Web Content Accessibility Guidelines 2.0 (WCAG 2.0) covers a wide range of issues and recommendations for making Web content more accessible. This document contains principles, guidelines, success criteria, benefits, and examples that define and explain the requirements for making Web-based information and applications accessible. "Accessible" means usable to a wide range of people with disabilities, including blindness and low vision, deafness and hearing loss, learning difficulties, cognitive limitations, limited movement, speech difficulties, and others. Following these guidelines will also make your Web content more accessible to the vast majority of users, including older users. It will also enable people to access Web content using many different devices - including a wide variety of assistive technologies.
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 Introduction to Web Content Accessibility Guidelines (WCAG) 2.0 Working Draft Documents is also available.
Until WCAG 2.0 advances to W3C Recommendation, the current and referenceable document is Web Content Accessibility Guidelines 1.0 (WCAG 1.0), published as a W3C Recommendation May 1999.
This document is for review by the WCAG WG and is subject to change without notice. This document has no formal standing within W3C. Please consult the group's home page and the W3C technical reports index for information about the latest publications by this group.
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/.
The Web Content Accessibility Guidelines Working Group (WCAG WG) encourages feedback about this Working Draft. In particular, should WCAG 2.0 have 2 or 3 levels of conformance? Should a validity success criterion be addressed at Level 1 or Level 2 (refer to "Validity and Accessibility" for a summary of recent discussion)? If you have previously raised an issue, does this draft address it? Since the 19 November 2004 WCAG 2.0 Working Draft, the WCAG WG has focused on addressing comments received on previous drafts. For rationale and background on some of the proposals in this draft, please refer to "Issue Tracking for WCAG 2.0 Working Draft" for a list of open issues related to this Working Draft. The "History of Changes to WCAG 2.0 Working Drafts" is also available.
Please send your comments by 2 August 2005 to email@example.com. The archives for this list are publicly available. Archives of the WCAG WG mailing list discussions are also publicly available.
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.
The WCAG WG intends to publish WCAG 2.0 as a W3C Recommendation. Until that time Web Content Accessibility Guidelines 1.0 (WCAG 1.0) is the stable, referenceable version. This Working Draft does not supercede WCAG 1.0.
This document was produced under the 5 February 2004 W3C Patent Policy. The Working Group maintains a public list of patent disclosures relevant to this document; 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) with respect to this specification should disclose the information in accordance with section 6 of the W3C Patent Policy.
This document has been produced as part of the W3C Web Accessibility Initiative (WAI). The goals of the WCAG WG are discussed in the Working Group charter. The WCAG WG is part of the WAI Technical Activity.
You are reading the Web Content Accessibility Guidelines (WCAG) 2.0. This is one of several documents that define and explain the requirements for making Web-based information and applications accessible to a wide range of people with disabilities, including blindness and low vision, deafness and hearing loss, learning difficulties, cognitive limitations, limited movement, speech difficulties, and others. Following these guidelines will also make your Web content more accessible to the vast majority of users, including older users. It will also enable people to access Web content using many different devices - including a wide variety of assistive technologies.
WCAG 2.0 covers a wide range of issues and recommendations for making Web content more accessible. In general, however, the guidelines do not include standard usability recommendations except where they have specific impact on accessibility.
WCAG 2.0 includes:
Guidelines for each principle
Success criteria for each guideline
Descriptions of examples and benefits
Information about conformance to WCAG 2.0
Information about the Working Group's approach to defining baseline assumptions about the technologies that are available to end users
An appendix containing definitions, references, and other support information.
The four principles of accessibility are as follows:
Content must be perceivable.
User interface components in the content must be operable.
Content and controls must be understandable.
Content must be robust enough to work with current and future technologies.
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 apply the principle. Under each guideline there are several success criteria that express what it means to follow the guideline. The success criteria are written as statements that will be either true or false when specific Web content is tested against the success criteria. The success criteria are grouped into three levels of conformance. (For more information about conformance, see the section titled Conformance, below.)
The principles, guidelines, and success criteria represent concepts that apply to all Web-based content. They explain what it means for web content to be accessible, 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, including those that do not yet exist.
When WCAG 2.0 becomes a W3C Recommendation, normative sections of this document will specify what is required for conformance and will have undergone the full process that is required for W3C Recommendations. The principles, guidelines, and success criteria are all normative. The Glossary and the Conformance section are also normative.
The principles and guidelines give direction and guidance to Web authors. The success criteria are written as true/false statements so that they can be used in determining conformance. Only the success criteria are testable.
Success criteria should be interpreted in the context of the intention expressed in the guideline to which they belong. Likewise, each guideline should be understood in the context of the principle under which it appears.
WCAG 2.0 also includes material that is designated as "informative" rather than normative. Informative sections of this document are clearly marked, both visually and by the label "Informative." Informative material is not required for conformance. However, informative sections of this document and related informative documents may aid in understanding the intent of the success criteria and how to apply them.
Besides this Introduction, informative sections of WCAG 2.0 include:
Examples sections: Descriptions of content that satisfies the success criteria
Benefits sections: Explanations of how the success criteria benefit people with specific disabilities
Baseline section: Information about the Working Group's approach to defining assumptions about what technologies are available to end users of Web content - and therefore to the authors of that content.
Checklist: A list of all the success criteria.
WCAG 1.0 section: Information about similarities and differences between WCAG 2.0 and the earlier WCAG 1.0, published in 1999. Authors and organizations whose sites currently conform to WCAG 1.0 should consult this section to find out if any additional action is needed to conform to WCAG 2.0.
Only WCAG 2.0 (this document) contains normative material. Therefore, readers should consult WCAG 2.0 in order to determine the exact wording of the guidelines and success criteria and for information about documenting conformance. The other documents in this set are informative: their entire purpose is to help readers understand what WCAG 2.0 requires and how to produce conforming content. These informative documents are written for different audiences, including but not limited to:
people who create Web content
developers who write code
Currently, these informative documents include:
Guide to WCAG 2.0: Describes the intent of each success criterion and defines the key terms needed to understand it. Links to applicable general techniques that do not depend on a specific technology and provides links to relevant techniques for different technologies. For example, the Guide to Guideline 1.2 Level 1 Success Criterion 1 provides definitions of multimedia and captions, and explains the intent of the success criterion. It then links to general techniques for creating captions that do not depend upon specific technologies as well as linking to techniques for using SMIL (Synchronized Multimedia Integration Language) and other technologies to synchronize captions with multimedia. It also describes examples of content that meets the success criterion and describes how the success criterion helps people with disabilities.
General Techniques for WCAG 2.0: Describes techniques that do not depend on a specific technology and provides links to relevant techniques for different technologies. For example, the Guide to Guideline 1.1 Level 1 Success Criterion 1 explains how to write an effective text alternative that conveys the same information as a piece of non-text content. Can be accessed directly from the WCAG 2.0 site or from the Guide to WCAG 2.0.
HTML and XHTML Techniques for WCAG 2.0: Intended for Web developers, this document lists examples showing how to use HTML and XHTML for specific accessibility-related tasks, including both techniques that are sufficient to satisfy specific success criteria and advisory techniques that demonstrate good practices beyond what is required. Also provides information about baseline assumptions related to techniques. Can be accessed directly from the WCAG 2.0 site or from the Guide to WCAG 2.0.
CSS Techniques for WCAG 2.0: Intended for Web developers, this document lists examples showing how to use Cascading Style Sheets (CSS) together with HTML and XHTML for specific accessibility-related tasks, including both techniques that are sufficient to satisfy specific success criteria and advisory techniques that demonstrate good practices beyond what is required. Also provides information about baseline assumptions related to techniques. Can be accessed directly from the WCAG 2.0 site or from the Guide to WCAG 2.0.
The Working Group plans to publish a number of other technology-specific Techniques documents in addition to those listed above, 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.
Every attempt has been made to make WCAG 2.0 and the related documents listed above as readable and usable as possible while still 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 the glossary. The Working Group recognizes that readers who are new to accessibility may need or want additional information. For these readers, the work of the Education and Outreach Working Group of the Web Accessibility Initiative is highly recommended. The articles called Getting Started: Making a Web Site Accessible and How People with Disabilities Use the Web are especially useful.
Editorial Note: There is continuing discussion about the number of conformance levels. This Working Draft of WCAG 2.0 includes three levels of conformance, but there is also strong support for a two-level conformance scheme. The issues are too complex to include in a short editorial note. Therefore, the WCAG WG has prepared an overview of the the issues surrounding different conformance schemes. The Working Group invites comments and feedback.
Conformance means that Web content satisfies the success criteria defined in this document. This section outlines the conformance scheme used throughout this document.
The success criteria for each guideline are organized into three (3) levels of conformance.
Level 1 success criteria:
Achieve a minimum level of accessibility through markup, scripting, or other technologies that interact with or enable access through user agents, including assistive technologies.
Can reasonably be applied to all Web resources.
Level 2 success criteria:
Achieve an enhanced level of accessibility through one or both of the following:
markup, scripting, or other technologies that interact with or enable access through user agents, including assistive technologies
the design of the content and presentation
Can reasonably be applied to all Web resources.
Level 3 success criteria:
Achieve additional accessibility enhancements for people with disabilities.
Are not applicable to all Web resources.
Some guidelines do not contain level 1 success criteria, and others do not contain level 2 success criteria.
This method of grouping success criteria differs in important ways from the approach taken in WCAG 1.0. In WCAG 1.0, each checkpoint is assigned a "priority" according to its impact on accessibility for users. Thus Priority 3 checkpoints appear to be less important than Priority 1 checkpoints. The Working Group now believes that all success criteria of WCAG 2.0 are essential for some people. Thus, the system of checkpoints and priorities used in WCAG 1.0 has been replaced by success criteria grouped under Levels 1, 2, and 3 as described above.
The Working Group believes that all success criteria should be testable. Tests can be done by computer programs or by people who understand this document. When multiple people who understand WCAG 2.0 test the same content using the same success criteria, the same results should be obtained.
WCAG 2.0 defines accessibility guidelines and success criteria as functional outcomes. These outcomes are described in a technology independent way in order to allow conformance using any Web technology that supports accessibility. WCAG 2.0 therefore does not require or prohibit the use of any specific technology. It is possible to conform to WCAG 2.0 using both W3C and non-W3C technologies, as long as they are supported by accessible user agents.
WCAG 2.0 uses the term user agents according to the definition published in the Glossary for the W3C's User Agent Accessibility Guidelines (UAAG) 1.0. UAAG 1.0 defines user agents in two ways.
The software and documentation components that together, conform to the requirements of the User Agent Accessibility Guidelines 1.0[UAAG10].
Any software that retrieves and renders Web content for users. This may include Web browsers, media players, plug-ins, and other programs - including assistive technologies - that help in retrieving and rendering Web content.
UAAG 1.0 most often uses the first definition. By contrast, WCAG 2.0 most often uses the second definition. It is important to note that assistive technologies are included in this definition. (Assistive technologies include screen readers, screen magnifiers, on screen and alternative keyboards, single switches, and a wide variety of input and output devices that meet the needs of people with disabilities.)
In choosing technologies to rely upon, developers need to know what technologies they can assume are supported by, and active in, accessible user agents. A set of such technologies is called a baseline. Developers must ensure that all information and functionality comprising the Web content conform to WCAG 2.0 assuming (a) that user agents support only the technologies in the baseline specified for the content and (b) that those technologies are active.
Baselines are defined outside the WCAG 2.0 guidelines as part of a more comprehensive accessibility policy. Baseline considerations will be significantly different if the entity defining the baseline can guarantee the availability of specific user agents.
Example 1: A private intranet
A company or government agency provides its employees with the information technology tools they need to do their jobs. The baseline for intranet sites used only by employees includes newer technologies that are supported only in the user agent which the organization provides for its employees.
Example 2: A government site that provides information to the public
A government agency publishes information intended for the general public. The specified baseline includes only technologies that have been widely supported by more than one accessible and affordable user agent for more than one release.
Example 3: A government adopts a guideline for use with accessible user agents in use by its citizens
A government periodically changes the baseline it requires for developers of public sites to reflect the increasing ability of affordable user agents (including assistive technology) to work with newer technologies.
Example 4: A government provides accessible user agents to all citizens
A government provides all citizens with user agents that support newer technologies. The government specifies a baseline that includes newer technologies that are supported in the user agents provided by that government.
Developers may also use technologies that are not in the specified baseline provided that the following are true:
The Web content still conforms using user agents that only support the technologies that are in the specified baseline (that is, the use of technologies that are not in the baseline does not "break" access to the Web content by user agents that don't support those technologies).
All content and functionality must be available using only the technologies in the specified baseline.
WCAG 2.0 conformance at level Triple-A means that all level 1, level 2 and level 3 success criteria in the guidelines are met assuming user agent support for only the technologies in the chosen baseline.
Conformance claims apply to delivery units and sets of delivery units. (In many cases, a "delivery unit" is the same as a "page." In other cases, however, such as Web applications, the term "page" may be inappropriate, so the Working Group has adopted the term "delivery unit" from the Device Independence Working Group.) All conformance claims must include at least the following information:
The version of the guidelines to which the conformance claim is made.
A list of one or more URIs or URI patterns, identifying the delivery units for which the claim is made.
The level of conformance being claimed.
A delivery unit conforms to WCAG 2.0 at a given conformance level only if all content provided by that delivery unit conforms at that level.
If multiple representations can be retrieved from a URI through content negotiation, then the conformance claim would be for the delivery unit that is returned when no negotiation is conducted (unless the server returns an error for that condition, in which case one of the negotiated forms must comply).
Editorial Note: There is some question as to whether URI is specific enough a reference to the material for which the claim is being made.
Editorial Note: A question has been raised as to whether the information required in items 1-3 above should all be transmitted in the HTTP header or in some other way.
Sometimes a delivery unit is assembled ("aggregated") from multiple sources that each have their own level of conformance. These sources are called authored units. The conformance level for a delivery unit that contains authored units is equal to the lowest conformance level claimed for the delivery unit content and any of the authored units it contains - including claims of aggregated units.
A delivery unit referred to by a URI conforms to WCAG 2.0 at a given conformance level only if all content provided by that delivery unit conforms at that level. For example, if the delivery unit provides information retrieved from a database in response to users' queries, all delivery units containing such information must satisfy the success criteria of WCAG 2.0 to the level at which conformance is claimed. In the case of content negotiation, WCAG 2.0 conformance is not required if the user agent requests a version of the content that does not meet WCAG 2.0 at the specified conformance level.
Editorial Note: We are currently looking at how to handle unknown or community-contributed, authored units that are created using an aggregator supplied tool. We are currently considering whether aggregated content would be judged to conform to WCAG if the aggregator supplied tool can conform to the authoring tools accessibility guidelines (ATAG) 2.0.
Conformance claims can be limited, or "scoped," to pertain to only some parts of a Web site. All conformance claims, however, must be directed to a URI or a range of URIs. Scoping to exclude a particular type of content (for example, images or scripts) from a site is not allowed since it would allow exclusion of individual success criteria. Scoping by URI to exclude sections of a site is allowed so that authors can make claims for just some parts of a site.
This Working Draft of WCAG 2.0 builds upon WCAG 1.0 and reflects feedback received since the publication of WCAG 1.0 in May 1999.
The Web Content Accessibility Guidelines Working Group is working to ensure that organizations and individuals who are currently using WCAG 1.0 (which remains stable and normative at this time) will be able to smoothly transition to WCAG 2.0. For more information about the similarities and differences between WCAG 1.0 Checkpoints and WCAG 2.0 Guidelines and success criteria, please refer to the (draft) Mapping between WCAG 1.0 and the WCAG 2.0 Working Draft.
Authors whose content currently conforms to WCAG 1.0 may wish to capitalize on past accessibility efforts when making the transition to WCAG 2.0. A qualified conformance statement could allow them this flexibility. For example, a conformance claim might include the following statement: "Materials created or modified before 31 December 2005 conform to WCAG 1.0. Materials created or modified on or after 31 December 2005 conform to WCAG 2.0."
Editorial Note: In some instances, the WCAG 2.0 Working Draft may be easier to conform to than the WCAG 1.0 Recommendation while other criteria might be harder to meet in WCAG 2.0 than in WCAG 1.0. The WCAG WG will consider the differences between WCAG 1.0 and WCAG 2.0 conformance and offer advice to developers who currently conform to WCAG 1.0. This advice might take the form of a WCAG 1.0 conformance profile to WCAG 2.0 and information about migrating from WCAG 1.0 to WCAG 2.0. This advice is not yet available.
Editorial Note: The WCAG Working Group continues to wrestle with the challenge of defining the roles and responsibilities of authors and user agents, respectively, in making Web content accessible. In WCAG 1.0, we identified shortcomings in user agents and created guidelines that contained phrases like, "until user agents..." Many of the same issues exist today, but we are looking for a more effective mechanism to address them than creating "temporary bridge" guidelines designed to make up for the shortcomings of user agents.
The Working Group is well aware that there is intense interest in our approach to the challenge of defining "baseline" assumptions about the technologies available to users. This Working Draft of WCAG 2.0 represents a continued evolution of that approach, and the Working Group welcomes comments and suggestions from the community.
At a meeting in October 2004, the WCAG WG agreed to explore the advantages and disadvantages of adopting the Priority 1 checkpoints of the User Agent Accessibility Guidelines (UAAG) 1.0 as a baseline for WCAG 2.0. The Working Group then went on to investigate the implications of writing WCAG 2.0 guidelines under the assumption that all users had user agents that conform to all of the priority 1 checkpoints from UAAG 1.0.
Today, however, no single user agent meets all of the UAAG 1.0 priority 1 checkpoints. If WCAG 2.0 adopts an assumption that user agents conform to UAAG 1.0 priority 1 checkpoints, there will be some shortfall between Web content that meets WCAG 2.0 and currently available user agents. In addition, our analysis of UAAG 1.0 determined that adopting UAAG 1.0 as a baseline for WCAG 2.0 would not resolve certain questions that are crucial for content authors. Specifically, adopting UAAG 1.0 as a baseline would not allow authors to assume that user agents and assistive technologies would be able to interact effectively with scripted content or content that relies upon Cascading Style Sheets.
At a meeting in March 2005, the WCAG Working Group reluctantly concluded that UAAG 1.0 did not provide an appropriate baseline for WCAG 2.0. Further, after vigorous debate, the Working Group agreed to explore a very different approach: we agreed to explore the implications of not setting a baseline in the WCAG 2.0 guidelines while at the same time continuing to search for ways to support UAAG 1.0 in our guidelines and success criteria. Following that meeting, Working Group participants analyzed the implications of this approach from many different angles. We explored how not setting a baseline might require us to provide guidance for authors, policy makers, and others about several baselines. We analyzed the impact of this approach on the wording of guidelines and success criteria. We also explored the implications for our technology-specific Techniques documents, concluding that it might be necessary to provide information about how each technique works within one or more baselines. To date, our analyses and subsequent work on guidelines, success criteria, and techniques appear to support the new approach. This Working Draft reflects the results so far. The Working Group continues to test its assumptions and decisions, and we welcome this opportunity to learn from the community's response to our work.
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 will play an important role in creating Web content that conforms to the Web Content Accessibility Guidelines. 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 help to make their tools more aware of the Web Content Accessibility Guidelines by following the Authoring Tool Accessibility Guidelines. We encourage users and purchasers of authoring tools to consider conformance to the Authoring Tool Accessibility Guidelines as a criterion when selecting tools.
Editorial Note: The Authoring Tool Accessibility Guidelines Working Group has published Working Drafts of ATAG 2.0. The above references will need to be updated as ATAG 2.0 moves through recommendation track.
For all non-text content that is used to convey information, text alternatives identify the non-text content and convey the same information. For multimedia, provide a text-alternative that identifies the multimedia.
Refer to guideline 1.2 for requirements for synchronized alternatives for multimedia.
For functional non-text content, text alternatives serve the same purpose as the non-text content. If text alternatives can not serve the same purpose as the functional non-text content, text alternatives identify the purpose of the functional non-text content
For live audio-only or live video-only content, text alternatives at least identify the purpose of the content with a descriptive label.
Refer to guideline 1.2 for guidance on content that combines live audio and video.
People who are blind, have low vision, have cognitive disabilities can have text alternatives read aloud to them by assistive technology.
People who have trouble reading text may use tools that both read text aloud and highlight the words as they are read. In some cases, it may be difficult for someone to recognize visual information and the text alternative may help him or her understand the purpose of the non-text content.
People who are deaf, are hard of hearing, or who are having trouble understanding audio information for any reason can read the text presentation or have it translated and presented as sign language by assistive technology.
People who are deaf-blind can read the text in braille.
Additionally, text alternatives support the ability to search for non-text content and to repurpose content in a variety of ways.
Example 1: an image used as a button.
A magnifying glass icon is used to link to the search page of a Web site. A screen reader identifies the button as a link and speaks the text alternative, "Search."
Example 2: a data chart.
A bar chart compares how many widgets were sold in June, July, and August. The short label says, "Figure one - Sales in June, July and August." The longer description identifies the type of chart, provides a high-level summary of the data comparable to that available from the chart, and provides the data in a table.
Example 3: an audio recording of a speech (no video).
The link to an audio clip says, "Chairman's speech to the assembly." A link to a text transcript is provided immediately after the link to the audio clip.
Example 4: a recording of a symphony.
The Mars Philharmonic Orchestra's "Upcoming performances" page has a link to a 3 minute clip of the orchestra's rendition of Beethoven's 5th Symphony. The purpose is to encourage readers to buy tickets to a live performance. The link to the audio clip says, "Beethoven's 5th Symphony performed by the Mars Philharmonic Orchestra." On the same page is information about Beethoven and the 5th Symphony. Elsewhere on the Mars Philharmonic Orchestra's Web site is an educational area. There is a link to the same 3 minute clip of the orchestra performing Beethoven's 5th Symphony. The link is the same, "Beethoven's 5th Symphony performed by the Mars Philharmonic Orchestra." However, the page describes how this clip relates to the drama that Beethoven creates in his 5th symphony and describes a specific rhythm captured in this clip. It goes on to explain how this symphony "crystallized Beethoven's mature compositional innovations."
Example 5: an animation that illustrates how a car engine works.
An animation shows how a car engine works. There is no audio and the animation is part of a tutorial that describes how an engine works. All that is needed is a description of the image. From "How car engines work: Internal combustion"
Example 6: a pair of images used to create a visual effect.
Two images are used to create curved edges on a "tab" interface. The images do not provide information, functionality, or a sensory experience and are marked such that they can be ignored by an assistive technology.
Example 7: an internet radio station.
A radio station broadcasts over the internet. The station's Web site describes the type of music played, a schedule of the shows, and the "current song" is updated each time the DJ starts a new track. Interviews are recorded and published in the archives. Transcripts of the archived interviews are provided per Guideline 1.2 Provide synchronized alternatives for multimedia.
Editorial Note: Does the above example help to clarify level 1 success criterion 5 or does it need additional clarification?
Example 8: a traffic Web camera.
A Web site allows end-users to select from a variety of Web cameras positioned throughout a major city. After a camera is selected, the image updates every 2 minutes. A short text alternative identifies the Web camera as, "TraffiCam." The site also provides a table of travel times for each of the routes covered by the Web cameras. The table is also updated every 2 minutes.
Editorial Note: As currently written, guideline 1.1 requires "a text-alternative that identifies the multimedia" and guideline 1.2 requires synchronized alternatives (captions). There are two questions regarding this approach that we are soliciting feedback on:
Should a text transcript be required in addition to captions at Level 1?
There is concern by some that the captioning requirement is too high a bar at Level 1. Should it be moved out of level 1 or should it remain at Level 1 and use the scoping mechanism to scope uncaptioned multimedia out of the conformance claim?
Editorial Note: Unlike captions, audio description is not covered by guideline 1.1- it's purely a guideline 1.2 issue. There are several questions about how to offer guidance about when audio description is required. As with captions, Is there support for leaving the requirement at Level 1 and using the scoping mechanism to scope undescribed multimedia out of the conformance claim? Further, guidance on writing descriptions, providing descriptions so that not everyone hears them, and when descriptions are appropriate will be addressed in the Guide and General Techniques.
Sign language interpretation is provided for multimedia
Extended audio descriptions of video are provided for prerecorded multimedia.
Audio descriptions of video are provided for live multimedia.
People who are deaf or have a hearing loss can access the auditory information through captions.
People who are blind or have low vision as well as those with cognitive disabilities who have difficulty interpreting visually what is happening benefit from audio descriptions of visual information.
Example 1: a movie with audio description.
Transcript of audio based on the first few minutes of, "Teaching Evolution Case Studies, Bonnie Chen" (copyright WGBH and Clear Blue Sky Productions, Inc.)
Describer: A title, "Teaching Evolution Case Studies. Bonnie Chen." Now, a teacher shows photographs.
Bonnie Chen: These are all shot at either the Everglades...for today you just happen to be a species of wading bird that has a beak like this."
Describer: She hands them each two flat, thin wooden blades
Example 2: a captioned tutorial.
A video clip shows how to tie a knot. The captions read, "(music)
USING ROPE TO TIE KNOTS
WAS AN IMPORTANT SKILL
FOR THE LIKES OF SAILORS, SOLDIERS, AND WOODSMEN."
From Sample Transcript Formatting by Whit Anderson
Editorial Note: Examples to be developed: an animation with soundtrack of music with lyrics, an interactive slide show, an animation with musical soundtrack. [Issue #1534]
Editorial Note: The concepts of "reliable" and "standard" need to be incorporated into the definition of "programmatically determined."
When information is conveyed by color, the color can be programmatically determined or the information is also conveyed through another means that does not depend on the user's ability to differentiate colors.
Any information that is conveyed by color is visually evident when color is not available.
When content is arranged in a sequence that affects its meaning, that sequence can be determined programmatically.
Separating content and structure from presentation allows Web content to be presented differently to meet the needs and constraints of different users without losing any of the information or structure. For example, information can be presented via speech or braille (text) that was originally intended to be presented visually.
It can also facilitate automatic emphasis of structure or more efficient navigation.
All of these can benefit people with cognitive, physical, hearing, and visual disabilities.
Editorial Note: These examples are improvements on previous drafts, but are HTML-specific. These will be generalized in future drafts.
Example 1: A form that mentions in text which required fields are missing.
When a user submits a form without filling in all the required fields, a message appears that informs the user which fields are missing. The missing fields are also indicated in color to help people with cognitive limitations recognize what fields need attention. Because the message is also available in text, people who cannot see color well will still know which fields they have to correct.
Example 2: A bus schedule where the headers have been associated with the cells.
A bus schedule consists of a table with the bus stops listed vertically and the different trips listed horizontally. Each cell contains the time when that bus will be at that bus stop. Structural markup has been used to associate that cell with both the corresponding bus stop and the corresponding trip.
Example 3: A form where the labels for the checkboxes have been associated with the checkboxes.
In a form where users can select different options using checkboxes, the labels for the checkboxes have been associated with the checkboxes. This benefits different types of users. It allows users who are blind to determine what the checkbox is for. People with limited motor functions can check the checkbox more easily because they can click anywhere on the label instead of just on the checkbox.
Text and diagrams that are presented over a background image, color, or text have a contrast greater than X1 where the whiter element is at least Y1 as measured by _____.
Text that is presented over a background pattern of lines which are within 500% +/- of the stem width of the characters or their serifs must have a contrast between the characters and the lines that is greater than X2, where the whiter element is at least Y2.
A mechanism is available to turn off background audio that plays automatically.
Editorial Note: The working group is seeking an algorithm that measures contrast in a way that is accurate and testable enough that we could include it in the guidelines. One algorithm, which comes from the Techniques For Accessibility Evaluation And Repair Tools document, is currently under consideration for inclusion in the techniques, but the group has not yet found something that is specific enough to be included at the guidelines level.
Text is not presented over any background (image, text, color or pattern), or if any background is present, the contrast between the text and the background is greater than X2.
Audio content does not contain background sounds or the background sounds are at least 20 decibels lower than the foreground audio content, with the exception of occasional sound effects.
A 20 decibel difference in sound level is roughly 4 times quieter (or louder). Background sound that meets this requirement will be approximately four times (4x) quieter than the foreground audio content.
Individuals with low vision can easily read characters in the content even if they don't have the wide field of view or full range of color perception used by fully sighted persons to separate text from background images. This will also aid comprehension for individuals with cognitive disabilities who benefit from easy discernment of text. Visual contrast also helps individuals with hearing impairments who are aided by clear visual representation of information
Individuals with hearing impairments that limit their ability to hear all of the frequencies of speech can make out the words from the sounds they can hear because they are not mixed with residual sounds from music or other background sounds.
Audio contrast is also known as "signal to noise ratio" by audiologists, where "signal" refers to the foreground and "noise" refers to the background.
Example 1: a background image on a page.
A background image and text are arranged so that there is no image behind the text or the image is so faint that the difference between the darkest part of the image and the text (which is dark) meets the standard foreground/background contrast requirements. The image behind the text also does not contain lines that are about the same width as the characters so they do not interfere with character recognition. This example could also apply to light letters on a dark background.
Example 2: speech over background sounds.
Because speech is often naturally mixed with background sounds (movies, live news etc) and cannot be easily removed or separated, captions are provided (under guideline 1.2) to make dialog understandable. However not all people can see or read the captions. Where speech is mixed or recorded so that it is at least 20 db above any background sounds, most people do not need to rely on captions to understand the dialog.
This includes author-provided accessibility features.
Other interfaces (such as a mouse) can be provided in addition to keyboard operation.
Refer to guideline 4.2 for information regarding user agent support.
Individuals who are blind (and cannot use pointing devices) can have access to the functionality of the Web content or site.
Individuals with severe physical disabilities can use speech input (which simulates keystrokes or commands) to both enter data and operate the interface elements on the page.
Example 1: operation with multiple input devices.
The content relies only on focus-in, focus-out, and activation events; these are defined in the API of the environment for which the content is written, and are intended to be operable by a variety of input devices, including pointing devices, keyboards and speech input systems.
Example 2: examples of Web content that would and would not be operable from a keyboard interface
If it's written to be operable from a computer keyboard, it conforms.
If it's written to be used on a device that does not usually have a keyboard such as a cell phone, but it can be controlled by an optional keyboard for that device, it conforms. (A person who needs a keyboard - or alternate keyboard - can use it to control the application.)
If it's written to be used with a device that does not have a keyboard, but it could also be used by similar devices that do and it would work with their keyboard, it conforms. (A person who needs a keyboard would not buy the device without the keyboard. That device may itself not be considered accessible. But the content can be controlled from a device with a keyboard and therefore conforms to this guideline.)
If it's written to work with devices that do not have keyboards and it can not be used by any other devices that do have keyboards, then it does not conform. (It cannot be accessed via keyboard.)
Content is designed so that time-outs are not an essential part of interaction, or at least one of the following is true for each time-out that is a function of the content:
the user is allowed to deactivate the time-out or;
the user is allowed to adjust the time-out over a wide range which is at least ten times the length of the default setting or;
the user is warned before time expires, allowed to extend the time-out with a simple action (for example, "hit any key") and given at least 20 seconds to respond or;
the time-out is an important part of a real-time event (for example, an auction), and no alternative to the time-out is possible or;
the time-out is part of an activity where timing is essential (for example, competitive gaming or time-based testing) and time limits can not be extended further without invalidating the activity.
Except for real-time events, timing is not an essential part of the event or activity presented by the content.
Non-emergency interruptions, such as the availability of updated content, can be postponed or suppressed by the user.
When an authenticated session has an inactivity timeout, the user can continue the activity without loss of data after re-authenticating.
People with reading disabilities, cognitive disabilities, and learning disabilities who may need more time to read and comprehend written text can have additional time to read the information.
People with physical disabilities can access content that is updated often.
Examples of functionality that must meet the success criteria of this checkpoint:
blinking or scrolling text,
dialog that disappears after a short period,
shutdown or deactivation of resource if activity is not received in a set amount of time.
Example 1: blinking text.
Client-side scripting is used to create blinking text. The content provides an option that allows the user to turn off the blinking.
Example 2: a news site that is updated regularly.
A news site causes its front page to be updated every half hour. The front page contains minimal text and primarily consists of links to content. A user who does not wish the page to update selects a checkbox. The checkbox is in the "user preferences" portion of the site which is one of the first links on each page.
Other National or International General Flash or Red Flash guidance can be used in place of adapted ITC Guidance.
More than one way is available to locate content within a set of delivery units.
Editorial Note: There are some concerns about how this criterion would apply to web applications where the only way to expose certain types of content would require the user to follow a specific path.
Blocks of content that are repeated on multiple perceivable units are implemented so that they can be bypassed.
Delivery units have descriptive titles
How to provide descriptive titles. (Informative)
When a page or other delivery unit is navigated sequentially, elements receive focus in an order that follows relationships and sequences in the content.
Information about the user's location within a set of delivery units is available.
When the logical structure is provided in markup or a data model,
Users with physical disabilities can use structure to more easily jump between paragraphs, chapters, sections etc.
Users with cognitive disabilities can use structure (chapter titles, headers, etc.) to provide more context for the text that follows them. They also provide warning of a change in context and reorient the user to the new focus.
Users with blindness or low vision can jump from header to header to get an overview or to more quickly "skim" to the section they are interested in.
Readers with low vision can sometimes (depending on display technology) change how chapter titles and headers are displayed to make them more visible and easier to use when skimming the document.
the content can be presented on a variety of devices because the device software can choose only those elements of the content that it is able to display and display them in the most effective way for that device.
Providing different navigation mechanisms can provide a better match between different people's skills, background knowledge, visual vs. text orientation, and the type of information they are seeking at the moment.
Individuals with cognitive disabilities may find it easier to ask for what they want than to deduce its location from categorical choices.
Individuals with low vision or blindness may find search techniques that fetch everything that relates to a topic of interest to be easier than techniques that require them to scan lists or content for the items.
Presentation that emphasizes structure:
enables users with cognitive and visual disabilities to orient themselves within the content,
enables all users to move quickly through the content and notice major content divisions
enables all users, but particularly users with visual or cognitive disabilities to focus on important content,
enables all users, but particularly users with visual or cognitive disabilities to distinguish the different types of content.
Example 1: documentation for a product.
Identifying chapters in the structure of a book is appropriate and accepted way of labeling the structure. Within the chapters, headings identify (label) changes in context and highlight ideas contained in the following text. Differences between the appearance of the chapter title and the section headings helps the user understand the hierarchy and relationship between the title and headings. The difference might be font size and margin indentation when presented visually, and spoken in a different voice or preceded by a sound when presented auditorily.
Example 2: a scalable image of a bicycle.
Lines and a circle (spokes and rim) are grouped into a "wheel." Lines in a triangle that attach to each wheel are grouped into a "frame."
Example 3: user interface.
User interface controls are divided into organized groups.
Example 4: a data table.
Groups of rows or columns are labeled with headers.
Example 5: an audio presentation.
An audio rendering of a document, generated according to a style sheet, uses a different, more formal voice to read titles and headers so the listener can easily identify the words as a title and not part of the running text.
If an input error is detected, the error is identified and provided to the user in text.
If an input error is detected and suggestions for correction are known and can be provided without jeopardizing the security or purpose of the content, the error is identified and the suggestions are provided to the user.
For forms that cause legal or financial transactions to occur, that modify or delete data in remote data storage systems, or that submit test responses, at least one of the following is true:
Actions are reversible.
Actions are checked for errors before going on to the next step in the process.
The user is able to review and confirm or correct information before submitting it.
Identifying typing errors helps users who are blind, individuals with motor disabilities who may press keys by mistake, and those with certain types of learning disabilities who have difficulty writing text.
Certain disabilities make it more difficult to operate input devices, resulting in more input errors. For example, individuals with limited motor functions are more likely to make errors when they operate a mouse or a keyboard. Speech recognition systems may find it more difficult to recognize the speech of individuals with speech disabilities. Features that assist in recognizing and correcting errors benefit individuals with these types of disabilities.
Example 1: Identifying errors in a form submission.
An airline web site offers a special promotion on discounted flights. The user is asked to complete a simple form that asks for personal information such as name, address, phone number, seating preference and e-mail address. If any of the fields of the form are either not completed or completed incorrectly, the user is warned of the input error. The user is then presented with the same form, all previously and correctly entered information is still available. The user is asked to make corrections to any form field marked with a red arrow or two asterisks. Note: color alone is not used to indicate errors.
Example 2: Username and password errors.
A Web page requires the user to enter both a username and password. If either is incorrect, the user is informed that there was an error but, for security reasons, is not informed as to which field, the username or the password, is in error and suggestions for correcting are not offered.
Example 3: An online test.
A Web site provides an online test for certification in a particular field of study. The test identifies incorrect answers to the user but does not offer suggestions for correcting them. The purpose of the online test is to test the user's knowledge, therefore, providing hints on correct answers would go against the purpose of the Web site.
Example 4: Order confirmation.
A Web retailer offers online shopping for customers. When an order is submitted, the order information, including items ordered, quantity of each ordered, shipping address, and payment method, are displayed allowing the user to inspect the order for correctness. The user can either confirm the order or make changes.
Example 5: A selection list to reduce errors.
A Web retailer offers online shopping for customers interested in fly fishing gear. When the user is asked for his/her country, a pulldown list of countries is offered instead of having the user enter the information by typing. To possibly make things easier, the user is informed that countries are listed in alphabetical order.
Example 6: Search engine features.
A search engine is provided with a variety of search options for different skill levels and preferences. It includes an option to check the spelling of the search terms and offers "best guess" alternatives, query-by-example searches, and similarity searches.
Example 7: Spell checking in feedback forms.
A banking Web site provides a form for customers to submit questions or suggestions. The form user interface includes an optional spell-checking feature for the text input area where the question or suggestion is entered.
Example 8: Expected date format in a form.
In a form, there is a text box for "birthday". Next to this text box is the text "(MM-DD-YYYY)" to indicate the format in which the date should be entered.
This requirement does not apply to individual words or to phrases that have become part of the primary language of the content.
A mechanism is available for finding definitions for all words in text content.
Editorial Note: Further work on this criterion is needed, but techniques are needed first.
How to provide a mechanism for finding definitions.. (Informative)
A mechanism is available for identifying specific definitions of words used in an unusual or restricted way, including idioms and jargon.
Editorial Note: We need to define tests for "unusual or restricted way."
A mechanism for finding the expanded form of acronyms and abbreviations is available.
Section titles are descriptive.
How to provide descriptive section titles.. (Informative)
When text requires reading ability at or above the upper secondary education level, one or more of the following supplements is available:
A text summary that requires reading ability no higher than primary education level.
Graphical illustrations of concepts or processes that must be understood in order to use the content.
A spoken version of the text content.
Editorial Note: Definitions of primary and secondary education level will be provided.
How to provide supplements to text.. (Informative)
Phrases from various languages are often interspersed in writing. When these phrases are identified, a speech synthesizer can voice text with the appropriate accent and pronunciation. When they are not identified, the speech synthesizer will use the default accent and pronunciation of the language on the rest of the content, which can make the phrase unintelligible. Identifying changes in language will also allow a tool to ask for automatic translations of that content. When editing content, authoring tools can switch between appropriate spelling dictionaries.
Providing the expansion of abbreviations and acronyms not only helps people who are not familiar with the abbreviation or acronym but can clarify which meaning of an abbreviation or acronym is appropriate to use. For example, the acronym "ADA" stands for both the American with Disabilities Act as well as the American Dental Association.
Defining key terms and specialized language will help people who are not familiar with the topic.
Facilitating unambiguous decoding of characters and words in content is also helpful for individuals who are learning to read or learning a second language.
All users, especially those with cognitive, learning, and/or reading disabilities benefit from the use of clear and simple writing. This should not discourage you from expressing complex or technical ideas.
Using clear and simple language also benefits people whose first language differs from your own, including those people who communicate primarily in sign language.
Sounds, graphics, videos and animations can help make concepts presented in a Web site easier to understand, especially for people with cognitive, reading, or learning disabilities or those who are unfamiliar with the language of the text of the site.
Summarizing information that is difficult to understand helps people who do not read well.
Providing a summary of the visual cues that show relationships between complex information helps people who do not use visual cues or who have difficulty using visual cues. For example, people who are completely blind do not use any visual cues, while people with dyslexia or with low vision might have difficulty interpreting visual cues.
Designers need to be cautious in deciding when to use illustrations. Reading a picture is probably a learned activity that is easier for some than others. Some users skip the pictures; others read only the pictures. Designers must also recognize that visual conventions are not universal and that individuals develop their own mental schema and expectations in interpreting visual information.
Example 1: an abbreviation in a page title.
In the following heading, "People of the W3C." the abbreviation "W3C" is marked as an abbreviation. Because it has been marked appropriately, the user agent would be able to speak the letters of the abbreviation one at a time rather than attempting to pronounce it as though it were a word.
Example 2: a French phrase in an English sentence.
In the following sentence, "And with a certain je ne sais quoi, she entered both the room, and his life, forever." the French phrase "je ne sais quoi" is marked as French. Depending on the markup language, English may either be marked as the language for the entire document except where specified, or marked at the paragraph level.
Example 3: a description of a process.
A page describes how to learn to play soccer. Each step in learning the fundamentals of the game is illustrated with a photograph of a player doing what is described in the text.
Example 4: a description of a complex natural event.
A Web page discusses Mt. Pinatubo in the Phillipines. The page includes a description of the 1991 eruption as well as photos of the eruption and its aftermath. The page also includes a brief explanation of why volcanoes erupt. To clarify this explanation, there is also a link to an accessible video and 3D simulation of what happened underneath the crust and within the volcano during the eruption.
Example 6: stock trading data.
A news site is comparing the performance of the economy from 3rd quarter of this year with 3rd quarter from the last 3 years. They compare prices of the most popular stocks. They present the data in a bar graph with a link to the raw data they used to create the bar graph.
Example 7: history of music.
A grandfather's hobby is listening to and playing music. He creates a Web site that includes examples of many different types of music and musical instruments. When describing specific types of music, he links to a short sound clip.
Components that are repeated on multiple delivery units within a set of delivery units occur in the same order each time they are repeated.
When any component receives focus, it does not cause a change of context.
Changing the setting of any input field does not automatically cause a change of context .
Components that have the same functionality in multiple delivery units within a set of delivery units are labeled consistently.
Providing consistent and predictable responses to user actions is important feedback for users. This lets them know that your site is working properly and encourages them to continue interacting with the content. When users receive an unexpected response, they might conclude that something is wrong or broken. Some people might become so confused they will not be able to use your site.
Individuals who are unable to detect changes of context or may not realize that the context has changed are less likely to become disoriented while navigating a site. This applies to people in the following ways:
Individuals who are blind or have low vision may have difficulty knowing when a visual context change, such as a new window popping up, has occurred. In this case, warning users of context changes in advance minimizes confusion when the user discovers that the back button no longer behaves as expected.
Some individuals with low vision, with dyslexia and who have difficulty interpreting visual cues may benefit from additional cues in order to detect changes of context.
Example 1: a form to deactivate pop-up windows.
A checkbox is provided on a page of links to let the user select whether they want the resultant pages to appear in new windows or not.
Example 2: a warning is given before displaying a pop-up window.
At the end of a news story, several links are provided for more information. At the beginning of each link is an icon of an arrow with the text equivalent, "Link will open in new window."
Example 3: frames that do not track history making the back button behave unexpectedly.
Example 4: forms.
Editorial Note: These examples need to be completed or replaced with better examples.
Editorial Note: The success criteria, examples and benefits have not been included in this Working Draft because there is ongoing discussion about the priority of validity requirements in these guidelines. A summary of the issues, background, and questions for discussion to find a consensus-based outcome are available at Validity and Accessibility.
If content does not meet all level 1 success criteria, then an alternate form is provided that does meet all level 1 success criteria.
If the user can enter the content using the keyboard, then the user can exit the content using the keyboard.
The role, state, and value can be programmatically determined for every user interface component of the web content that accepts input from the user or changes dynamically in response to user input or external events.
The label of each user interface control that accepts input from the user can be programmatically determined and is explicitly associated with the control.
The states and values of content that can be changed via the user interface can also be changed programmatically.
Changes to content, structure, selection, focus, attributes, values, state, and relationships within the content can be programmatically determined.
Content implemented using technologies outside of baseline follows all WCAG requirements supported by the technology.
Authors who ensure the accessibility of user interfaces within their content will:
encounter fewer challenges when implementing these guidelines,
avoid the need to create custom solutions and workarounds to address accessibility concerns,
avoid the need to provide accessible alternate versions for content rendered in a technology that does not fully address these guidelines.
Benefits of determining and documenting technology requirements:
Individuals can identify (either through site documentation or automatically through metadata) whether or not they are likely to be able to use a site. In conjunction with a search engine or a proxy server, this could be used to automatically filter out sites a user can not access or to automatically filter to the top sites that would be most usable.
Documenting technology requirements will cause authors to evaluate assumptions about user agents and will minimize the number of sites that are inadvertently inaccessible because they are unaware of backward compatibility issues.
Benefits of ensuring user interface accessibility and providing accessible alternatives:
Individuals who must use alternative browsing technologies and devices will be able to access the content.
Individuals who can not afford or otherwise do not have access to newer technologies also benefit from backward compatibility in that they will not need to purchase upgrades or equipment as often.
Example 1: an online store that lists required technologies.
By documenting minimum user agent requirements, the store makes it possible for people using particular technologies to determine whether they are going to have trouble using the store or its checkout mechanism before they begin shopping. This prevents users from finding that, after they have selected their products and initiated a checkout process, they are unable to complete their transaction. They can, therefore, choose alternatives where they can be assured greater success.
Example 2: an intranet site that transforms gracefully.
A large company was concerned about the ability to address individuals at many diverse office locations that have different technology bases. To address the problem, they created two versions of their content and documented the requirements for each, making it easy for individual locations to determine which version would work best for their technologies.
Example 3: an informational site ensuring backward compatibility.
An information site covers a wide variety of subjects and wants to enable their visitors to quickly find the topics they're looking for. To do this, they have implemented an interactive menu system that is only supported in the most recent version of two popular user agents. To ensure that their visitors who do not use these specific user agents are still able to effectively use the site, a navigation mechanism that does not depend on the interactive menu system they are using is presented to user agents that do not support the newer technology.
Example 4: accessible APIs.
A Java applet uses the accessibility API defined by the language. Refer to the IBM Guidelines for Writing Accessible Applications Using 100% Pure Java.
Editorial Note: The WCAG WG has not tackled the definitions of the terms that we are using and acknowledges that we sometimes use terms inconsistently. We need to coordinate our terms and definitions with the WAI Glossary and are working on proposals for a variety of definitions. We have been looking at the UAAG 1.0 glossary and other glossaries within the W3C. A list of open issues related to this glossary is available.
An activity where timing is essential is an activity where timing is part of the design of the activity. Removal of the time element would change the performance of the participants. Versions of the activity (e.g. test) that have no time basis or time-outs might be preferred and may be required for some venues but this would require a complete redesign of the activity (e.g. test) and may change the character and validation methodology and would therefore not fall under these guidelines.
A picture created by a spatial arrangement of characters (typically from the 95 printable characters defined by ASCII).
Additional audio narration that explains important details that cannot be understood from the main soundtrack alone. During pauses in dialog, audio descriptions of video provide information about actions, characters, scene changes and on-screen text to people who are blind or visually impaired.
Some set of material created as a single entity by an author. Examples include a collection of markup, a style sheet, and a media resource, such as an image or audio clip.
This term was taken verbatim from Glossary of Terms for Device Independence.
Images that appear behind or to the back of the visual field.
Set of technologies assumed to be supported by, and enabled in, user agents in order for Web content to conform to these guidelines.
Some examples of entities that may set baselines that an author may have to follow include the author, a company, a customer and government entities.
Editorial Note: In the techniques document we plan to discuss techniques for conforming to WCAG 2.0 based on three different baselines (i.e. assumptions of technologies supported and active in user agents).
Content that blinks is content that turns on and off between .5 and 4 times per second.
Synchronized transcripts of dialogue and important sound effects. Captions provide access to multimedia for people who are deaf or hard of hearing.
A change of user agent, viewport, user interface controls, or focus; or complete change of content.
A sequence of flashes or rapidly changing image sequences is not permitted when both the following occur:
the combined area of flashes occurring concurrently (but not necessarily contiguously) occupies more than one quarter of any 335 x 268 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 by 768 pixels and
there are more than three flashes within any one-second period.
For the general flash threshold, a flash is defined as a pair of opposing changes in luminance (i.e., an increase in luminance followed by a decrease, or a decrease followed by an increase) of ___ per rectangle meter (cd.m-2) or more and where the screen luminance of the darker image is below ___.
Thresholds are based on ITC Guidance Note for Licensees on Flashing Images and Regular Patterns in Television (Revised and re-issued July 2001) as modified by the Wisconsin Computer Equivalence Algorithm.
A transition to or from a saturated red at any luminance level is not permitted when both of the following occur:
the combined area of flashes occurring concurrently occupies more than one quarter of any 335 x 268 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 by 768 pixels and
there are more than three flashes within any one-second period.
For the red flash threshold, a flash is defined as any pair of opposing transitions to or from a saturated red exceeding __ % of ___. (See note below)
Thresholds are based on ITC Guidance Note for Licensees on Flashing Images and Regular Patterns in Television (Revised and re-issued July 2001) as modified by the Wisconsin Computer Equivalence Algorithm.
The international definitions for spatial pattern threshold are changing and we will adopt the new standards as they are released. If not available we will remove the L3 SC.
Information in the delivery unit that is used by the user agent to generate perceivable units. This includes the code and markup that define the structure, presentation, and interaction, as well as text, images, and sounds that convey information to the end-user.
This term was taken verbatim from Glossary of Terms for Device Independence.
A section of code that responds to an action taken by the user (or user agent). On Web pages, events are usually user actions such as moving the mouse, typing, etc. An event handler determines the response to that action. A technology specific event handler only responds to an action by one kind of input device. An abstract event handler is one which can be activated by a variety of input devices.
In cases where a longer audio description is necessary but there is not a sufficient pause in the audio to accommodate it, the audio and video are paused while the audio and description plays. When the description has finished playing, the video and dialog resume playback. Extended and "regular" descriptions may be mixed in a single multimedia presentation.
A feature is a specific component of a technology, for example an element in a markup language or a function call in an Application Programming Interface. Typically, a given feature may only be available in specific versions of the technology, and thus may need to be noted explicitly in the required list.
Foreign passages or phrases are passages or phrases in a language that is different from the language of the surrounding text.
Performs or is able to perform one or more actions in response to user input.
On devices that do not have a built-in or attached keyboard, there is often an alternate method for connecting a keyboard to the device for the purpose of generating text or an internal method for generating text. Allowing control via the "keyboard interface" means that the content could be controlled through commands issued from the keyboard or by alternate methods that are capable of generating text as if a keyboard had been used.
Link refers to a hyperlink between the current document and a single destination. (Here, "link" refers to a single "arc" in the XML Linking Language (XLink) Version 1.0 specification.) Only links which are available to be activated by the user need to meet accessibility requirements. This excludes links that are activated automatically or programmatically.
The content is marked in a fashion that would allow the user to determine that provocative material can be avoided. Some methods that might be used for this include:
metadata on the page
information in the title (so search engine shows it)
notification on the page before provocative information is encountered.
Editorial Note: This definition needs work.
For the purposes of these guidelines, multimedia refers to combined audio and video presentations. It also includes audio-only and video-only presentations that include interaction.
Natural languages are those used by humans to communicate, including spoken, written, and signed languages.
Something that allows the user to locate and/or move to a different piece of content than the one currently with focus. Examples of navigational features are links and components that are grouped so they can be bypassed.
Content that is not represented by a Unicode character or sequence of Unicode characters.
functional non-text content - content that is capable of performing one or more actions in response to user input and is not text.
Editorial Note: We need to decide which term to use here to refer to programs that run in the context of user agents.(ex. applet, embedded programmatic object, functional component)
non-text content used to convey information - content that communicates ideas, data, facts [@@include info from definition of information] and is not text.
non-text content that is intended to create a specific sensory experience - arrangements of sounds, colors, forms, movements, or other elements in a manner that cause a reaction in the viewer or listener.
Required for conformance.
The result of a user agent rendering the contents of a delivery unit. User agents may or may not render all information in a delivery unit. In some cases, a single delivery unit may be rendered as multiple perceivable units. For example, a single html file that is rendered as a set of presentation slides. Most perceivable units contain presentation and the means for interaction. However, for some devices such as printers, a perceivable unit may only contain presentation.
Presentation is the rendering of the content and structure in a form that can be sensed by the user.
An interface component created by the author that is in addition to those provided by the user agent. For example, an HTML checkbox would not be a programmatic user interface component because the author is using an interface component supported by the user agent. A checkbox function implemented in script, however, would be a programmatic user interface component because it provides functionality that is not known or supported by user agents and can not be made accessible by user agents even if the user agent complied with UAAG.
programmatically determined means that the specific value can be determined in a standard, machine or software readable form.
Editorial Note: We need to define this term.
Real-time events are those that are based on the occurrence of events in real-time where the events are not under the control of the author.
A regular expression as defined in XML Schema Part 2: Datatypes, Appendix F.
Editorial Note: We need to include a definition of specific sensory experience. (per 13 June 2005 face to face meeting)
The way the parts of an authored unit are organized in relation to each other and;
The way a collection of authored units is organized in relation to a delivery unit and;
The way a collection of delivery units is organized
Editorial Note: Examples still need work. [Issue #506]
A book is divided into chapters, paragraphs, lists, etc. Chapter titles help the reader anticipate the meaning of the following paragraphs. Lists clearly indicate separate, yet related ideas. All of these divisions help the reader anticipate changes in context.
A bicycle is divided into wheels and a frame. Further, a wheel is divided into a tire and a rim. In an image of the bicycle, one group of circles and lines becomes "wheel" while another group becomes "frame."
Technology means a data format, programming or markup language, protocol or API.
A sequence of characters. Characters are those included in the Unicode/ISO/IEC 106464 repertoire.
Content might be unfamiliar if you are using terms specific to a particular community. For example, many of the terms used in this document are specific to the disability community.
Unicode is a universal character set that defines all the characters needed for writing the majority of living languages in use on computers. For more information refer to the Unicode Consortium or to Tutorial: Character sets & encodings in XHTML, HTML and CSS produced by the W3C Internationalization Activity.
A URI pattern is a regular expression identifying a set of resources. A resource belongs to the set if the regular expression matches its URI.
in order to be included in the set, the resource must exist; the regular expression may, and typically will, match URIs that do not refer to any existing resource.
In this document, the term "user agent" is used in two ways:
The software and documentation components that together, conform to the requirements of the User Agent Accessibility Guidelines 1.0 (UAAG 1.0). This is the most common use of the term in this document and is the usage in the UAAG checkpoints.
Any software that retrieves and renders Web content for users. This may include Web browsers, media players, plug-ins, and other programs — including assistive technologies — that help in retrieving and rendering Web content.
This term was taken verbatim from User Agent Accessibility Guidelines 1.0 (UAAG 1.0) Glossary
A time-based presentation that only contains video.
The Wisconsin Computer Equivalence Algorithm is a method for applying the United Kingdom's "ITC Guidance Note for Licensees on Flashing Images and Regular Patterns in Television (Revised and re-issued July 2001)" to content displayed on a computer screen, such as Web pages and other computer content. The ITC Guidance Document is based on the assumption that the television screen occupies the central ten degrees of vision. This is not accurate for a screen which is located in front of a person. The Wisconsin Algorithm basically carries out the same analysis as the ITC Guidelines except that is does it on every possible ten degree window for a prototypical computer display.
Editorial Note: Links to references will be provided when they become available.
Since the release of WCAG 1.0 in May 1999, the WCAG Working Group has received feedback on priorities of checkpoints, the usability of the set of documents, and requests for clarifications on the meaning of specific checkpoints and what is needed to satisfy them. Thus, it is intended that WCAG 2.0, when it eventually becomes a W3C Recommendation:
will be more efficiently organized,
may adjust the priority of some checkpoints,
may modify, remove, or add requirements due to changes in Web technologies since the publication of WCAG 1.0,
will incorporate the Errata from WCAG 1.0,
will reflect the experience gained in implementing WCAG 1.0.
For a detailed comparison, refer to the Mapping Between WCAG 1.0 and the WCAG 2.0 Working Draft.
We hope that WCAG 2.0 will have several improvements over WCAG 1.0. While the primary goal of WCAG 2.0 is the same as WCAG 1.0 (to promote accessibility of Web content) additional goals for WCAG 2.0 include improvements that will:
Ensure that requirements may be applied across technologies
Ensure that the conformance requirements are clear
Ensure that the deliverables are easy to use
Write to a more diverse audience
Clearly identify who benefits from accessible content
Ensure that the revision is "backward compatible" with WCAG 1.0
For more information about the intended improvements in WCAG 2.0 Working Draft, please refer to Requirements for WCAG 2.0.
Editorial Note: Links within the document will be turned into references and the links to those documents will be listed here. They are inline for the time being.