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Link to original content: https://w3c.github.io/wcag21/guidelines/
Copyright © 2017-2018 W3C® (MIT, ERCIM, Keio, Beihang). W3C liability, trademark and document use rules apply.
Web Content Accessibility Guidelines (WCAG) 2.1 covers a wide range of recommendations for making Web content more accessible. Following these guidelines will make content more accessible to a wider range of people with disabilities, including accommodations for blindness and low vision, deafness and hearing loss, limited movement, speech disabilities, photosensitivity, and combinations of these, and some accommodation for learning disabilities and cognitive limitations; but will not address every user need for people with these disabilities. These guidelines address accessibility of web content on desktops, laptops, tablets, and mobile devices. Following these guidelines will also often make Web content more usable to users in general.
WCAG 2.1 success criteria are written as testable statements that are not technology-specific. Guidance about satisfying the success criteria in specific technologies, as well as general information about interpreting the success criteria, is provided in separate documents. See Web Content Accessibility Guidelines (WCAG) Overview for an introduction and links to WCAG technical and educational material.
WCAG 2.1 extends Web Content Accessibility Guidelines 2.0 [WCAG20], which was published as a W3C Recommendation December 2008. Content that conforms to WCAG 2.1 also conforms to WCAG 2.0. The WG intends that for policies requiring conformance to WCAG 2.0, WCAG 2.1 can provide an alternate means of conformance. The publication of WCAG 2.1 does not deprecate or supersede WCAG 2.0. While WCAG 2.0 remains a W3C Recommendation, the W3C advises the use of WCAG 2.1 to maximize future applicability of accessibility efforts. The W3C also encourages use of the most current version of WCAG when developing or updating Web accessibility policies.
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 https://www.w3.org/TR/.
This is an Editors' Draft of Web Content Accessibility Guidelines (WCAG) 2.1. WCAG 2.1 is a W3C Recommendation. This draft incorporates errata and are described in the change log. At some point these changes might be incorporated into a Edited or Amended Recommendation.
To comment, file an issue in the W3C WCAG GitHub repository. Although the proposed Success Criteria in this document reference issues tracking discussion, the Working Group requests that public comments be filed as new issues, one issue per discrete comment. It is free to create a GitHub account to file issues. If filing issues in GitHub is not feasible, send email to public-agwg-comments@w3.org (comment archive).
This document was published by the Accessibility Guidelines Working Group as an Editor's Draft. Comments regarding this document are welcome. Please send them to public-agwg-comments@w3.org (subscribe, archives).
Publication as an Editor's 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 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.
This document is governed by the 1 February 2018 W3C Process Document.
This section is non-normative.
Web Content Accessibility Guidelines (WCAG) 2.1 defines how to make Web content more accessible to people with disabilities. Accessibility involves a wide range of disabilities, including visual, auditory, physical, speech, cognitive, language, learning, and neurological disabilities. Although these guidelines cover a wide range of issues, they are not able to address the needs of people with all types, degrees, and combinations of disability. These guidelines also make Web content more usable by older individuals with changing abilities due to aging and often improve usability for users in general.
WCAG 2.1 is developed through the W3C process in cooperation with individuals and organizations around the world, with a goal of providing a shared standard for Web content accessibility that meets the needs of individuals, organizations, and governments internationally. WCAG 2.1 builds on WCAG 2.0 [WCAG20], which in turn built on WCAG 1.0 [WAI-WEBCONTENT] and is designed to apply broadly to different Web technologies now and in the future, and to be testable with a combination of automated testing and human evaluation. For an introduction to WCAG, see the Web Content Accessibility Guidelines (WCAG) Overview.
Significant challenges were encountered in defining additional criteria to address cognitive, language, and learning disabilities, including a short timeline for development as well as challenges in reaching consensus on testability, implementability, and international considerations of proposals. Work will carry on in this area in future versions of WCAG. We encourage authors to refer to our supplemental guidance on improving inclusion for people with disabilities, including learning and cognitive disabilities, people with low-vision, and more.
Web accessibility depends not only on accessible content but also on accessible Web browsers and other user agents. Authoring tools also have an important role in Web accessibility. For an overview of how these components of Web development and interaction work together, see:
The individuals and organizations that use WCAG vary widely and include Web designers and developers, policy makers, purchasing agents, teachers, and students. In order to meet the varying needs of this audience, several layers of guidance are provided including overall principles, general guidelines, testable success criteria and a rich collection of sufficient techniques, advisory techniques, and documented common failures with examples, resource links and code.
Principles - At the top are four principles that provide the foundation for Web accessibility: perceivable, operable, understandable, and robust. See also Understanding the Four Principles of Accessibility.
Guidelines - Under the principles are guidelines. The 13 guidelines provide the basic goals that authors should work toward in order to make content more accessible to users with different disabilities. The guidelines are not testable, but provide the framework and overall objectives to help authors understand the success criteria and better implement the techniques.
Success Criteria - For each guideline, testable success criteria are provided to allow WCAG 2.1 to be used where requirements and conformance testing are necessary such as in design specification, purchasing, regulation, and contractual agreements. In order to meet the needs of different groups and different situations, three levels of conformance are defined: A (lowest), AA, and AAA (highest). Additional information on WCAG levels can be found in Understanding Levels of Conformance.
Sufficient and Advisory Techniques - For each of the guidelines and success criteria in the WCAG 2.1 document itself, the working group has also documented a wide variety of techniques. The techniques are informative and fall into two categories: those that are sufficient for meeting the success criteria and those that are advisory. The advisory techniques go beyond what is required by the individual success criteria and allow authors to better address the guidelines. Some advisory techniques address accessibility barriers that are not covered by the testable success criteria. Where common failures are known, these are also documented. See also Sufficient and Advisory Techniques in Understanding WCAG 2.1.
All of these layers of guidance (principles, guidelines, success criteria, and sufficient and advisory techniques) work together to provide guidance on how to make content more accessible. Authors are encouraged to view and apply all layers that they are able to, including the advisory techniques, in order to best address the needs of the widest possible range of users.
Note that even content that conforms at the highest level (AAA) will not be accessible to individuals with all types, degrees, or combinations of disability, particularly in the cognitive language and learning areas. Authors are encouraged to consider the full range of techniques, including the advisory techniques, as well as to seek relevant advice about current best practice to ensure that Web content is accessible, as far as possible, to this community. Metadata may assist users in finding content most suitable for their needs.
The WCAG 2.0 document is designed to meet the needs of those who need a stable, referenceable technical standard. Other documents, called supporting documents, are based on the WCAG 2.1 document and address other important purposes, including the ability to be updated to describe how WCAG would be applied with new technologies. Supporting documents include:
How to Meet WCAG 2.1 - A customizable quick reference to WCAG 2.1 that includes all of the guidelines, success criteria, and techniques for authors to use as they are developing and evaluating Web content. This includes content from WCAG 2.0 and WCAG 2.1 and can be filtered in many ways to help authors focus on relevant content.
Understanding WCAG 2.1 - A guide to understanding and implementing WCAG 2.1. There is a short "Understanding" document for each guideline and success criterion in WCAG 2.1 as well as key topics.
Techniques for WCAG 2.1 - A collection of techniques and common failures, each in a separate document that includes a description, examples, code and tests.
The WCAG Documents - A diagram and description of how the technical documents are related and linked.
See Web Content Accessibility Guidelines (WCAG) Overview for a description of the WCAG 2.1 supporting material, including education resources related to WCAG 2. Additional resources covering topics such as the business case for Web accessibility, planning implementation to improve the accessibility of Web sites, and accessibility policies are listed in WAI Resources.
WCAG 2.1 meets a set of requirements for WCAG 2.1 which, in turn, inherit requirements from WCAG 2.0. Requirements structure the overall framework of guidelines and ensure backwards compatibility. The Working Group also used a less formal set of acceptance criteria for success criteria, to help ensure success criteria are similar in style and quality to those in WCAG 2.0. These requirements constrained what could be included in WCAG 2.1. This constraint was important to preserve its nature as a dot-release of WCAG 2.
WCAG 2.1 was initiated with the goal to improve accessibility guidance for three major groups: users with cognitive or learning disabilities, users with low vision, and users with disabilities on mobile devices. Many ways to meet these needs were proposed and evaluated, and a set of these were refined by the Working Group. Structural requirements inherited from WCAG 2.0, clarity and impact of proposals, and timeline led to the final set of success criteria included in this version. The Working Group considers that WCAG 2.1 incrementally advances web content accessibility guidance for all these areas, but underscores that not all user needs are met by these guidelines.
WCAG 2.1 builds on and is backwards compatible with WCAG 2.0, meaning web pages that conform to WCAG 2.1 also conform to WCAG 2.0. Authors that are required by policy to conform with WCAG 2.0 will be able to update content to WCAG 2.1 without losing conformance with WCAG 2.0. Authors following both sets of guidelines should be aware of the following differences:
WCAG 2.1 extends WCAG 2.0 by adding new success criteria, definitions to support them, guidelines to organize the additions, and a couple additions to the conformance section. This additive approach helps to make it clear that sites which conform to WCAG 2.1 also conform to WCAG 2.0, thereby meeting conformance obligations that are specific to WCAG 2.0. The Accessibility Guidelines Working Group recommends that sites adopt WCAG 2.1 as their new conformance target, even if formal obligations mention WCAG 2.0, to provide improved accessibility and to anticipate future policy changes.
The following Success Criteria are new in WCAG 2.1:
Many of these success criteria reference new terms that have also been added to the glossary and form part of the normative requirements of the success criteria.
In the Conformance section, a third note about page variants has been added to Full Pages, and an option for machine-readable metadata added to Optional Components of a Conformance Claim.
In order to avoid confusion for implementers for whom backwards compatibility to WCAG 2.0 is important, new success criteria in WCAG 2.1 have been appended to the end of the set of success criteria within their guideline. This avoids the need to change the section number of success criteria from WCAG 2.0, which would be caused by inserting new success critera between existing success ccriteria in the guideline, but it means success criteria in each guideline are no longer grouped by conformance level. The order of success criteria within each guideline does not imply information about conformance level; only the conformance level indicator (A / AA / AAA) on the success criterion itself indicates this. The WCAG 2.1 Quick Reference provides ways to view success criteria grouped by conformance level, along with many other filter and sort options.
WCAG 2.1 uses the same conformance model as WCAG 2.0 with a couple additions, which is described in the Conformance section. It is intended that sites that conform to WCAG 2.1 also conform to WCAG 2.0, which means they meet the requirements of any policies that reference WCAG 2.0, while also better meeting the needs of users on the current Web.
In parallel with WCAG 2.1, the Accessibility Guidelines Working Group is developing another major version of accessibility guidelines. The result of this work is expected to be a more substantial restructuring of web accessibility guidance than would be realistic for dot-releases of WCAG 2. The work follows a research-focused, user-centered design methodology to produce the most effective and flexible outcome, including the roles of content authoring, user agent support, and authoring tool support. This is a multi-year effort, so WCAG 2.1 is needed as an interim measure to provide updated web accessibility guidance to reflect changes on the web since the publication of WCAG 2.0. The Working Group might also develop additional interim versions, continuing with WCAG 2.2, on a similar short timeline to provide additional support while the major version is completed.
Information and user interface components must be presentable to users in ways they can perceive.
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.
(Level A)
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.
If non-text content is a control or accepts user input, then it has a name that describes its purpose. (Refer to Success Criterion 4.1.2 for additional requirements for controls and content that accepts user input.)
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.)
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.
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.
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.
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.
Provide alternatives for time-based media.
(Level A)
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:
An alternative for time-based media is provided that presents equivalent information for prerecorded audio-only content.
Either an alternative for time-based media or an audio track is provided that presents equivalent information for prerecorded video-only content.
(Level A)
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.
(Level A)
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.
(Level AA)
Captions are provided for all live audio content in synchronized media.
(Level AA)
Audio description is provided for all prerecorded video content in synchronized media.
(Level AAA)
Sign language interpretation is provided for all prerecorded audio content in synchronized media.
(Level AAA)
Where pauses in foreground audio are insufficient to allow audio descriptions to convey the sense of the video, extended audio description is provided for all prerecorded video content in synchronized media.
(Level AAA)
An alternative for time-based media is provided for all prerecorded synchronized media and for all prerecorded video-only media.
(Level AAA)
An alternative for time-based media that presents equivalent information for live audio-only content is provided.
Create content that can be presented in different ways (for example simpler layout) without losing information or structure.
(Level A)
Information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text.
(Level A)
When the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined.
(Level A)
Instructions provided for understanding and operating content do not rely solely on sensory characteristics of components such as shape, color, size, visual location, orientation, or sound.
For requirements related to color, refer to Guideline 1.4.
(Level AA)
Content does not restrict its view and operation to a single display orientation, such as portrait or landscape, unless a specific display orientation is essential.
Examples where a particular display orientation may be essential are a bank check, a piano application, slides for a projector or television, or virtual reality content where binary display orientation is not applicable.
(Level AA)
The purpose of each input field collecting information about the user can be programmatically determined when:
(Level AAA)
In content implemented using markup languages, the purpose of User Interface Components, icons, and regions can be programmatically determined.
Make it easier for users to see and hear content including separating foreground from background.
(Level A)
Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.
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.
(Level A)
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.
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.
(Level AA)
The visual presentation of text and images of text has a contrast ratio of at least 4.5:1, except for the following:
Large-scale text and images of large-scale text have a contrast ratio of at least 3:1;
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.
Text that is part of a logo or brand name has no contrast requirement.
(Level AA)
Except for captions and images of text, text can be resized without assistive technology up to 200 percent without loss of content or functionality.
(Level AA)
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:
The image of text can be visually customized to the user's requirements;
A particular presentation of text is essential to the information being conveyed.
Logotypes (text that is part of a logo or brand name) are considered essential.
(Level AAA)
The visual presentation of text and images of text has a contrast ratio of at least 7:1, except for the following:
Large-scale text and images of large-scale text have a contrast ratio of at least 4.5:1;
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.
Text that is part of a logo or brand name has no contrast requirement.
(Level AAA)
For prerecorded audio-only content that (1) contains primarily speech in the foreground, (2) is not an audio CAPTCHA or audio logo, and (3) is not vocalization intended to be primarily musical expression such as singing or rapping, at least one of the following is true:
The audio does not contain background sounds.
The background sounds can be turned off.
The background sounds are at least 20 decibels lower than the foreground speech content, with the exception of occasional sounds that last for only one or two seconds.
Per the definition of "decibel," background sound that meets this requirement will be approximately four times quieter than the foreground speech content.
(Level AAA)
For the visual presentation of blocks of text, a mechanism is available to achieve the following:
(Level AAA)
Images of text are only used for pure decoration or where a particular presentation of text is essential to the information being conveyed.
Logotypes (text that is part of a logo or brand name) are considered essential.
(Level AA)
Content can be presented without loss of information or functionality, and without requiring scrolling in two dimensions for:
Except for parts of the content which require two-dimensional layout for usage or meaning.
Note: 320 CSS pixels is equivalent to a starting viewport width of 1280 CSS pixels wide at 400% zoom. For web content which are designed to scroll horizontally (e.g. with vertical text), the 256 CSS pixels is equivalent to a starting viewport height of 1024px at 400% zoom.
Examples of content which require two-dimensional layout are images, maps, diagrams, video, games, presentations, data tables, and interfaces where it is necessary to keep toolbars in view while manipulating content.
(Level AA)
The visual presentation of the following have a contrast ratio of at least 3:1 against adjacent color(s):
(Level AA)
In content implemented using markup languages that support the following text style properties, no loss of content or functionality occurs by setting all of the following and by changing no other style property:
Exception: Human languages and scripts that do not make use of one or more of these text style properties in written text can conform using only the properties that exist for that combination of language and script.
(Level AA)
Where receiving and then removing pointer hover or keyboard focus triggers additional content to become visible and then hidden, the following are true:
Exception: The visual presentation of the additional content is controlled by the user agent and is not modified by the author.
Examples of additional content controlled by the user agent include browser tooltips created through use of the HTML title attribute.
Custom tooltips, sub-menus, and other nonmodal popups that display on hover and focus are examples of additional content covered by this criterion.
User interface components and navigation must be operable.
Make all functionality available from a keyboard.
(Level A)
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.
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.
This does not forbid and should not discourage providing mouse input or other input methods in addition to keyboard operation.
(Level A)
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.
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.
(Level AAA)
All functionality of the content is operable through a keyboard interface without requiring specific timings for individual keystrokes.
(Level A)
If a keyboard shortcut is implemented in content using only letter (including upper- and lower-case letters), punctuation, number, or symbol characters, then at least one of the following is true:
Provide users enough time to read and use content.
(Level A)
For each time limit that is set by the content, at least one of the following is true:
The user is allowed to turn off the time limit before encountering it; or
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
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
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
The time limit is essential and extending it would invalidate the activity; or
The time limit is longer than 20 hours.
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.
(Level A)
For moving, blinking, scrolling, or auto-updating information, all of the following are true:
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
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.
For requirements related to flickering or flashing content, refer to Guideline 2.3.
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.
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.
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.
(Level AAA)
Timing is not an essential part of the event or activity presented by the content, except for non-interactive synchronized media and real-time events.
(Level AAA)
Interruptions can be postponed or suppressed by the user, except interruptions involving an emergency.
(Level AAA)
When an authenticated session expires, the user can continue the activity without loss of data after re-authenticating.
(Level AAA)
Users are warned of the duration of any user inactivity that could cause data loss, unless the data is preserved for more than 20 hours when the user does not take any actions.
Privacy regulations may require explicit user consent before user identification has been authenticated and before user data is preserved. In cases where the user is a minor, explicit consent may not be solicited in most jurisdictions, countries or regions. Consultation with privacy professionals and legal counsel is advised when considering data preservation as an approach to satisfy this success criterion.
Do not design content in a way that is known to cause seizures or physical reactions.
(Level A)
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.
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.
(Level AAA)
Web pages do not contain anything that flashes more than three times in any one second period.
(Level AAA)
Motion animation triggered by interaction can be disabled, unless the animation is essential to the functionality or the information being conveyed.
Make it easier for users to operate functionality through various inputs beyond keyboard.
(Level A)
All functionality that uses multipoint or path-based gestures for operation can be operated with a single pointer without a path-based gesture, unless a multipoint or path-based gesture is essential.
This requirement applies to web content that interprets pointer actions (i.e. this does not apply to actions that are required to operate the user agent or assistive technology).
(Level A)
For functionality that can be operated using a single pointer, at least one of the following is true:
Functions that emulate a keyboard or numeric keypad key press are considered essential.
This requirement applies to web content that interprets pointer actions (i.e. this does not apply to actions that are required to operate the user agent or assistive technology).
(Level A)
For user interface components with labels that include text or images of text, the name contains the text that is presented visually.
A best practice is to have the text of the label at the start of the name.
(Level A)
Functionality that can be operated by device motion or user motion can also be operated by user interface components and responding to the motion can be disabled to prevent accidental actuation, except when:
(Level AAA)
The size of the target for pointer inputs is at least 44 by 44 CSS pixels except when:
(Level AAA)
Web content does not restrict use of input modalities available on a platform except where the restriction is essential, required to ensure the security of the content, or required to respect user settings.
Information and the operation of user interface must be understandable.
Make text content readable and understandable.
(Level A)
The default human language of each Web page can be programmatically determined.
(Level AA)
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.
(Level AAA)
A mechanism is available for identifying specific definitions of words or phrases used in an unusual or restricted way, including idioms and jargon.
(Level AAA)
A mechanism for identifying the expanded form or meaning of abbreviations is available.
(Level AAA)
When text requires reading ability more advanced than the lower secondary education level after removal of proper names and titles, supplemental content, or a version that does not require reading ability more advanced than the lower secondary education level, is available.
(Level AAA)
A mechanism is available for identifying specific pronunciation of words where meaning of the words, in context, is ambiguous without knowing the pronunciation.
Make Web pages appear and operate in predictable ways.
(Level A)
When any user interface component receives focus, it does not initiate a change of context.
(Level A)
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.
(Level AA)
Components that have the same functionality within a set of Web pages are identified consistently.
(Level AAA)
Changes of context are initiated only by user request or a mechanism is available to turn off such changes.
Help users avoid and correct mistakes.
(Level A)
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.
(Level A)
Labels or instructions are provided when content requires user input.
(Level AA)
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.
(Level AA)
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:
(Level AAA)
Context-sensitive help is available.
(Level AAA)
For Web pages that require the user to submit information, at least one of the following is true:
Content must be robust enough that it can be interpreted by by a wide variety of user agents, including assistive technologies.
Maximize compatibility with current and future user agents, including assistive technologies.
(Level A)
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.
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.
(Level A)
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.
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.
(Level AA)
In content implemented using markup languages, status messages can be programmatically determined through role or properties such that they can be presented to the user by assistive technologies without receiving focus.
This section lists requirements for conformance to WCAG 2.1. It also gives information about how to make conformance claims, which are optional. Finally, it describes what it means to be accessibility supported, since only accessibility-supported ways of using technologies can be relied upon for conformance. Understanding Conformance includes further explanation of the accessibility-supported concept.
The main content of WCAG 2.1 is normative and defines requirements that impact conformance claims. Introductory material, appendices, sections marked as "non-normative", diagrams, examples, and notes are informative (non-normative). Non-normative material provides advisory information to help interpret the guidelines but does not create requirements that impact a conformance claim.
The key words MAY, MUST, MUST NOT, NOT RECOMMENDED, RECOMMENDED, SHOULD, and SHOULD NOT are to be interpreted as described in [RFC2119].
In order for a Web page to conform to WCAG 2.1, all of the following conformance requirements must be satisfied:
One of the following levels of conformance is met in full.
Although conformance can only be achieved at the stated levels, authors are encouraged to report (in their claim) any progress toward meeting success criteria from all levels beyond the achieved level of conformance.
It is not recommended that Level AAA conformance be required as a general policy for entire sites because it is not possible to satisfy all Level AAA Success Criteria for some content.
Conformance (and conformance level) is for full Web page(s) only, and cannot be achieved if part of a Web page is excluded.
For the purpose of determining conformance, alternatives to part of a page's content are considered part of the page when the alternatives can be obtained directly from the page, e.g., a long description or an alternative presentation of a video.
Authors of Web pages that cannot conform due to content outside of the author's control may consider a Statement of Partial Conformance.
New A full page includes each variation of the page that is automatically presented by the page for various screen sizes (e.g. variations in a responsive Web page). Each of these variations needs to conform (or needs to have a conforming alternate version) in order for the entire page to conform.
When a Web page is one of a series of Web pages presenting a process (i.e., a sequence of steps that need to be completed in order to accomplish an activity), all Web pages in the process conform at the specified level or better. (Conformance is not possible at a particular level if any page in the process does not conform at that level or better.)
An online store has a series of pages that are used to select and purchase products. All pages in the series from start to finish (checkout) conform in order for any page that is part of the process to conform.
Only accessibility-supported ways of using technologies are relied upon to satisfy the success criteria. Any information or functionality that is provided in a way that is not accessibility supported is also available in a way that is accessibility supported. (See Understanding accessibility support.)
If technologies are used in a way that is not accessibility supported, or if they are used in a non-conforming way, then they do not block the ability of users to access the rest of the page. In addition, the Web page as a whole continues to meet the conformance requirements under each of the following conditions:
In addition, the following success criteria apply to all content on the page, including content that is not otherwise relied upon to meet conformance, because failure to meet them could interfere with any use of the page:
If a page cannot conform (for example, a conformance test page or an example page), it cannot be included in the scope of conformance or in a conformance claim.
For more information, including examples, see Understanding Conformance Requirements.
Conformance is defined only for Web pages. However, a conformance claim may be made to cover one page, a series of pages, or multiple related Web pages.
Conformance claims are not required. Authors can conform to WCAG 2.1 without making a claim. However, if a conformance claim is made, then the conformance claim must include the following information:
A concise description of the Web pages, such as a list of URIs for which the claim is made, including whether subdomains are included in the claim.
The Web pages may be described by list or by an expression that describes all of the URIs included in the claim.
Web-based products that do not have a URI prior to installation on the customer's Web site may have a statement that the product would conform when installed.
If a conformance logo is used, it would constitute a claim and must be accompanied by the required components of a conformance claim listed above.
In addition to the required components of a conformance claim above, consider providing additional information to assist users. Recommended additional information includes:
Refer to Understanding Conformance Claims for more information and example conformance claims.
Refer to Understanding Metadata for more information about the use of metadata in conformance claims.
Sometimes, Web pages are created that will later have additional content added to them. For example, an email program, a blog, an article that allows users to add comments, or applications supporting user-contributed content. Another example would be a page, such as a portal or news site, composed of content aggregated from multiple contributors, or sites that automatically insert content from other sources over time, such as when advertisements are inserted dynamically.
In these cases, it is not possible to know at the time of original posting what the uncontrolled content of the pages will be. It is important to note that the uncontrolled content can affect the accessibility of the controlled content as well. Two options are available:
A determination of conformance can be made based on best knowledge. If a page of this type is monitored and repaired (non-conforming content is removed or brought into conformance) within two business days, then a determination or claim of conformance can be made since, except for errors in externally contributed content which are corrected or removed when encountered, the page conforms. No conformance claim can be made if it is not possible to monitor or correct non-conforming content;
OR
A "statement of partial conformance" may be made that the page does not conform, but could conform if certain parts were removed. The form of that statement would be, "This page does not conform, but would conform to WCAG 2.1 at level X if the following parts from uncontrolled sources were removed." In addition, the following would also be true of uncontrolled content that is described in the statement of partial conformance:
A "statement of partial conformance due to language" may be made when the page does not conform, but would conform if accessibility support existed for (all of) the language(s) used on the page. The form of that statement would be, "This page does not conform, but would conform to WCAG 2.1 at level X if accessibility support existed for the following language(s):"
shortened form of a word, phrase, or name where the abbreviation has not become part of the language
This includes initialisms and acronyms where:
initialisms are shortened forms of a name or phrase made from the initial letters of words or syllables contained in that name or phrase
Not defined in all languages.
SNCF is a French initialism that contains the initial letters of the Société Nationale des Chemins de Fer, the French national railroad.
ESP is an initialism for extrasensory perception.
acronyms are abbreviated forms made from the initial letters or parts of other words (in a name or phrase) which may be pronounced as a word
NOAA is an acronym made from the initial letters of the National Oceanic and Atmospheric Administration in the United States.
Some companies have adopted what used to be an initialism as their company name. In these cases, the new name of the company is the letters (for example, Ecma) and the word is no longer considered an abbreviation.
supported by users' assistive technologies as well as the accessibility features in browsers and other user agents
To qualify as an accessibility-supported use of a Web content technology (or feature of a technology), both 1 and 2 must be satisfied for a Web content technology (or feature):
The way that the Web content technology is used must be supported by users' assistive technology (AT). This means that the way that the technology is used has been tested for interoperability with users' assistive technology in the human language(s) of the content,
AND
The Web content technology must have accessibility-supported user agents that are available to users. This means that at least one of the following four statements is true:
The technology is supported natively in widely-distributed user agents that are also accessibility supported (such as HTML and CSS);
OR
The technology is supported in a widely-distributed plug-in that is also accessibility supported;
OR
The content is available in a closed environment, such as a university or corporate network, where the user agent required by the technology and used by the organization is also accessibility supported;
OR
The user agent(s) that support the technology are accessibility supported and are available for download or purchase in a way that:
The WCAG Working group and the W3C do not specify which or how much support by assistive technologies there must be for a particular use of a Web technology in order for it to be classified as accessibility supported. (See Level of Assistive Technology Support Needed for "Accessibility Support".)
Web technologies can be used in ways that are not accessibility supported as long as they are not relied upon and the page as a whole meets the conformance requirements, including Conformance Criterion 4 and Conformance Criterion 5, are met.
When a Web Technology is used in a way that is "accessibility supported," it does not imply that the entire technology or all uses of the technology are supported. Most technologies, including HTML, lack support for at least one feature or use. Pages conform to WCAG only if the uses of the technology that are accessibility supported can be relied upon to meet WCAG requirements.
When citing Web content technologies that have multiple versions, the version(s) supported should be specified.
One way for authors to locate uses of a technology that are accessibility supported would be to consult compilations of uses that are documented to be accessibility supported. (See Understanding Accessibility-Supported Web Technology Uses.) Authors, companies, technology vendors, or others may document accessibility-supported ways of using Web content technologies. However, all ways of using technologies in the documentation would need to meet the definition of accessibility-supported Web content technologies above.
document including correctly sequenced text descriptions of time-based visual and auditory information and providing a means for achieving the outcomes of any time-based interaction
A screenplay used to create the synchronized media content would meet this definition only if it was corrected to accurately represent the final synchronized media after editing.
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)
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.
picture created by a spatial arrangement of characters or glyphs (typically from the 95 printable characters defined by ASCII)
hardware and/or software that acts as a user agent, or along with a mainstream user agent, to provide functionality to meet the requirements of users with disabilities that go beyond those offered by mainstream user agents
functionality provided by assistive technology includes alternative presentations (e.g., as synthesized speech or magnified content), alternative input methods (e.g., voice), additional navigation or orientation mechanisms, and content transformations (e.g., to make tables more accessible).
Assistive technologies often communicate data and messages with mainstream user agents by using and monitoring APIs.
The distinction between mainstream user agents and assistive technologies is not absolute. Many mainstream user agents provide some features to assist individuals with disabilities. The basic difference is that mainstream user agents target broad and diverse audiences that usually include people with and without disabilities. Assistive technologies target narrowly defined populations of users with specific disabilities. The assistance provided by an assistive technology is more specific and appropriate to the needs of its target users. The mainstream user agent may provide important functionality to assistive technologies like retrieving Web content from program objects or parsing markup into identifiable bundles.
Assistive technologies that are important in the context of this document include the following:
the technology of sound reproduction
Audio can be created synthetically (including speech synthesis), recorded from real world sounds, or both.
narration added to the soundtrack to describe important visual details that cannot be understood from the main soundtrack alone
Audio description of video provides information about actions, characters, scene changes, on-screen text, and other visual content.
In standard audio description, narration is added during existing pauses in dialogue. (See also extended audio description.)
Where all of the video information is already provided in existing audio, no additional audio description is necessary.
Also called "video description" and "descriptive narration."
a time-based presentation that contains only audio (no video and no interaction)
switch back and forth between two visual states in a way that is meant to draw attention
See also flash. It is possible for something to be large enough and blink brightly enough at the right frequency to be also classified as a flash.
more than one sentence of text
initialism for "Completely Automated Public Turing test to tell Computers and Humans Apart"
CAPTCHA tests often involve asking the user to type in text that is displayed in an obscured image or audio file.
A Turing test is any system of tests designed to differentiate a human from a computer. It is named after famed computer scientist Alan Turing. The term was coined by researchers at Carnegie Mellon University.
synchronized visual and/or text alternative for both speech and non-speech audio information needed to understand the media content
Captions are similar to dialogue-only subtitles except captions convey not only the content of spoken dialogue, but also equivalents for non-dialogue audio information needed to understand the program content, including sound effects, music, laughter, speaker identification and location.
Closed Captions are equivalents that can be turned on and off with some players.
Open Captions are any captions that cannot be turned off. For example, if the captions are visual equivalent images of text embedded in video.
Captions should not obscure or obstruct relevant information in the video.
In some countries, captions are called subtitles.
Audio descriptions can be, but do not need to be, captioned since they are descriptions of information that is already presented visually.
major changes in the content of the Web page that, if made without user awareness, can disorient users who are not able to view the entire page simultaneously
Changes in context include changes of:
A change of content is not always a change of context. Changes in content, such as an expanding outline, dynamic menu, or a tab control do not necessarily change the context, unless they also change one of the above (e.g., focus).
Opening a new window, moving focus to a different component, going to a new page (including anything that would look to a user as if they had moved to a new page) or significantly re-arranging the content of a page are examples of changes of context.
satisfying all the requirements of a given standard, guideline or specification
version that
for which at least one of the following is true:
In this definition, "can only be reached" means that there is some mechanism, such as a conditional redirect, that prevents a user from "reaching" (loading) the non-conforming page unless the user had just come from the conforming version.
The alternate version does not need to be matched page for page with the original (e.g., the conforming alternate version may consist of multiple pages).
If multiple language versions are available, then conforming alternate versions are required for each language offered.
Alternate versions may be provided to accommodate different technology environments or user groups. Each version should be as conformant as possible. One version would need to be fully conformant in order to meet conformance requirement 1.
The conforming alternative version does not need to reside within the scope of conformance, or even on the same Web site, as long as it is as freely available as the non-conforming version.
Alternate versions should not be confused with supplementary content, which support the original page and enhance comprehension.
Setting user preferences within the content to produce a conforming version is an acceptable mechanism for reaching another version as long as the method used to set the preferences is accessibility supported.
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
help text that provides information related to the function currently being performed
Clear labels can act as context-sensitive help.
(L1 + 0.05) / (L2 + 0.05), where
Contrast ratios can range from 1 to 21 (commonly written 1:1 to 21:1).
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.
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.
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.
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.
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.
any sequence where words and paragraphs are presented in an order that does not change the meaning of the content
visual angle of about 0.0213 degrees
A CSS pixel is the canonical unit of measure for all lengths and measurements in CSS. This unit is density-independent, and distinct from actual hardware pixels present in a display. User agents and operating systems should ensure that a CSS pixel is set as closely as possible to the CSS Values and Units Module Level 3 reference pixel [css3-values], which takes into account the physical dimensions of the display and the assumed viewing distance (factors that cannot be determined by content authors).
platform event that occurs when the trigger stimulus of a pointer is depressed
The down-event may have different names on different platforms, such as "touchstart" or "mousedown".
a sudden, unexpected situation or occurrence that requires immediate action to preserve health, safety, or property
if removed, would fundamentally change the information or functionality of the content, and information and functionality cannot be achieved in another way that would conform
audio description that is added to an audiovisual presentation by pausing the video so that there is time to add additional description
This technique is only used when the sense of the video would be lost without the additional audio description and the pauses between dialogue/narration are too short.
a pair of opposing changes in relative luminance that can cause seizures in some people if it is large enough and in the right frequency range
See general flash and red flash thresholds for information about types of flash that are not allowed.
See also blinking.
processes and outcomes achievable through user action
a flash or rapidly changing image sequence is below the threshold (i.e., content passes) if any of the following are true:
where:
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.
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.)
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.
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]
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).
language that is spoken, written or signed (through visual or tactile means) to communicate with humans
See also sign language.
phrase whose meaning cannot be deduced from the meaning of the individual words and the specific words cannot be changed without losing the meaning
idioms cannot be translated directly, word for word, without losing their (cultural or language-dependent) meaning.
In English, "spilling the beans" means "revealing a secret." However, "knocking over the beans" or "spilling the vegetables" does not mean the same thing.
In Japanese, the phrase "さじを投げる" literally translates into "he throws a spoon," but it means that there is nothing he can do and finally he gives up.
In Dutch, "Hij ging met de kippen op stok" literally translates into "He went to roost with the chickens," but it means that he went to bed early.
text that has been rendered in a non-text form (e.g., an image) in order to achieve a particular visual effect
This does not include text that is part of a picture that contains significant other visual content.
A person's name on a nametag in a photograph.
for information purposes and not required for conformance
Content required for conformance is referred to as "normative."
information provided by the user that is not accepted
This includes:
words used in a particular way by people in a particular field
The word StickyKeys is jargon from the field of assistive technology/accessibility.
interface used by software to obtain keystroke input
A keyboard interface allows users to provide keystroke input to programs even if the native technology does not contain a keyboard.
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.
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.
alternative means of triggering an action by the pressing of one or more keys
text or other component with a text alternative that is presented to a user to identify a component within Web content
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.
The term label is not limited to the label element in HTML.
with at least 18 point or 14 point bold or font size that would yield equivalent size for Chinese, Japanese and Korean (CJK) fonts
Fonts with extraordinarily thin strokes or unusual features and characteristics that reduce the familiarity of their letter forms are harder to read, especially at lower contrast levels.
Font size is the size when the content is delivered. It does not include resizing that may be done by a user.
The actual size of the character that a user sees is dependent both on the author-defined size and the user's display or user-agent settings. For many mainstream body text fonts, 14 and 18 point is roughly equivalent to 1.2 and 1.5 em or to 120% or 150% of the default size for body text (assuming that the body font is 100%), but authors would need to check this for the particular fonts in use. When fonts are defined in relative units, the actual point size is calculated by the user agent for display. The point size should be obtained from the user agent, or calculated based on font metrics as the user agent does, when evaluating this success criterion. Users who have low vision would be responsible for choosing appropriate settings.
When using text without specifying the font size, the smallest font size used on major browsers for unspecified text would be a reasonable size to assume for the font. If a level 1 heading is rendered in 14pt bold or higher on major browsers, then it would be reasonable to assume it is large text. Relative scaling can be calculated from the default sizes in a similar fashion.
The 18 and 14 point sizes for roman texts are taken from the minimum size for large print (14pt) and the larger standard font size (18pt). For other fonts such as CJK languages, the "equivalent" sizes would be the minimum large print size used for those languages and the next larger standard large print size.
transactions where the person incurs a legally binding obligation or benefit
A marriage license, a stock trade (financial and legal), a will, a loan, adoption, signing up for the army, a contract of any type, etc.
nature of the result obtained by activating a hyperlink
information captured from a real-world event and transmitted to the receiver with no more than a broadcast delay
A broadcast delay is a short (usually automated) delay, for example used in order to give the broadcaster time to cue or censor the audio (or video) feed, but not sufficient to allow significant editing.
If information is completely computer generated, it is not live.
the two or three year period of education that begins after completion of six years of school and ends nine years after the beginning of primary education
This definition is based on the International Standard Classification of Education [UNESCO].
process or technique for achieving a result
The mechanism may be explicitly provided in the content, or may be relied upon to be provided by either the platform or by user agents, including assistive technologies.
The mechanism needs to meet all success criteria for the conformance level claimed.
media that presents no more information than is already presented in text (directly or via text alternatives)
A media alternative for text is provided for those who benefit from alternate representations of text. Media alternatives for text may be audio-only, video-only (including sign-language video), or audio-video.
addition of steps between conditions to create the illusion of movement or to give a sense of a smooth transition
For example, an element which moves into place or changes size while appearing is considered to be animated. An element which appears instantly without transitioning is not using animation. Motion animation does not include changes of color, blurring or opacity.
text by which software can identify a component within Web content to the user
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.
This is unrelated to the name attribute in HTML.
navigated in the order defined for advancing focus (from one element to the next) using a keyboard interface
any content that is not a sequence of characters that can be programmatically determined or where the sequence is not expressing something in human language
This includes ASCII Art (which is a pattern of characters), emoticons, leetspeak (which uses character substitution), and images representing text
required for conformance
One may conform in a variety of well-defined ways to this document.
Content identified as "informative" or "non-normative" is never required for conformance.
on the most common sized desktop/laptop display with the viewport maximized
Since people generally keep their computers for several years, it is best not to rely on the latest desktop/laptop display resolutions but to consider the common desktop/laptop display resolutions over the course of several years when making this evaluation.
stopped by user request and not resumed until requested by user
input device that can target a specific coordinate (or set of coordinates) on a screen, such as a mouse, pen, or touch contact
See also Pointer Events pointer definition [pointerevents].
information that is not live
rendering of the content in a form to be perceived by users
six year time period that begins between the ages of five and seven, possibly without any previous education
This definition is based on the International Standard Classification of Education [UNESCO].
series of user actions where each action is required in order to complete an activity
Successful use of a series of Web pages on a shopping site requires users to view alternative products, prices and offers, select products, submit an order, provide shipping information and provide payment information.
An account registration page requires successful completion of a Turing test before the registration form can be accessed.
determined by software from author-supplied data provided in a way that different user agents, including assistive technologies, can extract and present this information to users in different modalities
Determined in a markup language from elements and attributes that are accessed directly by commonly available assistive technology.
Determined from technology-specific data structures in a non-markup language and exposed to assistive technology via an accessibility API that is supported by commonly available assistive technology.
additional information that can be programmatically determined from relationships with a link, combined with the link text, and presented to users in different modalities
In HTML, information that is programmatically determinable from a link in English includes text that is in the same paragraph, list, or table cell as the link or in a table header cell that is associated with the table cell that contains the link.
Since screen readers interpret punctuation, they can also provide the context from the current sentence, when the focus is on a link in that sentence.
set by software using methods that are supported by user agents, including assistive technologies
serving only an aesthetic purpose, providing no information, and having no functionality
Text is only purely decorative if the words can be rearranged or substituted without changing their purpose.
The cover page of a dictionary has random words in very light text in the background.
event that a) occurs at the same time as the viewing and b) is not completely generated by the content
A Webcast of a live performance (occurs at the same time as the viewing and is not prerecorded).
An on-line auction with people bidding (occurs at the same time as the viewing).
Live humans interacting in a virtual world using avatars (is not completely generated by the content and occurs at the same time as the viewing).
perceivable, programmatically determined section of content
In HTML, any area designated with a landmark role would be a region.
meaningful associations between distinct pieces of content
the relative brightness of any point in a colorspace, normalized to 0 for darkest black and 1 for lightest white
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:
and RsRGB, GsRGB, and BsRGB are defined as:
The "^" character is the exponentiation operator. (Formula taken from [sRGB] and [IEC-4WD]).
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.
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).
Tools are available that automatically do the calculations when testing contrast and flash.
A MathML version of the relative luminance definition is available.
the content would not conform if that technology is turned off or is not supported
text or number by which software can identify the function of a component within Web content
A number that indicates whether an image functions as a hyperlink, command button, or check box.
same result when used
A submit "search" button on one Web page and a "find" button on another Web page may both have a field to enter a term and list topics in the Web site related to the term submitted. In this case, they would have the same functionality but would not be labeled consistently.
same position relative to other items
Items are considered to be in the same relative order even if other items are inserted or removed from the original order. For example, expanding navigation menus may insert an additional level of detail or a secondary navigation section may be inserted into the reading order.
the success criterion does not evaluate to 'false' when applied to the page
a self-contained portion of written content that deals with one or more related topics or thoughts
A section may consist of one or more paragraphs and include graphics, tables, lists and sub-sections.
collection of web pages that share a common purpose and that are created by the same author, group or organization
Examples include a publication which is split across multiple Web pages, where each page contains one chapter or other significant section of the work. The publication is logically a single contiguous unit, and contains navigation features that enable access to the full set of pages.
Different language versions would be considered different sets of Web pages.
a language using combinations of movements of the hands and arms, facial expressions, or body positions to convey meaning
translation of one language, generally a spoken language, into a sign language
True sign languages are independent languages that are unrelated to the spoken language(s) of the same country or region.
pointer input that operates with one point of contact with the screen, including single taps and clicks, double-taps and clicks, long presses, and path-based gestures
a sensory experience that is not purely decorative and does not primarily convey important information or perform a function
Examples include a performance of a flute solo, works of visual art etc.
dynamic property expressing characteristics of a user interface component that may change in response to user action or automated processes
States do not affect the nature of the component, but represent data associated with the component or user interaction possibilities. Examples include focus, hover, select, press, check, visited/unvisited, and expand/collapse.
change in content that is not a change of context, and that provides information to the user on the success or results of an action, on the waiting state of an application, on the progress of a process, or on the existence of errors
property whose value determines the presentation (e.g. font, color, size, location, padding, volume, synthesized speech prosody) of content elements as they are rendered (e.g. onscreen, via loudspeaker, via braille display) by user agents
Style properties can have several origins:
additional content that illustrates or clarifies the primary content
An audio version of a Web page.
An illustration of a complex process.
A paragraph summarizing the major outcomes and recommendations made in a research study.
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
region of the display that will accept a pointer action, such as the interactive area of a user interface component
If two or more touch targets are overlapping, the overlapping area should not be included in the measurement of the target size, except when the overlapping targets perform the same action or open the same page.
mechanism for encoding instructions to be rendered, played or executed by user agents
As used in these guidelines "Web Technology" and the word "technology" (when used alone) both refer to Web Content Technologies.
Web content technologies may include markup languages, data formats, or programming languages that authors may use alone or in combination to create end-user experiences that range from static Web pages to synchronized media presentations to dynamic Web applications.
Some common examples of Web content technologies include HTML, CSS, SVG, PNG, PDF, Flash, and JavaScript.
sequence of characters that can be programmatically determined, where the sequence is expressing something in human language
Text that is programmatically associated with non-text content or referred to from text that is programmatically associated with non-text content. Programmatically associated text is text whose location can be programmatically determined from the non-text content.
An image of a chart is described in text in the paragraph after the chart. The short text alternative for the chart indicates that a description follows.
Refer to Understanding Text Alternatives for more information.
platform event that occurs when the trigger stimulus of a pointer is released
The up-event may have different names on different platforms, such as "touchend" or "mouseup".
words used in such a way that requires users to know exactly which definition to apply in order to understand the content correctly
The term "gig" means something different if it occurs in a discussion of music concerts than it does in article about computer hard drive space, but the appropriate definition can be determined from context. By contrast, the word "text" is used in a very specific way in WCAG 2.1, so a definition is supplied in the glossary.
any software that retrieves and presents Web content for users
Web browsers, media players, plug-ins, and other programs — including assistive technologies — that help in retrieving, rendering, and interacting with Web content.
data that is intended to be accessed by users
This does not refer to such things as Internet logs and search engine monitoring data.
Name and address fields for a user's account.
a part of the content that is perceived by users as a single control for a distinct function
Multiple user interface components may be implemented as a single programmatic element. Components here is not tied to programming techniques, but rather to what the user perceives as separate controls.
User interface components include form elements and links as well as components generated by scripts.
What is meant by "component" or "user interface component" here is also sometimes called "user interface element".
An applet has a "control" that can be used to move through content by line or page or random access. Since each of these would need to have a name and be settable independently, they would each be a "user interface component."
any continuous period of time where no user actions occur
The method of tracking will be determined by the web site or application.
the technology of moving or sequenced pictures or images
Video can be made up of animated or photographic images, or both.
a time-based presentation that contains only video (no audio and no interaction)
object in which the user agent presents content
The user agent presents content through one or more viewports. Viewports include windows, frames, loudspeakers, and virtual magnifying glasses. A viewport may contain another viewport (e.g., nested frames). Interface components created by the user agent such as prompts, menus, and alerts are not viewports.
This definition is based on User Agent Accessibility Guidelines 1.0 Glossary [UAAG10].
the font, size, color, and background can be set
a non-embedded resource obtained from a single URI using HTTP plus any other resources that are used in the rendering or intended to be rendered together with it by a user agent
Although any "other resources" would be rendered together with the primary resource, they would not necessarily be rendered simultaneously with each other.
For the purposes of conformance with these guidelines, a resource must be "non-embedded" within the scope of conformance to be considered a Web page.
A Web resource including all embedded images and media.
A Web mail program built using Asynchronous JavaScript and XML (AJAX). The program lives entirely at http://example.com/mail, but includes an inbox, a contacts area and a calendar. Links or buttons are provided that cause the inbox, contacts, or calendar to display, but do not change the URI of the page as a whole.
A customizable portal site, where users can choose content to display from a set of different content modules.
When you enter "http://shopping.example.com/" in your browser, you enter a movie-like interactive shopping environment where you visually move around in a store dragging products off of the shelves around you and into a visual shopping cart in front of you. Clicking on a product causes it to be demonstrated with a specification sheet floating alongside. This might be a single-page Web site or just one page within a Web site.
This section contains a listing of common user interface component input purposes. The terms below are not keywords that must be used, but instead represent purposes that must be captured in the taxonomy adopted by a webpage. Where applicable, authors mark up controls with the chosen taxonomy to indicate the semantic purpose. This provides the potential for user agents and assistive technologies to apply personalized presentations that can enable more people to understand and use the content.
The list of input type purposes is based on the control purposes defined in the HTML 5.2 Autofill field section, but it is important to understand that a different technology may have some or all of the same concepts defined in its specification and only the concepts that are mapped to the meanings below are required.
The following input control purposes are intended to relate to the user of the content and pertain only to information related to that individual.
This section shows changes proposed for WCAG 2.1 since its publication as a W3C Recommendation. These changes are also recorded as errata.
The full commit history to WCAG 2.1 is available.
No changes have been made to date.
Additional information about participation in the Accessibility Guidelines Working Group (AG WG) can be found on the Working Group home page.
Paul Adam, Jenae Andershonis, Wilhelm Joys Andersen, Andrew Arch, Avi Arditti, Aries Arditi, Mark Barratt, Mike Barta, Sandy Bartell, Kynn Bartlett, Chris Beer, Charles Belov, Marco Bertoni, Harvey Bingham, Chris Blouch, Paul Bohman, Frederick Boland, Denis Boudreau, Patrice Bourlon, Andy Brown, Dick Brown, Doyle Burnett, Raven Calais, Ben Caldwell, Tomas Caspers, Roberto Castaldo, Sofia Celic-Li, Sambhavi Chandrashekar, Mike Cherim, Jonathan Chetwynd, Wendy Chisholm, Alan Chuter, David M Clark, Joe Clark, Darcy Clarke, James Coltham, Earl Cousins, James Craig, Tom Croucher, Pierce Crowell, Nir Dagan, Daniel Dardailler, Geoff Deering, Sébastien Delorme, Pete DeVasto, Iyad Abu Doush, Sylvie Duchateau, Cherie Eckholm, Roberto Ellero, Don Evans, Gavin Evans, Neal Ewers, Steve Faulkner, Bengt Farre, Lainey Feingold, Wilco Fiers, Michel Fitos, Alan J. Flavell, Nikolaos Floratos, Kentarou Fukuda, Miguel Garcia, P.J. Gardner, Alistair Garrison, Greg Gay, Becky Gibson, Al Gilman, Kerstin Goldsmith, Michael Grade, Karl Groves, Loretta Guarino Reid, Jon Gunderson, Emmanuelle Gutiérrez y Restrepo, Brian Hardy, Eric Hansen, Benjamin Hawkes-Lewis, Sean Hayes, Shawn Henry, Hans Hillen, Donovan Hipke, Bjoern Hoehrmann, Allen Hoffman, Chris Hofstader, Yvette Hoitink, Martijn Houtepen, Carlos Iglesias, Richard Ishida, Jonas Jacek, Ian Jacobs, Phill Jenkins, Barry Johnson, Duff Johnson, Jyotsna Kaki, Shilpi Kapoor, Leonard R. Kasday, Kazuhito Kidachi, Ken Kipness, Johannes Koch, Marja-Riitta Koivunen, Preety Kumar, Kristjan Kure, Andrew LaHart, Gez Lemon, Chuck Letourneau, Aurélien Levy, Harry Loots, Scott Luebking, Tim Lacy, Jim Ley, Alex Li, William Loughborough, N Maffeo, Mark Magennis, Kapsi Maria, Luca Mascaro, Matt May, Sheena McCullagh, Liam McGee, Jens Oliver Meiert, Niqui Merret, Jonathan Metz, Alessandro Miele, Steven Miller, Mathew J Mirabella, Matt May, Marti McCuller, Sorcha Moore, Charles F. Munat, Robert Neff, Charles Nevile, Liddy Nevile, Dylan Nicholson, Bruno von Niman, Tim Noonan, Sebastiano Nutarelli, Graham Oliver, Sean B. Palmer, Devarshi Pant, Nigel Peck, Anne Pemberton, David Poehlman, Ian Pouncey, Charles Pritchard, Kerstin Probiesch, W Reagan, Adam Victor Reed, Chris Reeve, Chris Ridpath, Lee Roberts, Mark Rogers, Raph de Rooij, Gregory J. Rosmaita, Matthew Ross, Sharron Rush, Joel Sanda, Janina Sajka, Roberto Scano, Gordon Schantz, Tim van Schie, Wolf Schmidt, Stefan Schnabel, Cynthia Shelly, Glenda Sims, John Slatin, Becky Smith, Jared Smith, Andi Snow-Weaver, Neil Soiffer, Mike Squillace, Michael Stenitzer, Diane Stottlemyer, Christophe Strobbe, Sarah J Swierenga, Jim Thatcher, Terry Thompson, Justin Thorp, David Todd, Mary Utt, Jean Vanderdonckt, Carlos A Velasco, Eric Velleman, Gijs Veyfeyken, Dena Wainwright, Paul Walsch, Daman Wandke, Richard Warren, Elle Waters, Takayuki Watanabe, Gian Wild, David Wooley, Wu Wei, Kenny Zhang, Leona Zumbo.
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