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Copyright © 2008 W3C® (MIT, ERCIM, Keio), All Rights Reserved. W3C liability, trademark and document use rules apply.
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 often make your Web content more usable to users in general.
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.
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.
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.
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:
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.
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.
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).
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 email@example.com. The archives for the public comments list are publicly available. Archives of the WCAG WG mailing list discussions are also publicly available.
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.
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.[begin delete] These guidelines also often make content more usable in general. [end delete] 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. [begin change]These guidelines[end change] also make Web content more usable by older individuals with changing abilities due to aging [begin add]and often improve usability for users in general [2453] [end add].
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:
The individuals and organizations that use WCAG vary widely and include [begin add]Web designers and developers[end add][begin delete]Webmasters[end delete], 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 [begin add]common[end add] 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. [begin add]Some advisory techniques address accessibility barriers that are not covered by the testable success criteria. [2461] [end add] [begin add]Where common failures are known, these are also documented. [2540] [end add] See also Sufficient and Advisory Techniques in Understanding WCAG 2.0.
All of these layers of guidance ([begin add]principles, [end add]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.
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 [begin add]including the ability to be updated to describe how WCAG would be applied with new technologies [2540] [end add]. 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.
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.
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".
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.
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.
This section is normative.
1.1.1 Non-text Content: All non-text content [begin add]that is presented to the user [end add]has a text alternative that [begin add]serves the equivalent purpose[end add][begin delete]presents equivalent information[end delete], 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.
Media, Test, Sensory: If it is (1) synchronized media, (2) audio-only or video-only content, (3) a test or exercise that (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 for text that is clearly labeled as such. (For synchronized media, see also .)[end delete]
Note: Prerecorded audio-only and video-only files [begin change]are addressed[end change] under Success Criterion 1.1.1, which requires text alternatives that present equivalent information.
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.
1.1.2 Live Audio-only: All live audio-only content has a text alternative (Level AAA)
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.
1.2.3 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
Note: For 1.2.3, 1.2.5, 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.
1.2.5 Audio Description: Audio description is provided for [begin add]all[end add] prerecorded [begin add]video content in[end add] 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 [begin add]all[end add] prerecorded [begin add]audio content in[end add] synchronized media. (Level AAA) How to Meet 1.2.6 Understanding 1.2.6
1.2.7 Audio Description (Extended): Extended audio description [begin delete]of video [end delete]is provided for [begin add]all[end add] prerecorded [begin add]video content in[end add] 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 [begin add]and a text alternative that presents equivalent information is provided for all prerecorded video-only media[end add].[begin delete], except if the synchronized media is an media alternative for text and is clearly labeled as such[end delete] (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.[begin delete]All live audio-only content has a text alternative.[end delete] (Level AAA) How to Meet 1.2.9 Understanding 1.2.9[end change]
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.
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. [2458]
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 [begin delete]which can be set [end delete][begin add]independently[end add][begin delete]to be a different level[end delete] from the [begin add]overall[end add] system volume level. [2459] (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 [begin change]images of large-scale text[end change] 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. [2381]
Note: Success Criteria 1.4.3 and 1.4.6 can be met via a contrast control available on or from the page. [2434]
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 [begin delete]accessibility supported [2439] [end delete]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 [begin change]images of large-scale text[end change] 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. [2381]
Note: Success Criteria 1.4.3 and 1.4.6 can be met via a contrast control available on or from the page. [2434]
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: [begin add]Per the definition of "decibel,"[end add] background sound that meets this requirement will be approximately [begin add]four times quieter than[end add][begin delete]one quarter as loud as[end delete] the foreground speech content. [2460]
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 [begin add]or glyphs (40 if CJK)[end add] [2546]
text is not [begin add]justified (aligned to both the left and the right margins)[end add][begin delete]aligned on both the left and the right[end delete] [2463]
line spacing [begin add](leading)[end add] is at least space-and-a-half within paragraphs, and paragraph spacing [begin change]is at least 1.5 times larger than the[end change] line spacing [2464] [2444]
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 [begin add]on a full-screen window [2377] [end add]
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.
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
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 [begin add]is essential and extending it would invalidate[end add][begin delete] cannot be extended without invalidating[end delete] the activity; or [2395] [2402]
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 [begin add]to those places where there is no other option[end add][begin delete]for no reason [2540] [end delete]. 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[end add]
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.
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.[end delete]
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.[end add]
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
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 it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference.
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
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 [begin add]of the words, in context, [end add] is ambiguous without knowing the pronunciation. [2474] (Level AAA) How to Meet 3.1.6 Understanding 3.1.6
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
3.3.1 Error Identification: If an input error is [begin add]automatically [end add]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 [begin add]automatically[end add] 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.
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. [2539] (Level A) How to Meet 4.1.1 Understanding 4.1.1[end change]
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: [begin add]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.[end add][begin delete]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.[end delete] (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.
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 [begin change]describes[end change] 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 [begin change]the accessibility-supported[end change] concept.[end change]
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.[end add]
2. Full pages: Conformance [begin add](and conformance level) [2540] [end add] 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.[end add]
3. Complete processes: When [begin add]a Web page is one of a series of Web pages presenting a process (i.e. a sequence of [end add][begin delete]a series of Web pages present sequential [end delete]steps that need to be completed in order to accomplish an activity[begin add])[end add] all Web pages in the [begin add]process[end add][begin delete]series[end delete] conform at [begin add]the specified[end add][begin delete]a particular[end delete] level [begin add]or better[end add]. (Conformance is not possible at [begin add]a particular level if any page in the process does[end add][begin delete]any level if all pages in the sequence do[end delete] not conform at that level [begin add]or better[end add].) [2540] [2477]
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) [begin delete]must [end delete]conform in order for any page that is part of the [begin add]process[end add][begin delete]sequence[end delete] 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. [begin add]In addition[end add][begin delete]Specifically[end delete], 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, [begin add]including examples,[end add] see Understanding Conformance Requirements.
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.
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 [begin add](including version number)[end add] that includes all of the Web content technologies relied upon.
Note: When citing technology (Web content) that have multiple versions, the version(s) supported must be specified.
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. [2506]
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.
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[begin delete] to the bottom[end delete], or applications supporting user-contributed content. [begin add]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.[end add][begin delete]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.[end delete] [2509] [2493]
In [begin delete]both of [2511] [end delete]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[begin delete] immediately[end delete] removed or made conforming) [begin add]within two business days, [end add]then a determination or claim of conformance can be made since, except for errors in externally contributed content which are corrected or removed [begin add]when encountered[end add][begin delete] immediately[end delete], the page conforms. No conformance claim can be made if it is not possible to monitor or correct non-conforming content; [2512]
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:
is not content that is under the author's control
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.)
This section is normative.
shortened form of a word, phrase, or name[begin delete] where the original expansion has not been rejected by the organization that it refers to and [2510] [end delete] where the abbreviation has not become part of the language
Note 1: This includes initialisms and acronyms where:
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.
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.
Note 2: There are some companies that have adopted what used to be an initialism as their company name. In these cases, the new name of the company is the letters (for example, Ecma) and the word is no longer considered to be an abbreviation. [2510][end add]
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 1 and 2 must be satisfied for a Web content technology (or feature):
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,
The Web content technology must have accessibility-supported user agents that are available to users. This means that at least one of the following four statements is true:
The technology is supported natively in widely-distributed user agents that are also accessibility supported (such as HTML and CSS);
The technology is supported in a widely-distributed plug-in that is also accessibility supported;
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;
The user agent(s) that support the technology are accessibility supported and are available for download or purchase in a way that:
does not cost a person with a disability any more than a person without a disability and
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 4: Accessibility-Supported Technologies Only 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 is 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 Web content technologies that have multiple versions, the version(s) supported should be specified.
Note 5: The easiest way to be sure that the Web content 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 Web content technologies. However, all technologies on the list would need to meet the definition of accessibility supported Web content technologies above.
activity where moving, blinking, scrolling, or auto-updating is central to the design of the activity and removal would fundamentally change the functionality of the content[end delete]
the purpose cannot be determined from the link and all information of the Web page presented to the user simultaneously with the link (i.e. readers without disabilities would not know what a link would do until they activated it)
Example: The word guava in the following sentence "One of the notable exports is guava" is a link. The link could lead to a definition of guava, a chart listing the quantity of guava exported or a photograph of people harvesting guava. Until the link is activated, all readers are unsure and the person with a disability is not at any disadvantage.
picture created by a spatial arrangement of characters or glyphs (typically from the 95 printable characters defined by ASCII).
hardware and/or software that acts as a user agent, or along with a mainstream user agent, to provide functionality to meet the requirements of users with disabilities that go beyond those offered by mainstream user agents
Note 1: functionality provided by assistive technology includes 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 functionality to assistive technologies like retrieving Web content from program objects or parsing markup into identifiable bundles.
Example: 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 head pointers, 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.
the technology of sound reproduction [2393]
Note: Audio can be created synthetically (including speech synthesis), recorded from real world sounds, or both.
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: Where all of the video information is already provided in existing audio, no additional audio description is necessary. [2393][end add]
Note 4: Also called "video description" and "descriptive narration."
a time-based [begin delete]live [end delete]presentation that contains only audio (no video and no interaction)
switch back and forth between two visual states in a way that is meant to draw attention
Note: See also flash. It is possible for something to be large enough and blink brightly enough at the right frequency to be also classified as a flash.
more than one sentence of text
[begin add]synchronized visual or text alternative for both dialog and non-dialog audio information needed to understand the media content[end add][begin delete]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 [end delete] [2561] [2518]
Note 1: Captions are similar to dialog-only subtitles except captions convey not only the content of spoken dialog, but also equivalents for non-dialog audio information needed to understand the program content, including sound effects, music, laughter, speaker identification and location.[end add]
Note 2: Closed Captions are equivalents that can be turned on and off with some players.[end add]
Note 3: Open Captions are any captions that cannot be turned off. For example, if the captions are visual equivalent images of text embedded in video.[end add]
Note 4: Captions should not obscure or obstruct relevant information in the video.[end add]
Note 5: In some countries, captions are called subtitles.[end add]
Note 6: Audio descriptions can be, but do not need to be, captioned since they are descriptions of information that is already presented visually.
Note 7: 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.[end delete]
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]
satisfying all the requirements of a given standard, guideline or specification
version that
conforms at the designated level, and
provides all of the same information and functionality in the same human language, and
is as up to date as the non-conforming content, and
for which at least one of the following is true:
the conforming version can be reached from the non-conforming page via an accessibility supported mechanism, or
the non-conforming version can only be reached from the conforming version, or
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 conforming alternate version may consist of multiple pages).
Note 3: If multiple language versions are available, then conforming alternate 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 would need to be fully conformant in order to meet conformance requirement 1.
Note 5: The conforming alternative version does not need to reside within the scope of conformance as long as it is as freely available as the non-conforming version.
Note 6: Alternate versions should not be confused with supplementary content , which support the original page and enhance comprehension.
Note 7: 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.
major changes in the content of the Web page that, if made without user awareness, can disorient users who are not able to view the entire page simultaneously [2571][end add]
Changes in context include changes of:[end change]
Note: A change of content is not always a change of context. [begin add]Changes in content, such as an expanding outline or dynamic menu, do not necessarily change the context, unless they also change one of the above (e.g. focus).[end add][begin delete]Small changes in content, such as an expanding outline or dynamic menu, do not change the context.[end delete]
Example 1: Opening a new window, moving focus to a different component, going to a new page (including anything that would look to a user as if they had moved to a new page) or significantly re-arranging the content of a page are examples of changes of context. [2445][end add]
Example 2: Submitting a form, opening a new window, or moving focus to a different component are examples of changes of context.[end delete]
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
help text that provides information related to the function currently being performed
(L1 + 0.05) / (L2 + 0.05), where
L1 is the relative luminance of the lighter of the [begin delete]foreground or background [end delete]colors, and
L2 is the relative luminance of the darker of the [begin delete]foreground or background [end delete]colors. [2548]
Note 1: Contrast ratios can range from 1 to 21 (commonly written 1:1 to 21:1).
Note 2: Because authors do not have control over user settings as to how text is rendered (for example font smoothing or anti-aliasing), the contrast ratio for text can be evaluated with anti-aliasing turned off.[end change]
Note 3: For the purpose of Success Criteria 1.4.3 and 1.4.6, contrast is measured with respect to the specified background over which the text is rendered in normal usage. If no background color is specified, then white is assumed. [2548][end change]
Note 4: Background color is the specified color of content over which the text is to be rendered in normal usage. It is a failure if no background color is specified when the text 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 a failure if no text color is specified when a background color is specified. [2548][end change]
Note 5: When there is a border around the letter, the border can add contrast and would be used in calculating the contrast between the letter and its background. A narrow border around the letter would be used as the letter. A wide border around the letter that fills in the inner details of the letters acts as a halo and would be considered background. [2508][end add]
Note 6: WCAG conformance should be evaluated for color pairs specified in the content that an author would expect to appear adjacent in typical presentation. Authors need not consider unusual presentations, such as color changes made by the user agent, except where caused by authors code. [2508][end add]
Note 7: For colors that are dithered at the source, use the average values of the colors that are dithered (average R, average G, and average B). If dithered at destination, then the source value is used.[end delete]
any sequence where words and paragraphs are presented in an order that does not change the meaning of the content [2391][end add]
a sudden, unexpected situation or occurrence that requires immediate action to preserve health, safety, or property
if removed, would fundamentally change the information or functionality of the content, and information and functionality can not be achieved in another way that would conform
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[begin add] and the pauses between dialog/narration are too short [2549] [end add].
a pair of opposing changes in relative luminance [begin change]that can[end change] cause seizures in some people if it is large enough and in the right frequency range
Note 1: See general flash and red flash thresholds for information about types of flash that are not allowed.
Note 2: See also blinking.
processes and outcomes achievable through user action
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.
a flash or rapidly changing image sequence is below the threshold (i.e. content passes) if any of the following are true:[end add]
a sequence of flash or rapidly changing image sequences where all three of the following are true:[end delete]
there are [begin add]no[end add] more than three General Flashes and / or [begin add]no[end add] more than three Red Flashes within any one-second period; [begin add]or[end add][begin delete]and[end delete]
the combined area of flashes occurring concurrently occupies [begin add]no[end add] more than a total of .006 steradians within any 10 degree visual field on the screen (25% of any 10 degree visual field on the screen) at typical viewing distance
the flashing is below 50 Hz; and[end delete]
A General Flash is defined as a pair of opposing changes in relative luminance of 10% or more of the maximum relative luminance where the relative luminance of the darker image is below 0.80; and where "a pair of opposing changes" is an increase followed by a decrease, or a decrease followed by an increase, and
A Red Flash is defined as any pair of opposing transitions involving a saturated red.
Exception: Flashing that is a fine, balanced, pattern such as white noise or an alternating checkerboard pattern with "squares" smaller than 0.1 degree [begin add](of visual field at typical viewing distance) [2551] [end add] on a side does not violate the thresholds.
Note 1: For general software or 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 (e.g. 15-17 inch screen at 22-26 inches). (Higher resolutions displays showing the same rendering of the content yield smaller and safer images so it is lower resolutions that are used to define the thresholds.)
Note 2: A transition is the change in relative luminance (or relative luminance/color for red flashing) between adjacent peaks and valleys in a plot of relative luminance (or relative luminance/color for red flashing) measurement against time. A flash consists of two opposing transitions.
Note 3: The current working definition in the field for "pair of opposing transitions involving a saturated red" is where, for either or both states involved in each transition, R/(R+ G + B) >= 0.8, and the change in the value of (R-G-B)x320 is > 20 (negative values of (R-G-B)x320 are set to zero) for both transitions. R, G, B values range from 0-1 as specified in "relative luminance" definition. [HARDING-BINNIE]
Note 4: Tools are available that will carry out analysis from video screen capture. [begin add]However, no tool is necessary to evaluate for this condition if flashing is less than or equal to 3 flashes in any one second. Content automatically passes (see #1 and #2 above).[end add]
Note 5: No tool is necessary to evaluate for this condition if flashing is less than or equal to 3 flashes in any one second or greater than 50 Hz. Content automatically passes (see #1 and #2 above).[end delete]
Note 6: 50 Hz is used to coincide with the AC line frequency in Europe and other countries. However almost half of the photosensitive population is susceptible to 50 Hz flashing whereas only 15 % are susceptible to 60 Hz. 75 Hz or higher is recommended where possible.[end delete]
language that is spoken, written or signed (through visual or tactile means) to communicate with humans
Note: See also sign language.
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 cannot be translated directly, word for word, without losing their (cultural or language-dependent) meaning.
Example 1: 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 2: 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 3: 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.
text that has been rendered in a non-text form (e.g. an image) in order to achieve a particular visual effect[end add]
Note: This does not include text that is part of a picture that contains significant other visual content.
Example: A person's name on a nametag in a photograph.
text that is inconsequential to the meaning of the image
Example: In a photo of two men talking on a street corner, there is a sign on a store in the background.
for information purposes and not required for conformance
Note: Content required for conformance is referred to as "normative."
information provided by the user that is not accepted
Note: This includes:
Information that is required by the Web page but omitted by the user
Information that is provided by the user but that falls outside the required data format or values
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.
interface used by software to obtain keystroke input
Note 1: A keyboard interface allows users to provide keystroke input to programs even if the native technology does not contain a keyboard.
Example: A touchscreen 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.
text or other component with a text alternative that is presented to a user to identify a component within Web content
Note 1: 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.
Note 2: The term label is not limited to the label element in HTML.
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.
Note 4: When using text without specifying the font size, the smallest font size used on major browsers for unspecified text would be a reasonable size to assume for the font. If a level 1 heading is rendered in 14pt bold or higher on major browsers, then it would be reasonable to assume it is large text. Relative scaling can be calculated from the default sizes in a similar fashion. [2430] [2381][end add]
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.
information captured from a real-world event and transmitted to the receiver with no more than a broadcast delay
Note 1: A broadcast delay is a short (usually automated) delay, for example used in order to give the broadcaster time to queue or censor the audio (or video) feed, but not sufficient to allow significant editing.
Note 2: If information is completely computer generated, it is not live.
nature of the result obtained by activating a hyperlink
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 the International Standard Classification of Education [UNESCO].
process or technique for achieving a result
Note 1: The mechanism may be explicitly provided in the content, or may be relied upon to be provided by either the platform or by user agents, including assistive technologies.
Note 2: The mechanism needs to meet all success criteria for the conformance level claimed.
media that presents no more information than is already presented in text (directly or via text alternatives)
Note: A media alternative for text is provided for those who benefit from alternate representations of text. Media alternatives for text may be audio-only, video-only (including sign-language video), or audio-video.
would be invalid if presented in text
Example: Color blindness test, hearing test, vision exercise, spelling test.
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 in the order defined for advancing focus (from one element to the next) using [begin add]a keyboard interface[end add][begin delete]the keyboard [end delete]
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
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.
on the most common sized desktop/laptop display with the viewport maximized [2377][end add]
stopped by user request and not resumed until requested by user
rendering of the content in a form to be perceived by users
six year time period that begins between the ages of five and seven, possibly without any previous education
Note: This definition is based on the International Standard Classification of Education [UNESCO].
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.
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 1: Determined in a markup language from elements and attributes that are accessed directly by commonly available assistive technology.
Example 2: 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.
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.
set by software using methods that are supported by user agents, including assistive technologies
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.
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 [begin add]virtual[end add][begin delete]fantasy [2556] [end delete] world using avatars (is not completely generated by the content and occurs at the same time as the viewing).
meaningful associations between distinct pieces of content
the relative [begin delete]perceived [end delete]brightness of any point [begin add]in a colorspace[end add], normalized to 0 for [begin add]darkest[end add] black and 1 for [begin add]lightest[end add][begin delete]maximum[end delete] white
Note 1: [begin add]For the sRGB colorspace, [end add]the relative luminance of a[begin delete]n sRGB[end delete] 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
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: If dithering occurs after delivery, then the source color value is used. For colors that are dithered at the source, the average values of the colors that are dithered should be used (average R, average G, and average B).[end change]
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.
the content would not conform if that technology is turned off or is not supported
text or [begin delete]a [end delete]number by which software can identify the function of a component within Web content [2557]
Example: A number that indicates whether an image functions as a hyperlink, command button, or check box.
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 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.
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.
the success criterion does not evaluate to 'false' when applied to the page
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.
A self-contained portion of written content that deals with one or more related topics or thoughts
Note: A section may consist of one or more paragraphs and include graphics, tables, lists and sub-sections.
a language using combinations of movements of the hands and arms, facial expressions, or body positions to convey meaning
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.
additional content that illustrates or clarifies the primary content
audio or video synchronized with another format for presenting information and/or with time-based interactive components[begin add], unless the media is a media alternative for text that is clearly labeled as such[end add] [2393]
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.
sequence of characters that can be programmatically determined, where the sequence is expressing something in human language
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.
words used in such a way [begin change]that requires users to[end change] 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.
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.
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.
a part of the content that is perceived by users as a single control for a distinct function
Note 1: 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.
Note 2: User interface components include form elements and links as well as components generated by scripts. [2405][end add]
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."
the technology of moving or sequenced pictures or images [2393]
Note: Video can be made up of animated or photographic images, or both.
a time-based [begin delete]live [end delete]presentation that contains only video (no audio and no interaction)
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). [begin change]Interface components created by the user agen[end change]t such as prompts, menus, and alerts are not viewports.
Note 2: This definition is based on User Agent Accessibility Guidelines 1.0 Glossary.
the font, size, color, and background can be set [2544][end add]
a non-embedded resource obtained from a single URI using HTTP 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://example.com/mail, but includes an inbox, a contacts area and a calendar. Links or buttons are provided that cause 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 around in a store dragging products off of the shelves around you and into a visual shopping cart in front of you. Clicking on a product causes it to be demonstrated with a specification sheet floating alongside.[begin add]This might be a single page Web site or just one page within a Web site. [2564] [end add]
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.
Bruce Bailey (US Access-Board)
Frederick Boland (NIST)
Judy Brewer (W3C / MIT)
Chris Brownrigg (Boeing)
Ben Caldwell (Trace R&D Center, University of Wisconsin-Madison)
Roberto Castaldo (IWA / HWG)
Sofia Celic (Vision Australia)
Michael Cooper (W3C / MIT)
Roberto Ellero (International Webmasters Association / HTML Writers Guild)
Bengt Farre (W3C Invited Expert)
Nikolaos Floratos (ANEC)
Loretta Guarino Reid (Google)
Katie Haritos-Shea (W3C Invited Expert)
Sean Hayes (Microsoft)
Andrew Kirkpatrick (Adobe)
Andrew LaHart (IBM)
Gez Lemon (International Webmasters Association / HTML Writers Guild)
Alex Li (SAP AG)
David MacDonald (E-Ramp Inc.)
Roberto Scano (International Webmasters Association / HTML Writers Guild)
Cynthia Shelly (Microsoft)
Andi Snow-Weaver (IBM)
Christophe Strobbe (DoArch, K.U.Leuven)
Makoto Ueki (Infoaxia)
Gregg Vanderheiden (Trace R&D Center, University of Wisconsin)
Jenae Andershonis, Avi Arditti, Aries Arditi, Mike Barta, Sandy Bartell, Kynn Bartlett, Marco Bertoni, Harvey Bingham, Paul Bohman, Dick Brown, Doyle Burnett, Jonathan Chetwynd, Wendy Chisholm, Alan Chuter, David M Clark, Joe Clark, Tom Croucher, Nir Dagan, Daniel Dardailler, Geoff Deering, Don Evans, Alan J. Flavell, Becky Gibson, Al Gilman, Kerstin Goldsmith, Jon Gunderson, Emmanuelle Gutiérrez y Restrepo, Eric Hansen, Shawn Henry, 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, Luca Mascaro, Mathew J Mirabella, Charles McCathieNevile, Matt May, Marti McCuller, Sorcha Moore, 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, John Slatin, Justin Thorp, Gian Sampson-Wild, Joel Sanda, Neil Soiffer, Jim Thatcher, Takayuki Watanabe, Jason White.
This section is informative.