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Introduction To Website Content Accessibility Guidelines (WCAG 2.1)

World Wide Web Consortium Logo - WCAG guidelines

The original and complete set of website accessibility guidelines (WCAG 2.1) can be found at: https://www.w3.org/TR/WCAG21/ This article is only intended to be an introduction and point of reference for the complete version.

This version:
https://www.w3.org/TR/2018/REC-WCAG21-20180605/
Latest editor’s draft:
https://w3c.github.io/wcag/21/guidelines/
Implementation report:
https://www.w3.org/WAI/WCAG21/implementation-report/
Previous version:
https://www.w3.org/TR/2018/PR-WCAG21-20180424/
Previous Recommendation:
https://www.w3.org/TR/2008/REC-WCAG20-20081211/
Editors:
Andrew Kirkpatrick (Adobe)
Joshue O Connor (Invited Expert, InterAccess)
Alastair Campbell (Nomensa)
Michael Cooper (W3C)
WCAG 2.0 Editors (until December 2008):
Ben Caldwell (Trace R&D Center, University of Wisconsin-Madison)
Loretta Guarino Reid (Google, Inc.)
Gregg Vanderheiden (Trace R&D Center, University of Wisconsin-Madison)
Wendy Chisholm (W3C)
John Slatin (Accessibility Institute, University of Texas at Austin)
Jason White (University of Melbourne)
Please check the errata for any errors or issues reported since publication.

See also translations.

This document is also available in non-normative formats, available from Alternate Versions of Web Content Accessibility Guidelines 2.1.

Copyright © 2017-2018 W3C® (MIT, ERCIM, Keio, Beihang). W3C liability, trademark and document use rules apply.

Abstract
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, photo-sensitivity, 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 [WCAG 2.0], 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.

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 https://www.w3.org/TR/.

This is a Recommendation of WCAG 2.1 by the Accessibility Guidelines Working Group.

This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C’s role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.

By publishing this Recommendation, W3C expects the functionality specified in this Recommendation will not be affected by changes to CSS Values and Units Module Level 3 or by Pointer Events Level 2. The Working Group will continue to track these specifications.

To comment, file an issue in the W3C WCAG GitHub repository. 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). Comments received on the WCAG 2.1 Recommendation cannot result in changes to this version of t

he guidelines, but may be addressed in errata or future versions of WCAG. The Working Group does not plan to make formal responses to comments. A list of issues filed as well as Archives of the AG WG mailing list discussions are publicly available, and future work undertaken by the Working Group may address comments received on this document.

This document was published by the Accessibility Guidelines Working Group as a Recommendation.

Please see the Working Group’s implementation report.

This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C’s role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.

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.

Table Of Contents
Abstract
Status of This Document
Introduction
0.1 Background on WCAG 2
0.2 WCAG 2 Layers of Guidance
0.3 WCAG 2.1 Supporting Documents
0.4 Requirements for WCAG 2.1
0.5 Comparison with WCAG 2.0
0.5.1 New Features in WCAG 2.1
0.5.2 Numbering in WCAG 2.1
0.5.3 Conformance to WCAG 2.1
0.6 Later Versions of Accessibility Guidelines
1.Perceivable
1.1 Text Alternatives
1.1.1 Non-text Content
1.2 Time-based Media
1.2.1 Audio-only and Video-only (Prerecorded)
1.2.2 Captions (Prerecorded)
1.2.3 Audio Description or Media Alternative (Prerecorded)
1.2.4 Captions (Live)
1.2.5 Audio Description (Prerecorded)
1.2.6 Sign Language (Prerecorded)
1.2.7 Extended Audio Description (Prerecorded)
1.2.8 Media Alternative (Prerecorded)
1.2.9 Audio-only (Live)
1.3 Adaptable
1.3.1 Info and Relationships
1.3.2 Meaningful Sequence
1.3.3 Sensory Characteristics
1.3.4 Orientation
1.3.5 Identify Input Purpose
1.3.6 Identify Purpose
1.4 Distinguishable
1.4.1 Use of Color
1.4.2 Audio Control
1.4.3 Contrast (Minimum)
1.4.4 Resize text
1.4.5 Images of Text
1.4.6 Contrast (Enhanced)
1.4.7 Low or No Background Audio
1.4.8 Visual Presentation
1.4.9 Images of Text (No Exception)
1.4.10 Reflow
1.4.11 Non-text Contrast
1.4.12 Text Spacing
1.4.13 Content on Hover or Focus
2.Operable
2.1 Keyboard Accessible
2.1.1 Keyboard
2.1.2 No Keyboard Trap
2.1.3 Keyboard (No Exception)
2.1.4 Character Key Shortcuts
2.2 Enough Time
2.2.1 Timing Adjustable
2.2.2 Pause, Stop, Hide
2.2.3 No Timing
2.2.4 Interruptions
2.2.5 Re-authenticating
2.2.6 Timeouts
2.3 Seizures and Physical Reactions
2.3.1 Three Flashes or Below Threshold
2.3.2 Three Flashes
2.3.3 Animation from Interactions
2.4 Navigable
2.4.1 Bypass Blocks
2.4.2 Page Titled
2.4.3 Focus Order
2.4.4 Link Purpose (In Context)
2.4.5 Multiple Ways
2.4.6 Headings and Labels
2.4.7 Focus Visible
2.4.8 Location
2.4.9 Link Purpose (Link Only)
2.4.10 Section Headings
2.5 Input Modalities
2.5.1 Pointer Gestures
2.5.2 Pointer Cancellation
2.5.3 Label in Name
2.5.4 Motion Actuation
2.5.5 Target Size
2.5.6 Concurrent Input Mechanisms
3.Understandable
3.1 Readable
3.1.1 Language of Page
3.1.2 Language of Parts
3.1.3 Unusual Words
3.1.4 Abbreviations
3.1.5 Reading Level
3.1.6 Pronunciation
3.2 Predictable
3.2.1 On Focus
3.2.2 On Input
3.2.3 Consistent Navigation
3.2.4 Consistent Identification
3.2.5 Change on Request
3.3 Input Assistance
3.3.1 Error Identification
3.3.2 Labels or Instructions
3.3.3 Error Suggestion
3.3.4 Error Prevention (Legal, Financial, Data)
3.3.5 Help
3.3.6 Error Prevention (All)
4.Robust
4.1 Compatible
4.1.1 Parsing
4.1.2 Name, Role, Value
4.1.3 Status Messages
5.Conformance
5.1 Interpreting Normative Requirements
5.2 Conformance Requirements
5.2.1 Conformance Level
5.2.2 Full pages
5.2.3 Complete processes
5.2.4 Only Accessibility-Supported Ways of Using Technologies
5.2.5 Non-Interference
5.3 Conformance Claims (Optional)
5.3.1 Required Components of a Conformance Claim
5.3.2 Optional Components of a Conformance Claim
5.4 Statement of Partial Conformance – Third Party Content
5.5 Statement of Partial Conformance – Language
6.Glossary
7.Input Purposes for User Interface Components
A. Acknowledgments
A.1 Participants of the AG WG active in the development of this document:
A.2 Other previously active WCAG WG participants and other contributors to WCAG 2.0, WCAG 2.1, or supporting resources
A.3 Enabling funders
B.References
B.1 Normative references
B.2 Informative references
Introduction
This section is non-normative.

0.1 Background on WCAG 2§
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:

Essential Components of Web Accessibility
User Agent Accessibility Guidelines (UAAG) Overview
Authoring Tool Accessibility Guidelines (ATAG) Overview
0.2 WCAG 2 Layers of Guidance§
The individuals and organizations that use WCAG vary widely and include Web designers and developers, policy makers, purchasing agents, teachers, and students. In order to meet the varying needs of this audience, several layers of guidance are provided including overall principles, general guidelines, testable success criteria and a rich collection of sufficient techniques, advisory techniques, and documented common failures with examples, resource links and code.

Principles – At the top are four principles that provide the foundation for Web accessibility: perceivable, operable, understandable, and robust. See also Understanding the Four Principles of Accessibility.

Guidelines – Under the principles are guidelines. The 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 2.0 to be used where requirements and conformance testing are necessary such as in design specification, purchasing, regulation, and contractual agreements. In order to meet the needs of different groups and different situations, three levels of conformance are defined: A (lowest), AA, and AAA (highest). Additional information on WCAG levels can be found in Understanding Levels of Conformance.

Sufficient and Advisory Techniques – For each of the guidelines and success criteria in the WCAG 2.0 document itself, the working group has also documented a wide variety of techniques. The techniques are informative and fall into two categories: those that are sufficient for meeting the success criteria and those that are advisory. The advisory techniques go beyond what is required by the individual success criteria and allow authors to better address the guidelines. Some advisory techniques address accessibility barriers that are not covered by the testable success criteria. Where common failures are known, these are also documented. See also Sufficient and Advisory Techniques in Understanding WCAG 2.0.

All of these layers of guidance (principles, guidelines, success criteria, and sufficient and advisory techniques) work together to provide guidance on how to make content more accessible. Authors are encouraged to view and apply all layers that they are able to, including the advisory techniques, in order to best address the needs of the widest possible range of users.

Note that even content that conforms at the highest level (AAA) will not be accessible to individuals with all types, degrees, or combinations of disability, particularly in the cognitive language and learning areas. Authors are encouraged to consider the full range of techniques, including the advisory techniques, as well as to seek relevant advice about current best practice to ensure that Web content is accessible, as far as possible, to this community. Metadata may assist users in finding content most suitable for their needs.

0.3 WCAG 2.1 Supporting Documents§
The WCAG 2.0 document is designed to meet the needs of those who need a stable, referenceable technical standard. Other documents, called supporting documents, are based on the WCAG 2.0 document and address other important purposes, including the ability to be updated to describe how WCAG would be applied with new technologies. Supporting documents include:

How to Meet WCAG 2.1 – 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 2.0 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.

0.4 Requirements for WCAG 2.1§
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.

0.5 Comparison with WCAG 2.0§
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:

0.5.1 New Features in WCAG 2.1§
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:

1.3.4 Orientation (AA)
1.3.5 Identify Input Purpose (AA)
1.3.6 Identify Purpose (AAA)
1.4.10 Reflow (AA)
1.4.11 Non-Text Contrast (AA)
1.4.12 Text Spacing (AA)
1.4.13 Content on Hover or Focus (AA)
2.1.4 Character Key Shortcuts (A)
2.2.6 Timeouts (AAA)
2.3.3 Animation from Interactions (AAA)
2.5.1 Pointer Gestures (A)
2.5.2 Pointer Cancellation (A)
2.5.3 Label in Name (A)
2.5.4 Motion Actuation (A)
2.5.5 Target Size (AAA)
2.5.6 Concurrent Input Mechanisms (AAA)
4.1.3 Status Messages (AA)
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.

0.5.2 Numbering in WCAG 2.1§
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.

0.5.3 Conformance to WCAG 2.1§
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.

0.6 Later Versions of Accessibility Guidelines§
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.

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