Understanding WCAG 2.0

A guide to understanding and implementing WCAG 2.0

W3C Working Draft 30 April 2008

This version:
Latest version:
Previous version:
Ben Caldwell, Trace R&D Center, University of Wisconsin-Madison
Michael Cooper, W3C
Loretta Guarino Reid, Google, Inc.
Gregg Vanderheiden, Trace R&D Center, University of Wisconsin-Madison
Previous Editors:
Wendy Chisholm (until July 2006 while at W3C)
John Slatin (until June 2006 while at Accessibility Institute, University of Texas at Austin)

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This document, "Understanding WCAG 2.0," is an essential guide to understanding and using Web Content Accessibility Guidelines 2.0 [WCAG20]. It is part of a series of documents that support WCAG 2.0. Please note that the contents of this document are informative (they provide guidance), and not normative (they do not set requirements for conforming to WCAG 2.0).

WCAG 2.0 establishes a set of Success Criteria to define conformance to the WCAG 2.0 Guidelines. A Success Criterion is a testable statement that will be either true or false when applied to specific Web content. "Understanding WCAG 2.0" provides detailed information about each Success Criterion, including its intent, the key terms that are used in the Success Criterion, and how the Success Criteria in WCAG 2.0 help people with different types of disabilities. This document also provides examples of Web content that meet the success criterion using various Web technologies (for instance, HTML, CSS, XML), and common examples of Web content that does not meet the success criterion.

This document indicates specific techniques to meet each Success Criterion. Details for how to implement each technique are available in Techniques and Failures for WCAG 2.0, but "Understanding WCAG 2.0" provides the information about the relationship of each technique to the Success Criteria. Techniques are categorized by the level of support they provide for the Success Criteria. "Sufficient techniques" are sufficient to meet a particular Success Criterion (either by themselves or in combination with other techniques), while other techniques are advisory and therefore optional. None of the techniques are required to meet WCAG 2.0, although some may be the only known method if a particular technology is used. "Advisory techniques" are not sufficient to meet the Success Criteria on their own (because they are not testable or provide incomplete support) but it is encouraged that authors follow them when possible to provide enhanced accessibility. Another support category is "Failure techniques", which describe authoring practices known to cause Web content not to conform to WCAG 2.0. Although failure techniques provide advisory information about certain authoring practices, authors must avoid those practices in order to meet the WCAG 2.0 Success Criteria.

This document is part of a series of documents published by the W3C Web Accessibility Initiative (WAI) to support WCAG 2.0.

Status of this Document

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

This is a Public Working Draft of "Understanding WCAG 2.0". The Web Content Accessibility Guidelines Working Group considers this document to be important for understanding the success criteria in the Web Content Accessibility Guidelines 2.0 Candidate Recommendation (WCAG 2.0). Please note that the contents of this document are informative (they provide guidance), and not normative (they do not set requirements for conforming to WCAG 2.0).

This version of Understanding WCAG 2.0 includes clarifications about success criteria whose purpose and implementation were not clearly understandable in the 11 December 2007 Last Call Working Draft of WCAG 2.0, and includes new Success Criteria. Changes to the set of techniques applicable to a particular Success Criterion are also recorded here; see Techniques for WCAG 2.0 for more information. A summary of changes is available in the form of a version of Understanding WCAG 2.0 with changes marked inline (all elements combined into one file).

One of the requirements for WCAG 2.0 to advance to Proposed Recommendation is that all sufficient techniques for each Success Criterion listed in this document contain test procedures. This means that all sufficient techniques will need to be documented, with no placeholder technique titles with a "future link" designation. Any sufficient techniques not documented by the time WCAG 2.0 advances to Proposed Recommendation will be removed. Materials from the public to assist in documenting these techniques are particularly welcomed. Please use the Techniques Submission Form to submit techniques.

Other comments on this document are also welcomed during the Candidate Recommendation period of WCAG 2.0. Your comments on this Working Draft will help the WCAG Working Group improve the document before it is published as a Working Group Note when WCAG 2.0 becomes a W3C Recommendation. While comments are not required in a particular time frame, the WCAG Working Group expects to have collected all implementations by 30 June 2008 and comments are most useful if they arrive by that time. The Working Group requests that comments be made using the provided online comment form. If this is not possible, comments can also be sent to public-comments-wcag20@w3.org. The archives for the public comments list are publicly available. Archives of the WCAG WG mailing list discussions are also publicly available.

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 Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress. This document will be published as a W3C Working Group Note at the time that WCAG 2.0 becomes a W3C Recommendation.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. The group does not expect this document to become a W3C Recommendation. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

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