W3C

Guidance on Applying WCAG 2.0 to Non-Web Information and Communications Technologies

W3C Editor's Draft 11 13 December 2012

This version:
http://www.w3.org/WAI/GL/2012/WD-wcag2ict-20121126/ http://www.w3.org/WAI/GL/2012/WD-wcag2ict-20121213/
Latest published version:
http://www.w3.org/TR/wcag2ict/
Previous version:
http://www.w3.org/WAI/GL/2012/WD-wcag2ict-20121126/
Latest editor's draft:
http://www.w3.org/WAI/GL/wcag2ict/
Editors:
Shadi Abou-Zahra, W3C Michael Cooper, W3C
Andi Snow-Weaver, IBM Corporation
Authors:
Judy Brewer, W3C
Peter Korn, Oracle Corporation
Loïc Martínez Normand, Universidad Politécnica de Madrid
Mike Pluke, Invited Expert
Andi Snow-Weaver, IBM Corporation
Gregg Vanderheiden, Invited Expert, Trace Research and Development Center

Abstract

This document, “ Guidance on Applying WCAG 2.0 to non-Web Information and Communications Technologies ” describes how the Web Content Accessibility Guidelines (WCAG) 2.0 and its principles, guidelines, success criteria and conformance model can be applied to non-Web Information and Communications Technologies (ICT), specifically non-Web documents and software aspects of products. It provides informative guidance (guidance that is not normative and does not set requirements).

This document is intended to become a Working Group Note, and is part of a series of technical and educational documents published by the W3C Web Accessibility Initiative (WAI) and available from the WCAG 2.0 Overview .

Status of This Document

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

This document is an Editors' Draft being developed by the  WCAG2ICT Task Force  ( Work Statement ) under the coordination and review of the Web Content Accessibility Guidelines Working Group  (WCAG WG), which is part of the Web Accessibility Initiative (WAI) of the World Wide Web Consortium  (W3C). Following further public review and refinement, it is expected to progress to a  Working Group Note . The WCAG2ICT Task Force's work is consistent with the  WCAG WG Charter  that includes the following under its  scope : “Coordinating with other entities adopting and using WCAG 2.0”.

This draft includes changes made in response to  comments received  by 7 September 2012 in response to the earlier  call for public review  of the 27 July 2012 First Public Working Draft of this document. The task force has not yet completed processing all comments. For this Working Draft, the WCAG WG particularly seeks comments on:

The focus of this review is on the “Additional Guidance” sections, which start with the words “Additional guidance when applying…” and which are visually indicated with blue boxes, rather than on the wording excerpted from other WCAG 2.0 documents.  Please send any comments on the “Additional Guidance” sections of this document by @@ January 15 February 2013  to the public mailing list  public-wcag2ict-comments@w3.org Please include the following in your comments: the title of the document, location within the document, the concern, the suggested change, and any additional rationale for your comment.

This document includes many excerpts from “Understanding WCAG 2.0,” each of which is prefaced with the words “Intent from …” and which are also visually indicated with a yellow background. While comments on excerpted text from Understanding WCAG 2.0 may help inform clarifications and updates to text from Understanding WCAG 2.0 or from other WCAG 2.0 supporting documents, those documents will continue to focus on Web technologies and will not be changed to address non-Web ICT. @@For For comments on Understanding WCAG, please use the  Comment Form online  per the  follow the comment instructions , so in that your comments are automatically entered into the comment-tracking database. Alternatively, you may send them to the e-mail address above. document.

Please note that WCAG 2.0 itself is a stable Web standard. Comments on this document will not directly affect WCAG 2.0 wording.

Publication as an Editors' Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

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

Table of Contents

1. Introduction

This Working Draft provides informative guidance (guidance that is not normative, and that does not set requirements) with regard to the interpretation and application of  Web Content Accessibility Guidelines (WCAG) 2.0 . This document is intended to become a   Working Group Note (in contrast to WCAG 2.0, which is a W3C Recommendation and also an International Organization for Standardization (ISO) / International Electrotechnical Commission (IEC) standard). Specifically, this Working Draft provides informative guidance on applying WCAG 2.0 Level A and AA success criteria to non-Web information and communications technologies (ICT), specifically non-Web documents and software.

This document is intended to help clarify how to use WCAG 2.0 to make non-Web documents and software more accessible to people with disabilities. Addressing accessibility involves addressing the needs of people with auditory, cognitive, neurological, physical, speech, and visual disabilities, and the needs of people with accessibility requirements due to aging. Although this document covers a wide range of issues, it is not able to address all the needs of all people with disabilities. Because WCAG 2.0 was developed for the Web, addressing accessibility for non-Web documents and software may involve provisions beyond those included in this document. Authors and developers are encouraged to seek relevant advice about current best practices to ensure that non-Web documents and software are accessible, as far as possible, to people with disabilities.

While WCAG 2.0 was designed to be technology-neutral, it assumes the presence of a “user agent” such as a browser, media player, or assistive technology as a means to access Web content. Therefore, the application of WCAG 2.0 to documents and software in non-Web contexts required some interpretation in order to determine how the intent of each WCAG 2.0 success criterion could be met in these different contexts of use. The bulk of the Task Force's work therefore involved evaluating how each WCAG 2.0 success criterion would apply in the context of non-Web ICT, if it were applied to non-Web ICT.

The Task Force found that the majority of success criteria from WCAG 2.0 can apply to non-Web documents and software with no or only minimal changes. Specifically, of the thirty-eight Level A and AA success criteria, twenty-six did not include any Web related terms and apply directly as written and as described in the “Intent” sections from the updated “ Understanding WCAG 2.0 ”. Thirteen of these twenty-six applied without any additional notes. The other thirteen applied as written but additional notes were also provided for assistance in applying them to either or both non-Web documents and software.

Of the remaining twelve success criteria, the Task Force found that nine eight of them apply as written when replacing certain Web specific terms or phrases like “Web page(s)” with non-Web terms or phrases like “non-Web document(s) and software” or “for non-Web documents and software that use markup languages, in such a way that…” etc. Additional notes were also provided to assist in the application of these.

The remaining three four success criteria apply in situations when “a set of Web pages”, or “multiple Web pages” share some characteristic or behavior. For these, the task force found that (with substitutions) the success criteria apply to non-Web documents fairly straightforwardly. The task force does not yet have guidance for how to apply these three four success criteria in a software context.

Excluded from Scope

The following aspects are out of scope for this document:

Document Overview

This document includes excerpted text from WCAG 2.0 principles, guidelines, and success criteria, as quoted from WCAG 2.0 without any changes. It also includes excerpted text from the “Intent” sections of the WCAG 2.0 supporting document  Understanding WCAG 2.0 (Editors' Draft) , as clarified based on input from Task Force discussions and responses to public comments after review and approval by the WCAG Working Group. The guidance provided by the WCAG2ICT for each success criteria is preceded by a title beginning  “Additional Guidance...”. This guidance was created by the WCAG2ICT Task Force, then reviewed and approved by the WCAG Working Group.  

Later drafts of this document may include excerpts from the Conformance Section of WCAG 2.0 and Understanding WCAG 2.0, together with “Additional Guidance” from the Task Force following review and approval by the WCAG Working Group; however, this draft does not include any guidance on conformance. Later drafts may include "Additional Guidance" on level AAA success criteria.

Additional supporting documents for WCAG 2.0, such as the  WCAG 2.0 Overview Techniques for WCAG 2.0 , and  How to Meet WCAG 2.0: A customizable quick reference , remain available for Web content, but have not been changed to apply to non-Web documents and software.

Document Conventions

The following stylistic conventions are used in this document:

2. Key Terms

There are several terms used throughout WCAG 2.0 that need to be interpreted differently when applied to non-Web ICT. These include: “content” and “user agent”. Further, the term “Web page” in WCAG 2.0 is replaced with newly defined terms “document” and “software”. “software”, and both "set of web pages" and "multiple web pages" are replaced with the newly defined term "set of documents".

Further information on usage of these terms follows.

Content (on and off the Web)

WCAG 2.0 defines CONTENT as:

content (web content)

information and sensory experience to be communicated to the user by means of a user agent , including code or markup that defines the content's structure, presentation, and interactions

For non-Web content we need to view this a bit more broadly. Within our document, we use the term content as follows:

content (non-web content)

information and sensory experience to be communicated to the user by means of software , including code or markup that defines the content's structure, presentation, and interactions

Note: Non-Web content occurs in two places; documents and software. When content occurs in a document, a user agent is needed in order to communicate the content's information and sensory experience to the user. When content occurs in software, a separate user agent isn't required - the software itself performs that function.

Within WCAG2ICT wherever “content” or “Web content” appears in a success criterion or Intent it should be replaced with “content” using the definition above.

Document

The term  Document , as used in WCAG2ICT, has the meaning below:

document (as used in WCAG2ICT)

assembly of content, such as a file, set of files, or streamed media that is not part of software and that does not include its own user agent

Note 1. A documents always requires a user agent to present its content to the user.

Note 2. Letters, spreadsheets, emails, books, pictures, presentations, and movies are examples of documents.

Note 3. Anything that can present its own content without involving a user agent, such as a self playing book, is not a document but is software.

Note 4. A single document may be composed of multiple files such as the video content, closed caption text, etc. This fact is not usually apparent to the end-user consuming the document/content. This is similar to how a single Web page can be composed of content from multiple URIs (e.g. the page text, images, the JavaScript, a CSS file etc.).

Set of documents

The term Set of documents , as used in WCAG2ICT has the meaning below:

set of documents (non-web) (as used in WCAG2ICT)

group of documents that are published together, and where the items all refer to each other by name or link.

Note 1:   Republishing or bundling previously published documents as a collection does not constitute a set of documents.

Note 2:  If a set is broken apart, the individual parts are no longer part of a set, and would be evaluated as any other individual document is evaluated.

One example of a set of documents would be a three-part report where each part is a separate file. At the beginning of each file the table of contents for “navigating” to the other parts is repeated.

Software

The term  Software as used in WCAG2ICT, has the meaning below:

software (as used in WCAG2ICT)

software products or software aspects of hardware-software products that have a user interface and do not require a separate user agent to present any of its content

Note 1. For software, the user interface and any other embedded content is covered by these guidelines. The software provides a function equivalent to a user agent for the embedded content.

Note 2. Software without a user interface does not have content and is not covered by these guidelines. For example, driver software with no user interface would not be covered.

Note 3 . Because software with a user interface provides a function equivalent to a user agent in addition to content, the application of some WCAG 2.0 success criteria would be different for content embedded in software versus content in a document, where it is viewed through a separate user agent (e.g. browser, player, viewer, etc.).

User Agent

WCAG 2.0 defines user agent as follows:

user agent

any software that retrieves and presents Web content for users

Example: Web browsers, media players, plug-ins, and other programs — including  assistive technologies  — that help in retrieving, rendering, and interacting with Web content.

For non-Web ICT, “user agent” needs to be viewed differently. In WCAG 2.0, the term “user agent” only  refers to retrieval and display of  Web content.  For non-Web ICT, the term “user agent” refers to retrieval and display of separate content that is  not on the Web , which WCAG2ICT refers to as a “document”.    Within WCAG2ICT, the term “user agent” is used as follows:

user agent

any software that retrieves and presents documents for users

Note 1.   Software that only displays the content contained within it is not considered to be a user agent. It is just considered to be software.

Note 2.   An example of software that is not a user agent is a calculator application that doesn't retrieve the calculations from outside the software to present it to a user. In this case, the calculator software is not a user agent, it is simply software with a user interface.

Note 3: Software that only shows a preview of content such as a thumbnail or other non-fully functioning presentation is not providing user agent functionality.

3. Closed Functionality

Many As noted in the Introduction, WCAG 2.0  assumes the presence of a “user agent” such as a browser, media player, or assistive technology as a means to access Web content. Furthermore, many of the success criteria in WCAG 2.0 assume Web content will be accessed by ICT that has assistive technologies connected to it, where the assistive technologies present the Web content to the people with disabilities in accessible form. ICT products with "closed functionality" do not allow the use of some assistive technologies for all of their functions. In many cases such ICT products also lack a “user agent” or their equivalent.  As a result, ICT following these success criteria by themselves will not make information accessible on ICT with closed functionality. Something else needs to be provided or be required in order to make the information addressed in these success criteria accessible.  It is outside the task force work statement to say what the additional measures are,  but we can point out which success criteria depend on assistive technologies - and therefore would not work by themselves in products with closed functionality. 

Because closed functionality, by definition, does not allow a user to attach assistive technology, WCAG success criteria that assume the presence of assistive technology will not facilitate accessibility as WCAG 2.0 intends. Where assistive technologies cannot be used, other output and input solutions are needed to achieve the intent of these success criteria.

Examples of products with closed functionality include:

See Success Criteria Problematic for Closed Functionality for a list of success criteria for which this is relevant.

4. Comments by Guideline and Success Criterion

The sections that follow are organized according to the principles, guidelines, and success criteria from WCAG 2.0. The text of the item from WCAG 2.0 is copied as quoted text. Following that, the “intent” from Understanding WCAG 2.0 is copied as quoted text. Finally, the guidance of this document is provided. In visual presentations this is set out in a box with a blue bar to the left, to highlight that this is the content specific to this document.

Principle 1: Perceivable

Information and user interface components must be presentable to users in ways they can perceive.

Guideline 1.1: Text Alternatives

From Guideline 1.1 :

Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language.

Intent from Understanding Guideline 1.1 in Understanding WCAG 2.0 :

The purpose of this guideline is to ensure that all non-text content is also available in text . "Text" refers to electronic text, not an image of text. Electronic text has the unique advantage that it is presentation neutral. That is, it can be rendered visually, auditorily, tactilely, or by any combination. As a result, information rendered in electronic text can be presented in whatever form best meets the needs of the user. It can also be easily enlarged, spoken aloud so that it is easier for people with reading disabilities to understand, or rendered in whatever tactile form best meets the needs of a user.

Note: While changing the content into symbols includes changing it into graphic symbols for people with developmental disorders and speech comprehension difficulties, it is not limited to this use of symbols.

Additional guidance when applying Guideline 1.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 1.1.

Success Criterion 1.1.1: Non-text Content (Level A)

From Success Criterion 1.1.1 :

All non-text content that is presented to the user has a text alternative that serves the equivalent purpose, except for the situations listed below.

  • Controls, Input: If non-text content is a control or accepts user input, then it has a name that describes its purpose. (Refer to Guideline 4.1 for additional requirements for controls and content that accepts user input.)

  • Time-Based Media: If non-text content is time-based media, then text alternatives at least provide descriptive identification of the non-text content. (Refer to Guideline 1.2 for additional requirements for media.)

  • Test: If non-text content is a test or exercise that would be invalid if presented in text , then text alternatives at least provide descriptive identification of the non-text content.

  • Sensory: If non-text content is primarily intended to create a specific sensory experience , then text alternatives at least provide descriptive identification of the non-text content.

  • CAPTCHA : If the purpose of non-text content is to confirm that content is being accessed by a person rather than a computer, then text alternatives that identify and describe the purpose of the non-text content are provided, and alternative forms of CAPTCHA using output modes for different types of sensory perception are provided to accommodate different disabilities.

  • Decoration, Formatting, Invisible: If non-text content is pure decoration , is used only for visual formatting, or is not presented to users, then it is implemented in a way that it can be ignored by assistive technology .

Intent from Understanding Success Criterion 1.1.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to make information conveyed by non-text content accessible through the use of a text alternative. Text alternatives are a primary way for making information accessible because they can be rendered through any sensory modality (for example, visual, auditory or tactile) to match the needs of the user. Providing text alternatives allows the information to be rendered in a variety of ways by a variety of user agents. For example, a person who cannot see a picture can have the text alternative read aloud using synthesized speech. A person who cannot hear an audio file can have the text alternative displayed so that he or she can read it. In the future, text alternatives will also allow information to be more easily translated into sign language or into a simpler form of the same language.

Note on CAPTCHA

CAPTCHAs are a controversial topic in the accessibility community. As is described in the paper Inaccessibility of CAPTCHA , CAPTCHAs intrinsically push the edges of human abilities in an attempt to defeat automated processes. Every type of CAPTCHA will be unsolvable by users with certain disabilities. However, they are widely used, and the Web Content Accessibility Guidelines Working Group believes that if CAPTCHAs were forbidden outright, Web sites would choose not to conform to WCAG rather than abandon CAPTCHA. This would create barriers for a great many more users with disabilities. For this reason the Working Group has chosen to structure the requirement about CAPTCHA in a way that meets the needs of most people with disabilities, yet is also considered adoptable by sites. Requiring two different forms of CAPTCHA on a given site ensures that most people with disabilities will find a form they can use.

Because some users with disabilities will still not be able to access sites that meet the minimum requirements, the Working Group provides recommendations for additional steps. Organizations motivated to conform to WCAG should be aware of the importance of this topic and should go as far beyond the minimum requirements of the guidelines as possible. Additional recommended steps include:

  • Providing more than two modalities of CAPTCHAs

  • Providing access to a human customer service representative who can bypass CAPTCHA

  • Not requiring CAPTCHAs for authorized users

Additional information

Non-text content can take a number of forms, and this Success Criterion specifies how each is to be handled.

For non-text content that is not covered by one of the other situations listed below, such as charts, diagrams, audio recordings, pictures, and animations, text alternatives can make the same information available in a form that can be rendered through any modality (for example, visual, auditory or tactile). Short and long text alternatives can be used as needed to convey the information in the non-text content. Note that prerecorded audio-only and prerecorded video-only files are covered here. Live-audio-only and Live-video-only files are covered below (see 3rd paragraph following this one).

For non-text content that is a control or accepts user input , such as images used as submit buttons, image maps or complex animations, a name is provided to describe the purpose of the non-text content so that the person at least knows what the non-text content is and why it is there.

Non-text content that is time-based media is made accessible through 1.2 . However, it is important that users know what it is when they encounter it on a page so they can decide what action if any they want to take with it. A text alternative that describes the time-based media and/or gives its title is therefore provided.

For Live Audio-only and live video-only content , it can be much more difficult to provide text alternatives that provide equivalent information as live audio-only and live video-only content. For these types of non-text content, text alternatives provide a descriptive label.

Sometimes a test or exercise must be partially or completely presented in non-text format. Audio or visual information is provided that cannot be changed to text because the test or exercise must be conducted using that sense. For example, a hearing test would be invalid if a text alternative were provided. A visual skill development exercise would similarly make no sense in text form. And a spelling test with text alternatives would not be very effective. For these cases, text alternatives should be provided to describe the purpose of the non-text content; of course, the text alternatives would not provide the same information needed to pass the test.

Sometimes content is primarily intended to create a specific sensory experience that words cannot fully capture. Examples include a symphony performance, works of visual art etc. For such content, text alternatives at least identify the non-text content with a descriptive label and where possible, additional descriptive text. If the reason for including the content in the page is known and can be described it is helpful to include that information.

Sometimes there are non-text exercises that are used to prove you are human. To avoid spam robots and other software from gaining access to a site a device called a CAPTCHA is used. These usually involve visual or auditory tasks that are beyond the current capabilities of Web robots. Providing a text alternative to them would however make them operable by Robots, thus defeating their purpose. In this case a text alternative would describe the purpose of the CAPTCHA, and alternate forms using different modalities would be provided to address the needs of people with different disabilities.

Sometimes there is non-text content that really is not meant to be seen or understood by the user. Transparent images used to move text over on a page; an invisible image that is used to track usage statistics; and a swirl in the corner that conveys no information but just fills up a blank space to create an aesthetic effect are all examples of this. Putting alternative text on such items just distracts people using screen readers from the content on the page. Not marking the content in any way, though, leaves users guessing what the non-text content is and what information they may have missed (even though they have not missed anything in reality). This type of non-text content, therefore, is marked or implemented in a way that assistive technologies (AT) will ignore it and not present anything to the user.

Specific Benefits of Success Criterion 1.1.1
  • This Success Criterion helps people who have difficulty perceiving visual content. Assistive technology can read text aloud, present it visually, or convert it to braille.

  • Text alternatives may help some people who have difficulty understanding the meaning of photographs, drawings, and other images (e.g., line drawings, graphic designs, paintings, three-dimensional representations), graphs, charts, animations, etc.

  • People who are deaf, are hard of hearing, or who are having trouble understanding audio information for any reason can read the text presentation. Research is ongoing regarding automatic translation of text into sign language.

  • 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.

Additional guidance when applying Success Criterion 1.1.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note 1: CAPTCHAs do not currently appear outside of the Web. However, if they do appear, this guidance is accurate. If they do not appear then the success criterion would be met automatically, as with any situation where a success criterion talks about something that is not present.

Note 2: See also the discussion on Closed Functionality in the Introduction.

Guideline 1.2: Time-based Media

From Guideline 1.2 :

Provide alternatives for time-based media.

Intent from Understanding Guideline 1.2 in Understanding WCAG 2.0 :

The purpose of this guideline is to provide access to time-based and synchronized media.This includes media that is:

  • audio-only

  • video-only

  • audio-video

  • audio and/or video combined with interaction

To make it easy for authors to quickly determine which success criteria apply to their content, the type of media each success criterion applies to is included in its short name.

For audio-only or video-only media, you only need to apply the success criteria that say " audio-only " or " video-only " in their short name. If your media is not audio-only or video-only , then all the rest of the success criteria apply.

Media can also be live or prerecorded . Each of the success criterion short names clearly tells you if the success criterion applies to live or prerecorded media.

Synchronized media is defined in the glossary as:

synchronized media

audio or video synchronized with another format for presenting information and/or with time-based interactive components, unless the media is a media alternative for text that is clearly labeled as such

Note that an audio file accompanied by interaction is covered here, as is a video-only file that involves interaction. These are covered because interaction must take place at a particular time. Having a text transcript that said, "for more information, click now," would not be very helpful since the reader would have no idea when the audio said, "now." As a result, synchronized captions would be needed.

Sometimes, there is so much dialogue that audio description cannot fit into existing pauses in the dialogue. The option at Level A to provide an alternative for time-based media instead of audio description for synchronized media would allow access to all of the information in the synchronized media. This option also allows access to the visual information in non-visual form when audio description is not provided for some other reason.

For synchronized media that includes interaction, interactive elements (for example links) could be embedded in the alternative for time-based media.

This guideline also includes (at Level AAA) sign language interpretation for synchronized media as well as an approach called extended audio description. In extended audio description, the video is frozen periodically to allow more audio description to take place than is possible in the existing pauses in the dialogue. This is a case where higher-level Success Criteria build upon the requirements of lower-level Success Criterion with the intention of having cumulative, progressively stronger, requirements.

Additional guidance when applying Guideline 1.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 1.2.

Success Criterion 1.2.1: Audio-only and Video-only (Prerecorded) (Level A)

From Success Criterion 1.2.1 :

For prerecorded audio-only and prerecorded video-only media, the following are true, except when the audio or video is a media alternative for text and is clearly labeled as such:

  • Prerecorded Audio-only: An alternative for time-based media is provided that presents equivalent information for prerecorded audio-only content.

  • Prerecorded Video-only: Either an alternative for time-based media or an audio track is provided that presents equivalent information for prerecorded video-only content.

Intent from Understanding Success Criterion 1.2.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to make information conveyed by prerecorded audio-only and prerecorded video-only content available to all users. Alternatives for time-based media that are text based make information accessible because text can be rendered through any sensory modality (for example, visual, auditory or tactile) to match the needs of the user. In the future, text could also be translated into symbols, sign language or simpler forms of the language (future).

An example of pre-recorded video with no audio information or user interaction is a silent movie. The purpose of the transcript is to provide an equivalent to what is presented visually. For prerecorded video content, authors have the option to provide an audio track. The purpose of the audio alternative is to be an equivalent to the video. This makes it possible for users with and without vision impairment to review content simultaneously. The approach can also make it easier for those with cognitive, language and learning disabilities to understand the content because it would provide parallel presentation.

Note: A text equivalent is not required for audio that is provided as an equivalent for video with no audio information. For example, it is not required to caption video description that is provided as an alternative to a silent movie.

See also Understanding Success Criterion 1.2.9 Audio-only (Live)

Specific Benefits of Success Criterion 1.2.1
  • This Success Criterion helps people who have difficulty perceiving visual content. Assistive technology can read text alternatives aloud, present them visually, or convert them to braille.

  • Alternatives for timed-based media that are text based may help some people who have difficulty understanding the meaning of prerecorded video 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. Research is ongoing regarding automatic translation of text into sign language.

  • People who are deaf-blind can read the text in braille.

  • Additionally, text supports the ability to search for non-text content and to repurpose content in a variety of ways.

Additional guidance when applying Success Criterion 1.2.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note 1: The alternative can be provided directly in the non-web document or software – or provided in a conforming alternate version .

Note 2: See also the discussion on Closed Functionality in the Introduction.

Success Criterion 1.2.2: Captions (Prerecorded) (Level A)

From Success Criterion 1.2.2 :

Captions are provided for all prerecorded audio content in synchronized media , except when the media is a media alternative for text and is clearly labeled as such.

Intent from Understanding Success Criterion 1.2.2 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to enable people who are deaf or hard of hearing to watch synchronized media presentations. Captions provide the part of the content available via the audio track. Captions not only include dialogue, but identify who is speaking and include non-speech information conveyed through sound, including meaningful sound effects.

It is acknowledged that at the present time there may be difficulty in creating captions for time-sensitive material and this may result in the author being faced with the choice of delaying the information until captions are available, or publishing time-sensitive content that is inaccessible to the deaf, at least for the interval until captions are available. Over time, the tools for captioning as well as building the captioning into the delivery process can shorten or eliminate such delays.

Captions are not needed when the synchronized media is, itself, an alternate presentation of information that is also presented via text on the Web page. For example, if information on a page is accompanied by a synchronized media presentation that presents no more information than is already presented in text, but is easier for people with cognitive, language, or learning disabilities to understand, then it would not need to be captioned since the information is already presented on the page in text or in text alternatives (e.g., for images).

See also Understanding Success Criterion 1.2.4 Captions (Live) .

Specific Benefits of Success Criterion 1.2.2
  • People who are deaf or have a hearing loss can access the auditory information in the synchronized media content through captions.

Additional guidance when applying Success Criterion 1.2.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note: The WCAG 2.0 definition of “captions” notes that “in some countries, captions are called subtitles”. They are also sometimes referred to as “subtitles for the hearing impaired.” Per the definition in WCAG 2.0, to meet this success criterion, whether called captions or subtitles, they would have to provide “synchronized visual and/or text alternative for both speech and non-speech audio information needed to understand the media content” where non-speech information includes “sound effects, music, laughter, speaker identification and location”.

Success Criterion 1.2.3: Audio Description or Media Alternative (Prerecorded) (Level A)

From Success Criterion 1.2.3 :

An alternative for time-based media or audio description of the prerecorded video content is provided for synchronized media , except when the media is a media alternative for text and is clearly labeled as such.

Intent from Understanding Success Criterion 1.2.3 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to provide people who are blind or visually impaired access to the visual information in a synchronized media presentation. This Success Criterion describes two approaches, either of which can be used.

One approach is to provide audio description of the video content. The audio description augments the audio portion of the presentation with the information needed when the video portion is not available. During existing pauses in dialogue, audio description provides information about actions, characters, scene changes, and on-screen text that are important and are not described or spoken in the main sound track.

The second approach involves providing all of the information in the synchronized media (both visual and auditory) in text form. An alternative for time-based media provides a running description of all that is going on in the synchronized media content. The alternative for time-based media reads something like a screenplay or book. Unlike audio description, the description of the video portion is not constrained to just the pauses in the existing dialogue. Full descriptions are provided of all visual information, including visual context, actions and expressions of actors, and any other visual material. In addition, non-speech sounds (laughter, off-screen voices, etc.) are described, and transcripts of all dialogue are included. The sequence of description and dialogue transcripts are the same as the sequence in the synchronized media itself. As a result, the alternative for time-based media can provide a much more complete representation of the synchronized media content than audio description alone.

If there is any interaction as part of the synchronized media presentation (e.g., "press now to answer the question") then the alternative for time-based media would provide hyperlinks or whatever is needed to provide the same functionality.

Note 1: For 1.2.3, 1.2.5, and 1.2.7, if all of the information in the video track is already provided in the audio track, no audio description is necessary.

Note 2: 1.2.3, 1.2.5, and 1.2.8 overlap somewhat with each other. This is to give the author some choice at the minimum conformance level, and to provide additional requirements at higher levels. At Level A in Success Criterion 1.2.3, authors do have the choice of providing either an audio description or a full text alternative. If they wish to conform at Level AA, under Success Criterion 1.2.5 authors must provide an audio description - a requirement already met if they chose that alternative for 1.2.3, otherwise an additional requirement. At Level AAA under Success Criterion 1.2.8 they must provide an extended text description. This is an additional requirement if both 1.2.3 and 1.2.5 were met by providing an audio description only. If 1.2.3 was met, however, by providing a text description, and the 1.2.5 requirement for an audio description was met, then 1.2.8 does not add new requirements.

See also Understanding Success Criterion 1.2.5 Audio Description (Prerecorded) , Understanding Success Criterion 1.2.7 Extended Audio Description (Prerecorded) and Understanding Success Criterion 1.2.8 Media Alternative (Prerecorded) .

Specific Benefits of Success Criterion 1.2.3
  • This Success Criterion may help some people who have difficulty watching video or other synchronized media content, including people who have difficulty perceiving or understanding moving images.

Additional guidance when applying Success Criterion 1.2.3 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note 1: The WCAG 2.0 definition of “audio description” says that “audio description” is “Also called ‘video description’ and ‘descriptive narration’”.

Note 2: Secondary or alternate audio tracks are commonly used for this purpose.

Note 3: See also the discussion on Closed Functionality in the Introduction.

Success Criterion 1.2.4: Captions (Live) (Level AA)

From Success Criterion 1.2.4 :

Captions are provided for all live audio content in synchronized media .

Intent from Understanding Success Criterion 1.2.4 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to enable people who are deaf or hard of hearing to watch real-time presentations. Captions provide the part of the content available via the audio track. Captions not only include dialogue, but also identify who is speaking and notate sound effects and other significant audio.

This success criterion was intended to apply to broadcast of synchronized media and is not intended to require that two-way multimedia calls between two or more individuals through web apps must be captioned regardless of the needs of users. Responsibility for providing captions would fall to the content providers (the callers) or the “host” caller, and not the application.

Specific Benefits of Success Criterion 1.2.4
  • People who are deaf or have a hearing loss can access the auditory information in the synchronized media content through captions.

Additional guidance when applying Success Criterion 1.2.4 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note: The WCAG 2.0 definition of “captions” notes that “In some countries, captions are called subtitles”. They are also sometimes referred to as “subtitles for the hearing impaired.” Per the definition in WCAG 2.0, to meet this success criterion, whether called captions or subtitles, they would have to provide “synchronized visual and/or text alternative for both speech and non-speech audio information needed to understand the media content” where non-speech information includes “sound effects, music, laughter, speaker identification and location”.

Success Criterion 1.2.5: Audio Description (Prerecorded) (Level AA)

From Success Criterion 1.2.5 :

Audio description is provided for all prerecorded video content in synchronized media .

Intent from Understanding Success Criterion 1.2.5 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to provide people who are blind or visually impaired access to the visual information in a synchronized media presentation. The audio description augments the audio portion of the presentation with the information needed when the video portion is not available. During existing pauses in dialogue, audio description provides information about actions, characters, scene changes, and on-screen text that are important and are not described or spoken in the main sound track.

Note 1: For 1.2.3, 1.2.5, and 1.2.7, if all of the information in the video track is already provided in the audio track, no audio description is necessary.

Note 2: 1.2.3, 1.2.5, and 1.2.8 overlap somewhat with each other. This is to give the author some choice at the minimum conformance level, and to provide additional requirements at higher levels. At Level A in Success Criterion 1.2.3, authors do have the choice of providing either an audio description or a full text alternative. If they wish to conform at Level AA, under Success Criterion 1.2.5 authors must provide an audio description - a requirement already met if they chose that alternative for 1.2.3, otherwise an additional requirement. At Level AAA under Success Criterion 1.2.8 they must provide an extended text description. This is an additional requirement if both 1.2.3 and 1.2.5 were met by providing an audio description only. If 1.2.3 was met, however, by providing a text description, and the 1.2.5 requirement for an audio description was met, then 1.2.8 does not add new requirements.

Specific Benefits of Success Criterion 1.2.5
  • People who are blind or have low vision as well as those with cognitive limitations who have difficulty interpreting visually what is happening benefit from audio description of visual information.

Additional guidance when applying Success Criterion 1.2.5 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note1: The WCAG 2.0 definition of “audio description” says that audio description is “Also called ‘video description’ and ‘descriptive narration’”.

Note2: Secondary or alternate audio tracks are commonly used for this purpose.

Guideline 1.3: Adaptable

From Guideline 1.3 :

Create content that can be presented in different ways (for example simpler layout) without losing information or structure.

Intent from Understanding Guideline 1.3 in Understanding WCAG 2.0 :

The purpose of this guideline is to ensure that all information is available in a form that can be perceived by all users, for example, spoken aloud, or presented in a simpler visual layout. If all of the information is available in a form that can be determined by software, then it can be presented to users in different ways (visually, audibly, tactilely etc.). If information is embedded in a particular presentation in such a way that the structure and information cannot be programmatically determined by the assistive technology, then it cannot be rendered in other formats as needed by the user.

The Success Criteria under this guideline all seek to ensure that different types of information that are often encoded in presentation are also available so that they can be presented in other modalities.

  • structure: the way the parts of a Web page are organized in relation to each other; and the way a collection of Web pages is organized

  • presentation: rendering of the content in a form that can be perceived by users

Additional guidance when applying Guideline 1.3 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 1.3.

Success Criterion 1.3.1: Info and Relationships (Level A)

From Success Criterion 1.3.1 :

Information, structure , and relationships conveyed through presentation can be programmatically determined or are available in text.

Intent from Understanding Success Criterion 1.3.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that information and relationships that are implied by visual or auditory formatting are preserved when the presentation format changes. For example, the presentation format changes when the content is read by a screen reader or when a user style sheet is substituted for the style sheet provided by the author.

Sighted users perceive structure and relationships through various visual cues — headings are often in a larger, bold font separated from paragraphs by blank lines; list items are preceded by a bullet and perhaps indented; paragraphs are separated by a blank line; items that share a common characteristic are organized into tabular rows and columns; form fields may be positioned as groups that share text labels; a different background color may be used to indicate that several items are related to each other; words that have special status are indicated by changing the font family and /or bolding, italicizing, or underlining them ; items that share a common characteristic are organized into a table where the relationship of cells sharing the same row or column and the relationship of each cell to its row and/or column header are necessary for understanding; and so on. Having these structures and these relationships programmatically determined or available in text ensures that information important for comprehension will be perceivable to all.

Auditory cues may be used as well. For example, a chime might indicate the beginning of a new section; a change in voice pitch or speech rate may be used to emphasize important information or to indicate quoted text; etc.

When such relationships are perceivable to one set of users, those relationships can be made to be perceivable to all. One method of determining whether or not information has been properly provided to all users is to access the information serially in different modalities.

If links to glossary items are implemented using anchor elements (or the proper link element for the technology in use) and identified using a different font face, a screen reader user will hear that the item is a link when the glossary term is encountered even though they may not receive information about the change in font face. An on-line catalog may indicate prices using a larger font colored red. A screen reader or person who cannot perceive red, still has the information about the price as long as it is preceded by the currency symbol.

Some technologies do not provide a means to programmatically determine some types of information and relationships. In that case then there should be a text description of the information and relationships. For instance, "all required fields are marked with an asterisk (*)". The text description should be near the information it is describing (when the page is linearized), such as in the parent element or in the adjacent element.

There may also be cases where it may be a judgment call as to whether the relationships should be programmatically determined or be presented in text. However, when technologies support programmatic relationships, it is strongly encouraged that information and relationships be programmatically determined rather than described in text.

Note: It is not required that color values be programmatically determined. The information conveyed by color cannot be adequately presented simply by exposing the value. Therefore, Success Criterion 1.4.1 addresses the specific case of color, rather than Success Criterion 1.3.1.

Specific Benefits of Success Criterion 1.3.1
  • This Success Criterion helps people with different disabilities by allowing user agents to adapt content according to the needs of individual users.

  • Users who are blind (using a screen reader) benefit when information conveyed through color is also available in text (including text alternatives for images that use color to convey information).

  • Users who are deaf-blind using braille (text) refreshable displays may be unable to access color-dependent information.

Additional guidance when applying Success Criterion 1.3.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note 1: In software, programmatic determinability is best achieved through the use of accessibility services provided by platform software to enable interoperability between software and assistive technologies.

Note 2: See also the discussion on Closed Functionality in the Introduction.

Success Criterion 1.3.2: Meaningful Sequence (Level A)

From Success Criterion 1.3.2 :

When the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined .

Intent from Understanding Success Criterion 1.3.2 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to enable a user agent to provide an alternative presentation of content while preserving the reading order needed to understand the meaning. It is important that it be possible to programmatically determine at least one sequence of the content that makes sense. Content that does not meet this Success Criterion may confuse or disorient users when assistive technology reads the content in the wrong order, or when alternate style sheets or other formatting changes are applied.

A sequence is meaningful if the order of content in the sequence cannot be changed without affecting its meaning. For example, if a page contains two independent articles, the relative order of the articles may not affect their meaning, as long as they are not interleaved. In such a situation, the articles themselves may have meaningful sequence, but the container that contains the articles may not have a meaningful sequence.

The semantics of some elements define whether or not their content is a meaningful sequence. For instance, in HTML, text is always a meaningful sequence. Tables and ordered lists are meaningful sequences, but unordered lists are not.

The order of content in a sequence is not always meaningful. For example, the relative order of the main section of a Web page and a navigation section does not affect their meaning. They could occur in either order in the programmatically determined reading sequence. As another example, a magazine article contains several callout sidebars. The order of the article and the sidebars does not affect their meaning. In these cases there are a number of different reading orders for a Web page that can satisfy the Success Criterion.

For clarity:

  1. Providing a particular linear order is only required where it affects meaning.

  2. There may be more than one order that is "correct" (according to the WCAG 2.0 definition).

  3. Only one correct order needs to be provided.

Specific Benefits of Success Criterion 1.3.2
  • This Success Criterion may help people who rely on assistive technologies that read content aloud. The meaning evident in the sequencing of the information in the default presentation will be the same when the content is presented in spoken form.

Additional guidance when applying Success Criterion 1.3.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note: See also the discussion on Closed Functionality in the Introduction.

Success Criterion 1.3.3: Sensory Characteristics (Level A)

From Success Criterion 1.3.3 :

Instructions provided for understanding and operating content do not rely solely on sensory characteristics of components such as shape, size, visual location, orientation, or sound.

Note: For requirements related to color, refer to Guideline 1.4 .

Intent from Understanding Success Criterion 1.3.3 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that all users can access instructions for using the content, even when they cannot perceive shape or size or use information about spatial location or orientation. Some content relies on knowledge of the shape or position of objects that are not available from the structure of the content (for example, "round button" or "button to the right"). Some users with disabilities are not able to perceive shape or position due to the nature of the assistive technologies they use. This Success Criterion requires that additional information be provided to clarify anything that is dependent on this kind of information.

Providing information using shape and/or location, however, is an effective method for many users including those with cognitive limitations. This provision should not discourage those types of cues as long as the information is also provided in other ways.

In some languages, it is commonly understood that "above" refers to the content previous to that point in the content and "below" refers to the content after that point. In such languages, if the content being referenced is in the appropriate place in the reading order and the references are unambiguous, statements such as "choose one of the links below" or "all of the above" would conform to this Success Criterion.

WCAG was designed to apply only to controls that were displayed on a web page. The intent was to avoid describing controls solely via references to visual or auditory cues. When applying this to instructions for operating physical hardware controls (e.g. a web kiosk with dedicated content), tactile cues on the hardware might be described (e.g. the arrow shaped key, the round key on the right side). This success criterion is not intended to prevent the use of tactile cues in instructions.

Specific Benefits of Success Criterion 1.3.3
  • People who are blind and people who have low vision may not be able to understand information if it is conveyed by shape and/or location. Providing additional information other than shape and/or location will allow them to understand the information conveyed by shape and/or alone.

Additional guidance when applying Success Criterion 1.3.3 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Guideline 1.4: Distinguishable

From Guideline 1.4 :

Make it easier for users to see and hear content including separating foreground from background.

Intent from Understanding Guideline 1.4 in Understanding WCAG 2.0 :

While some guidelines are focused on making information available in a form that can be presented in alternate formats, this guideline is concerned with making the default presentation as easy to perceive as possible to people with disabilities. The primary focus is on making it easier for users to separate foreground information from the background. For visual presentations this involves making sure that information presented on top of a background contrasts sufficiently with the background. For audio presentations this involves making sure that foreground sounds are sufficiently louder than the background sounds. Individuals with visual and hearing disabilities have much greater difficulty separating foreground and background information.

Additional guidance when applying Guideline 1.4 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 1.4.

Success Criterion 1.4.1: Use of Color (Level A)

From Success Criterion 1.4.1 :

Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.

Note: This success criterion addresses color perception specifically. Other forms of perception are covered in Guideline 1.3 including programmatic access to color and other visual presentation coding.

Intent from Understanding Success Criterion 1.4.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that all users can access information that is conveyed by color differences, that is, by the use of color where each color has a meaning assigned to it. If the information is conveyed through color differences in an image (or other non-text format), the color may not be seen by users with color deficiencies. In this case, providing the information conveyed with color through another visual means ensures users who cannot see color can still perceive the information.

Color is an important asset in design of Web content, enhancing its aesthetic appeal, its usability, and its accessibility. However, some users have difficulty perceiving color. People with partial sight often experience limited color vision, and many older users do not see color well. In addition, people using text-only, limited-color or monochrome displays and browsers will be unable to access information that is presented only in color.

Examples of information conveyed by color differences: “required fields are red", “error is shown in red", and “Mary's sales are in red, Tom's are in blue". Examples of indications of an action include: using color to indicate that a link will open in a new window or that a database entry has been updated successfully. An example of prompting a response would be: using highlighting on form fields to indicate that a required field had been left blank.

Note: This should not in any way discourage the use of color on a page, or even color coding if it is redundant with other visual indication.

Specific Benefits of Success Criterion 1.4.1
  • Users with partial sight often experience limited color vision.

  • Some older users may not be able to see color well.

  • Users who have color-blindness benefit when information conveyed by color is available in other visual ways.

  • People using text-only, limited color, or monochrome displays may be unable to access color-dependent information.

  • Users who have problems distinguishing between colors can look or listen for text cues.

  • People using Braille displays or other tactile interfaces can detect text cues by touch.

Additional guidance when applying Success Criterion 1.4.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Success Criterion 1.4.2: Audio Control (Level A)

From Success Criterion 1.4.2 :

If any audio on a Web page plays automatically for more than 3 seconds, either a mechanism is available to pause or stop the audio, or a mechanism is available to control audio volume independently from the overall system volume level.

Note: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether or not it is used to meet other success criteria) must meet this success criterion. See Conformance Requirement 5: Non-Interference .

Intent from Understanding Success Criterion 1.4.2 in Understanding WCAG 2.0 :

Individuals who use screen reading software can find it hard to hear the speech output if there is other audio playing at the same time. This difficulty is exacerbated when the screen reader's speech output is software based (as most are today) and is controlled via the same volume control as the sound. Therefore, it is important that the user be able to turn off the background sound. Note: Having control of the volume includes being able to reduce its volume to zero.

Note: Playing audio automatically when landing on a page may affect a screen reader user's ability to find the mechanism to stop it because they navigate by listening and automatically started sounds might interfere with that navigation. Therefore, we discourage the practice of automatically starting sounds (especially if they last more than 3 seconds), and encourage that the sound be started by an action initiated by the user after they reach the page, rather than requiring that the sound be stopped by an action of the user after they land on the page.

See also Understanding Success Criterion 1.4.7 Low or No Background Audio .

Specific Benefits of Success Criterion 1.4.2
  • Individuals who use screen reading technologies can hear the screen reader without other sounds playing. This is especially important for those who are hard of hearing and for those whose screen readers use the system volume (so they cannot turn sound down and screen reader up).

  • This Success Criterion also benefits people who have difficulty focusing on visual content (including text) when audio is playing.

Additional guidance when applying Success Criterion 1.4.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above) replacing “on a Web page” with “in a non-web document or software ” and software”, “any content” with “any part of a non-web document or software ”. software”, “whole page” with “whole document or software”, and “on the Web page” with “in the document or software”.

With these substitutions, it would read:

1.4.2 Audio Control: If any audio in a non-web document or software plays automatically for more than 3 seconds, either a mechanism is available to pause or stop the audio, or a mechanism is available to control audio volume independently from the overall system volume level. (Level A)

Note: Since any part of a non-web document or software that does not meet this success criterion can interfere with a user's ability to use the whole page, document or software , all content on in the Web page document or software (whether or not it is used to meet other success criteria) must meet this success criterion. See Conformance Requirement 5: Non-Interference.

Success Criterion 1.4.3: Contrast (Minimum) (Level AA)

From Success Criterion 1.4.3 :

The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for the following:

  • Large Text: Large-scale text and images of large-scale text have a contrast ratio of at least 3:1;

  • Incidental: Text or images of text that are part of an inactive user interface component , that are pure decoration , that are not visible to anyone, or that are part of a picture that contains significant other visual content, have no contrast requirement.

  • Logotypes: Text that is part of a logo or brand name has no minimum contrast requirement.

Intent from Understanding Success Criterion 1.4.3 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to provide enough contrast between text and its background so that it can be read by people with moderately low vision (who do not use contrast-enhancing assistive technology). For people without color deficiencies, hue and saturation have minimal or no effect on legibility as assessed by reading performance (Knoblauch et al., 1991). Color deficiencies can affect luminance contrast somewhat. Therefore, in the recommendation, the contrast is calculated in such a way that color is not a key factor so that people who have a color vision deficit will also have adequate contrast between the text and the background.

Text that is decorative and conveys no information is excluded. For example, if random words are used to create a background and the words could be rearranged or substituted without changing meaning, then it would be decorative and would not need to meet this criterion.

Text that is larger and has wider character strokes is easier to read at lower contrast. The contrast requirement for larger text is therefore lower. This allows authors to use a wider range of color choices for large text, which is helpful for design of pages, particularly titles. 18 point text or 14 point bold text is judged to be large enough to require a lower contrast ratio. (See The American Printing House for the Blind Guidelines for Large Printing and The Library of Congress Guidelines for Large Print under Resources ). "18 point" and "bold" can both have different meanings in different fonts but, except for very thin or unusual fonts, they should be sufficient. Since there are so many different fonts, the general measures are used and a note regarding fancy or thin fonts is included.

Note: Because different image editing applications default to different pixel densities ( e.g. 72 PPI or 96 PPI), specifying point sizes for fonts from within an image editing application can be unreliable when it comes to presenting text at a specific size. When creating images of large-scale text, authors should ensure that the text in the resulting image is roughly equivalent to 1.2 and 1.5 em or to 120% or 150% of the default size for body text. For example, for a 72 PPI image, an author would need to use approximately 19 pt and 24 pt font sizes in order to successfully present images of large-scale text to a user.

The previously-mentioned contrast requirements for text also apply to images of text (text that has been rendered into pixels and then stored in an image format) as stated in Success Criterion 1.4.3.

This requirement applies to situations in which images of text were intended to be understood as text. Incidental text, such as in photographs that happen to include a street sign, are not included. Nor is text that for some reason is designed to be invisible to all viewers. Stylized text, such as in corporate logos, should be treated in terms of its function on the page, which may or may not warrant including the content in the text alternative. Corporate visual guidelines beyond logo and logotype are not included in the exception.

In this provision there is an exception that reads "that are part of a picture that contains significant other visual content,". This exception is intended to separate pictures that have text in them from images of text that are done to replace text in order to get a particular look.

Note 1: Some people with cognitive disabilities require color combinations or hues that have low contrast, and therefore we allow and encourage authors to provide mechanisms to adjust the foreground and background colors of the content. Some of the combinations that could be chosen may have contrast levels that will be lower than those found in the Success Criteria. This is not a violation of this Success Criteria provided there is a mechanism that will return to the default values set out in the Success Criteria.

Note 2: Images of text do not scale as well as text because they tend to pixelate. It is also harder to change foreground and background contrast and color combinations for images of text, which is necessary for some users. Therefore, we suggest using text wherever possible, and when not, consider supplying an image of higher resolution.

Although this Success Criterion only applies to text, similar issues occur for data presented in charts or graphs. Good color contrast should also be provided for data presented in these forms.

See also Understanding Success Criterion 1.4.6 Contrast (Enhanced) .

Rationale for the Ratios Chosen

A contrast ratio of 3:1 is the minimum level recommended by [ISO-9241-3] and [ANSI-HFES-100-1988] for standard text and vision. The 4.5:1 ratio is used in this provision to account for the loss in contrast that results from moderately low visual acuity, congenital or acquired color deficiencies, or the loss of contrast sensitivity that typically accompanies aging.

The rationale is based on a) adoption of the 3:1 contrast ratio for minimum acceptable contrast for normal observers, in the ANSI standard, and b) the empirical finding that in the population, visual acuity of 20/40 is associated with a contrast sensitivity loss of roughly 1.5 [ARDITI-FAYE] . A user with 20/40 would thus require a contrast ratio of 3 * 1.5 = 4.5 to 1. Following analogous empirical findings and the same logic, the user with 20/80 visual acuity would require contrast of about 7:1.

Hues are perceived differently by users with color vision deficiencies (both congenital and acquired) resulting in different colors and relative luminance contrasts than for normally sighted users. Because of this, effective contrast and readability are different for this population. However, color deficiencies are so diverse that prescribing effective general use color pairs (for contrast) based on quantitative data is not feasible. Requiring good luminance contrast accommodates this by requiring contrast that is independent of color perception. Fortunately, most of the luminance contribution is from the mid and long wave receptors which largely overlap in their spectral responses. The result is that effective luminance contrast can generally be computed without regard to specific color deficiency, except for the use of predominantly long wavelength colors against darker colors (generally appearing black) for those who have protanopia. (We provide an advisory technique on avoiding red on black for that reason). For more information see [ARDITI-KNOBLAUCH] [ARDITI-KNOBLAUCH-1996] [ARDITI] .

The contrast ratio of 4.5:1 was chosen for level AA because it compensated for the loss in contrast sensitivity usually experienced by users with vision loss equivalent to approximately 20/40 vision. (20/40 calculates to approximately 4.5:1.) 20/40 is commonly reported as typical visual acuity of elders at roughly age 80. [GITTINGS-FOZARD]

The contrast ratio of 7:1 was chosen for level AAA because it compensated for the loss in contrast sensitivity usually experienced by users with vision loss equivalent to approximately 20/80 vision. People with more than this degree of vision loss usually use assistive technologies to access their content (and the assistive technologies usually have contrast enhancing, as well as magnification capability built into them). The 7:1 level therefore generally provides compensation for the loss in contrast sensitivity experienced by users with low vision who do not use assistive technology and provides contrast enhancement for color deficiency as well.

Note: Calculations in [ISO-9241-3] and [ANSI-HFES-100-1988] are for body text. A relaxed contrast ratio is provided for text that is much larger.

Notes on formula

Conversion from nonlinear to linear RGB values is based on IEC/4WD 61966-2-1 [IEC-4WD] and on "A Standard Default Color Space for the Internet - sRGB" [sRGB] .

The formula (L1/L2) for contrast is based on [ISO-9241-3] and [ANSI-HFES-100-1988] standards.

The ANSI/HFS 100-1988 standard calls for the contribution from ambient light to be included in the calculation of L1 and L2. The .05 value used is based on Typical Viewing Flare from [IEC-4WD] and the [sRGB] paper by M. Stokes et al.

This Success Criterion and its definitions use the terms "contrast ratio" and "relative luminance" rather than "luminance" to reflect the fact that Web content does not emit light itself. The contrast ratio gives a measure of the relative luminance that would result when displayed. (Because it is a ratio, it is dimensionless.)

Note 1: Refer to related resources for a list of tools that utilize the contrast ratio to analyze the contrast of Web content.

Note 2: See also Understanding Success Criterion 2.4.7 Focus Visible for techniques for indicating keyboard focus.

Note 3: It is sometimes helpful for authors to not specify colors for certain sections of a page in order to help users who need to view content with specific color combinations to view the content in their preferred color scheme. Refer to Understanding Success Criterion 1.4.5 Images of Text for more information.

Specific Benefits of Success Criterion 1.4.3
  • People with low vision often have difficulty reading text that does not contrast with its background. This can be exacerbated if the person has a color vision deficiency that lowers the contrast even further. Providing a minimum luminance contrast ratio between the text and its background can make the text more readable even if the person does not see the full range of colors. It also works for the rare individuals who see no color.

Additional guidance when applying Success Criterion 1.4.3 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Success Criterion 1.4.4: Resize text (Level AA)

From Success Criterion 1.4.4 :

Except for captions and images of text , text can be resized without assistive technology up to 200 percent without loss of content or functionality.

Intent from Understanding Success Criterion 1.4.4 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that visually rendered text, including text-based controls (text characters that have been displayed so that they can be seen [vs. text characters that are still in data form such as ASCII]) can be scaled successfully so that it can be read directly by people with mild visual disabilities, without requiring the use of assistive technology such as a screen magnifier. Users may benefit from scaling all content on the Web page, but text is most critical.

The scaling of content is primarily a user agent responsibility. User agents that satisfy UAAG 1.0 Checkpoint 4.1 allow users to configure text scale. The author's responsibility is to create Web content that does not prevent the user agent from scaling the content effectively. Authors may satisfy this Success Criterion by verifying that content does not interfere with user agent support for resizing text, including text-based controls, or by providing direct support for resizing text or changing the layout. An example of direct support might be via server-side script that can be used to assign different style sheets.

The author cannot rely on the user agent to satisfy this Success Criterion for HTML content if users do not have access to a user agent with zoom support. For example, if they work in an environment that requires them to use IE 6 or Firefox.

If the author is using a technology whose user agents do not provide zoom support, the author is responsible to provide this type of functionality directly or to provide content that works with the type of functionality provided by the user agent. If the user agent doesn't provide zoom functionality but does let the the user change the text size, the author is responsible for ensuring that the content remains usable when the text is resized.

Some user interface components that function as a label and require activation by the user to access content are not wide enough to accommodate the label's content. For example, in Web mail applications the subject column may not wide enough to accommodate every possible subject header, but activating the subject header takes the user to the full message with the full subject header. In Web-based spreadsheets, cell content that is too long to be displayed in a column can be truncated, and the full content of the cell is available to the user when the cell receives focus. The content of a user interface component may also become too wide in user interfaces where the user can resize the column width. In this type of user interface component, line wrapping is not required; truncation is acceptable if the component's full content is available on focus or after user activation and an indication that this information can be accessed, is provided to the user in some way besides the fact that it is truncated.

Content satisfies the Success Criterion if it can be scaled up to 200%, that is, up to twice the width and height. Authors may support scaling beyond that limit, however, as scaling becomes more extreme, adaptive layouts may introduce usability problems. For example, words may be too wide to fit into the horizontal space available to them, causing them to be truncated; layout constraints may cause text to overlap with other content when it is scaled larger; or only one word of a sentence may fit on each line, causing the sentence to be displayed as a vertical column of text that is difficult to read.

The working group feels that 200% is a reasonable accommodation that can support a wide range of designs and layouts, and complements older screen magnifiers that provide a minimum magnification of 200%. Above 200%, zoom (which resizes text, images, and layout regions and creates a larger canvas that may require both horizontal and vertical scrolling) may be more effective than text resizing. Assistive technology dedicated to zoom support would usually be used in such a situation and may provide better accessibility than attempts by the author to support the user directly.

Note: Images of text do not scale as well as text because they tend to pixelate, and therefore we suggest using text wherever possible. It is also harder to change foreground and background contrast and color combinations for images of text, which are necessary for some users.

See also Understanding Success Criterion 1.4.8 Visual Presentation .

Specific Benefits of Success Criterion 1.4.4
  • This Success Criterion helps people with low vision by letting them increase text size in content so that they can read it.

Additional guidance when applying Success Criterion 1.4.4 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note 1:  Content for which there are software players, viewers or editors with a 200 percent zoom feature would automatically meet this success criterion when used with such players, unless the content will not work with zoom.

Note 2: The INTENT refers to the ability to allow users to enlarge the text on screen at least up to 200 % without needing to use assistive technologies. This means that the application provides some means for enlarging the text 200% (zoom or otherwise) without loss of content or functionality or that the application works with the platform features that meet this requirement.

Note 3: See also the discussion on Closed Functionality in the Introduction.

Success Criterion 1.4.5: Images of Text (Level AA)

From Success Criterion 1.4.5 :

If the technologies being used can achieve the visual presentation, text is used to convey information rather than images of text except for the following:

  • Customizable: The image of text can be visually customized to the user's requirements;

  • Essential: A particular presentation of text is essential to the information being conveyed.

Note: Logotypes (text that is part of a logo or brand name) are considered essential.

Intent from Understanding Success Criterion 1.4.5 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to encourage authors, who are using technologies which are capable of achieving their desired default visual presentation, to enable people who require a particular visual presentation of text to be able to adjust the text presentation as needed. This includes people who require the text in a particular font size, foreground and background color, font family, line spacing or alignment.

If an author can use text to achieve the same visual effect, he or she should present the information as text rather than using an image. If for any reason, the author cannot format the text to get the same effect, the effect won't be reliably presented on the commonly available user agents, or using a technology to meet this criterion would interfere with meeting other criterion such as 1.4.4, then an image of text can be used. This includes instances where a particular presentation of text is essential to the information being conveyed, such as type samples, logotypes, branding, etc. Images of text may also be used in order to use a particular font that is either not widely deployed or which the author doesn't have the right to redistribute, or to ensure that the text would be anti-aliased on all user agents.

Images of text can also be used where it is possible for users to customize the image of text to match their requirements.

The definition of image of text contains the note: "Note: This does not include text that is part of a picture that contains significant other visual content." Examples of such pictures include graphs, screenshots, and diagrams which visually convey important information through more than just text.

Techniques for satisfying this Success Criterion are the same as those for Success Criterion 1.4.9, except that they only need to apply if the visual presentation can be achieved with the technologies that the author is using. For Success Criterion 1.4.9, the sufficient techniques would be applied only when the user can customize the output.

See also Understanding Success Criterion 1.4.9 Images of Text (No Exception) .

Specific Benefits of Success Criterion 1.4.5
  • People with low vision (who may have trouble reading the text with the authored font family, size and/or color).

  • People with visual tracking problems (who may have trouble reading the text with the authored line spacing and/or alignment).

  • People with cognitive disabilities that affect reading.

Additional guidance when applying Success Criterion 1.4.5 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note: See also the discussion on Closed Functionality in the Introduction.

Principle 2: Operable

User interface components and navigation must be operable.

Guideline 2.1: Keyboard Accessible

From Guideline 2.1 :

Make all functionality available from a keyboard.

Intent from Understanding Guideline 2.1 in Understanding WCAG 2.0 :

If all functionality can be achieved using the keyboard, it can be accomplished by keyboard users, by speech input (which creates keyboard input), by mouse (using on-screen keyboards), and by a wide variety of assistive technologies that create simulated keystrokes as their output. No other input form has this flexibility or is universally supported and operable by people with different disabilities, as long as the keyboard input is not time-dependent.

Note that providing universal keyboard input does not mean that other types of input should not be supported. Optimized speech input, optimized mouse/pointer input, etc., are also good. The key is to provide keyboard input and control as well.

Some devices do not have native keyboards—for example, a PDA or cell phone. If these devices have a Web browsing capability, however, they will have some means of generating text or "keystrokes". This guideline uses the term " keyboard interface " to acknowledge that Web content should be controlled from keystrokes that may come from a keyboard, keyboard emulator, or other hardware or software that generates keyboard or text input.

Additional guidance when applying Guideline 2.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 2.1.

Success Criterion 2.1.1: Keyboard (Level A)

From Success Criterion 2.1.1 :

All functionality of the content is operable through a keyboard interface without requiring specific timings for individual keystrokes, except where the underlying function requires input that depends on the path of the user's movement and not just the endpoints.

Note 1: This exception relates to the underlying function, not the input technique. For example, if using handwriting to enter text, the input technique (handwriting) requires path-dependent input but the underlying function (text input) does not.

Note 2: This does not forbid and should not discourage providing mouse input or other input methods in addition to keyboard operation.

Intent from Understanding Success Criterion 2.1.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that, wherever possible, content can be operated through a keyboard or keyboard interface (so an alternate keyboard can be used). When content can be operated through a keyboard or alternate keyboard, it is operable by people with no vision (who cannot use devices such as mice that require eye-hand coordination) as well as by people who must use alternate keyboards or input devices that act as keyboard emulators. Keyboard emulators include speech input software, sip-and-puff software, on-screen keyboards, scanning software and a variety of assistive technologies and alternate keyboards. Individuals with low vision also may have trouble tracking a pointer and find the use of software much easier (or only possible) if they can control it from the keyboard.

Examples of "specific timings for individual keystrokes" include situations where a user would be required to repeat or execute multiple keystrokes within a short period of time or where a key must be held down for an extended period before the keystroke is registered.

The phrase "except where the underlying function requires input that depends on the path of the user's movement and not just the endpoints" is included to separate those things that cannot reasonably be controlled from a keyboard.

Most actions carried out by a pointing device can also be done from the keyboard (for example, clicking, selecting, moving, sizing). However, there is a small class of input that is done with a pointing device that cannot be done from the keyboard in any known fashion without requiring an inordinate number of keystrokes. Free hand drawing, watercolor painting, and flying a helicopter through an obstacle course are all examples of functions that require path dependent input. Drawing straight lines, regular geometric shapes, re-sizing windows and dragging objects to a location (when the path to that location is not relevant) do not require path dependent input.

The use of MouseKeys would not satisfy this Success Criterion because it is not a keyboard equivalent to the application; it is a mouse equivalent (i.e., it looks like a mouse to the application).

It is assumed that the design of user input features takes into account that operating system keyboard accessibility features may be in use. For example, modifier key locking may be turned on. Content continues to function in such an environment, not sending events that would collide with the modifier key lock to produce unexpected results.

Specific Benefits of Success Criterion 2.1.1
  • People who are blind (who cannot use devices such as mice that require eye-hand coordination)

  • People with low vision (who may have trouble finding or tracking a pointer indicator on screen)

  • Some people with hand tremors find using a mouse very difficult and therefore usually use a keyboard

Additional guidance when applying Success Criterion 2.1.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note 1: This does not imply that software must directly support a keyboard or “keyboard interface”. Nor does it imply that software must provide a soft keyboard. Underlying platform software may provide device independent input services to applications that enable operation via a keyboard. Software that supports operation via such platform device independent services would be operable by a keyboard and would comply.

Note 2: See also the discussion on Closed Functionality in the Introduction.

Success Criterion 2.1.2: No Keyboard Trap (Level A)

From Success Criterion 2.1.2 :

If keyboard focus can be moved to a component of the page using a keyboard interface , then focus can be moved away from that component using only a keyboard interface, and, if it requires more than unmodified arrow or tab keys or other standard exit methods, the user is advised of the method for moving focus away.

Note: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference .

Intent from Understanding Success Criterion 2.1.2 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that that content does not "trap" keyboard focus within subsections of content on a Web page. This is a common problem when multiple formats are combined within a page and rendered using plug-ins or embedded applications.

There may be times when the functionality of the Web page restricts the focus to a subsection of the content, as long as the user knows how to leave that state and "untrap" the focus.

Specific Benefits of Success Criterion 2.1.2
  • People who rely on a keyboard or keyboard interface to use the Web including people who are blind and people with physical disabilities.

Additional guidance when applying Success Criterion 2.1.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note: Standard exit methods may vary by platform. For example, on many desktop platforms, the Escape key is a standard method for exiting.

Guideline 2.2: Enough Time

From Guideline 2.2 :

Provide users enough time to read and use content.

Intent from Understanding Guideline 2.2 in Understanding WCAG 2.0 :

Many users who have disabilities need more time to complete tasks than the majority of users: they may take longer to physically respond, they may take longer to read things, they may have low vision and take longer to find things or to read them, or they may be accessing content through an assistive technology that requires more time. This guideline focuses on ensuring that users are able to complete the tasks required by the content with their own individual response times. The primary approaches deal with eliminating time constraints or providing users enough additional time to allow them to complete their tasks. Exceptions are provided for those cases where this is not possible.

Additional guidance when applying Guideline 2.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 2.2.

Success Criterion 2.2.1: Timing Adjustable (Level A)

From Success Criterion 2.2.1 :

For each time limit that is set by the content, at least one of the following is true:

  • Turn off: The user is allowed to turn off the time limit before encountering it; or

  • Adjust: The user is allowed to adjust the time limit before encountering it over a wide range that is at least ten times the length of the default setting; or

  • Extend: The user is warned before time expires and given at least 20 seconds to extend the time limit with a simple action (for example, "press the space bar"), and the user is allowed to extend the time limit at least ten times; or

  • Real-time Exception: The time limit is a required part of a real-time event (for example, an auction), and no alternative to the time limit is possible; or

  • Essential Exception: The time limit is essential and extending it would invalidate the activity; or

  • 20 Hour Exception: The time limit is longer than 20 hours.

Note: This success criterion helps ensure that users can complete tasks without unexpected changes in content or context that are a result of a time limit. This success criterion should be considered in conjunction with Success Criterion 3.2.1 , which puts limits on changes of content or context as a result of user action.

Intent from Understanding Success Criterion 2.2.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that users with disabilities are given adequate time to interact with Web content whenever possible. People with disabilities such as blindness, low vision, dexterity impairments, and cognitive limitations may require more time to read content or to perform functions such as filling out on-line forms. If Web functions are time-dependent, it will be difficult for some users to perform the required action before a time limit occurs. This may render the service inaccessible to them. Designing functions that are not time-dependent will help people with disabilities succeed at completing these functions. Providing options to disable time limits, customize the length of time limits, or request more time before a time limit occurs helps those users who require more time than expected to successfully complete tasks. These options are listed in the order that will be most helpful for the user. Disabling time limits is better than customizing the length of time limits, which is better than requesting more time before a time limit occurs.

Any process that happens without user initiation after a set time or on a periodic basis is a time limit. This includes partial or full updates of content (for example, page refresh), changes to content, or the expiration of a window of opportunity for a user to react to a request for input.

It also includes content that is advancing or updating at a rate beyond the user's ability to read and/or understand it. In other words, animated, moving or scrolling content introduces a time limit on a users ability to read content.

In some cases, however, it is not possible to change the time limit (for example, for an auction or other real-time event) and exceptions are therefore provided for those cases.

Notes regarding server time limits

  • Timed server redirects can be found below under Common Failures.

  • Non-timed server redirects (e.g., 3xx response codes) are not applicable because there is no time limit: they work instantly.

  • This Success Criterion applies only to time limits that are set by the content itself. For example, if a time limit is included in order to address security concerns, it would be considered to have been set by the content because it is designed to be part of the presentation and interaction experience for that content. Time limits set externally to content, such as by the user agent or by factors intrinsic to the Internet are not under the author's control and not subject to WCAG conformance requirements. Time limits set by Web servers should be under the author's/organization's control and are covered. (Success Criteria 2.2.3 , 2.2.4 and 2.2.5 may also apply.)

  • Ten times the default was chosen based on clinical experience and other guidelines. For example, if 15 seconds is allowed for a user to respond and hit a switch, 150 seconds would be sufficient to allow almost all users to hit a switch even if they had trouble.

  • 20 seconds was also based on clinical experience and other guidelines. 20 seconds to hit 'any switch' is sufficient for almost all users including those with spasticity. Some would fail, but some would fail all lengths of time. A reasonable period for requesting more time is required since an arbitrarily long time can provide security risks to all users, including those with disabilities, for some applications. For example, with kiosks or terminals that are used for financial transactions, it is quite common for people to walk away without signing off. This leaves them vulnerable to those walking up behind them. Providing a long period of inactivity before asking, and then providing a long period for the person to indicate that they are present can leave terminals open for abuse. If there is no activity the system should ask if the user is there. It should then ask for an indication that a person is there ('hit any key') and then wait long enough for almost anyone to respond. For "hit any key," 20 seconds would meet this. If the person indicates that they are still present, the device should return the user to the exact condition that existed before it asked the question.

  • 20 hours was chosen as an upper limit because it is longer than a full waking day.

In cases where timing is not an intrinsic requirement but giving users control over timed events would invalidate the outcome, a third party can control the time limits for the user (for example, granting double time on a test).

See also Understanding Success Criterion 2.2.3 No Timing .

Specific Benefits of Success Criterion 2.2.1
  • People with physical disabilities often need more time to react, to type and to complete activities. People with low vision need more time to locate things on screen and to read. People who are blind and using screen readers may need more time to understand screen layouts, to find information and to operate controls. People who have cognitive or language limitations need more time to read and to understand. People who are deaf and communicate in sign language may need more time to read information printed in text (which may be a second language for some).

  • In circumstances where a sign-language interpreter may be relating audio content to a user who is deaf, control over time limits is also important.

  • People with reading disabilities, cognitive limitations, and learning disabilities who may need more time to read or comprehend information can have additional time to read the information by pausing the content.

Additional guidance when applying Success Criterion 2.2.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Success Criterion 2.2.2: Pause, Stop, Hide (Level A)

From Success Criterion 2.2.2 :

For moving, blinking , scrolling, or auto-updating information, all of the following are true:

  • Moving, blinking, scrolling: For any moving, blinking or scrolling information that (1) starts automatically, (2) lasts more than five seconds, and (3) is presented in parallel with other content, there is a mechanism for the user to pause , stop, or hide it unless the movement, blinking, or scrolling is part of an activity where it is essential ; and

  • Auto-updating: For any auto-updating information that (1) starts automatically and (2) is presented in parallel with other content, there is a mechanism for the user to pause, stop, or hide it or to control the frequency of the update unless the auto-updating is part of an activity where it is essential.

Note 1: For requirements related to flickering or flashing content, refer to Guideline 2.3 .

Note 2: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference .

Note 3: Content that is updated periodically by software or that is streamed to the user agent is not required to preserve or present information that is generated or received between the initiation of the pause and resuming presentation, as this may not be technically possible, and in many situations could be misleading to do so.

Note 4: An animation that occurs as part of a preload phase or similar situation can be considered essential if interaction cannot occur during that phase for all users and if not indicating progress could confuse users or cause them to think that content was frozen or broken.

Intent from Understanding Success Criterion 2.2.2 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to avoid distracting users during their interaction with a Web page.

"Moving, blinking and scrolling" refers to content in which the visible content conveys a sense of motion. Common examples include motion pictures, synchronized media presentations, animations, real-time games, and scrolling stock tickers. "Auto-updating" refers to content that updates or disappears based on a preset time interval. Common time-based content includes audio, automatically updated weather information, news, stock price updates, and auto-advancing presentations and messages. The requirements for moving, blinking and scrolling content and for auto-updating content are the same except that:

  • authors have the option of providing the user with a means to control the frequency of updates when content is auto-updating and

  • there is no five second exception for auto-updating since it makes little sense to auto-update for just three seconds and then stop

Content that moves or auto-updates can be a barrier to anyone who has trouble reading stationary text quickly as well as anyone who has trouble tracking moving objects. It can also cause problems for screen readers.

Moving content can also be a severe distraction for some people. Certain groups, particularly those with attention deficit disorders, find blinking content distracting, making it difficult for them to concentrate on other parts of the Web page. Five seconds was chosen because it is long enough to get a user's attention, but not so long that a user cannot wait out the distraction if necessary to use the page.

Content that is paused can either resume in real-time or continue playing from the point in the presentation where the user left off.

  1. Pausing and resuming where the user left off is best for users who want to pause to read content and works best when the content is not associated with a real-time event or status.

    Note: See Understanding Success Criterion 2.2.1 Timing Adjustable for additional requirements related to time-limits for reading.

  2. Pausing and jumping to current display (when pause is released) is better for information that is real-time or "status" in nature. For example, weather radar, a stock ticker, a traffic camera, or an auction timer, would present misleading information if a pause caused it to display old information when the content was restarted.

    Note: Hiding content would have the same result as pausing and jumping to current display (when pause is released).

For a mechanism to be considered "a mechanism for the user to pause," it must provide the user with a means to pause that does not tie up the user or the focus so that the page cannot be used. The word "pause" here is meant in the sense of a "pause button" although other mechanisms than a button can be used. Having an animation stop only so long as a user has focus on it (where it restarts as soon as the user moves the focus away) would not be considered a "mechanism for the user to pause" because it makes the page unusable in the process and would not meet this SC.

It is important to note that the terms "blinking" and "flashing" can sometimes refer to the same content.

  • "Blinking" refers to content that causes a distraction problem. Blinking can be allowed for a short time as long as it stops (or can be stopped)

  • "Flashing" refers to content that can trigger a seizure (if it is more than 3 per second and large and bright enough). This cannot be allowed even for a second or it could cause a seizure. And turning the flash off is also not an option since the seizure could occur faster than most users could turn it off.

  • Blinking usually does not occur at speeds of 3 per second or more, but it can. If blinking occurs faster than 3 per second, it would also be considered a flash.

Specific Benefits of Success Criterion 2.2.2
  • Providing content that stops blinking after five seconds or providing a mechanism for users to stop blinking content allows people with certain disabilities to interact with the Web page.

  • One use of content that blinks is to draw the visitor's attention to that content. Although this is an effective technique for all users with vision, it can be a problem for some users if it persists. For certain groups, including people with low literacy, reading and intellectual disabilities, and people with attention deficit disorders, content that blinks may make it difficult or even impossible to interact with the rest of the Web page.

Additional guidance when applying Success Criterion 2.2.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note: While the success criteria uses the term “information”, the WCAG 2.0 INTENT section makes it clear that this is to be applied to all content. Any content, whether informative or decorative, that is updated automatically, blinks, or moves may create an accessibility barrier.

Guideline 2.3: Seizures

From Guideline 2.3 :

Do not design content in a way that is known to cause seizures.

Intent from Understanding Guideline 2.3 in Understanding WCAG 2.0 :

Some people with seizure disorders can have a seizure triggered by flashing visual content. Most people are unaware that they have this disorder until it strikes. In 1997, a cartoon on television in Japan sent over 700 children to the hospital, including about 500 who had seizures. Warnings do not work well because they are often missed, especially by children who may in fact not be able to read them.

The objective of this guideline is to ensure that content that is marked as conforming to WCAG 2.0 avoids the types of flash that are most likely to cause seizure when viewed even for a second or two.

Additional guidance when applying Guideline 2.3 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 2.3.

Success Criterion 2.3.1: Three Flashes or Below Threshold (Level A)

From Success Criterion 2.3.1 :

Web pages do not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds .

Note: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference .

Intent from Understanding Success Criterion 2.3.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to allow users to access the full content of a site without inducing seizures due to photosensitivity.

Individuals who have photosensitive seizure disorders can have a seizure triggered by content that flashes at certain frequencies for more than a few flashes. People are even more sensitive to red flashing than to other colors, so a special test is provided for saturated red flashing. These guidelines are based on guidelines for the broadcasting industry as adapted for computer screens, where content is viewed from a closer distance (using a larger angle of vision).

Flashing can be caused by the display, the computer rendering the image or by the content being rendered. The author has no control of the first two. They can be addressed by the design and speed of the display and computer. The intent of this criterion is to ensure that flicker that violates the flash thresholds is not caused by the content itself. For example, the content could contain a video clip or animated image of a series of strobe flashes, or close-ups of rapid-fire explosions.

This Success Criterion replaces a much more restrictive criterion in WCAG 1.0 that did not allow any flashing (even of a single pixel) within a broad frequency range (3 to 50 Hz). This Success Criterion is based on existing specifications in use in the UK and by others for television broadcast and has been adapted for computer display viewing. The 1024 x 768 screen is used as the reference screen resolution for the evaluation. The 341 x 256 pixel block represents a 10 degree viewport at a typical viewing distance. (The 10 degree field is taken from the original specifications and represents the central vision portion of the eye, where people are most susceptible to photo stimuli.)

The combined area of flashes occurring concurrently and contiguously means the total area that is actually flashing at the same time. It is calculated by adding up the contiguous area that is flashing simultaneously within any 10 degree angle of view.

Note: The terms "blinking" and "flashing" can sometimes refer to the same content.

  • "Blinking" refers to content that causes a distraction problem. Blinking can be allowed for a short time as long as it stops (or can be stopped)

  • "Flashing" refers to content that can trigger a seizure (if it is more than 3 per second and large and bright enough). This cannot be allowed even for a second or it could cause a seizure. And turning the flash off is also not an option since the seizure could occur faster than most users could turn it off.

  • Blinking usually does not occur at speeds of 3 per second or more, but it can. If blinking occurs faster than 3 per second, it would also be considered a flash.

Specific Benefits of Success Criterion 2.3.1
  • Individuals who have seizures when viewing flashing material will be able to view all of the material on a site without having a seizure and without having to miss the full experience of the content by being limited to text alternatives. This includes people with photosensitive epilepsy as well as other photosensitive seizure disorders.

Additional guidance when applying Success Criterion 2.3.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above), replacing “Web pages” with “non-web documents or software ” software” , “the whole page” with “the whole non-web document or software” and “the Web page” with “the non-web document or software”.

With these substitutions, it would read:

2.3.1 Three Flashes or Below Threshold: non-web documents or software do not contain anything that flashes more than three times in any one second period, or the flash is below the general flash and red flash thresholds. (Level A)

Note: Since any content that does not meet this success criterion can interfere with a user's ability to use the whole non-Web document or software , all content on the non-web document or software (whether it is used to meet other success criteria or not) must meet this success criterion. See Conformance Requirement 5: Non-Interference .

Principle 3: Understandable

Information and the operation of user interface must be understandable.

Guideline 3.1: Readable

From Guideline 3.1 :

Make text content readable and understandable.

Intent from Understanding Guideline 3.1 in Understanding WCAG 2.0 :

The intent of this guideline is to allow text content to be read by users and by assistive technology, and to ensure that information necessary for understanding it is available.

People with disabilities experience text in many different ways. For some the experience is visual; for some it is auditory; for some it is tactile; for still others it is both visual and auditory. Some users experience great difficulty in recognizing written words yet understand extremely complex and sophisticated documents when the text is read aloud, or when key processes and ideas are illustrated visually or interpreted as sign language. For some users, it is difficult to infer the meaning of a word or phrase from context, especially when the word or phrase is used in an unusual way or has been given a specialized meaning; for these users the ability to read and understand may depend on the availability of specific definitions or the expanded forms of acronyms or abbreviations. User agents, including speech-enabled as well as graphical applications, may be unable to present text correctly unless the language and direction of the text are identified; while these may be minor problems for most users, they can be enormous barriers for users with disabilities. In cases where meaning cannot be determined without pronunciation information (for example, certain Japanese Kanji characters), pronunciation information must be available as well

Additional guidance when applying Guideline 3.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 3.1.

Success Criterion 3.1.1: Language of Page (Level A)

From Success Criterion 3.1.1 :

The default human language of each Web page can be programmatically determined .

Intent from Understanding Success Criterion 3.1.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that content developers provide information in the Web page that user agents need to present text and other linguistic content correctly. Both assistive technologies and conventional user agents can render text more accurately when the language of the Web page is identified. Screen readers can load the correct pronunciation rules. Visual browsers can display characters and scripts correctly. Media players can show captions correctly. As a result, users with disabilities will be better able to understand the content.

The default human language of the Web page is the default text-processing language as discussed in Internationalization Best Practices: Specifying Language in XHTML & HTML Content . When a Web page uses several languages, the default text-processing language is the language which is used most. (If several languages are used equally, the first language used should be chosen as the default human language.)

Note: For multilingual sites targeting Conformance Level A, the Working Group strongly encourages developers to follow Success Criterion 3.1.2 as well even though that is a Level AA Success Criterion.

Specific Benefits of Success Criterion 3.1.1

This Success Criterion helps:

  • people who use screen readers or other technologies that convert text into synthetic speech;

  • people who find it difficult to read written material with fluency and accuracy, such as recognizing characters and alphabets or decoding words;

  • people with certain cognitive, language and learning disabilities who use text-to-speech software

  • people who rely on captions for synchronized media.

Additional guidance when applying Success Criterion 3.1.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above) replacing “each Web page”  with non-web documents or software . software.

With these substitutions, it would read:

3.1.1 Language of Page: The default human language of non-web documents or software can be programmatically determined. (Level A) 

Note 1: Where software platforms provide a “locale/language” setting, applications that use that setting and render their interface in that “locale/language” would comply with this success criterion. Applications that do not use the platform “locale/language setting” but instead use an accessibility supported method for exposing the human language of the software would also comply with this success criterion. Applications implemented in technologies where assistive technologies cannot determine the human language and that do not support the platform “locale/language” setting may not be able to meet this success criterion in that locale/language.

Note 2: See also the discussion on Closed Functionality in the Introduction.

Success Criterion 3.1.2: Language of Parts (Level AA)

From Success Criterion 3.1.2 :

The human language of each passage or phrase in the content can be programmatically determined except for proper names, technical terms, words of indeterminate language, and words or phrases that have become part of the vernacular of the immediately surrounding text.

Intent from Understanding Success Criterion 3.1.2 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that user agents can correctly present content written in multiple languages. This makes it possible for user agents and assistive technologies to present content according to the presentation and pronunciation rules for that language. This applies to graphical browsers as well as screen readers, braille displays, and other voice browsers.

Both assistive technologies and conventional user agents can render text more accurately if the language of each passage of text is identified. Screen readers can use the pronunciation rules of the language of the text. Visual browsers can display characters and scripts in appropriate ways. This is especially important when switching between languages that read from left to right and languages that read from right to left, or when text is rendered in a language that uses a different alphabet. Users with disabilities who know all the languages used in the Web page will be better able to understand the content when each passage is rendered appropriately.

When no other language has been specified for a phrase or passage of text, its human language is the default human language of the Web page (see Success Criterion 3.1.1). So the human language of all content in single language documents can be programmatically determined.

Individual words or phrases in one language can become part of another language. For example, "rendezvous" is a French word that has been adopted in English, appears in English dictionaries, and is properly pronounced by English screen readers. Hence a passage of English text may contain the word "rendezvous" without specifying that its human language is French and still satisfy this Success Criterion. Frequently, when the human language of text appears to be changing for a single word, that word has become part of the language of the surrounding text. Because this is so common in some languages, single words should be considered part of the language of the surrounding text unless it is clear that a change in language was intended. If there is doubt whether a change in language is intended, consider whether the word would be pronounced the same (except for accent or intonation) in the language of the immediately surrounding text.

Most professions require frequent use of technical terms which may originate from a foreign language. Such terms are usually not translated to all languages. The universal nature of technical terms also facilitate communication between professionals.

Some common examples of technical terms include: Homo sapiens, Alpha Centauri, hertz, and habeas corpus.

Identifying changes in language is important for a number of reasons:

  • It allows braille translation software to follow changes in language, e.g., substitute control codes for accented characters, and insert control codes necessary to prevent erroneous creation of Grade 2 braille contractions.

  • Speech synthesizers that support multiple languages will be able to speak the text in the appropriate accent with proper pronunciation. If changes are not marked, the synthesizer will try its best to speak the words in the default language it works in. Thus, the French word for car, "voiture" would be pronounced "voyture" by a speech synthesizer that uses English as its default language.

  • Marking changes in language can benefit future developments in technology, for example users who are unable to translate between languages themselves will be able to use machines to translate unfamiliar languages.

  • Marking changes in language can also assist user agents in providing definitions using a dictionary.

Specific Benefits of Success Criterion 3.1.2

This Success Criterion helps:

  • people who use screen readers or other technologies that convert text into synthetic speech;

  • people who find it difficult to read written material with fluency and accuracy, such as recognizing characters and alphabets, decoding words, and understanding words and phrases;

  • people with certain cognitive, language and learning disabilities who use text-to-speech software;

  • people who rely on captions to recognize language changes in the soundtrack of synchronized media content.

Additional guidance when applying Success Criterion 3.1.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above) replacing “content”  with “the non-web document or software ”. software”.

With these substitutions, it would read:

3.1.2 Language of Parts: The human language of each passage or phrase in the non-web document or software can be programmatically determined except for proper names, technical terms, words of indeterminate language, and words or phrases that have become part of the vernacular of the immediately surrounding text. (Level AA)

Note 1: There are some software and non-web document technologies where there is no assistive technology supported method for marking the language for the different passages or phrases in the non-web document or software, and it would not be possible to meet this success criterion with those technologies.

Note 2: See also the discussion on Closed Functionality in the Introduction.

Guideline 3.2: Predictable

From Guideline 3.2 :

Make Web pages appear and operate in predictable ways.

Intent from Understanding Guideline 3.2 in Understanding WCAG 2.0 :

The intent of this Guideline is to help users with disabilities by presenting content in a predictable order from Web page to Web page and by making the behavior of functional and interactive components predictable. It is difficult for some users to form an overview of the Web page: screen readers present content as a one-dimensional stream of synthetic speech that makes it difficult to understand spatial relationships. Users with cognitive limitations may become confused if components appear in different places on different pages.

For example, people who use screen magnifiers see only part of the screen at any point in time; a consistent layout makes it easier for them to find navigation bars and other components. Placing repeated components in the same relative order within a set of Web pages allows users with reading disabilities to focus on an area of the screen rather than spending additional time decoding the text of each link. Users with limited use of their hands can more easily determine how to complete their tasks using the fewest keystrokes.

Additional guidance when applying Guideline 3.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 3.2.

Success Criterion 3.2.1: On Focus (Level A)

From Success Criterion 3.2.1 :

When any component receives focus, it does not initiate a change of context .

Intent from Understanding Success Criterion 3.2.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that functionality is predictable as visitors navigate their way through a document. Any component that is able to trigger an event when it receives focus must not change the context. Examples of changing context when a component receives focus include, but are not limited to:

  • forms submitted automatically when a component receives focus;

  • new windows launched when a component receives focus;

  • focus is changed to another component when that component receives focus;

Focus may be moved to a control either via the keyboard ( e.g. tabbing to a control) or the mouse ( e.g. clicking on a text field). Moving the mouse over a control does not move the focus unless scripting implements this behavior. Note that for some types of controls, clicking on a control may also activate the control ( e.g. button), which may, in turn, initiate a change in context.

Note: What is meant by "component" here is also sometimes called "user interface element" or "user interface component''.

Specific Benefits of Success Criterion 3.2.1
  • This Success Criterion helps people with visual disabilities, cognitive limitations, and motor impairments by reducing the chance that a change of context will occur unexpectedly.

Additional guidance when applying Success Criterion 3.2.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Success Criterion 3.2.2: On Input (Level A)

From Success Criterion 3.2.2 :

Changing the setting of any user interface component does not automatically cause a change of context unless the user has been advised of the behavior before using the component.

Intent from Understanding Success Criterion 3.2.2 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that entering data or selecting a form control has predictable effects. Changing the setting of any user interface component is changing some state in the control that will persist when the user is no longer interacting with it. So checking a checkbox or entering text into a text field changes its setting, but activating a link or a button does not. Changes in context can confuse users who do not easily perceive the change or are easily distracted by changes. Changes of context are appropriate only when it is clear that such a change will happen in response to the user's action.

Note: This Success Criterion covers changes in context due to changing the setting of a control. Clicking on links or tabs in a tab control is activating the control, not changing the setting of that control.

Note: What is meant by "component" and "user interface component" here is also sometimes called "user interface element".

Specific Benefits of Success Criterion 3.2.2
  • This Success Criterion helps users with disabilities by making interactive content more predictable. Unexpected changes of context can be so disorienting for users with visual disabilities or cognitive limitations that they are unable to use the content.

  • Individuals who are unable to detect changes of context are less likely to become disoriented while navigating a site. For example:

    • Individuals who are blind or have low vision may have difficulty knowing when a visual context change has occurred, such as a new window popping up. 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 reading and intellectual disabilities, and others who have difficulty interpreting visual cues may benefit from additional cues in order to detect changes of context.

Additional guidance when applying Success Criterion 3.2.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Success Criterion 3.2.3: Consistent Navigation (Level AA)

From Success Criterion 3.2.3 :

Navigational mechanisms that are repeated on multiple Web pages within a set of Web pages occur in the same relative order each time they are repeated, unless a change is initiated by the user.

Intent from Understanding Success Criterion 3.2.3 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to encourage the use of consistent presentation and layout for users who interact with repeated content within a set of Web pages and need to locate specific information or functionality more than once. Individuals with low vision who use screen magnification to display a small portion of the screen at a time often use visual cues and page boundaries to quickly locate repeated content. Presenting repeated content in the same order is also important for visual users who use spatial memory or visual cues within the design to locate repeated content.

It is important to note that the use of the phrase "same order" in this section is not meant to imply that subnavigation menus cannot be used or that blocks of secondary navigation or page structure cannot be used. Instead, this Success Criterion is intended to assist users who interact with repeated content across Web pages to be able to predict the location of the content they are looking for and find it more quickly when they encounter it again.

Users may initiate a change in the order by using adaptive user agents or by setting preferences so that the information is presented in a way that is most useful to them.

Specific Benefits of Success Criterion 3.2.3
  • Ensuring that repeated components occur in the same order on each page of a site helps users become comfortable that they will able to predict where they can find things on each page. This helps users with cognitive limitations , users with low vision , users with intellectual disabilities , and also those who are blind .

Additional guidance when applying Success Criterion 3.2.3 to Electronic Non-Web Documents and Software Aspects of Products: Software:

For Documents:

This applies as written and described in INTENT of Understanding WCAG 2.0 (above), replacing “Web pages” with “documents” and assuming that “set” means a group “set of items 1) that are published together, and 2) where the items all refer to each other by name or link. Web pages” with “set of non-web documents”.

With these substitutions, it would read:

3.2.3 Consistent Navigation: Navigational mechanisms that are repeated on multiple documents within a set of set of non-web documents occur in the  same relative order  each time they are repeated, unless a change is initiated by the user.

Note 1: Republishing or bundling previously published Documents as a collection does not constitute a set of Documents. Note 2: If a set is broken apart, the individual parts are no longer part of a set, and would be evaluated as any other individual documents.  One example of a set documents would be a 3 part report where each part is a separate file. At the beginning of each file the table of contents for “navigating” to the other parts is repeated. Each table of contents might have additional navigation mechanisms for the particular chapter in which it is included, but the items that are repeated in all of the chapters (i.e. the navigation mechanisms to the other chapters) would be in the same order relative to each other.

For Software: 

The WCAG2ICT Task Force has not yet produced additional guidance for software for Success Criterion 3.2.3.

Success Criterion 3.2.4: Consistent Identification (Level AA)

From Success Criterion 3.2.4 :

Components that have the same functionality within a set of Web pages are identified consistently.

Intent from Understanding Success Criterion 3.2.4 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure consistent identification of functional components that appear repeatedly within a set of Web pages. A strategy that people who use screen readers use when operating a Web site is to rely heavily on their familiarity with functions that may appear on different Web pages. If identical functions have different labels on different Web pages, the site will be considerably more difficult to use. It may also be confusing and increase the cognitive load for people with cognitive limitations. Therefore, consistent labeling will help.

This consistency extends to the text alternatives. If icons or other non-text items have the same functionality, then their text alternatives should be consistent as well.

Specific Benefits of Success Criterion 3.2.4
  • People who learn functionality on one page on a site can find the desired functions on other pages if they are present.

  • When non-text content is used in a consistent way to identify components with the same functionality, people with difficulty reading text or detecting text alternatives can interact with the Web without depending on text alternatives.

  • People who depend on text alternatives can have a more predictable experience. They can also search for the component if it has a consistent label on different pages.

Additional guidance when applying Success Criterion 3.2.4 to Electronic Non-Web Documents and Software Aspects of Products: Software:

For Documents:

This applies directly as written, written and as described in INTENT from of Understanding WCAG 2.0 (above) (above), replacing “a set “set of Web pages” with “a “set of non-web document or software”. documents”.

With these substitutions, it would read:

3.2.4: Consistent Identification: Components that have the same functionality within a set of non-web document or software documents are identified consistently. (Level AA)

For Software: 

The WCAG2ICT Task Force has not yet produced additional guidance for software for Success Criterion 3.2.4.

Guideline 3.3: Input Assistance

From Guideline 3.3 :

Help users avoid and correct mistakes.

Intent from Understanding Guideline 3.3 in Understanding WCAG 2.0 :

Everyone makes mistakes. However, people with some disabilities have more difficulty creating error-free input. In addition, it may be harder for them to detect that they have made an error. Typical error indication methods may not be obvious to them because of a limited field of view, limited color perception, or use of assistive technology. This guideline seeks to reduce the number of serious or irreversible errors that are made, increase the likelihood that all errors will be noticed by the user, and help users understand what they should do to correct an error.

Additional guidance when applying Guideline 3.3 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 3.3.

Success Criterion 3.3.1: Error Identification (Level A)

From Success Criterion 3.3.1 :

If an input error is automatically detected, the item that is in error is identified and the error is described to the user in text.

Intent from Understanding Success Criterion 3.3.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that users are aware that an error has occurred and can determine what is wrong. The error message should be as specific as possible. In the case of an unsuccessful form submission, re-displaying the form and indicating the fields in error is insufficient for some users to perceive that an error has occurred. Screen reader users, for example, will not know there was an error until they encounter one of the indicators. They may abandon the form altogether before encountering the error indicator, thinking that the page simply is not functional. Per the definition in WCAG 2.0, an "input error" is information provided by the user that is not accepted. This includes:

  • information that is required by the web page but omitted by the user, or

  • information that is provided by the user but that falls outside the required data format or allowed values.

For example:

  • the user fails to enter the proper abbreviation in to state, province, region, etc. field;

  • the user enters a state abbreviation that is not a valid state;

  • the user enters a non existent zip or postal code;

  • the user enters a birth date 2 years in the future;

  • the user enters alphabetic characters or parentheses into their phone number field that only accepts numbers;

  • the user enters a bid that is below the previous bid or the minimum bid increment.

Note: If a user enters a value that is too high or too low, and the coding on the page automatically changes that value to fall within the allowed range, the user's error would still need to be described to them as required by the success criterion. Such an error description telling the person of the changed value would meet both this success criterion (Error Identification) and Success Criterion 3.3.3 (Error Suggestion) .

The identification and description of an error can be combined with programmatic information that user agents or assistive technologies can use to identify an error and provide error information to the user. For example, certain technologies can specify that the user's input must not fall outside a specific range, or that a form field is required. Currently, few technologies support this kind of programmatic information, but the Success Criterion does not require, nor prevent it.

It is perfectly acceptable to indicate the error in other ways such as image, color etc, in addition to the text description.

See also Understanding Success Criterion 3.3.3 Error Suggestion .

Specific Benefits of Success Criterion 3.3.1
  • Providing information about input errors in text allows users who are blind or colorblind to perceive the fact that an error occurred.

  • This Success Criterion may help people with cognitive, language, and learning disabilities who have difficulty understanding the meaning represented by icons and other visual cues.

Additional guidance when applying Success Criterion 3.3.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note: See also the discussion on Closed Functionality in the Introduction.

Success Criterion 3.3.2: Labels or Instructions (Level A)

From Success Criterion 3.3.2 :

Labels or instructions are provided when content requires user input.

Intent from Understanding Success Criterion 3.3.2 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to help users avoid making mistakes when their input is required. To help avoid mistakes it is good user interface design to provide simple instructions and cues for entering information. Some users with disabilities may be more likely to make mistakes than users without disabilities or recovery from mistakes may be more difficult, making mistake avoidance an important strategy for users with disabilities. People with disabilities rely on well documented forms and procedures to interact with a page. Blind users need to know exactly what information should be entered into form fields and what the available choices are. Simple instructions visually connected to form controls can assist users with cognitive disabilities or those accessing a page using a screen magnifier.

The intent of this Success Criterion is not to clutter the page with unnecessary information but to provide important cues and instructions that will benefit people with disabilities. Too much information or instruction can be just as much of a hindrance as too little. The goal is to make certain that enough information is provided for the user to accomplish the task without undue confusion or navigation.

Note: If labels are provided, the label relationship to the object labeled must be programmatically determined or described in text per Understanding Success Criterion 1.3.1 Info and Relationships .

Specific Benefits of Success Criterion 3.3.2
  • Label elements associated with input elements insure that information about the input field is spoken by screen readers when the field receives focus.

  • Field labels located in close proximity to the associated field assist users of screen magnifiers because the field and label are more likely to visible within the magnified area of the page.

  • Providing examples of expected data formats help users with cognitive, language and learning disabilities to enter information correctly.

  • Clearly identifying required fields prevents a keyboard only user from submitting an incomplete form and having to navigate the redisplayed form to find the uncompleted field and provide the missing information.

Additional guidance when applying Success Criterion 3.3.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Success Criterion 3.3.3: Error Suggestion (Level AA)

From Success Criterion 3.3.3 :

If an input error is automatically detected and suggestions for correction are known, then the suggestions are provided to the user, unless it would jeopardize the security or purpose of the content.

Intent from Understanding Success Criterion 3.3.3 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that users receive appropriate suggestions for correction of an input error if it is possible. The WCAG 2.0 definition of "input error" says that it is "information provided by the user that is not accepted" by the system. Some examples of information that is not accepted include information that is required but omitted by the user and information that is provided by the user but that falls outside the required data format or allowed values.

Success Criterion 3.3.1 provides for notification of errors. However, persons with cognitive limitations may find it difficult to understand how to correct the errors. People with visual disabilities may not be able to figure out exactly how to correct the error. In the case of an unsuccessful form submission, users may abandon the form because they may be unsure of how to correct the error even though they are aware that it has occurred.

The content author may provide the description of the error, or the user agent may provide the description of the error based on technology-specific, programmatically determined information.

Specific Benefits of Success Criterion 3.3.3
  • Providing information about how to correct input errors allows users who have learning disabilities to fill in a form successfully. Users who are blind or have impaired vision understand more easily the nature of the input error and how to correct it. People with motion impairment can reduce the number of times they need to change an input value.

Additional guidance when applying Success Criterion 3.3.3 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Success Criterion 3.3.4: Error Prevention (Legal, Financial, Data) (Level AA)

From Success Criterion 3.3.4 :

For Web pages that cause legal commitments or financial transactions for the user to occur, that modify or delete user-controllable data in data storage systems, or that submit user test responses, at least one of the following is true:

  1. Reversible: Submissions are reversible.

  2. Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them.

  3. Confirmed: A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission.

Intent from Understanding Success Criterion 3.3.4 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to help users with disabilities avoid serious consequences as the result of a mistake when performing an action that cannot be reversed. For example, purchasing non-refundable airline tickets or submitting an order to purchase stock in a brokerage account are financial transactions with serious consequences. If a user has made a mistake on the date of air travel, he or she could end up with a ticket for the wrong day that cannot be exchanged. If the user made a mistake on the number of stock shares to be purchased, he or she could end up purchasing more stock than intended. Both of these types of mistakes involve transactions that take place immediately and cannot be altered afterwards, and can be very costly. Likewise, it may be an unrecoverable error if users unintentionally modify or delete data stored in a database that they later need to access, such as their entire travel profile in a travel services web site. When referring to modification or deletion of 'user controllable' data, the intent is to prevent mass loss of data such as deleting a file or record. It is not the intent to require a confirmation for each save command or the simple creation or editing of documents, records or other data.

Users with disabilities may be more likely to make mistakes. People with reading disabilities may transpose numbers and letters, and those with motor disabilities may hit keys by mistake. Providing the ability to reverse actions allows users to correct a mistake that could result in serious consequences. Providing the ability to review and correct information gives the user an opportunity to detect a mistake before taking an action that has serious consequences.

User-controllable data is user-viewable data that the user can change and/or delete through an intentional action. Examples of the user controlling such data would be updating the phone number and address for the user's account, or deleting a record of past invoices from a website. It does not refer such things as internet logs and search engine monitoring data that the user can't view or interact with directly.

Specific Benefits of Success Criterion 3.3.4
  • Providing safeguards to avoid serious consequences resulting from mistakes helps users with all disabilities who may be more likely to make mistakes.

Additional guidance when applying Success Criterion 3.3.4 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above) replacing “a set of Web pages” with “a non-web document or software”.

With these substitutions, it would read:

3.3.4 Error Prevention (Legal, Financial, Data): For a non-web document or software that cause legal commitments or financial transactions for the user to occur, that modify or delete user-controllable data in data storage systems, or that submit user test responses, at least one of the following is true: (Level AA)

  1. Reversible: Submissions are reversible.

  2. Checked: Data entered by the user is checked for input errors and the user is provided an opportunity to correct them.

  3. Confirmed: A mechanism is available for reviewing, confirming, and correcting information before finalizing the submission.

Principle 4: Robust

Content must be robust enough that it can be interpreted reliably by a wide variety of user agents, including assistive technologies.

Guideline 4.1: Compatible

From Guideline 4.1 :

Maximize compatibility with current and future user agents, including assistive technologies.

Intent from Understanding Guideline 4.1 in Understanding WCAG 2.0 :

The purpose of this guideline is to support compatibility with current and future user agents, especially assistive technologies (AT). This is done both by 1) ensuring that authors do not do things that would break AT (e.g., poorly formed markup) or circumvent AT (e.g., by using unconventional markup or code) and 2) exposing information in the content in standard ways that assistive technologies can recognize and interact with. Since technologies change quickly, and AT developers have much trouble keeping up with rapidly changing technologies, it is important that content follow conventions and be compatible with APIs so that AT can more easily work with new technologies as they evolve.

Additional guidance when applying Guideline 4.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

The WCAG2ICT Task Force has not yet reviewed at the Guideline level; see success criteria below for guidance on Guideline 4.1.

Success Criterion 4.1.1: Parsing (Level A)

From Success Criterion 4.1.1 :

In content implemented using markup languages, elements have complete start and end tags, elements are nested according to their specifications, elements do not contain duplicate attributes, and any IDs are unique, except where the specifications allow these features.

Note: Start and end tags that are missing a critical character in their formation, such as a closing angle bracket or a mismatched attribute value quotation mark are not complete.

Intent from Understanding Success Criterion 4.1.1 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that user agents, including assistive technologies, can accurately interpret and parse content. If the content cannot be parsed into a data structure, then different user agents may present it differently or be completely unable to parse it. Some user agents use "repair techniques" to render poorly coded content.

Since repair techniques vary among user agents, authors cannot assume that content will be accurately parsed into a data structure or that it will be rendered correctly by specialized user agents, including assistive technologies, unless the content is created according to the rules defined in the formal grammar for that technology. In markup languages, errors in element and attribute syntax and failure to provide properly nested start/end tags lead to errors that prevent user agents from parsing the content reliably. Therefore, the Success Criterion requires that the content can be parsed using only the rules of the formal grammar.

Note 1: The concept of "well formed" is close to what is required here. However, exact parsing requirements vary amongst markup languages, and most non XML-based languages do not explicitly define requirements for well formedness. Therefore, it was necessary to be more explicit in the success criterion in order to be generally applicable to markup languages. Because the term "well formed" is only defined in XML, and (because end tags are sometimes optional) valid HTML does not require well formed code, the term is not used in this success criterion.

Note 2: With the exception of one success criterion ( Understanding Success Criterion 1.4.4 Resize text , which specifically mentions that the effect specified by the success criterion must be achieved without relying on an assistive technology) authors can meet the success criteria with content that assumes use of an assistive technology (or access features in use agents) by the user, where such assistive technologies (or access features in user agents) exist and are available to the user.

Specific Benefits of Success Criterion 4.1.1
  • Ensuring that Web pages have complete start and end tags and are nested according to specification helps ensure that assistive technologies can parse the content accurately and without crashing.

Additional guidance when applying Success Criterion 4.1.1 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above) replacing “In content implemented using markup languages” with “For non-Web documents or software that use markup languages, in such a way that the markup is separately exposed and available to assistive technology or to a user-selectable user agent”.

With these substitutions, it would read:

4.1.1 Parsing:   For non-Web documents or software that use markup languages, in such a way that the markup is separately exposed and available to assistive technology or to a user-selectable user agent , elements have complete start and end tags, elements are nested according to their specifications, elements do not contain duplicate attributes, and any IDs are unique, except where the specifications allow these features. (Level A)

Note:  Start and end tags that are missing a critical character in their formation, such as a closing angle bracket or a mismatched attribute value quotation mark are not complete.

Note: Markup is not always available to assistive technology or to user selectable user agents such as browsers.  Software sometimes uses markup languages internally for persistence of the software user interface, in ways where it is never available to assistive technology (either directly or through a document object model (DOM)), or to a user agent (such as a browser). In such cases, conformance to this provision would have no impact on accessibility as it can for Web Content where it is exposed.

Examples of markup that is separately exposed and available to assistive technology and to user agents include: documents encoded in HTML, ODF, and OOXML. In these examples, the markup can be parsed entirely in two ways: (a) by assistive technologies which may directly open the document, (b) by assistive technologies using DOM APIs of user agents for these document formats.

Examples of markup used internally for persistence of the software user interface that are never exposed to assistive technology include: XUL, GladeXML, and FXML. In these examples assistive technology only interacts with the user interface of generated software.

Note: See also the discussion on Closed Functionality in the Introduction.

Success Criterion 4.1.2: Name, Role, Value (Level A)

From Success Criterion 4.1.2 :

For all user interface components (including but not limited to: form elements, links and components generated by scripts), the name and role can be programmatically determined ; states, properties, and values that can be set by the user can be programmatically set ; and notification of changes to these items is available to user agents , including assistive technologies .

Note: This success criterion is primarily for Web authors who develop or script their own user interface components. For example, standard HTML controls already meet this success criterion when used according to specification.

Intent from Understanding Success Criterion 4.1.2 in Understanding WCAG 2.0 :

The intent of this Success Criterion is to ensure that Assistive Technologies (AT) can gather information about, activate(or set) and keep up to date on the status of user interface controls in the content.

When standard controls from accessible technologies are used, this process is straightforward. If the user interface elements are used according to specification the conditions of this provision will be met. (See examples of Success Criterion 4.1.2 below)

If custom controls are created, however, or interface elements are programmed (in code or script) to have a different role and/or function than usual, then additional measures need to be taken to ensure that the controls provide important information to assistive technologies and allow themselves to be controlled by assistive technologies.

A particularly important state of a user interface control is whether or not it has focus. The focus state of a control can be programmatically determined, and notifications about change of focus are sent to user agents and assistive technology. Other examples of user interface control state are whether or not a checkbox or radio button has been selected, or whether or not a collapsible tree or list node is expanded or collapsed.

Note: Success Criterion 4.1.2 requires a programmatically determinable name for all user interface components. Names may be visible or invisible. Occasionally, the name must be visible, in which case it is identified as a label. Refer to the definition of name and label in the glossary for more information.

Specific Benefits of Success Criterion 4.1.2
  • Providing role, state, and value information on all user interface components enables compatibility with assistive technology, such as screen readers, screen magnifiers, and speech recognition software, used by people with disabilities.

Additional guidance when applying Success Criterion 4.1.2 to Electronic Non-Web Documents and Software Aspects of Products: Software:

This applies directly as written, and as described in INTENT from Understanding WCAG 2.0 (above).

Note 1: For conforming to this success criterion, it is usually best practice for software user interfaces to use the accessibility services provided by platform software. These accessibility services enable interoperability between software user interfaces and assistive technologies in standardised ways. Most platform accessibility services go beyond programmatic exposure of name and role, and programmatic setting of states, properties and values (and notification of same), and specify additional information that could or should be exposed and/or set (for instance, a list of the available actions for a given user interface component, and a means to programmatically execute one of the listed actions).

Note 2: For document formats that support interoperability with assistive technology, standard user interface components often meet this success criterion when used according to the general design and accessibility guidance for the document format.

Note 3: See also the discussion on Closed Functionality in the Introduction.

5. Comments on Conformance

The WCAG2ICT Task Force has not yet reviewed the conformance criteria.

6. Comments on Definitions in WCAG 2.0 Glossary in Appendix A

The following is a complete list of definitions from the WCAG 2.0 glossary. Some items apply to all technologies and do not require additional guidance in this document; guidance on the remainder follows.

Glossary Items that Apply to All Technologies

The following glossary items apply to all technologies and do not require further interpretation for non-Web Information and Communications Technologies.

Glossary Items Pending Discussion

The following items may require additional guidance but the task force has not yet completed discussion.

Glossary Items with Specific Guidance

The following glossary entries from WCAG 2.0 have additional interpretive guidance provided.

ambiguous to users in general

From the WCAG 2.0 definition for ambiguous to users in general :

the purpose cannot be determined from the link and all information of the Web page presented to the user simultaneously with the link (i.e., readers without disabilities would not know what a link would do until they activated it)

Example: The word guava in the following sentence "One of the notable exports is guava" is a link. The link could lead to a definition of guava, a chart listing the quantity of guava exported or a photograph of people harvesting guava. Until the link is activated, all readers are unsure and the person with a disability is not at any disadvantage.

This applies directly as written, and as described in the WCAG 2.0 glossary, replacing “Web page” with “non-Web document or software”.

With these substitutions, it would read:

ambiguous to users in general

the purpose cannot be determined from the link and all information of the non-web document or software presented to the user simultaneously with the link (i.e., readers without disabilities would not know what a link would do until they activated it)

Example: The word guava in the following sentence "One of the notable exports is guava" is a link. The link could lead to a definition of guava, a chart listing the quantity of guava exported or a photograph of people harvesting guava. Until the link is activated, all readers are unsure and the person with a disability is not at any disadvantage.

content (Web content)

From the WCAG 2.0 definition for content (Web content) :

information and sensory experience to be communicated to the user by means of a user agent , including code or markup that defines the content's structure , presentation , and interactions

contrast ratio

From the WCAG 2.0 definition for contrast ratio :

(L1 + 0.05) / (L2 + 0.05), where

Note 1: Contrast ratios can range from 1 to 21 (commonly written 1:1 to 21:1).

Note 2: Because authors do not have control over user settings as to how text is rendered (for example font smoothing or anti-aliasing), the contrast ratio for text can be evaluated with anti-aliasing turned off.

Note 3: For the purpose of Success Criteria 1.4.3 and 1.4.6, contrast is measured with respect to the specified background over which the text is rendered in normal usage. If no background color is specified, then white is assumed.

Note 4: Background color is the specified color of content over which the text is to be rendered in normal usage. It is a failure if no background color is specified when the text color is specified, because the user's default background color is unknown and cannot be evaluated for sufficient contrast. For the same reason, it is a failure if no text color is specified when a background color is specified.

Note 5: When there is a border around the letter, the border can add contrast and would be used in calculating the contrast between the letter and its background. A narrow border around the letter would be used as the letter. A wide border around the letter that fills in the inner details of the letters acts as a halo and would be considered background.

Note 6: WCAG conformance should be evaluated for color pairs specified in the content that an author would expect to appear adjacent in typical presentation. Authors need not consider unusual presentations, such as color changes made by the user agent, except where caused by authors' code.

This applies directly as written, and as described in the WCAG 2.0 glossary. 

Because relative luminance is defined such that it cannot directly apply to hardware we draw the reader's attention to the note in the introduction which reads: “This document does not comment on hardware aspects of products, non-UI aspects of platforms, or the application of WCAG 2.0 for user-interface components as a category, because the basic constructs on which the WCAG 2.0 and/or its conformance are built do not apply to these.”

general flash and red flash thresholds

From the WCAG 2.0 definition for general flash and red flash thresholds :

a flash or rapidly changing image sequence is below the threshold (i.e., content passes ) if any of the following are true:

  1. there are no more than three general flashes and / or no more than three red flashes within any one-second period; or

  2. the combined area of flashes occurring concurrently occupies no more than a total of .006 steradians within any 10 degree visual field on the screen (25% of any 10 degree visual field on the screen) at typical viewing distance

where:

  • A general flash is defined as a pair of opposing changes in relative luminance of 10% or more of the maximum relative luminance where the relative luminance of the darker image is below 0.80; and where "a pair of opposing changes" is an increase followed by a decrease, or a decrease followed by an increase, and

  • A red flash is defined as any pair of opposing transitions involving a saturated red.

Exception: Flashing that is a fine, balanced, pattern such as white noise or an alternating checkerboard pattern with "squares" smaller than 0.1 degree (of visual field at typical viewing distance) on a side does not violate the thresholds.

Note 1: For general software or Web content, using a 341 x 256 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 x 768 pixels will provide a good estimate of a 10 degree visual field for standard screen sizes and viewing distances (e.g., 15-17 inch screen at 22-26 inches). (Higher resolutions displays showing the same rendering of the content yield smaller and safer images so it is lower resolutions that are used to define the thresholds.)

Note 2: A transition is the change in relative luminance (or relative luminance/color for red flashing) between adjacent peaks and valleys in a plot of relative luminance (or relative luminance/color for red flashing) measurement against time. A flash consists of two opposing transitions.

Note 3: The current working definition in the field for "pair of opposing transitions involving a saturated red" is where, for either or both states involved in each transition, R/(R+ G + B) >= 0.8, and the change in the value of (R-G-B)x320 is > 20 (negative values of (R-G-B)x320 are set to zero) for both transitions. R, G, B values range from 0-1 as specified in “relative luminance” definition. [HARDING-BINNIE]

Note 4: Tools are available that will carry out analysis from video screen capture. However, no tool is necessary to evaluate for this condition if flashing is less than or equal to 3 flashes in any one second. Content automatically passes (see #1 and #2 above).

This applies directly as written, and as described in the WCAG 2.0 glossary.

Note: because this deals with relative luminance and not luminance, it can only be applied to information on a display, not to hardware sources of light.

keyboard interface

From the WCAG 2.0 definition for keyboard interface :

interface used by software to obtain keystroke input

Note 1: A keyboard interface allows users to provide keystroke input to programs even if the native technology does not contain a keyboard.

Example: A touchscreen PDA has a keyboard interface built into its operating system as well as a connector for external keyboards. Applications on the PDA can use the interface to obtain keyboard input either from an external keyboard or from other applications that provide simulated keyboard output, such as handwriting interpreters or speech-to-text applications with "keyboard emulation" functionality.

Note 2: Operation of the application (or parts of the application) through a keyboard-operated mouse emulator, such as MouseKeys, does not qualify as operation through a keyboard interface because operation of the program is through its pointing device interface, not through its keyboard interface.

This applies directly as written, and as described in the WCAG 2.0 glossary.

We draw the reader's attention to the note in SC 2.1.1 that uses this definition and which reads: “This does not imply that software must directly support a keyboard or ‘keyboard interface’. Nor does it imply that software must provide a soft keyboard. Underlying platform software may provide device independent input services to applications that enable operation via a keyboard. Software that supports operation via such platform device independent services would be operable by a keyboard and would comply.”

label

From the WCAG 2.0 definition for label :

text or other component with a text alternative that is presented to a user to identify a component within Web content

Note 1: A label is presented to all users whereas the name may be hidden and only exposed by assistive technology. In many (but not all) cases the name and the label are the same.

Note 2: The term label is not limited to the label element in HTML.

This applies directly as written, and as described in the WCAG 2.0 glossary replacing “Web Content” with “Content”. “content”.

With these substitutions, it would read:

label

text or other component with a text alternative that is presented to a user to identify a component within content

Note 1: A label is presented to all users whereas the name may be hidden and only exposed by assistive technology. In many (but not all) cases the name and the label are the same.

Note 2: The term label is not limited to the label element in HTML.

name

From the WCAG 2.0 definition for name :

text by which software can identify a component within Web content to the user

Note 1: The name may be hidden and only exposed by assistive technology, whereas a label is presented to all users. In many (but not all) cases, the label and the name are the same.

Note 2: This is unrelated to the name attribute in HTML.

This applies directly as written, and as described in the WCAG 2.0 glossary replacing “Web content” with “content”.

With these substitutions, it would read:

name

text by which software can identify a component within content to the user

Note 1: The name may be hidden and only exposed by assistive technology, whereas a label is presented to all users. In many (but not all) cases, the label and the name are the same.

Note 2: This is unrelated to the name attribute in HTML.

Note: “AccessibleName” (or whatever it is called in different APIs) of the Accessibility API of the platform is an example of such a name.

relative luminance

From the WCAG 2.0 definition for relative luminance :

the relative brightness of any point in a colorspace, normalized to 0 for darkest black and 1 for lightest white

Note 1: For the sRGB colorspace, the relative luminance of a color is defined as L = 0.2126 * R + 0.7152 * G + 0.0722 * B where R , G and B are defined as:

  • if R sRGB <= 0.03928 then R = R sRGB /12.92 else R = ((R sRGB +0.055)/1.055) ^ 2.4

  • if G sRGB <= 0.03928 then G = G sRGB /12.92 else G = ((G sRGB +0.055)/1.055) ^ 2.4

  • if B sRGB <= 0.03928 then B = B sRGB /12.92 else B = ((B sRGB +0.055)/1.055) ^ 2.4

and R sRGB , G sRGB , and B sRGB are defined as:

  • R sRGB = R 8bit /255

  • G sRGB = G 8bit /255

  • B sRGB = B 8bit /255

The "^" character is the exponentiation operator. (Formula taken from [sRGB] and [IEC-4WD] ).

Note 2: Almost all systems used today to view Web content assume sRGB encoding. Unless it is known that another color space will be used to process and display the content, authors should evaluate using sRGB colorspace. If using other color spaces, see Understanding Success Criterion 1.4.3 .

Note 3: If dithering occurs after delivery, then the source color value is used. For colors that are dithered at the source, the average values of the colors that are dithered should be used (average R, average G, and average B).

Note 4: Tools are available that automatically do the calculations when testing contrast and flash.

Note 5: A MathML version of the relative luminance definition is available.

This applies directly as written, and as described in the WCAG 2.0 glossary replacing “Web content” with “content”. 

With these substitutions, it would read:

relative luminance

the relative brightness of any point in a colorspace, normalized to 0 for darkest black and 1 for lightest white

Note 1: For the sRGB colorspace, the relative luminance of a color is defined as L = 0.2126 * R + 0.7152 * G + 0.0722 * B where R , G and B are defined as:

  • if R sRGB <= 0.03928 then R = R sRGB /12.92 else R = ((R sRGB +0.055)/1.055) ^ 2.4

  • if G sRGB <= 0.03928 then G = G sRGB /12.92 else G = ((G sRGB +0.055)/1.055) ^ 2.4

  • if B sRGB <= 0.03928 then B = B sRGB /12.92 else B = ((B sRGB +0.055)/1.055) ^ 2.4

and R sRGB , G sRGB , and B sRGB are defined as:

  • R sRGB = R 8bit /255

  • G sRGB = G 8bit /255

  • B sRGB = B 8bit /255

The "^" character is the exponentiation operator. (Formula taken from [sRGB] and [IEC-4WD] ).

Note 2: Almost all systems used today to view content assume sRGB encoding. Unless it is known that another color space will be used to process and display the content, authors should evaluate using sRGB colorspace. If using other color spaces, see Understanding Success Criterion 1.4.3 .

Note 3: If dithering occurs after delivery, then the source color value is used. For colors that are dithered at the source, the average values of the colors that are dithered should be used (average R, average G, and average B).

Note 4: Tools are available that automatically do the calculations when testing contrast and flash.

Note 5: A MathML version of the relative luminance definition is available.

Because relative luminance is defined such that it cannot directly apply to hardware we draw the reader's attention to the note in the introduction which reads: “This document does not comment on hardware aspects of products, non-UI aspects of platforms, or the application of WCAG 2.0 for user-interface components as a category, because the basic constructs on which the WCAG 2.0 and/or its conformance are built do not apply to these.”

role

From the WCAG 2.0 definition for role :

text or number by which software can identify the function of a component within Web content

Example: A number that indicates whether an image functions as a hyperlink, command button, or check box.

This applies directly as written, and as described in the WCAG 2.0 glossary replacing “Web content” with “content”.

With these substitutions, it would read:

role

text or number by which software can identify the function of a component within content

Example: A number that indicates whether an image functions as a hyperlink, command button, or check box.

Note: “AccessibleRole” (or however it is called in different APIs) of the Accessibility API of the platform is an example of such a role.

user agent

From the WCAG 2.0 definition for user agent :

any software that retrieves and presents Web content for users

Example: Web browsers, media players, plug-ins, and other programs — including assistive technologies — that help in retrieving, rendering, and interacting with Web content.

Appendix A. Success Criteria Problematic for Closed Functionality

The following success criteria will be problematic for developers of closed functionality. They either discuss making information available in text (which can be read by assistive technologies) or making it "programmatically determinable" (readable (rendered by a user agent, and readable by assistive technologies) or  discuss  doing something else to make content compatible with assistive technologies.   Alternate accessibility provisions would be needed that would address the purpose of these success criteria for the closed functionality aspects of products.

Note 1: Some of the above success criteria would apply to systems with closed functionality if they are partially closed or if they allow for the connection of some types of devices. For instance, 2.1.1 (Keyboard) would apply to systems which have closed functionality to screen readers but which have a physical keyboard or a connector for standard keyboards.

Note 2: While these guidelines are not suitable for closed functionality as written, they will inform and aid development of built-in accessible alternatives needed with closed functionality.

Appendix B. Acknowledgements

B.1 Participants in the WCAG2ICT Task Force

The following people were active participants in the WCAG2ICT Task Force , which had a primary role in preparation of this document:

B.2 Participants in the WCAG Working Group

The following people were active participants in the Web Content Accessibility Guidelines Working Group , which reviewed materials to ensure consistency with the intent of WCAG 2.0:

Enabling funders

This publication has been funded in part with Federal funds from the U.S. Department of Education, National Institute on Disability and Rehabilitation Research (NIDRR) under contract number ED-OSE-10-C-0067. The content of this publication does not necessarily reflect the views or policies of the U.S. Department of Education, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.

Appendix C. References

No references documented yet.