Introduction
This section is informative.
[begin add] This is a Working Draft of the Web Content Accessibility Guidelines (WCAG) version 2.0. WCAG is developed through the W3C process in cooperation with individuals and organizations around the world, with a goal of providing a single shared standard for Web accessibility that meets the needs of individuals, organizations, and governments internationally.
[end add] [begin add] WCAG 2.0 builds upon the work of WCAG 1.0 [WCAG10] with provisions that are more testable and that extend to a broader range of technologies including many that are new and evolving. WCAG 2.0 has been created to be technology independent. That is, the guidelines and success criteria in WCAG 2.0 can be applied across a wide range of existing and emerging Web technologies. Rather than specifying what technologies to use, WCAG 2.0 lays out general guidelines for using technologies along with specific testable success criteria for guiding and evaluating the use of the technologies.
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[begin delete]You are reading [begin add]a working draft of[end add] the Web Content Accessibility Guidelines (WCAG) version 2.0. This is the central document that defines the[end delete]
[begin add]WCAG 2.0 provides[end add] requirements for making Web content
[begin add]more[end add] accessible to a wide range of people with disabilities, including blindness and low vision, deafness and hearing loss, learning [begin change]disabilities[end change], cognitive limitations, limited movement, speech [begin change]disabilities[end change], and others. [begin add]Because many people develop vision, hearing, [begin add]cognitive[end add] or motion impairments as they age,[end add] following these guidelines will make your Web content more usable by many [begin delete]other users, including[end delete] older users. [begin delete]It will also enable people to access Web content using many different devices - including a wide variety of Assistive technology (as used in this document 732
) and mobile technologies.[end delete]
[begin add]However, even content that completely conforms to WCAG may not be fully accessible to every person with a disability. [end add]
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[end change] WCAG 2.0 covers a wide range of recommendations for making Web content more accessible. The guidelines do not include standard usability recommendations except where they have [begin delete]specific impact on accessibility.[end delete]
[begin add]a significantly greater impact on people with disabilities than on other people.
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[begin add] Although some of the accessibility issues of people with cognitive, language, and learning disabilities are addressed by WCAG 2.0, either directly or through assistive technologies, the WCAG 2.0 guidelines do not address many areas of need for people with these disabilities. There is a need for more research and development in this important area.
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The WCAG 2.0 document itself consists of:
[end delete] [begin delete] This introduction
Information about conformance to WCAG 2.0
Guidelines with success criteria for each guideline
"How to meet" [begin change]links to information about how to meet each success criterion, including a description of the intent of the success criterion, sufficient techniques for meeting it, examples, and benefits.
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A link to information about the Working Group's approach to accessibility-supported content technologies and defining assumptions about the technologies that are available to end users
Appendices containing definitions, [begin delete]a checklist, [end delete]references, and other support information.
[end delete] [begin add] Components of Web Accessibility
It is important to note that Web content is just one aspect of accessibility. Just as important as accessible Web content is the availability of accessible browsers (and other user agents) that can adapt and present the content in the best form for the user. Accessible Web technologies and accessible tools for creating Web content are also important. For an overview of the different components of accessibility and how they work together see:
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[begin change]WCAG 2.0 Supporting Documents[end change]
[begin add] WCAG 2.0 itself is a technical standard designed primarily for Web developers and designers, authoring tool developers, evaluation tool developers, and others who need a technical standard for Web accessibility. Due to the technical and technology-independent nature of the guidelines and success criteria, and because they say what needs to be done rather than how to do it, it may sometimes be difficult to use the guidelines or success criteria for specific advice for a particular technology (e.g. HTML, XHTML, JavaScript etc).
[end add] [begin add] In order to provide more concrete examples as well as specific techniques for meeting each of the success criteria, three support documents or collections have been developed by the working group to accompany the guidelines. These documents provide very specific guidance that can be used directly to meet the WCAG 2.0 guidelines.
[end add] [begin add] The overall set of documents from the working group consists of:
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The WCAG 2.0 Guidelines - (this document) - This document provides the guidelines, success criteria, conformance specifications as well as the definitions of terms used in the guidelines. The actual guidelines (including success criteria) are only 9 pages long.
WCAG 2.0 Quick Reference
- A concise summary that includes all of the WCAG 2.0 guidelines and success criteria (from above) along with a listing of different techniques that are sufficient to meet every success criterion. It also optionally lists advisory techniques and provides links to further information on each guideline and success criterion (in Understanding WCAG 2.0). Web authors may find this the most useful document when trying to make accessible Web sites and it is a good place to start if looking for practical guidance on all of the WCAG 2.0 requirements and specific techniques to meet them.
Understanding WCAG 2.0
- A collection of short (two to four page) "Understanding" documents for each section, guideline and success criterion in WCAG 2.0. Each of these short documents focuses on one guideline or success criterion. It provides the intent of the success criterion, definitions of key words, people who benefit, how to meet the success criteria, links to sufficient techniques and additional advisory techniques and examples. This collection is equivalent to an applications manual or book on WCAG 2.0.
Editorial Note: For this release, the collection is only available as a single long document. With the next release, the individual short documents will be available as well as the full collection as one large document if desired.
Techniques and Failures for WCAG 2.0
- A collection of documents each detailing one of the techniques (or known common failures) that have been documented so far. The techniques collection is continually expanding, with new techniques being added as they are completed. Due to the design of WCAG 2.0, the techniques collection can continue to grow even after the guidelines are released. The "Quick Reference" and "Understanding" documents tie the guidelines to the new techniques as they are created. Each technique document provides an overview of a single technique, notes about user agent (including assistive technology) support, examples (sometimes including code) and a test methodology for sufficient techniques (advisory techniques do not all have tests).
Editorial Note: For this release, the Techniques collection is also only available as a single long document. With the next release, the individual technique documents will be available as well as the full collection as one large document if desired.
[end add] [begin delete] In addition to the Web Content Accessibility Guidelines 2.0 (this document), there are a number of WCAG 2.0 related support documents that provide additional information and examples. These documents are informative only and do not define conformance to WCAG 2.0. Only the normative Web Content Accessibility Guidelines document itself can be used for determining conformance to these guidelines. Readers should consult WCAG 2.0 in order to determine the exact wording of the success criteria and for information about documenting conformance.
[end delete] [begin delete] The WCAG 2.0 related support documents in this set are provided to help readers understand WCAG 2.0 and how to produce conforming content. These informative documents are written to be used by a diverse audience, including, but not limited to people who create Web content, developers who write code, quality assurance or accessibility evaluators, policy makers, managers, and Web users.
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Currently, the WCAG 2.0 related support documents include:
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[end delete] [begin delete] people who create Web content,
developers who write code,
quality assurance or accessibility evaluators,
policy makers,
managers,
users
[end delete] [begin delete] Currently, these informative documents include:
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Essential Components of Web Accessibility
- Explains how the Web Content Accessibility Guidelines work with the other WAI guidelines (the User Agent Accessibility Guidelines and the Authoring Tool Accessibility Guidelines) and with assistive technologies to provide access to the Web by people with disabilities.
Overview of Web Content Accessibility Guidelines (WCAG) 2.0 Documents
- Provides an overview of WCAG 2.0 and its various informative support documents.
About Baselines for WCAG 2.0
- Provides additional information on baselines.
Understanding WCAG 2.0
- Provides information about each success criterion, including:
its intent,
key terms from the WCAG 2.0 Glossary needed to understand the success criterion,
names of and links to techniques that the working group deems sufficient to meet the success criterion, and
examples and benefits of the success criterion.
Note: Each of the "How to meet Success Criterion x.x.x" links in WCAG 2.0 links to the relevant section of the Understanding WCAG 2.0 document.
Techniques and Failures for WCAG 2.0
- Provide specific details on different techniques, including examples, code, and tests.
Note: The development of techniques documents is an ongoing process. Developers are encouraged to submit new techniques at any time.
Application Notes - Provide detailed application information in different areas. For example, an application note on forms will provide a collection of techniques and strategies for creating accessible forms. It will also summarize the different success criteria that relate to forms.
Note: Application notes are a future component that will be developed in conjunction with the Education and Outreach Working Group.
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WCAG 2.0 Quick Reference
- A summary of all WCAG 2.0 requirements (success criteria) and techniques sufficient to meet them.
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[end delete] [begin delete] The Working Group plans to publish a number of other technology-specific techniques documents and encourages development of techniques documents that show how to meet WCAG 2.0 using non-W3C technologies. Please visit the Working Group home page for a complete list of these and other informative documents related to WCAG 2.0.
[end delete] [begin delete] Every attempt has been made to make WCAG 2.0 and the related documents listed above as readable and usable as possible while retaining the accuracy and clarity needed in a technical specification. Sometimes technical terms are needed for clarity or testability. In these cases, the terms are defined in . To assist readers, there is a How to Meet link beside every success criterion that puts readers one click away from detailed information on that success criterion and two clicks away from the specific technique descriptions related to the success criterion.
[end delete] [begin delete] The Working Group recognizes that readers who are new to accessibility may need or want additional information. For these readers, the work of the Web Accessibility Initiative and its Education and Outreach Working Group is highly recommended. The articles called Getting Started: Making a Web Site Accessible and How People with Disabilities Use the Web are especially useful.
[end delete] [begin add] Additional Resource Documents on WCAG 2.0 and Web Accessibility
In addition to WCAG and its primary reference documents prepared by the WCAG Working group, there are a number of additional resource documents available on WCAG 2.0 and its relationship to Web accessibility. This set of documents will continue to grow even after the WCAG 2.0 is released. Documents available at the time of this document's release include:
Other documents under development include:
Transitioning from WCAG 1.0 to 2.0 - Information to facilitate transitioning from use of WCAG 1.0 to WCAG 2.0.
Application Notes - Provides detailed application information in different areas such as "Designing Accessible Web Forms," or "Creating Basic HTML Web Pages that are Accessible."
[begin delete] Authoring tools
A large part of Web content is created using authoring tools. These tools often determine how Web content is implemented, either by making authoring decisions directly or by limiting the choices available to the author. As a result, authoring tools [begin delete]will[end delete] play an important role in creating Web content that conforms to the Web Content Accessibility Guidelines
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. At the same time, we recommend that all authors become familiar with the Guidelines because this will help in creating accessible content and coverage of the Guidelines may vary between tools.
Developers of authoring tools can make their tools aware of the Web Content Accessibility Guidelines by following the Authoring Tool Accessibility Guidelines. The working group encourages users and purchasers of authoring tools to consider conformance to the Authoring Tool Accessibility Guidelines as a criterion when selecting tools. The current version at WCAG 2.0's release is Authoring
Tool Accessibility Guidelines 1.0. However, version 2.0 is nearing completion and it is based on WCAG 2.0. The latest version of the Authoring Tool Accessibility Guidelines 2.0 can be found at http://www.w3.org/TR/ATAG20.
[end delete] [begin delete] The Role of User Agents
[begin delete] Web content is always rendered by a user agent. A user agent is any software that retrieves and [begin change]presents[end change] Web content for users and includes assistive technologies. Web content that conforms to WCAG 2.0 is most likely to be rendered correctly by user agents that conform to the User Agent Accessibility Guidelines (UAAG). For more information about the relationship between WCAG 2.0 and other WAI accessibility guidelines, see Essential Components of Web Accessibility.
[end delete] [begin add] Web content is always rendered by a user agent or combination of user agents, including assistive technologies. A user agent is any software that retrieves and [begin change]presents[end change] Web content for users.
[end add] [begin add] Different user agents, or user agents that support customization, let users customize the rendering of content into a form that best meets their needs. When Web content conforms to WCAG 2.0, the same information can be presented effectively in a variety of forms and modalities.
[end add] [begin add] WCAG 2.0 relies on user agents to present content in a way that meets the needs of users with disabilities. Web content that conforms to WCAG 2.0 is most likely to be accessible to users with disabilities when rendered by user agents that conform to the User Agent Accessibility Guidelines (UAAG). For more information about the relationship between WCAG 2.0 and other WAI accessibility guidelines, see Essential Components of Web Accessibility.
[end add] [end delete] [begin add] Organization of the WCAG 2.0 Document
The Four Principles
The guidelines and success criteria are organized around the following four principles. These four principles lay the foundation necessary for anyone to access and use Web content. Anyone who wants to use the Web must have content that is:
Perceivable - Information and user interface components must be perceivable by users;
Operable - User interface components must be operable by users;
Understandable - Information and operation of user interface must be understandable by users;
Robust - Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.
The Guidelines
Under each principle there is a list of guidelines that address the principle. There are a total of 12 guidelines. A convenient list of just the guidelines can be found in the table of contents.
[begin add] Success Criteria
Under each guideline, there are success criteria that describe specifically what must be achieved in order to conform to this standard. They are similar to the "checkpoints" in WCAG 1.0. Each success criterion is written as a statement that will be either true or false when specific Web content is tested against it.
All WCAG 2.0 success criteria are written to be testable. While some can be tested by computer programs, others require human testers for part or all of the test. The same results
should be obtained with a high level of confidence when people who understand how people with different types of disabilities use the Web test the same content.
Each success criterion for a guideline has a link to the section of the Quick Reference document that provides:
sufficient techniques for meeting the success criterion,
optional advisory techniques, and
links to descriptions of the intent of the success criteria, including benefits, and examples.
[begin add] Three levels of conformance
WCAG 2.0 success criteria are organized into three levels of conformance.
"A" (single-A) conformance: all Level A success criteria must be satisfied in order to achieve A (single-A) conformance.
"AA" (double-A) conformance: all Level A and Level AA success criteria must be satisfied in order to achieve AA (double-A) conformance.
"AAA" (triple-A) conformance: all Level A, AA, and AAA must be satisfied in order to achieve AAA (triple-A) conformance.
The word "levels" does not mean that some success criteria are more important than others. Each success criterion in WCAG 2.0 is essential to some users, and the levels build upon each other. [begin change]However, even content that conforms at AAA (triple-A) may not be fully accessible to every person with a disability or combination of disabilities, especially certain types of severe disabilities.
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In general, Level A success criteria achieve accessibility by supporting assistive technology while putting the fewest possible limits on presentation. Thus people with a wide range of disabilities using a wide range of assistive technologies, from voice input and eye-tracking devices to screen readers and screen magnifiers, are able to access content in different ways. In other words, Level A success criteria support the ability of both mainstream and specialized user agents to adapt content to formats that meet their users' needs.
The success criteria in Level AA provide additional support for assistive technology. At the same time, they also support direct access to content by the many people who use conventional user agents without assistive technology. In general, Level AA success criteria place more limits on visual presentation and other aspects of content than the success criteria in Level A.
Level AAA success criteria increase both direct access and access through assistive technology. They place tighter limits on both presentation and content, which means that some types of content may not be able to satisfy this level of conformance.
It is recommended that even if content does not conform at a specific level, that it conform to the extent possible.
[end add] [begin delete] The Four Principles of Accessibility
The WCAG 2.0 Guidelines are organized around the following four principles:
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Perceivable - Information and user interface must be perceivable by the user
Operable - User interface components must be operable by the user
Understandable - Information and operation of user interface must be understandable by the user
Robust - Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies
[end change] These four principles lay the foundation necessary for anyone to access and use Web content. WCAG 2.0 offers information about how to increase the ability of people with disabilities to perceive, operate and understand Web content. Under each principle there is a list of guidelines that address the principle. Under each guideline there are success criteria used to evaluate conformance to this standard for that guideline. Each success criterion is written as a statement that will be either true or false when specific Web content is tested against it. The success criteria are grouped into three levels of conformance, each representing a higher level of accessibility for that guideline.
The principles, guidelines, and success criteria represent concepts that address accessibility issues and needs, regardless of the technology used. They are not specific to HTML, XML, or any other technology. This approach makes it possible to apply WCAG 2.0 to a variety of situations and technologies[begin delete], including those that do not yet exist
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[begin change] The principles and guidelines give direction and guidance to Web authors. The success criteria are the basis for determining conformance to WCAG 2.0 and are written as true/false statements. The success criteria define the minimum that needs to be done for the three levels of conformance. Additional advisory techniques are also provided that can allow authors to go further in addressing the guidelines and making pages even more accessible.
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[end change] [begin add] For more information, refer to Understanding the Four Principles of Accessibility.
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[end add] [end delete] Important New Terms Used in WCAG 2.0
WCAG 2.0 includes several important new terms. [begin add]In some cases, these terms are just clarifications of concepts that have been in use but have not been clearly defined in the past. In other cases, they are terms that match new concepts that have been developed to cope with the new technologies that are continually emerging and with the accessibility issues and strategies that are emerging to address them.[end add]
[begin delete]These terms are defined in the Glossary (), and links to the definitions are provided whenever these and other important terms are used in the success criteria. The terms are introduced briefly here to make this new vocabulary easier to understand. [end delete]
[begin add] - Sufficient Techniques
For each success criterion, there is a list of techniques deemed by the Working Group to be sufficient to meet the requirement. For each sufficient technique, there is a test to determine whether the technique has been successfully implemented. If the test(s) for a "sufficient" technique (or combination of techniques) are passed, then that success criterion has been [begin change]satisfied[end change].
Passing all tests for all sufficient techniques is not necessary. Most success criteria have multiple "sufficient techniques" listed. Any of the listed "sufficient techniques" can be used to meet the success criterion.
Note that it is not necessary to meet a success criterion using one of the sufficient techniques that have been documented by the WCAG working group. There may be other techniques which are not documented by the working group that would also meet the success criterion. The working group went through the effort to document these "sufficient techniques" in order to make it easy for authors to identify techniques that meet each success criterion and to have confidence (and evidence) that the techniques meet the success criterion. When using other externally-provided techniques to meet WCAG 2.0 requirements, it is important that they be created by individuals or organizations who are knowledgeable about the requirements of WCAG 2.0 and the needs of people with disabilities. The working group will continue to add new "sufficient techniques" as they are identified, developed, or made effective by advances in user agents including assistive technologies.
- Advisory Techniques
In addition to the sufficient techniques, there are a number of techniques that may enhance accessibility that did not qualify as sufficient techniques because they are not testable, are not sufficient to meet the full requirements of the success criteria, and/or are good and effective techniques in some circumstances but not effective (and therefore sufficient) in others. These are listed as "Advisory Techniques." Authors are encouraged to use these techniques where appropriate. Although using them does not affect conformance, it can enhance accessibility for some users. Many of the advisory techniques are particularly helpful for people with cognitive, language, and learning disabilities, and use of these techniques will improve the accessibility of the content to people with these disabilities.
- Web Page
While not an entirely new term, 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. Technically a Web page, as defined in the glossary, is "a resource that is referenced by a URI and is not embedded in another resource, plus any other resources that are used in the rendering or intended to be rendered together with it." What this means is that a Web page is whatever you find at the end of a Web address that you visit. It includes Web applications, Webcasts, multimedia objects and other types of interactive content to which the word "page" may not typically apply. It is in this evolved sense of the concept that the term is used in WCAG 2.0.
For example, the term "Web page" would include a movie-like interactive shopping environment where the user visually moves about a store dragging products off of the shelves around them into a visual shopping cart in front of them where clicking on a product causes it to be demonstrated with a specification sheet alongside.
- Programmatically Determined
Several success criteria require that content (or certain aspects of content) can be "programmatically determined." This means that the content is delivered in such a way that user agents, including assistive technologies, can access the information. A critical element in having anything be "programmatically determined" is that assistive technologies are able to retrieve and use the information. This lets user agents and assistive technologies transform the content and present it to the user in different sensory modalities (e.g. vision, hearing) or styles of presentation. If assistive technologies cannot do this, then the information can not be said to be programmatically determined.
The term was created in order to allow the working group to clearly identify those places where information had to be accessible to assistive technologies (and other user agents acting as accessibility aids) without specifying exactly how this needed to be done. This is important because of the continually changing nature of the technologies. It is important neither to declare things as accessible because they might be in the future (when they aren't now) nor to declare things as inaccessible in a permanent way when they may very well become accessible in the future.
The use of the term allows the guidelines to identify what needs to be "programmatically determined" in order to meet the guidelines, and then have separate, updateable documents (the Quick Reference, Understanding, and Technique documents) list those techniques and technologies that meet the requirements over time.
- Accessibility Supported
In order for content created with Web technologies (such as HTML, CSS, PDF, GIF, MPEG, Flash etc.) to be accessible to people with different types of disabilities, it is essential that the technologies work with assistive technologies and the accessibility features of browsers and other user agents. In order for something to meet a success criterion that requires it to be "programmatically determined" for example, it would need to be implemented using a technology that has assistive technology support.
"Accessibility supported" means supported by users' assistive technologies as well as the accessibility features in browsers and other user agents.
Authors who don't know which technologies [begin add]or which aspects and features of a technology[end add] have support from assistive technologies should consult documented lists of technologies that are known to have accessibility support. Such lists can make it easier than it is today for an author to identify technologies or features of different technologies that are supported by assistive technologies and can be used to meet the success criteria that require assistive technology support (i.e. require that content can be programmatically determined.)
Editorial Note: The W3C WAI will be compiling existing information on its technologies. It is expected that other organizations will compile such information for their technologies. There will undoubtedly be others who create documented lists as well.
Editorial Note: The Baseline concept has been replaced by the "accessibility support" of Web technologies and "Documented lists of Web technologies that have accessibility support."
Note: The requirements for "accessibility support" of Web technologies are provided in the conformance section of these guidelines (See also Conformance.)
For more information, see Understanding accessibility support in Understanding WCAG 2.0.
[end add] [begin delete] While not an entirely new term, it is important to note that the term "Web page" has evolved to accommodate the increasingly dynamic nature of content. A Web page is a resource that is referenced by a Uniform Resource Identifier (URI) and is not embedded in another resource, plus any other resources that are used in the rendering or intended to be rendered together with it. It includes Web applications, Webcasts, multimedia objects and other types of interactive content to which the word "page" may not typically apply. It is in this evolved sense of the concept that the term is used in WCAG 2.0.
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[end delete] [begin delete] Example: A movie-like interactive shopping environment where the user visually moves about a store dragging products off of the shelves around them into a visual shopping cart in front of them where clicking on a product causes it to be demonstrated with a specification sheet alongside would be considered a "Web page."
[begin delete] The statements that define conformance in WCAG 2.0 are called "success criteria." Each success criterion is written as a testable statement and each is not technology-specific.
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[end delete] [begin delete] Several success criteria require that content (or certain aspects of content) can be "programmatically determined." [begin change]This means that the content is delivered in such a way that user agents, including assistive technologies, can access it. This lets user agents and assistive technologies transform the content and present it to the user in different sensory modalities or styles of presentation.
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[end change] This is important in order to allow assistive technologies to recognize it and present it to the user, even if the user requires a different sensory modality than the original. For example, some assistive technologies convert text into speech or braille. This will also allow content in the future to be translated into simpler forms for people with [begin change]cognitive, language, and learning disabilities[end change], or to allow access by other agent based technologies. This can happen only if the content itself can be programmatically determined.
[end delete] [begin delete] WCAG 2.0 also introduces the term "baseline" which allows WCAG 2.0 to adapt to changing technologies and to the needs of different countries and environments. Baselines are described in more detail in the conformance section and in About Baselines for WCAG 2.0.
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