W3C do not specify which or how many assistive technologies must support a Web technology in order for it to be classified as accessibility supported. (See Level of Assistive Technology Support Needed for "Accessibility Support".)

Note 2: Web technologies that are not accessibility supported can be used as long as they are not relied upon and the page as a whole meets the conformance requirements including Conformance Requirement 3 (Accessibility-Supported Technologies) and Conformance Requirement 5 (Non-Interference) are met.

Note 3: When a Web Technology is "accessibility supported," it does not imply that the entire technology must be supported. Most technologies lack support for at least one feature. When documenting "accessibility support" for a technology, the support for specific aspects, features, and extensions should be cited if the technology as a whole is not accessibility supported. A profile of a technology may be used to give a name to the set of aspects, features, or extensions of a technology that are "accessibility supported." Pages conform to WCAG only if aspects or features of the technology that are accessibility supported can be relied upon to meet WCAG requirements.

Note 4: When citing technologies that have multiple versions, the version(s) supported should be specified.

Note 5: The easiest way to be sure that the technologies and features being used and relied upon are accessibility supported is to use technologies from documented lists of accessibility supported Web content technologies. (See Understanding Documented lists of Web technologies with Accessibility Support.) Some authors, companies or others may wish to document and use their own lists of accessibility-supported technologies. However, all technologies on the list must meet the definition of accessibility supported content technologies above.

activity where moving, blinking, scrolling, or auto-updating is essential

activity where moving, blinking, scrolling, or auto-updating is central to the design of the activity and removal would fundamentallychange the functionality of the content

ASCII art

picture created by a spatial arrangement of characters or glyphs (typically from the 95 printable characters defined by ASCII).

assistive technology (as used in this document)

hardware and/or software that acts as a user agent, or along with a mainstream user agent, to provide services to meet the requirements of users with disabilities that go beyond those offered by the mainstream user agents

Note 1: Services provided by assistive technology include alternative presentations (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).

Note 2: Assistive technologies often communicate data and messages with mainstream user agents by using and monitoring APIs.

Note 3: The distinction between mainstream user agents and assistive technologies is not absolute. Many mainstream user agents provide some features to assist individuals with disabilities. The basic difference is that mainstream user agents target broad and diverse audiences that usually include people with and without disabilities. Assistive technologies target narrowly defined populations of users with specific disabilities. The assistance provided by an assistive technology is more specific and appropriate to the needs of its target users. The mainstream user agent may provide important services to assistive technologies like retrieving Web content from program objects or parsing markup into identifiable bundles.

Example: Examples of assistive technologies that are important in the context of this document include the following:

  • screen magnifiers, and other visual reading assistants, which are used by people with visual, perceptual and physical print disabilities to change text font, size, spacing, color, synchronization with speech, etc. in order to improve the visual readability of rendered text and images;

  • screen readers, which are used by people who are blind to read textual information through synthesized speech or braille;

  • text-to-speech software, which is used by some people with cognitive, language, and learning disabilities to convert text into synthetic speech;

  • voice recognition software, which may be used by people who have some physical disabilities;

  • alternative keyboards, which are used by people with certain physical disabilities to simulate the keyboard (including alternate keyboards that use headpointers, single switches, sip/puff and other special input devices.);

  • alternative pointing devices, which are used by people with certain physical disabilities to simulate mouse pointing and button activations.

audio and/or video alternative to text

media that presents no more information than is already presented in text (directly or via text alternatives)

Note: An audio and/or video alternative to text is provided for those who benefit from alternate representations of text. Audio and/or video alternative to text may be audio-only, video-only (including sign-language video), or audio-video.

audio description

narration added to the soundtrack to describe important visual details that cannot be understood from the main soundtrack alone

Note 1: Audio description of video provides information about actions, characters, scene changes, on-screen text, and other visual content.

Note 2: In standard audio description, narration is added during existing pauses in dialogue. (See also extended audio description.)

Note 3: Also called "video description" and "descriptive narration."

blink

switch back and forth between two visual states in a way that that does not qualify as flash (e.g. it is too slow and/or the change in relative luminance is too small to qualify as flashing)

Note: The slower blink is in contrast with flashing, which refers to rapid changes in brightness which can cause seizures. See general flash and red flash thresholds.

CAPTCHA

initialism for "Completely Automated Public Turing test to tell Computers and Humans Apart"

Note 1: CAPTCHA tests often involve asking the user to type in text that is displayed in an obscured image or audio file.

Note 2: A Turing test is any system of tests designed to differentiate a human from a computer. It is named after famed computer scientist Alan Turing. The term was coined by researchers at Carnegie Mellon University. [CAPTCHA]

captions

text presented and synchronized with synchronized media to provide not only the speech, but also non-speech information conveyed through sound, including meaningful sound effects and identification of speakers

Note 1: 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.

Note 2: Audio descriptions can be, but do not need to be, captioned since they are descriptions of information that is already presented visually.

changes of context

change of:

  1. user agent;

  2. viewport;

  3. focus;

  4. content that changes the meaning of the Web page.

Note: A change of content is not always a change of context. Small changes in content, such as an expanding outline or dynamic menu, do not change the context.

Example: Submitting a form, opening a new window, or moving focus to a different component are examples of changes of context.

conformance

satisfying all the requirements of a given standard, guideline or specification

conforming alternate version

version that

  1. conforms at the designated level, and

  2. provides all of the same information and functionality in the same human language, and

  3. is as up to date as the non-conforming content, and

  4. for which one of the following is true:

    1. the conforming version can be reached from the non-conforming page via an accessibility supported mechanism, or

    2. the non-conforming version can only be reached from the conforming version, or

    3. the non-conforming version can only be reached from a conforming page that also provides a mechanism to reach the conforming version

Note 1: In this definition, "can only be reached" means that there is some mechanism, such as a conditional re-direct, that prevents a user from "reaching" (loading) the non-conforming page unless the user had just come from the specified page.

Note 2: The alternate version does not need to be matched page for page with the original (e.g. the alternative to a page may consist of multiple pages).

Note 3: If multiple language versions are available, then conforming versions are required for each language offered.

Note 4: Alternate versions may be provided to accommodate different technology environments or user groups. Each version should be as conformant as possible. One version must be fully conformant in order to meet conformance requirement 1.

Note 5: Alternate versions should not be confused with supplementary information, which support the original page and enhance comprehension.

Note 6: Setting user preferences within the content to produce a conforming version is an acceptable mechanism for reaching another version as long as the method used to set the preferences is accessibility supported.

See Understanding Conforming Alternate Versions

content (Web content)

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

context-sensitive help

help text that provides information related to the function currently being performed

contrast ratio

(L1 + 0.05) / (L2 + 0.05), where

Note 1: Contrast ratios can range from 1 to 21 (commonly written 1:1 to 21:1).

Note 2: For dithered colors, use the average values of the colors that are dithered (average R, average G, and average B).

Note 3: Text can be evaluated with anti-aliasing turned off.

Note 4: Background color is the specified color of content over which the text is to be rendered in normal usage. If no background color is specified, then white is assumed.

Note 5: Background color is the specified color of content over which the text is to be rendered in normal usage. It is an error if no background color is specified when a foreground color is specified, because the user's default background color is unknown and cannot be evaluated for sufficient contrast. For the same reason, it is an error if no foreground color is specified when a background color is specified.

emergency

a sudden, unexpected situation or occurrence that requires immediate action to preserve health, safety, or property

extended audio description

audio description that is added to an audiovisual presentation by pausing the video so that there is time to add additional description

Note: This technique is only used when the sense of the video would be lost without the additional audio description.

flash

a pair of opposing changes in relative luminance of 10% or more where the relative luminance of the darker image is below 0.80

Note: Flash is characterized by rapid changes of relative luminance occurring more than three times per second, while blink is less than three times per second.

Note: See general flash threshold and red flash threshold for more precise information about the applicability and constraints of flash.

full text alternative for synchronized media including any interaction

document including correctly sequenced text descriptions of all visual settings, actions, speakers, and non-speech sounds, and transcript of all dialogue combined with a means of achieving any outcomes that are achieved using interaction (if any) during the synchronized media

Note: A screenplay used to create the synchronized media content would meet this definition only if it was corrected to accurately represent the final synchronized media after editing.

functionality

processes and outcomes achievable through user action

general flash and red flash thresholds

a sequence of flashes or rapidly changing image sequences where all three of the following occur:

  1. there are more than three flashes within any one-second period; and

  2. the flashing is below 50 Hz; and

  3. the combined area of flashes occurring concurrently and contiguously occupies more than a total of .006 steradians (25% of any 10 degree visual field on the screen).

For the general flash threshold, a flash is defined as a pair of opposing changes in relative luminance of 10% or more and the relative luminance of the darker image is below 0.80. An "opposing change" is an increase followed by a decrease, or a decrease followed by an increase.

For the red flash threshold, a flash is defined as any transition to or from a saturated red.

Note: For general Web content, using a 341 x 256 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 x 768 pixels will provide a good estimate of a 10 degree visual field for standard screen sizes and viewing distances.

human language

language that is spoken, written or signed (through visual or tactile means ) to communicate with humans

Note: See also sign language.

idiom

phrase whose meaning cannot be deduced from the meaning of the individual words and the specific words cannot be changed without losing the meaning

Note: idioms can usually not be translated directly, word for word, without losing their (cultural or language-dependent) meaning.

Example 1: In English, "kicking the bucket" means "dying," but the phrase cannot be changed to "kicking the buckets" or "kicking the tub" or "booting the bucket" or "knocking over the bucket" without losing its meaning.

Example 2: In English, "spilling the beans" means "revealing a secret." However, "knocking over the beans" or "spilling the vegetables" does not mean the same thing.

Example 3: In Japanese, the phrase "さじを投げる " literally translates into "he throws a spoon," but it means that there is nothing he can do and finally he gives up.

Example 4: In Dutch, "Hij ging met de kippen op stok" literally translates into "He went to roost with the chickens," but it means that he went to bed early.

informative

for information purposes and not required for conformance

Note: Content required for conformance is referred to as "normative."

input error

information provided by the user that is not accepted

Note: This includes:

  1. Information that is required by the Web page but omitted by the user

  2. Information that is provided by the user but that falls outside the required data format or values

jargon

words used in a particular way by people in a particular field

Example: The word StickyKeys is jargon from the field of assistive technology/accessibility.

keyboard interface

interface used by software to obtain keystroke input

Note 1: Allows users to provide keystroke input to programs even if the native technology does not contain a keyboard.

Example: A touch screen PDA has a keyboard interface built into its operating system as well as a connector for external keyboards. Applications on the PDA can use the interface to obtain keyboard input either from an external keyboard or from other applications that provide simulated keyboard output, such as handwriting interpreters or speech-to-text applications with "keyboard emulation" functionality.

Note 2: Operation of the application (or parts of the application) through a keyboard-operated mouse emulator, such as MouseKeys, does not qualify as operation through a keyboard interface because operation of the program is through its pointing device interface, not through its keyboard interface.

label

text or other component with a text alternative that is presented to a user to identify a component within Web content

Note: A label is presented to all users whereas the name may be hidden and only exposed by assistive technology. In many (but not all) cases the name and the label are the same.

larger scale (text)

with at least 18 point or 14 point bold or font size that would yield equivalent stroke width for Chinese, Japanese and Korean (CJK) fonts

Note 1: Fonts with extraordinarily thin strokes or unusual features and characteristics that reduce the familiarity of their letter forms are harder to read, especially at lower contrast levels.

Note 2: Font size is the size when the content is delivered. It does not include resizing that may be done by a user.

Note 3: The actual size of the character that a user sees in dependent both on the author-defined size and the users display or user-agent settings. This success criterion is based on common pixel sizes available today. Users who have low vision would be responsible for choosing appropriate settings.

legal commitments

transactions where the person incurs a legally binding obligation or benefit

Example: A marriage license, a stock trade (financial and legal), a will, a loan, adoption, signing up for the army, a contract of any type, etc.

live audio-only

A time-based live presentation that contains only audio (no video and no interaction)

live video-only

A time-based live presentation that contains only video (no audio and no interaction)

lower secondary education level

the two or three year period of education that begins after completion of six years of school and ends nine years after the beginning of primary education

Note: This definition is based on [UNESCO].

mechanism

process or technique for achieving a result

Note 1: The mechanism may be explicitly provided in the content, or may be relied on to be provided by either the platform or by user agents, including assistive technologies.

Note 2: The mechanism must meet all success criteria for the conformance level claimed.

must be presented in non-text format

would be invalid if presented in text

Example: Color blindness test, hearing test, vision exercise, spelling test.

name

text by which software can identify a component within Web content to the user

Note 1: The name may be hidden and only exposed by assistive technology, whereas a label is presented to all users. In many (but not all) cases, the label and the name are the same.

Note 2: This is unrelated to the name attribute in HTML.

navigated sequentially

navigated in the order defined for advancing focus from one element to the next with the keyboard

non-text content

any content that is not a sequence of characters that can be programmatically determined or where the sequence is not expressing something in human language

Note: This includes ASCII Art (which is a pattern of characters), emoticons, leetspeak (which is character substitution), and images representing text .

normative

required for conformance

Note 1: One may conform in a variety of well-defined ways to this document.

Note 2: Content identified as "informative" or "non-normative" is never required for conformance.

paused

stopped by user request and not resumed until requested by user

presentation

rendering of the content in a form to be perceived by users

primary education level

six year time period that begins between the ages of five and seven, possibly without any previous education

Note: This definition is based on [UNESCO].

process

series of user actions where each action is required in order to complete an activity

Example 1: Successful use of a series of Web pages on a shopping site requires users to view alternative products, prices and offers, select products, submit an order, provide shipping information and provide payment information.

Example 2: An account registration page requires successful completion of a Turing test before the registration form can be accessed.

programmatically determinable link context

additional information that can be programmatically determined from relationships with a link, combined with the link text, and presented to users in different modalities

Example: In HTML, information that is programmatically determinable from a link in English includes text that is in the same paragraph, list, or table cell as the link or in a table header cell that is associated with the table cell that contains the link.

Note: Since screen readers interpret punctuation, they can also provide the context from the current sentence, when the focus is on a link in that sentence.

programmatically determined

determined by software from author-supplied data provided in a way that different user agents, including assistive technologies, can extract and present this information to users in different modalities

Example: Determined in a markup language from elements and attributes that are accessed directly by commonly available assistive technology.

Example: Determined from technology-specific data structures in a non-markup language and exposed to assistive technology via an accessibility API that is supported by commonly available assistive technology.

programmatically set

set by software using methods that are supported by user agents, including assistive technologies

pure decoration

serving only an aesthetic purpose, providing no information, and having no functionality

Note: Text is only purely decorative if the words can be rearranged or substituted without changing their purpose.

Example: The cover page of a dictionary has random words in very light text in the background.

real-time event

event that a) occurs at the same time as the viewing and b) is not completely generated by the content

Example 1: A Webcast of a live performance (occurs at the same time as the viewing and is not prerecorded).

Example 2: An on-line auction with people bidding (occurs at the same time as the viewing).

Example 3: Live humans interacting in a fantasy world using avatars (is not completely generated by the content and occurs at the same time as the viewing).

relationships

meaningful associations between distinct pieces of content

relative luminance

the relative perceived brightness of any point, normalized to 0 for black and 1 for maximum white

Note 1: The relative luminance of an sRGB color is defined as L = 0.2126 * R + 0.7152 * G + 0.0722 * B where R, G and B are defined as:

  • if RsRGB <= 0.03928 then R = RsRGB/12.92 else R = ((RsRGB+0.055)/1.055) ^ 2.4

  • if GsRGB <= 0.03928 then G = GsRGB/12.92 else G = ((GsRGB+0.055)/1.055) ^ 2.4

  • if BsRGB <= 0.03928 then B = BsRGB/12.92 else B = ((BsRGB+0.055)/1.055) ^ 2.4

and RsRGB, GsRGB, and BsRGB are defined as:

  • RsRGB = R8bit/255

  • GsRGB = G8bit/255

  • BsRGB = B8bit/255

The "^" character is the exponentiation operator. (Formula taken from [sRGB] and [IEC-4WD]).

Note 2: Almost all systems used today to view Web content assume sRGB encoding. Unless it is known that another color space will be used to process and display the content, authors should evaluate using sRGB colorspace. If using other color spaces, see Understanding Success Criterion 1.4.3.

Note 3: For dithered colors, use average values of the colors used (average R, average G, and average B).

Note 4: Tools are available that automatically do the calculations when testing contrast and flash.

Note 5: A MathML version of the relative luminance definition is available.

relied upon (technologies that are)

the content would not conform if that technology is turned off or not supported

role

text or a number by which software can identify the function of a component within Web content

Example: A number that indicates whether an image functions as a hyperlink, command button, or check box.

same functionality

same result when used

Example: A submit "search" button on one Web page and a "find" button on another Web page may both have a field to enter a term and list topics in the Web site related to the term submitted. In this case, they would have the same functionality but would not be labeled consistently.

same relative order

same position relative to other items

Note: Items are considered to be in the same relative order even if other items are inserted or removed from the original order. For example, expanding navigation menus may insert an additional level of detail or a secondary navigation section may be inserted into the reading order.

satisfies a success criterion

the success criterion does not evaluate to 'false' when applied to the page

set of Web pages

collection of Web pages that share a common purpose and that are created by the same author, group or organization

Note: Different language versions would be considered different sets of Web pages .

sign language

a language using combinations of movements of the hands and arms, facial expressions, or body positions to convey meaning

sign language interpretation

translation of one language, generally a spoken language, into a sign language

Note: True sign languages are independent languages that are unrelated to the spoken language(s) of the same country or region.

specific sensory experience

a sensory experience that is not purely decorative and does not primarily convey important information or perform a function

Example: Examples include a performance of a flute solo, works of visual art etc.

structure
  1. The way the parts of a Web page are organized in relation to each other; and

  2. The way a collection of Web pages is organized

supplemental content

additional content that illustrates or clarifies the primary content

Example 1: An audio version of a Web page.

Example 2: An illustration of a complex process.

Example 3: A paragraph describing the major outcomes and recommendations made in a research study.

synchronized media

audio or video synchronized with another format for presenting information and/or with time-based interactive components

technology (Web content)

mechanism for encoding instructions to be rendered, played or executed by user agents

Note 1: As used in these guidelines "Web Technology" and the word "technology" (when used alone) both refer to Web Content Technologies.

Note 2: 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 synchronized media presentations to dynamic Web applications.

Example: Some common examples of Web content technologies include HTML, CSS, SVG, PNG, PDF, Flash, and JavaScript.

text

sequence of characters that can be programmatically determined, where the sequence is expressing something in human language

text alternative

programmatically determined text that is used in place of non-text content, or text that is used in addition to non-text content and referred to from the programmatically determined text

Example: An image of a chart is described in text in the paragraph after the chart. The short text-alternative for the chart indicates that a description follows.

used in an unusual or restricted way

words used in such a way that users must know exactly which definition to apply in order to understand the content correctly

Example: The term "gig" means something different if it occurs in a discussion of music concerts than it does in article about computer hard drive space, but the appropriate definition can be determined from context. By contrast, the word "text" is used in a very specific way in WCAG 2.0, so a definition is supplied in the glossary.

user agent

any software that retrieves and presents Web content for users

Example: Web browsers, media players, plug-ins, and other programs — including assistive technologies — that help in retrieving, rendering, and interacting with Web content.

user-controllable

data that is intended to be accessed by users

Note: This does not refer such things as internet logs and search engine monitoring data.

Example: Name and address fields for a user's account.

user interface component

a part of the content that is perceived by users as a single control for a distinct function

Note: Multiple user interface components may be implemented as a single programmatic element. Components here is not tied to programming techniques but rather to what the user perceives as separate controls.

Example: An applet has a "control" that can be used to move through content by line or page or random access. Since each of these would need to have a name and be setable independently, they would each be a "user interface component."

video

the technology of moving pictures or images

Note: Video can be made up of animated or photographic images, or both.

viewport

object in which the user agent presents content

Note 1: The user agent presents content through one or more viewports. Viewports include windows, frames, loudspeakers, and virtual magnifying glasses. A viewport may contain another viewport (e.g., nested frames). User agent user interface controls such as prompts, menus, and alerts are not viewports.

Note 2: This definition is based on User Agent Accessibility Guidelines 1.0 Glossary.

Web page

a non-embedded resource that is referenced by a URI plus any other resources that are used in the rendering or intended to be rendered together with it by a user agent

Note 1: Although any "other resources" would be rendered together with the primary resource, they would not necessarily be rendered simultaneously with each other.

Note 2: For the purposes of conformance with these guidelines, a resource must be "non-embedded" within the scope of conformance to be considered a Web page.

Example 1: A Web resource including all embedded images and media.

Example 2: A Web mail program built using Asynchronous JavaScript and XML (AJAX). The program lives entirely at http://mail.example.com, but includes an inbox, a contacts area and a calendar. Links or buttons are provided that cause the the inbox, contacts, or calendar to display, but do not change the URL of the page as a whole.

Example 3: A customizable portal site, where users can choose content to display from a set of different content modules.

Example 4: When you enter "http://shopping.example.com/" in your browser, you enter a movie-like interactive shopping environment where you visually move about a store dragging products off of the shelves around you into a visual shopping cart in front of you. Clicking on a product causes it to be demonstrated with a specification sheet floating alongside.

Appendix B: Acknowledgments

This section is informative.

This publication has been funded in part with Federal funds from the U.S. Department of Education under contract number ED05CO0039. The content of this publication does not necessarily reflect the views or policies of the U.S. Department of Education, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

Additional information about participation in the Web Content Accessibility Guidelines Working Group (WCAG WG) can be found on the Working Group home page.

Participants active in the WCAG WG at the time of publication

  • Bruce Bailey (US Access-Board)

  • Frederick Boland (NIST)

  • Judy Brewer (W3C / MIT)

  • Ben Caldwell (Trace R&D Center, University of Wisconsin-Madison)

  • Sofia Celic (Vision Australia)

  • Michael Cooper (W3C / MIT)

  • Roberto Ellero (International Webmasters Association / HTML Writers Guild)

  • Donald Evans (AOL)

  • Bengt Farre (W3C Invited Expert)

  • Becky Gibson (IBM)

  • Loretta Guarino Reid (Google)

  • Katie Haritos-Shea (W3C Invited Expert)

  • Sean Hayes (Microsoft)

  • Andrew LaHart (IBM)

  • Gez Lemon (International Webmasters Association / HTML Writers Guild)

  • Alex Li (SAP AG)

  • Luca Mascaro (International Webmasters Association / HTML Writers Guild)

  • David MacDonald (E-Ramp Inc.)

  • Sorcha Moore (Segala)

  • Roberto Scano (International Webmasters Association / HTML Writers Guild)

  • Cynthia Shelly (Microsoft)

  • John Slatin (Accessibility Institute, University of Texas at Austin)

  • Andi Snow-Weaver (IBM)

  • Christophe Strobbe (DoArch, K.U.Leuven)

  • Makoto Ueki (Infoaxia)

  • Gregg Vanderheiden (Trace R&D Center, University of Wisconsin)

Other previously active WCAG WG participants and other contributors to WCAG 2.0

Jenae Andershonis, Avi Arditti, Aries Arditi, Mike Barta, Sandy Bartell, Kynn Bartlett, Marco Bertoni, Harvey Bingham, Paul Bohman, Dick Brown, Doyle Burnett, Roberto Castaldo, Jonathan Chetwynd, Wendy Chisholm, Alan Chuter, David M Clark, Joe Clark, Tom Croucher, Nir Dagan, Daniel Dardailler, Geoff Deering, Alan J. Flavell, Al Gilman, Kerstin Goldsmith, Jon Gunderson, Emmanuelle Gutiérrez y Restrepo, Eric Hansen, Donovan Hipke, Bjoern Hoehrmann, Yvette Hoitink, Ian Jacobs, Phill Jenkins, Leonard R. Kasday, Ken Kipness, Andrew Kirkpatrick, Marja-Riitta Koivunen, Scott Luebking, Tim Lacy, Jim Ley, William Loughborough, Greg Lowney, Mathew J Mirabella, Charles McCathieNevile, Matt May, Marti McCuller, Charles F. Munat, Robert Neff, Bruno von Niman, Tim Noonan, Sebastiano Nutarelli, Graham Oliver, Sean B. Palmer, Sailesh Panchang, Anne Pemberton, David Poehlman, Adam Victor Reed, Chris Ridpath, Lee Roberts, Gregory J. Rosmaita, Lisa Seeman, Justin Thorp, Gian Sampson-Wild, Joel Sanda, Neil Soiffer, Jim Thatcher, Takayuki Watanabe, Jason White.

Appendix C: References

This section is informative.

CAPTCHA
The CAPTCHA Project, Carnegie Mellon University. The project is online at http://www.captcha.net.
IEC-4WD
IEC/4WD 61966-2-1: Colour Measurement and Management in Multimedia Systems and Equipment - Part 2.1: Default Colour Space - sRGB. May 5, 1998.
sRGB
"A Standard Default Color Space for the Internet - sRGB," M. Stokes, M. Anderson, S. Chandrasekar, R. Motta, eds., Version 1.10, November 5, 1996. A copy of this paper is available at http://www.w3.org/Graphics/Color/sRGB.html.
UNESCO
International Standard Classification of Education, 1997. A copy of the standard is available at http://www.unesco.org/education/information/nfsunesco/doc/isced_1997.htm.
WCAG10
Web Content Accessibility Guidelines 1.0, G. Vanderheiden, W. Chisholm, I. Jacobs, Editors, W3C Recommendation, 5 May 1999, http://www.w3.org/TR/1999/WAI-WEBCONTENT-19990505/. The latest version of WCAG 1.0 is available at http://www.w3.org/TR/WAI-WEBCONTENT/.