Web Content Accessibility Guidelines 2.0

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This is a Candidate Recommendation of Web Content Accessibility Guidelines 2.0 (WCAG 2.0) from the Web Content Accessibility Guidelines Working Group. This version integrates minor changes in response to comments received on the 11 December 2007 Last Call Working Draft. The Working Group received approximately 400 comments on this draft. Most of the changes were deemed non-substantive. A few substantive changes were made, which are marked as "at risk" because they have not yet had sufficient community review. There is a version of WCAG 2.0 with changes marked inline to facilitate review.

Much of the Working Group's response to these comments took the form of additional clarifications and techniques in the associated non-normative documents, Understanding WCAG 2.0 and Techniques for WCAG 2.0. Although those documents do not have the formal status that WCAG 2.0 itself has, they provide information important to understanding and implementing WCAG. The Working Group requests that reviewers consider the information in those documents in context of any review of WCAG 2.0.

Publication as a Candidate Recommendation indicates that the WCAG WG believes it has addressed all substantive issues and that the document is ready for trial implementations. The first public Working Draft of WCAG 2.0 was published 25 January 2001. Since then, the WCAG WG has published twelve Working Drafts, addressed more than 3000 issues, and developed a variety of support information for the guidelines. See How WAI Develops Accessibility Guidelines through the W3C Process for more background on document maturity levels.

Exit Criteria

The Web Content Accessibility Guidelines Working Group intends to submit this document for consideration as a W3C Proposed Recommendation as soon as the following conditions are met:

At least 10 conforming Web sites¹ are available, of which
- At least four conform at level A,
- At least four conform at level AA,
- At least two conform at level AAA;
At least one Web site is available which makes a Statement of Partial Conformance;
At least two implementations² exist for each success criterion;
Accessibility support documentation³ is available for at least two technologies with at least four platforms (operating system/user agent/assistive technology combinations);
All sufficient techniques listed in Understanding WCAG 2.0 at the end of the Candidate Recommendation period contain test procedures;
The Working Group has responded formally to all issues raised against this document related to any implementation efforts during the Candidate Recommendation period.

[1] The conforming Web sites should be distinct and independently developed, represent diverse types of content including Content Management System (CMS)-generated content, utilize diverse Web technologies including W3C and non-W3C technologies, and have a varied representation of primary languages and scripts. Web applications can be single Web pages; otherwise conformance claims for Web sites should contain a minimum of 5 Web pages. Some success criteria may be satisfied in the conforming Web sites by the absence of applicable content on the Web pages, but Web sites should exhibit positive implementations of a significant number of success criteria at the corresponding level of conformance.

[2] The implementations of success criteria need not be within the conforming Web sites. Note that these implementations must contain content of the type addressed by the individual success criterion, that is, they cannot satisfy the success criteria purely by the absence of applicable content on the Web pages.

[3] In the absence of documentation of accessibility-supported technologies, conforming sites may show evidence by testing with assistive technologies.

Besides these implementations, feedback on implementation and use of this specification is welcome, including from implementations not selected as part of the formal implementation report for exiting Candidate Recommendation.

The implementation results will be publicly released and are intended solely to be used as evidence of WCAG 2.0 implementability as a snapshot of the actual implementation behaviors at one moment of time. These implementations may not be the same as the Web sites available to the public.

Working closely with Web developers, we expect to receive initial implementations by 30 June 2008 and to show evidence of meeting the exit criteria by 31 August 2008.

Items at Risk

As a part of the Candidate Recommendation process, any items that might change or where there may not be implementations are to be marked as "at risk." "At risk" in no way implies that these success criteria are less important to accessibility. It is purely an artifact of the W3C requirement to identify any provision for which the Working Group believes it may not be able to document the required implementations by the end of the Candidate Recommendation period.

The following features are considered to be features at risk:

Criteria at Risk for Change

Success Criterion 1.2.1 - Audio-only and Video-only (Prerecorded), and Success Criterion 1.2.8 - Full Text Alternative: If implementation feedback from users indicates that the current version is less helpful than the version from 11 Dec 2007, these success criteria will revert to that version.
Success Criterion 1.4.3 - Contrast (Minimum): If implementation experience indicates that 5:1 is too restrictive, then the minimum ratio will be revised to 4.5:1 or to 4:1;
Success Criterion 2.2.2 - Pause, Stop, Hide: If implementation feedback from users indicates that the current version is less helpful than the version from 11 December 2007, or if it is determined that assistive technology can provide a way to stop moving content, this success criterion will revert to the Level AA fallback wording. The fallback wording for SC 2.2.2 would be:
2.2.2 Pause, Stop, Hide: For moving, blinking, scrolling, or auto-updating information, all of the following are true: (Level AA)
- Moving, blinking, scrolling: For any moving, blinking or scrolling information that (1) starts automatically, (2) lasts more than three seconds, and (3) is presented in parallel with other content, there is a mechanism for the user to pause or hide it unless the movement, blinking or scrolling is part of an activity where the changes are essential; and
- Auto-updating: For any auto-updating information that (1) starts automatically, (2) lasts more than three seconds, and (3) is presented in parallel with other content, there is a mechanism for the user to pause, hide, or control the frequency of the update; and
- Decoration: For any moving or blinking content that (1) starts automatically, (2) is presented in parallel with other content, (3) lasts more than three seconds, and (4) is pure decoration, there is a mechanism for the user to pause, stop, or hide it.

Criteria at Risk for Change or Becoming Advisory

Success Criterion 1.4.8 - Visual Presentation: If at least two implementations of this success criterion do not exist at the end of the Candidate Recommendation period, one or more of its clauses may be removed and its techniques listed as advisory (except where sufficient for other SC), or the success criterion itself may be removed if too many clauses need to be removed.

Criteria at Risk of Becoming Advisory

If at least two implementations of each of the following success criteria do not exist at the end of the Candidate Recommendation period, the success criteria may be removed and their techniques listed as advisory (except where sufficient for other SC).

Success Criterion 1.2.6 - Sign Language
Success Criterion 1.2.7 - Audio Description (Extended)
Success Criterion 1.2.8 - Full Text Alternatives
Success Criterion 1.2.9 - Live Audio-only

Comments

The Working Group requests that any comments be made using the provided online comment form. If this is not possible, comments can also be sent to public-comments-wcag20@w3.org. The archives for the public comments list are publicly available. Archives of the WCAG WG mailing list discussions are also publicly available.

Publication Information

This document has been produced as part of the W3C Web Accessibility Initiative (WAI). The goals of the WCAG Working Group are discussed in the WCAG Working Group charter. The WCAG Working Group is part of the WAI Technical Activity.

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

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

Introduction

This section is informative.

Web Content Accessibility Guidelines (WCAG) 2.0 defines how to make Web content more accessible to people with disabilities. Accessibility involves a wide range of disabilities, including visual, auditory, physical, speech, cognitive, language, learning, and neurological disabilities. 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. These guidelines also make Web content more usable by older individuals with changing abilities due to aging and often improve usability for users in general.

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 Web designers and developers, 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 common 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 where requirements and conformance testing are necessary such as in design specification, purchasing, regulation, and contractual agreements. In order to meet the needs of different groups and different situations, three levels of conformance are defined: A (lowest), AA, and AAA (highest). Additional information on 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 are informative and 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. Some advisory techniques address accessibility barriers that are not covered by the testable success criteria. Where common failures are known, these are also documented. See also Sufficient and Advisory Techniques in Understanding WCAG 2.0.

All of these layers of guidance (principles, 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. Metadata may assist users in finding content most suitable for their needs.

WCAG 2.0 Supporting Documents

The WCAG 2.0 document is designed to meet the needs of those who need a stable, referenceable technical standard. Other documents, called supporting documents, are based on the WCAG 2.0 document and address other important purposes including the ability to be updated to describe how WCAG would be applied with new technologies. Supporting documents include:

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.
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.
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. Each of these is introduced briefly below and defined more fully in the glossary.

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

The definition of "accessibility support" is provided in the Appendix A: Glossary section of these guidelines. For more information, see Understanding Accessibility Support.

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 that is presented to the user has a text alternative that serves the equivalent purpose, except for the situations listed below. (Level A) How to Meet 1.1.1 Understanding 1.1.1

Controls, Input: If non-text content is a control or accepts user input, then it has a name that describes its purpose. (Refer to Guideline 4.1 for additional requirements for controls and content that accepts user input.)
Time-Based Media: If non-text content is time-based media, then text alternatives at least provide descriptive identification of the non-text content. (Refer to Guideline 1.2 for additional requirements for media.)
Test: If non-text content is a test or exercise that must be presented in non-text format, then text alternatives at least provide descriptive identification of the non-text content.
Sensory: If non-text content is primarily intended to create a specific sensory experience, then text alternatives at least provide descriptive identification of the non-text content.
CAPTCHA: If the purpose non-text content 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 non-text content is pure decoration, is used only for visual formatting, or is not presented to users, then it is implemented in a way that it can be ignored by assistive technology.

Guideline 1.2 Time-based Media: Provide alternatives for time-based media Understanding Guideline 1.2

1.2.1 Audio-only and Video-only (Prerecorded): For prerecorded audio-only and prerecorded video-only media, the following are true, except when the audio or video is a media alternative for text and is clearly labeled as such: (Level A) How to Meet 1.2.1 Understanding 1.2.1

Prerecorded Audio-only: A text alternative is provided that presents equivalent information for prerecorded audio-only content.
Prerecorded Video-only: Either a text alternative or an audio track is provided that presents equivalent information for prerecorded video-only content.

1.2.2 Captions (Prerecorded): Captions are provided for all prerecorded audio content in synchronized media, except when the media is a media alternative for text and is clearly labeled as such. (Level A) How to Meet 1.2.2 Understanding 1.2.2

1.2.3 Audio Description or Full Text Alternative: A full text alternative for synchronized media including any interaction or audio description of the prerecorded video content is provided for synchronized media, except when the media is a media alternative for text and is clearly labeled as such. (Level A) How to Meet 1.2.3 Understanding 1.2.3

1.2.4 Captions (Live): Captions are provided for all live audio content in synchronized media. (Level AA) How to Meet 1.2.4 Understanding 1.2.4

1.2.5 Audio Description: Audio description is provided for all prerecorded video content in synchronized media. (Level AA) How to Meet 1.2.5 Understanding 1.2.5

1.2.6 Sign Language: Sign language interpretation is provided for all prerecorded audio content in synchronized media. (Level AAA) How to Meet 1.2.6 Understanding 1.2.6

1.2.7 Audio Description (Extended): Extended audio description is provided for all prerecorded video content in synchronized media. (Level AAA) How to Meet 1.2.7 Understanding 1.2.7

1.2.8 Full Text Alternative: A full text alternative for synchronized media including any interaction is provided for all prerecorded synchronized media and a text alternative that presents equivalent information is provided for all prerecorded video-only media. (Level AAA) How to Meet 1.2.8 Understanding 1.2.8

1.2.9 Live Audio-only: A text alternative that presents equivalent information for live audio-only content is provided. (Level AAA) How to Meet 1.2.9 Understanding 1.2.9

Candidate Recommendation Process Note: We are particularly looking for people interested in providing sites with implementations of Success Criterion 1.2.6, 1.2.7, 1.2.8, and 1.2.9. See Items at Risk for more information.

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, structure, 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. (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

Note: For requirements related to color, refer to Guideline 1.4.

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 is not 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 including programmatic access to color and other visual presentation coding.

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 independently from the overall 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 or not it is used to meet other success criteria) must meet this success criterion. See Conformance Requirement 5: Non-Interference.

1.4.3 Contrast (Minimum): The visual presentation of text and images of text has a contrast ratio of at least 5:1, except for the following: (Level AA) How to Meet 1.4.3 Understanding 1.4.3

Large Print: Large-scale text and images of large-scale text have a contrast ratio of at least 3:1;
Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are incidental text in an image, or that are not visible to anyone, have no minimum contrast requirement.
Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.

Candidate Recommendation Process Note: We are particularly looking for feedback on the contrast level for this success criterion (1.4.3). See Items at Risk for more information.

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

1.4.5 Images of Text: If the technologies being used can achieve the visual presentation, text is used to convey information rather than images of text except for the following: (Level AA) How to Meet 1.4.5 Understanding 1.4.5

Customizable: The image of text can be visually customized to the user's requirements;
Essential: A particular presentation of text is essential to the information being conveyed.

Note: Logotypes (text that is part of a logo or brand name) are considered essential.

1.4.6 Contrast (Enhanced): The visual presentation of text and images of text has a contrast ratio of at least 7:1, except for the following: (Level AAA) How to Meet 1.4.6 Understanding 1.4.6

Large Print: Large-scale text and images of large-scale text have a contrast ratio of at least 5:1;
Incidental: Text or images of text that are part of an inactive user interface component, that are pure decoration, that are incidental text in an image, or that are not visible to anyone, have no minimum contrast requirement.
Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.

1.4.7 Low or No Background Audio: For audio content that (1) is not an audio CAPTCHA and (2) contains speech in the foreground, at least one of the following is true: (Level AAA) How to Meet 1.4.7 Understanding 1.4.7

No Background: The audio does not contain background sounds.
Turn Off: The background sounds can be turned off.
20 dB: The background sounds are at least 20 decibels lower than the foreground speech content, with the exception of occasional sound effects.
Note: Per the definition of "decibel," background sound that meets this requirement will be approximately four times quieter than the foreground speech content.

1.4.8 Visual Presentation: For the visual presentation of blocks of text, a mechanism is available to achieve the following: (Level AAA) How to Meet 1.4.8 Understanding 1.4.8

foreground and background colors can be selected by the user
width is no more than 80 characters or glyphs (40 if CJK)
text is not justified (aligned to both the left and the right margins)
line spacing (leading) is at least space-and-a-half within paragraphs, and paragraph spacing is at least 1.5 times larger than the line spacing
text is resized without assistive technology up to 200 percent in a way that does not require the user to scroll horizontally to read a line of text on a full-screen window

Candidate Recommendation Process Note: We are particularly looking for people interested in provising sites with implementations of this success criterion (1.4.8). See Items at Risk for more information.

1.4.9 Images of Text (No Exception): Images of text are only used for pure decoration or where a particular presentation of text is essential to the information being conveyed. (Level AAA) How to Meet 1.4.9 Understanding 1.4.9

Note: Logotypes (text that is part of a logo or brand name) are considered essential.

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 No Keyboard Trap: If keyboard focus can be moved to a component of the page using a keyboard interface, then focus can be moved away from that component using only a keyboard interface, and, if it requires more than unmodified arrow or tab keys, the user is advised of the method for moving focus away. (Level A) How to Meet 2.1.2 Understanding 2.1.2

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 it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference.

2.1.3 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 2.1.3 Understanding 2.1.3

Guideline 2.2 Enough Time: Provide users 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 is essential and extending it would invalidate the activity; or
20 Hour Exception: The time limit is longer than 20 hours.

Note: This success criterion acts to ensure that changes in content or context as a result of a time limit will not occur unexpectedly, which could prevent 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 to those places where there is no other option. This success criterion should be considered in conjunction with Success Criterion 3.2.1 which puts limits on changes of content or context as a result of user action.

2.2.2 Pause, Stop, Hide: For moving, blinking, scrolling, or auto-updating information, all of the following are true: (Level A) How to Meet 2.2.2 Understanding 2.2.2

Moving, blinking, scrolling: For any moving, blinking or scrolling information that (1) starts automatically, (2) lasts more than five seconds, and (3) is presented in parallel with other content, there is a mechanism for the user to pause, stop, or hide it unless the movement, blinking, or scrolling is part of an activity where it is essential; and
Auto-updating: For any auto-updating information that (1) starts automatically, (2) lasts more than five seconds, and (3) is presented in parallel with other content, there is a mechanism for the user to pause, stop, or hide it or to control the frequency of the update unless the auto-updating is part of an activity where it is essential.

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 it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference.

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.

Note 4: An animation that occurs as part of a preload phase or similar situation can be considered essential if interaction cannot occur during that phase for all users, and if not indicating progress could confuse users or cause them to think that content was frozen or broken.

Candidate Recommendation Process Note: We are particularly looking for methods to meet Success Criterion 2.2.2 via user agent or assistive technology. See Items at Risk for more information.

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

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 navigate, find content and determine where they are Understanding Guideline 2.4

2.4.10 Section Headings: Section headings are used to organize the content. (Level AAA) How to Meet 2.4.10 Understanding 2.4.10

Note 1: "Heading" is used in its general sense and includes titles and other ways to add a heading to different types of content.

Note 2: This success criterion covers sections within writing, not user interface components. User Interface components are covered under Success Criterion 4.1.2.

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 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 except for proper names, technical terms, words of indeterminate language, and words or phrases that have become part of the vernacular of the immediately surrounding text. (Level AA) How to Meet 3.1.2 Understanding 3.1.2

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 identifying 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 of the words, in context, 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 automatically 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 automatically 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

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

Reversible: Submissions are reversible.
Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them.
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: In content implemented using markup languages, elements have complete start and end tags, elements are nested according to their specifications, elements do not contain duplicate attributes, and any IDs are unique, except where the specifications allow these features. (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 user interface components (including but not limited to: form elements, links and components generated by scripts), the name and role can be programmatically determined; states, properties, and values that can be set by the user can be 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 components. For example, standard HTML controls already meet this success criterion when used according to specification.

Conformance

This section is normative.

This section lists requirements for conformance to WCAG 2.0. It also gives information about how to make conformance claims, which are optional. Finally, it describes what it means for Web content technologies to be accessibility-supported, since only accessibility-supported technologies can be relied upon for conformance. Understanding Conformance includes further explanation of the accessibility-supported concept.

Conformance requirements

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

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 1: 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.

Note 2: It is not recommended that Level AAA conformance be required as a general policy for entire sites because it is not possible to satisfy all Level AAA Success Criteria for some content.

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

Note 1: 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, e.g., a long description.

Note 2: Web pages that cannot conform due to content outside of the author's control may consider a Statement of partial conformance.

3. Complete processes: When a Web page is one of a series of Web pages presenting a process (i.e. a sequence of steps that need to be completed in order to accomplish an activity) all Web pages in the process conform at the specified level or better. (Conformance is not possible at a particular level if any page in the process does not conform at that level or better.)

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) conform in order for any page that is part of the process to conform.

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

5. Non-Interference: If 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. In addition, the Web page as a whole continues to meet the conformance requirements under all of the following conditions:

when any technology that is not accessibility-supported is turned on in a user agent, and
when it is turned off in a user agent, and
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 criteria because they deal with things that could interfere with overall use of the page: 1.4.2 - Audio Control, 2.1.2 - No Keyboard Trap, 2.3.1 - Three Flashes or Below Threshold, and 2.2.2 - Pause, Stop, Hide.

Note: If a page cannot conform (for example, a conformance test page or an example page), it cannot be included in the scope of conformance or in a conformance claim.

For more information, including examples, 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:

Date of the claim
Guidelines title, version and URI "Web Content Accessibility Guidelines 2.0 at {URI of final document}"
Conformance level satisfied: (Level A, AA or AAA)
A concise description of the Web pages such 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.
A list of accessibility-supported technologies (including version number) that includes all of the Web content technologies relied upon.

Note: If a conformance logo is used, it would constitute a claim and must be accompanied by the required components of a conformance claim listed above.

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:

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.
A list of the specific technologies that are "used but not relied upon."
A list of user agents, including assistive technologies, that were used to test the content.
Information about any additional steps taken that go beyond the success criteria to enhance accessibility.
A machine-readable metadata version of the list of specific technologies that are relied upon.
A machine-readable metadata version of the conformance claim.

Note: Refer to Understanding Conformance Claims for more information and examples.

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, or applications supporting user-contributed content. Another example would be a page, such as a portal or news site, composed of content aggregated from multiple contributors, or sites that automatically insert content from other sources over time, such as when advertisements are inserted dynamically.

In 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:

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 removed or made conforming) within two business days, then a determination or claim of conformance can be made since, except for errors in externally contributed content which are corrected or removed when encountered, the page conforms. No conformance claim can be made if it is not possible to monitor or correct non-conforming content;
OR
A "statement of partial conformance" may be 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 that is excluded in the statement of partial conformance:
1. is not content that is under the author's control
2. is 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.)