W3C Recommendation 11 December 2008
This version: http://www.w3.org/TR/2008/REC-WCAG20-20081211/ Latest version: http://www.w3.org/TR/WCAG20/ Previous version: http://www.w3.org/TR/2008/PR-WCAG20-20081103/ Editors: Ben Caldwell, Trace R&D Center, University of Wisconsin-Madison Michael Cooper, W3C Loretta Guarino Reid, Google, Inc. Gregg Vanderheiden, Trace R&D Center, University of Wisconsin-Madison Previous Editors: Wendy Chisholm (until July 2006 while at W3C) John Slatin (until June 2006 while at Accessibility Institute, University of Texas at Austin) Jason White (until June 2005 while at University of Melbourne)
Please refer to the errata for this document, which may include normative corrections.
See also translations .
This document is also available in non-normative formats, available from Alternate Versions of Web Content Accessibility Guidelines 2.0 .
Web Content Accessibility Guidelines (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 disabilities, 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, is provided in separate documents. See Web Content Accessibility Guidelines (WCAG) Overview for an introduction and links to WCAG technical and educational material.
WCAG 2.0 succeeds Web Content Accessibility Guidelines 1.0 [WCAG10]. which was published as a W3C Recommendation May 1999. Although it is possible to conform either to WCAG 1.0 or to WCAG 2.0 (or both), the W3C recommends that new and updated content use WCAG 2.0. The W3C also recommends that Web accessibility policies reference 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 document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.
WCAG 2.0 is supported by 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 any comments be made using the provided online comment form. If this is not possible, comments can also be sent to firstname.lastname@example.org. The archives for the public comments list are publicly available. Comments received on the WCAG 2.0 Recommendation cannot result in changes to this version of the guidelines, but may be addressed in errata or future versions of WCAG. The Working Group does not plan to make formal responses to comments. Archives of the WCAG WG mailing list discussions are publicly available, and future work undertaken by the Working Group may address comments received on this document.
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 .
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.
Table of Contents
Web Content Accessibility Guidelines (WCAG) 2.0 defines how to make Web content more accessible to people with disabilities. Accessibility involves a wide range of disabilities, including visual, auditory, physical, speech, cognitive, language, learning, and neurological disabilities. Although these guidelines cover a wide range of issues, they are not able to address the needs of people with all types, degrees, and combinations of disability. These guidelines also make Web content more usable by older individuals with changing abilities due to aging and often improve usability for users in general.
Web accessibility depends not only on accessible content but also on accessible Web browsers and other user agents. Authoring tools also have an important role in Web accessibility. For an overview of how these components of Web development and interaction work together, see:
WCAG 2.0 Layers of Guidance
The individuals and organizations that use WCAG vary widely and include Web designers and developers, policy makers, purchasing agents, teachers, and students. In order to meet the varying needs of this audience, several layers of guidance are provided including overall principles. general guidelines. testable success criteria and a rich collection of sufficient techniques, advisory techniques. and documented common failures with examples, resource links and code.
Principles - At the top are four principles that provide the foundation for Web accessibility: perceivable, operable, understandable, and robust. See also Understanding the Four Principles of Accessibility .
Guidelines - Under the principles are guidelines. The 12 guidelines provide the basic goals that authors should work toward in order to make content more accessible to users with different disabilities. The 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. The advisory techniques go beyond what is required by the individual success criteria and allow authors to better address the guidelines. Some advisory techniques address accessibility barriers that are not covered by the testable success criteria. Where common failures are known, these are also documented. See also Sufficient and Advisory Techniques in Understanding WCAG 2.0 .
All of these layers of guidance (principles, guidelines, success criteria, and sufficient and advisory techniques) work together to provide guidance on how to make content more accessible. Authors are encouraged to view and apply all layers that they are able to, including the advisory techniques, in order to best address the needs of the widest possible range of users.
Note that even content that conforms at the highest level (AAA) will not be accessible to individuals with all types, degrees, or combinations of disability, particularly in the cognitive language and learning areas. Authors are encouraged to consider the full range of techniques, including the advisory techniques, as well as to seek relevant advice about current best practice to ensure that Web content is accessible, as far as possible, to this community. Metadata may assist users in finding content most suitable for their needs.
WCAG 2.0 Supporting Documents
The WCAG 2.0 document is designed to meet the needs of those who need a stable, referenceable technical standard. Other documents, called supporting documents, are based on the WCAG 2.0 document and address other important purposes, including the ability to be updated to describe how WCAG would be applied with new technologies. Supporting documents include:
How to Meet WCAG 2.0 - A customizable quick reference to WCAG 2.0 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 common failures, each in a separate document that includes a description, examples, code and tests.
The WCAG 2.0 Documents - A diagram and description of how the technical documents are related and linked.
See Web Content Accessibility Guidelines (WCAG) Overview for a description of the WCAG 2.0 supporting material, including education resources related to WCAG 2.0. Additional resources covering topics such as the business case for Web accessibility, planning implementation to improve the accessibility of Web sites, and accessibility policies are listed in WAI Resources.
Important Terms in WCAG 2.0
WCAG 2.0 includes three important terms that are different from WCAG 1.0. Each of these is introduced briefly below and defined more fully in the glossary.
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 found at a single URI. 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.
Using a technology in a way that is accessibility supported means that it works with assistive technologies (AT) and the accessibility features of operating systems, browsers, and other user agents. Technology features can only be relied upon to conform to WCAG 2.0 success criteria if they are used in a way that is "accessibility supported ". Technology features can be used in ways that are not accessibility supported (do not work with assistive technologies, etc.) as long as they are not relied upon to conform to any success criterion (i.e. the same information or functionality is also available another way that is supported).
The definition of "accessibility supported" is provided in the Appendix A: Glossary section of these guidelines. For more information, see Understanding Accessibility Support.
WCAG 2.0 Guidelines
Principle 1: Perceivable - Information and user interface components must be presentable to users in ways they can perceive.
Guideline 1.1 Text Alternatives: Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.
1.1.1 Non-text Content: All non-text content that is presented to the user has a text alternative that serves the equivalent purpose, except for the situations listed below. (Level A)
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 would be invalid if presented in text. then text alternatives at least provide descriptive identification of the non-text content.
Sensory: If non-text content is primarily intended to create a specific sensory experience. then text alternatives at least provide descriptive identification of the non-text content.
CAPTCHA : If the purpose of 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 .