W3C

Web Content Accessibility Guidelines 2.0

W3C Working Draft 18 April 2003

This version:
http://www.w3.org/WAI/GL/WCAG20/WD-WCAG20-20030418.html
Latest version:
http://www.w3.org/WAI/GL/WCAG20/
Previous version:
http://www.w3.org/WAI/GL/WCAG20/WD-WCAG20-20030108.html
Editors:
Ben Caldwell, Trace R&D Center
Wendy Chisholm, W3C
Jason White, University of Melbourne
Gregg Vanderheiden, Trace R&D Center

Abstract

W3C published the Web Content Accessibility Guidelines 1.0 (WCAG 1.0) as a Recommendation in May 1999. This Working Draft for version 2.0 builds on WCAG 1.0. It has the same aim: to explain how to make Web content accessible to people with disabilities and to define target levels of accessibility. Incorporating feedback on WCAG 1.0, this Working Draft of version 2.0 focuses on checkpoints. It attempts to apply checkpoints to a wider range of technologies and to use wording that may be understood by a more varied audience.

Status of this document

This document is prepared by the Web Content Accessibility Guidelines Working Group (WCAG WG) to show how more generalized (less HTML-specific) WCAG checkpoints might read. This draft is not yet based on consensus of the WCAG Working Group nor has it gone through W3C process. This Working Draft in no way supersedes WCAG 1.0.

Please refer to "Issue Tracking for WCAG 2.0 Working Draft" for a list of open issues related to this Working Draft. The "History of Changes to WCAG 2.0 Working Drafts" is also available.

This is a draft document and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". A list of current W3C Recommendations and other technical documents is available.

The Working Group welcomes comments on this document at w3c-wai-gl@w3.org. The archives for this list are publicly available.

Patent disclosures relevant to this specification may be found on the WCAG Working Group's patent disclosure page in conformance with W3C policy.

This document has been produced as part of the W3C Web Accessibility Initiative (WAI). The goals of the WCAG WG are discussed in the Working Group charter. The WCAG WG is part of the WAI Technical Activity.


Table of Contents


Introduction

Purpose

This document outlines design principles for creating accessible Web content. When these principles are ignored, individuals with disabilities may not be able to access the content at all, or they may be able to do so only with great difficulty. When these principles are employed, they also make Web content accessible to a variety of Web-enabled devices, such as phones, handheld devices, kiosks, network appliances, etc. By making content accessible to a variety of devices, that content will also be accessible to people in a variety of situations.

The design principles in this document represent broad concepts that apply to all Web-based content. They are not specific to HTML, XML, or any other technology. This approach was taken so that the design principles could be applied to a variety of situations and technologies, including those that do not yet exist.

How to read this document

In order to facilitate understanding of the guidelines and to help people focus in on just the parts they need, the guidelines are presented as a set of interrelated documents. There are basically 3 layers to the guidelines information.

1 - Top layer - Overview of Design Principles, Guidelines, Checkpoints

The top layer is titled "Web Content Accessibility Guidelines 2.0". It is the document you are currently reading. This document provides:

  1. An introduction
  2. The 5 major Guidelines for accessibility (Perceivable, Operable, Navigable, Understandable and Robust).
  3. The (non-technology-specific) checkpoints for each guideline (21 in total).
  4. Success criteria (normative), and definitions, benefits and examples (all non-normative) for each checkpoint
  5. An appendix containing definitions, references and other support information.

2 - Technology-specific Checklists

In addition to the general guidelines, there will be a series of technology-specific checklist documents. These documents will provide information on what is required when using different technologies in order to meet the WCAG 2.0 Working Draft access guidelines.

Reviewer's Note: These checklists do not yet exist. At the present time the checklists are expected to be non-normative, though no formal decision has been made.

3 - Bottom layer - Technology-specific application information

The Techniques Documents will include code examples, screen shots, and other information specific to a technology. These documents will be non-normative. They will contain different strategies for meeting the requirements as well as the current preferred approaches where they exist. Examples include:

(These will become active links as the corresponding working drafts are published)

Audience

These guidelines have been written to meet the needs of many different audiences from policy makers, to managers, to those who create Web content, to those who code the pages. Every attempt has been made to make the document as readable and usable as possible while still retaining the accuracy and clarity needed in a technical specification. For first time users, the work of the Education and Outreach Working Group of the Web Accessibility Initiative is highly recommended.

Scope

The guidelines cover a wide range of issues and recommendations for making Web content more accessible. They include recommendations to make pages accessible and usable by people with a full range of disabilities. In general, the guidelines do not include standard usability recommendations except where they have specific ramifications for accessibility beyond standard usability impacts.

Priorities and Techniques

This WCAG 2.0 Working Draft does not assign priorities to checkpoints, as did WCAG 1.0. Instead, each of the checkpoints has levels of implementation listed for it. There are 3 levels labeled "Minimum", "Level 2", and "Level 3". The main WCAG 2.0 Working Draft document does not include technology-specific implementation requirements or techniques, but it does include links to technology-specific requirements as well as technology-specific examples and techniques.

This Working Draft of WCAG 2.0 is a follow-on and evolution of WCAG 1.0 and reflects feedback received since the publication of WCAG 1.0 in May 1999. Although the same approaches to accessibility are followed in 1.0 and 2.0, the organization and structure have been improved significantly.

The Web Content Accessibility Guidelines Working Group is working carefully to enable organizations and individuals that are currently using WCAG 1.0 (which remains stable and referenceable at this time) to ensure that they will eventually be able to make a smooth transition to WCAG 2.0. To understand how this eventual transition would be facilitated, please refer to the (draft) Checkpoint Mapping Between WCAG 1.0 and the WCAG 2.0 Working Draft for more detail on current correspondences.

Conformance

Reviewer's Note: As we publish this Public Working Draft of WCAG 2.0, the WCAG WG is in the midst of addressing a variety of issues with conformance. This section outlines the conformance structure used throughout this document and advises the reader that the WCAG WG has discovered a variety of issues with this scheme. The issues are outlined for the reader's consideration. Feedback, comments, and proposals are encouraged. Further information about current proposals and recent discussion is available.

This draft uses the following three levels of conformance:

Minimum Level
includes success criteria for the checkpoint that address key problems and are applicable across the broad range of Web content and sites. Conformance at this level will substantially overcome the barriers for many people with disabilities, but there will be people with disabilities who will still not be able to access the content. No claim of conformance can be made unless the minimum level of conformance is achieved for all checkpoints.
Level 2
includes additional success criteria that increase the accessibility of Web content, but that are more difficult to implement on Web content in general or on specific types of content.
Level 3
represents the highest level of conformance in WCAG 2.0. It includes success criteria that may be very difficult as well as criteria that may not be possible at all for some types of content or some Web architectures.

Conformance Claims

If the above conformance levels are used, the rules regarding conformance claims would be:

  1. No conformance claim of any type may be made unless all MINIMUM Level success criteria have been met for all checkpoints in WCAG 2.0.
  2. If all of the checkpoints have been met at the MINIMUM Level, but only some of the criteria for Level 2 have been met, then a conformance claim at "LEVEL 1+" can be made.
  3. If all success criteria (for all checkpoints) are met at the MINIMUM Level and Level 2, then a claim conformance at "Level 2" can be made.
  4. If all of the success criteria for (for all checkpoints) are met at the MINIMUM and Level 2, as well as some, but not all of the criteria for Level 3, then a conformance claim can be made at "Level 2+".
  5. If all success criteria for all Levels have been met, then a conformance claim at "Level 3" can be made.

For conformance claims of Level 1+ and Level 2+, it is recommended (but not required) that sites report specifically which criteria they have met within each of the guidelines and checkpoints. WCAG 2.0 Techniques documents will provide examples that show how to report which success criteria have been met from Levels 2 and 3.

All conformance claims must include (at minimum):

  1. The version of the guidelines to which a conformance claim is made and the URI of the guidelines document.
  2. The scope of the conformance claim. The scope describes which parts of a site or application are included in the claim. Reviewer's Note: Should exclusions be allowed for certain types of content, such as third-party or copyrighted material that is being reprinted? How does one define scope? Is it an end-to-end process that the user should be able to complete? Is it a path through accessible content?
  3. The level at which conformance is claimed.
  4. The date the conformance claim was made.

Sites that conform to WCAG 1.0

Sites that currently conform to WCAG 1.0 that want to shift towards WCAG 2.0 will want to capitalize on past accessibility efforts. A qualified conformance statement could allow them this flexibility. For example, a conformance claim might include the following statement, "Materials created or modified before 24 April 2003 conform to WCAG 1.0. Materials created or modified on or after 24 April 2003 conform to WCAG 2.0."

Reviewer's Note: In some instances, the WCAG 2.0 Working Draft may be easier to conform to than the WCAG 1.0 Recommendation. However, the WCAG 2.0 Working Draft requires a minimum level of conformance to each checkpoint and this may make some parts of WCAG 2.0 harder to conform to than WCAG 1.0. For example, in WCAG 1.0 checkpoints related to providing navigation mechanisms are priority 2 and 3, while in this WCAG 2.0 Working Draft there are several minimum level success criteria for navigation mechanisms. This might be resolved by merging some checkpoints and moving some of the success criteria to the Second Level rather than the Minimum.

The WCAG WG is committed to making WCAG 2.0 backwards compatible with WCAG 1.0.

Issues with Requiring Changes in Content

Reviewer's Note: As the WCAG WG has discussed conformance, there has been concern about requiring changes in style and content to meet accessibility requirements. This section summarizes these issues.

The primary strategy to improve accessibility has been to supplement content with additional information. For example, text equivalents and structural markup enable a user agent or assistive technology to make the content accessible to the user. Some of the current checkpoints require authors to change the manner in which their primary content is expressed or presented. For example, checkpoint 1.4 (emphasize structure through presentation), checkpoint 3.1 (provide structure), 4.1 (write clearly) and 4.2 (supplement text with illustrations) all have requirements at the minimum level. There are two issues with altering the primary content rather than supplementing it:

  1. it potentially limits the author's freedom of expression,
  2. it is not appropriate or permissible in some circumstances, e.g., in the case of legal documents, and historical, artistic, and literary works.

Should minimum level success criteria that impose constraints on the author's means of expression be shifted to level 2? We have discussed a variety of potential future technologies (e.g., metadata). However, those tools are not widely deployed and the schema still in development. How should we address the tension between solving current problems without constraining the author's freedom of expression? How do we address the opportunities that emerging technologies such as metadata will provide? Can we achieve some of this with semantic markup and next generation assistive technologies?

Recent proposals significantly redefine the three levels. With the proposed priority schemes, success criteria that require changes in content are no longer in the minimum level. However, the following issues remain to be addressed:

Overview of Design Principles

The overall goal is to create Web content that is perceivable, operable, navigable, and understandable by the broadest possible range of users and compatible with their wide range of assistive technologies, now and in the future.

  1. Perceivable. Ensure that all content can be presented in form(s) that can be perceived by any user - except those aspects of the content that cannot be expressed in words.
  2. Operable. Ensure that the interface elements in the content are operable by any user.
  3. Navigable. Facilitate content orientation and navigation
  4. Understandable. Make it as easy as possible to understand the content and controls.
  5. Robust. Use Web technologies that maximize the ability of the content to work with current and future accessibility technologies and user agents.

Accessible Web content benefits a variety of people, not just people with disabilities. In the physical world, ramps are used by bicycles, people pushing strollers, and people in wheelchairs. Similarly, accessible Web content is usable by a variety of people with and without disabilities. For example, people who are temporarily operating under constrained conditions like operating in a noisy environment or driving their car where their eyes are busy. Likewise, a search engine can find a famous quote in a movie if the movie is captioned.

Note: These principles apply only to Web content presented to a human reader. A structured database or metadata collection where the data is intended for use by another machine and thus requires no interface lies outside the scope of these guidelines.

User needs

Here are a few scenarios, by no means an exhaustive list of the variations and types of disabilities and needs:

If Web content employs the design principles described in this document, then users should be able to access the content using adaptive strategies and assistive technologies. A screen reader is an example of an assistive technology that reads the page aloud. There are many other tools people with disabilities employ to make use of Web content. For more in-depth scenarios of people with disabilities using accessible and inaccessible Web content, please read "How People with Disabilities Use the Web".

Designing Accessible Web Content

These guidelines provide the basic requirements for designing accessible Web content. This document is not designed to provide the background needed to learn about accessible Web design in a thorough or effective manner for those interested in learning. Readers are therefore referred to the Education and Outreach Working Group of the Web Accessibility Initiative.


Guideline 1 - Perceivable.
Ensure that all intended function and information can be presented in form(s) that can be perceived by any user - except those aspects that cannot be expressed in words.

Essential to any access to Web content is the ability of the user to have the information presented in a form which they can perceive.

The checkpoints under this guideline impact individuals with sensory disabilities by allowing the information to be transformed and presented in a form which they can perceive. They also impact individuals with cognitive and language disabilities by ensuring that the information is in a format that can be perceived by mainstream and assistive technologies which can read the content to them as well as (increasingly over time) transform and present it in a form which is easier for them to understand.

Checkpoint 1.1 For all non-text content that can be expressed in words, provide a text equivalent of the function or information the non-text content was intended to convey.

Success Criteria

You will have successfully met Checkpoint 1.1 at the Minimum Level if:
  1. non-text content that can be expressed in words has a text-equivalent explicitly associated with it.
  2. non-text content that can not be expressed in words has a descriptive label provided as its text-equivalent.
    • The text equivalent should fulfill the same function as the author intended for the non-text content (i.e. it presents all of the intended information and/or achieves the same function of the non-text content).
You will have successfully met Checkpoint 1.1 at Level 2 if:
  1. the text-equivalent has been reviewed and is believed to fulfill the same function as the author intended for the non-text content (i.e. it presents all of the intended information and/or achieves the same function of the non-text content)
You will have successfully met Checkpoint 1.1 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:

Definitions (informative)

A text equivalent

Note: Text-equivalents should be easily convertible to braille or speech, displayed in a larger font or different colors, fed to language translators or abstracting software, etc.

Non-text content includes but is not limited to images, text in raster images, image map regions, animations (e.g., animated GIFs), ASCII art, images used as list bullets, spacers, graphical buttons, sounds (played with or without user interaction), stand-alone audio files, audio tracks of video, and video. Scripts, applets, and programmatic objects are not covered in this definition and are covered in checkpoint 5.4.

Benefits (informative)

Examples (informative)

Checkpoint 1.2 Provide synchronized media equivalents for time-dependent presentations.

Success criteria

You will have successfully met Checkpoint 1.2 at the Minimum Level if:
  1. an audio description is provided of all significant visual information in scenes, actions and events that cannot be perceived from the sound track alone.
    • Note: When adding audio description to existing materials, the amount of information conveyed through audio description is constrained by the amount of space available in the existing audio track. It may also be impossible or inappropriate to freeze the audio/visual program to insert additional audio description.
  2. all significant dialogue and sounds are captioned
    exception: if the Web content is real-time and audio-only and not time-sensitive and not interactive a transcript or other non-audio equivalent is sufficient.
  3. descriptions and captions are synchronized with the events they represent.
  4. if the Web content is real-time video with audio, real-time captions are provided unless the content:
    • is a music program that is primarily non-vocal
  5. If the Web content is real-time non-interactive video (e.g., a Webcam of ambient conditions), either provide an equivalent that conforms to checkpoint 1.1 (e.g., an ongoing update of weather conditions) or link to an equivalent that conforms to checkpoint 1.1 (e.g., a link to a weather Web site).
  6. if a pure audio or pure video presentation requires a user to respond interactively at specific times in the presentation, then a time-synchronized equivalent (audio, visual or text) presentation is provided.

exception: if content is rebroadcast from another medium or resource that complies to broadcast requirements for accessibility (independent of these guidelines), the rebroadcast satisfies the checkpoint if it complies with the other guidelines.

You will have successfully met Checkpoint 1.2 at Level 2 if:
  1. the audio description has been reviewed and is believed to include all significant visual information in scenes, actions and events (that can't be perceived from the sound track) to the extent possible given the constraints posed by the existing audio track (and constraints on freezing the audio/visual program to insert additional auditory description).
You will have successfully met Checkpoint 1.2 at Level 3 if:
  1. a text document that merges all audio descriptions and captions into a collated script (that provides dialog, important sounds and important visual information in a single text document) is provided.
  2. captions and audio descriptions are provided for all live broadcasts which provide the same information.
  3. The presentation does not require the user to read captions and the visual presentation simultaneously in order to understand the content.
The following are additional ideas for enhancing content along this particular dimension:

Definitions (informative)

A time-dependent presentation is a presentation which

Media equivalents present essential audio information visually (captions) and essential video information auditorily (audio descriptions).

Benefits (informative)

People without disabilities also benefit from the media equivalents.

Note: Time-dependent presentations requiring people to use a single sense to follow two or more things at the same time may present significant barriers to some users. Depending on the nature of the of presentation, it may be possible to avoid scenarios where, for example, a deaf user would be required to watch an action on the screen and read the captions at the same time. However, this would not be achievable for live broadcasts (e.g. a football game). Where possible, provide content so that it does not require tracking multiple simultaneous events with the same sense, or give the user the ability to freeze the video so that captions can be read without missing the video.

Examples (informative)

Checkpoint 1.3 Make all content and structure available independently of presentation.

Success criteria

You will have successfully met Checkpoint 1.3 at the Minimum Level if:
  1. any information that is conveyed through presentation formatting is also provided in either text or structure.
  2. the following can be derived programmatically (i.e. through assistive technology compatible markup or data model) from the content without interpreting presentation.
    1. any hierarchical elements and relationships, such as headings, paragraphs and lists
    2. any non-hierarchical relationships between elements such as cross-references and linkages, associations between labels and controls, associations between cells and their headers, etc.
    3. any emphasis
You will have successfully met Checkpoint 1.3 at Level 2 if:
You will have successfully met Checkpoint 1.3 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:

Definitions (informative)

Content is the information or meaning and function.

Presentation is the rendering of the content and structure in a form that can be sensed by the user.

Structure includes both hierarchical structure of the content and non-hierarchical relationships such as cross-references, or the correspondence between header and data cells in a table.

Benefits (informative)

Examples (informative)

Checkpoint 1.4 Emphasize structure through presentation(s), positioning, and labels.

Success criteria

You will have successfully met Checkpoint 1.4 at the Minimum Level if:
  1. the structural elements present have a different visual appearance or auditory characteristic than the other structural elements.
You will have successfully met Checkpoint 1.4 at Level 2 if:
  1. the structural emphases are chosen to be distinct for different major display types (e.g. black and white, small display, mono audio playback).
You will have successfully met Checkpoint 1.4 at Level 3 if:
  1. content is constructed such that users can control the presentation of the structural elements.
  2. alternate presentation formats are available to vary the emphasis of the structure.
The following are additional ideas for enhancing content along this particular dimension:

Note: Because the form and origin (including letters, art, historical documents, etc) of content varies so greatly, specific criteria for the type and amount of emphasis to be provided can not be standardized. Objective success criteria cannot therefore be formulated that would apply across media and documents. Advisory recommendations are however listed below to provide guidance in emphasizing the structure of content. See also the techniques documents for the different technologies.

  1. for visual presentations, use font variations, styles, size and white space to emphasize structure.
  2. use color and graphics to emphasize structure.
  3. for auditory presentations, use different voice characteristics and/sounds for major headings, sections and other structural elements.
  4. if content is targeted for a specific user group and the presentation of the structured content is not salient enough to meet the needs of your audience, use additional graphics, colors, sounds, and other aspects of presentation to emphasize the structure.
  5. provide a table of contents or navigation map of the document.

Note: Ensure that the structural and semantic distinctions are provided in the markup or data model. Refer to checkpoint 1.3.

Benefits (informative)

Presentation that emphasizes structure:

Examples (informative)

Checkpoint 1.5 Ensure that foreground content is easily differentiable from background for both auditory and visual presentations.

Success criteria

You will have successfully met Checkpoint 1.5 at the Minimum Level if:
  1. text content that is presented over a background image or pattern is implemented using mechanisms that allow the user to display the text without the background image or pattern.
You will have successfully met Checkpoint 1.5 at Level 2 if:
  1. when text content is presented over a background image or pattern, the text is easily readable when the page is viewed in 256 grayscale.
You will have successfully met Checkpoint 1.5 at Level 3 if:
  1. text content is not presented over a background image or pattern OR the text is easily readable when the page is viewed in black and white (no grayscale).
  2. audio content does not contain background sounds OR the background sounds are at least 20 db lower than the foreground audio content.
  3. text content is not presented over a background image or color OR the colors used for the text and background or background image pass the following test (from Techniques For Accessibility Evaluation And Repair Tools, dated April 26, 2000):
    • Two colors provide good color visibility if the brightness difference and the color difference between the two colors are greater than a set range.
    • Color brightness is determined by the following formula: ((Red value X 299) + (Green value X 587) + (Blue value X 114)) / 1000 Note: This algorithm is taken from a formula for converting RGB values to YIQ values. This brightness value gives a perceived brightness for a color.
    • Color difference is determined by the following formula: (maximum (Red value 1, Red value 2) - minimum (Red value 1, Red value 2)) + (maximum (Green value 1, Green value 2) - minimum (Green value 1, Green value 2)) + (maximum (Blue value 1, Blue value 2) - minimum (Blue value 1, Blue value 2))
    • The range for color brightness difference is 125. The range for color difference is 500.

    Reviewer's Note: There is some question about whether this algorithm yields content with sufficient contrast. The working group is currently in the process of researching a number of methods for determining sufficient contrast and color visibility.

The following are additional ideas for enhancing content along this particular dimension:

Benefits (informative)

Examples (informative)

Checkpoint 1.6 Provide information needed for unambiguous decoding of the characters and words in the content.

Success criteria

You will have successfully met Checkpoint 1.6 at the Minimum Level if:
  1. text in the content is provided in Unicode or sufficient information is provided so that it will be automatically mapped back to Unicode.
You will have successfully met Checkpoint 1.6 at Level 2 if:
  1. passages or fragments of text occurring within the content that are written in a language other than the primary natural language of the content as a whole, are identified, including specification of the language of the passage or fragment.
  2. abbreviations and acronyms are clearly identified where they occur. (See also checkpoint 4.3.)
  3. symbols such as diacritic marks that are found in standard usage of the natural language of the content, and necessary for unambiguous interpretation of words, are present or another standard mechanism for disambiguation is provided.
You will have successfully met Checkpoint 1.6 at Level 3 if:
  1. the primary natural language of the content is identified at the page level.
The following are additional ideas for enhancing content along this particular dimension:

Note: This checkpoint addresses the need for authors to provide sufficient information so that text can be identified correctly by technologies used to render the text (e.g. voice synthesizers) so that the words can be accurately produced and perceived. This checkpoint does not deal with providing definitions or expanded text for words, abbreviations, foreign phrases etc. These are covered under checkpoint 4.3 since they deal with understanding of the content.

Definitions (informative)

Natural languages are those used by humans to communicate, including spoken, written, and signed languages.

Benefits (informative)

Examples (informative)


Guideline 2 - Operable.
Ensure that the interface elements in the content are operable by any user.

Also essential to accessibility is the ability to be able to operate all of the interface elements on the page without requiring the use of specific input devices.

This guideline impacts individuals who are blind, individuals who have low vision and have trouble with eye-hand coordination input devices, individuals with physical disabilities who cannot handle direct pointing devices accurately, and individuals with language and learning disabilities who would like to use speech input now or in the future.

Checkpoint 2.1 Ensure that all of the functionality is operable at a minimum through a keyboard or keyboard interface.

Success criteria

You will have successfully met Checkpoint 2.1 at the Minimum Level if:
  1. all of the functionality of the content where the functionality or its outcome can be expressed concisely in words is operable at a minimum through a keyboard or keyboard interface.
    • Note: refer to checkpoint 5.3 for information regarding user agent support.
You will have successfully met Checkpoint 2.1 at Level 2 if:
  1. wherever a choice between event handlers is available and supported, the more abstract event is used.
You will have successfully met Checkpoint 2.1 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:

Definitions (informative)

A keyboard interface is the point where the application accepts any input that would come from the keyboard (or optional keyboard).

Benefits (informative)

Examples (informative)

Checkpoint 2.2 Allow users to control any time limits on their reading, interaction or responses unless control is not possible due to the nature of real-time events or competition.

Success criteria

You will have successfully met Checkpoint 2.2 at the Minimum Level if:
  1. at least one of the following is true for each time limit:
    1. the user is allowed to deactivate the time limits,
    2. or the user is allowed to adjust the time limit over a wide range which is at least 10 times the average user's preference,
    3. or the user is warned before time expires and given at least 10 seconds to extend the time limit,
    4. or the time limit is due to a real-time event (e.g. auction) and no alternative to the time limit is possible,
    5. or the time limit is part of a competitive activity where timing is an essential part of the activity (e.g. competitive gaming or time based testing).
You will have successfully met Checkpoint 2.2 at Level 2 if:
You will have successfully met Checkpoint 2.2 at Level 3 if:
  1. activities are designed so that time limits are not an essential part of the activity (e.g. competition, testing, etc. are not time based).
The following are additional ideas for enhancing content along this particular dimension:

Definitions (informative)

Real-time events are those that are based on the occurrence of events in real-time where the events are not under the control of the author.

A competitive activity is an activity where timing is an essential part of the design of the activity. Removal of the time element would change the performance of the participants. Versions of the activity (e.g. test) that have no time basis or time limits might be preferred and may be required for some venues but this would require a complete redesign of the activity (e.g. test) and may change the character and validation methodology and would therefore not fall under these guidelines.

Benefits (informative)

People with reading disabilities, cognitive disabilities, and learning disabilities often need longer than most people to read and comprehend written text. People with physical disabilities might not be able to move quickly or accurately enough to interact with moving objects.

Content that is updated often might not be processed and read in time or in the proper order by an assistive technology or voice browser.

Examples (informative)

Examples of content that requires a response within a timed interval:

Checkpoint 2.3 Avoid causing the screen to flicker.

Success criteria

You will have successfully met Checkpoint 2.3 at the Minimum Level if:
  1. At least one of the following is true:
    1. content was not designed to flicker (or flash) in the range of 3 to 49 Hz.
    2. Reviewer's Note: We would like to include a criteria here which would state that a test that was conducted and the pages passed. No test or tool exists yet though. We're looking into how such a test and/or tool might be designed.
    3. if flicker is unavoidable, the user is warned of the flicker before they go to the page, and as close a version of the content as is possible without flicker is provided.
You will have successfully met Checkpoint 2.3 at Level 2 if:
  1. animation or other content does not visibly or purposely flicker between 3 and 49 Hz.
  2. content that might create a problem has been tested [using XYZ tool]; only pages with unavoidable flicker remain and appropriate warnings along with a close alternative presentation have been provided for these pages.
  3. (tougher test - that would make pages pass with even slower equip. Equip might be old or just slow for other reasons)
You will have successfully met Checkpoint 2.3 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:

Reviewer's Note: Trace is currently in the process of exploring an automated flicker testing tool.

Benefits (informative)


Guideline 3 - Navigable.
Facilitate content orientation and navigation

Key to effective use of Web content is the ability to obtain and keep one's and the ability to efficiently move about the site, document or application.

Checkpoint 3.1 Provide structure within content.

Success criteria

You will have successfully met Checkpoint 3.1at the Minimum Level if:
  1. the following minimum structure elements are present.
    1. titles on major sections of long documents
    2. paragraphs
You will have successfully met Checkpoint 3.1 at Level 2 if:
  1. the content has been reviewed, taking into account the additional ideas listed below, and is believed to contain as much structure as is possible and appropriate
You will have successfully met Checkpoint 3.1 at Level 3 if:
  1. information is provided that would allow an assistive technology to determine at least one logical, linear reading order
  2. diagrams are constructed in a fashion so that they have structure that can be accessed by the user.
The following are additional ideas for enhancing content along this particular dimension

Note: Because the form and origin of content (including letters, poetry, historical documents, etc.) varies so greatly, specific criteria for the type and amount of structure to be put into content can not be standardized. Objective success criteria cannot therefore be formulated that would apply across media and documents. Advisory recommendations are, however, listed below to provide guidance in adding key structural elements into the content. See also the techniques documents for the different technologies.

  1. break up text into logical paragraphs.
  2. provide hierarchical sections and titles, particularly for longer documents
  3. reveal important non-hierarchical relationships, such as cross-references, or the correspondence between header and data cells in a table, so that they are represented unambiguously in the markup or data model.
  4. divide very large works into sections and or chapters with logical labels.
  5. others?

Definitions (informative)

The structure of content represents changes in context. For example,

  1. A book is divided into chapters, paragraphs, lists, etc. Chapter titles help the reader anticipate the meaning of the following paragraphs. Lists clearly indicate separate, yet related ideas. All of these divisions help the reader anticipate changes in context.
  2. A bicycle is divided into wheels and a frame. Further, a wheel is divided into a tire and a rim. In an image of the bicycle, one group of circles and lines becomes "wheel" while another group becomes "frame."

Benefits (informative)

When the logical structure is provided in markup or a data model,

Examples (informative)

Checkpoint 3.2 Provide multiple methods to explore sites that are more than two layers deep.

Success criteria

You will have successfully met Checkpoint 3.2 at the Minimum Level if:
  1. sites that have more than two layers have at least one other method for exploration besides using the links on the home page. (A home page and one layer of pages linked off of it would be two layers)
  2. a link to the alternate exploration method(s) is provided on the home page.
You will have successfully met Checkpoint 3.2 at Level 2 if:
  1. sites that have documents that span multiple files either provide the documents as a single file or provide a search function which would allow the user to search for a word across only the files that make up that document.
You will have successfully met Checkpoint 3.2 at Level 3 if:
  1. large documents (greater than 50,000 words) include multiple mechanisms for navigation such as a hyperlinked table of contents, internal hyperlinks, an ability to collapse by headers, etc.
The following are additional ideas for enhancing content along this particular dimension:

Definitions (informative)

A site navigation mechanism is a mechanism for easily orienting and moving about within the site. Site navigation mechanisms include but are not limited to:

Benefits (informative)

Checkpoint 3.3 Use consistent but not necessarily identical presentation.

Success criteria

You will have successfully met Checkpoint 3.3 at the Minimum Level if:
  1. key orientation and navigational elements are generally found in one or two locations or their locations are otherwise predictable.
You will have successfully met Checkpoint 3.3 at Level 2 if:
  1. the content has been reviewed, taking into account the additional ideas listed below, and it has been concluded that key orientation and navigational elements are generally found in one or two locations, or their locations are otherwise predictable
You will have successfully met Checkpoint 3.3 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:
  1. place navigation bars in a consistent location whenever possible
  2. similar layout for user interface components should be used for sections or whole site,
  3. similar user interface components should be labeled with similar terminology
  4. use headers consistently
  5. use templates for consistent presentation of sections or whole site
  6. pages with similar function should have similar appearance and layout

Definitions (informative)

Presentation includes, but is not limited to:

Benefits (informative)

Checkpoint 3.4 Provide consistent and predictable responses to user actions.

Success criteria

You will have successfully met Checkpoint 3.4 at the Minimum Level if:
  1. where inconsistent or unpredictable responses are essential to the function of the content (e.g. mystery games, adventure games, tests, etc.) the user is warned in advance of encountering them.
  2. wherever there are extreme changes in context, one of the following is true:
    1. an easy to find setting, that persists for the site visit, is provided for the user to deactivate processes or features that cause extreme changes in context or
    2. extreme changes in context are identified before they occur so the user can determine if they wish to proceed or so they can be prepared for the change
You will have successfully met Checkpoint 3.4 at Level 2 if:
  1. the content has been reviewed, and it has been found that where inconsistent or unpredictable responses are essential to its function (e.g. mystery games, adventure games, tests, etc.), the user is warned in advance of encountering them
You will have successfully met Checkpoint 3.4 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:
  1. controls that look or sound the same should be designed to act the same,
  2. conventions likely to be familiar to the user should be followed,
  3. unusual user interface features or behaviors that are likely to confuse the first-time user should be described to the user before they are encountered.

Definitions (informative)

Mechanisms that cause extreme changes in context include:

Common user actions include:

Common responses to user actions include:

It is important that responses to user actions be predictable and sensible to the end user and that interactions are consistent, both throughout the site and with commonly used interaction metaphors used throughout the Web.

Benefits (informative)

Note: Providing consistent and predictable responses to user actions is important feedback for the user. This lets them know that your site is working properly and encourages them to continue interacting with the content. When the user receives an unexpected response, they might conclude that something is wrong or broken. Some people might get so confused they will not be able to use your site.

Examples (informative)

Reviewer's Note: Some of these examples are very brief. Should they be expanded and clarified with further details?

Checkpoint 3.5 Provide methods to minimize error and provide graceful recovery.

Success criteria

You will have successfully met Checkpoint 3.5 at the Minimum Level if:
  1. if an error is detected, feedback is provided to the user identifying the error.
You will have successfully met Checkpoint 3.5 at Level 2 if:
  1. the content has been reviewed and is believed to have incorporated error prevention and recovery methods that are considered to be effective and appropriate
You will have successfully met Checkpoint 3.5 at Level 3 if:
  1. where possible, the user is allowed to select from a list of options as well as to generate input text directly
  2. errors are identified specifically and suggestions for correction are provided where possible
  3. checks for misspelled words are applied and correct spellings are suggested when text entry is required.
  4. where consequences are significant and time-response is not important, one of the following is true
    1. actions are reversible where possible
    2. where not reversible, actions are checked for errors in advance.
    3. where not reversible, and not checkable, a confirmation is asked before acceptance
The following are additional ideas for enhancing content along this particular dimension:

Benefits (informative)

Examples (informative)


Guideline 4 - Understandable.
Make it as easy as possible to understand the content and controls.

To help people understand the information you are presenting, consider the various ways that people learn. Keep in mind the variety of backgrounds and experiences people will bring to your site. Using language, illustrations, and concepts that they are likely to know, highlighting the differences and similarities between concepts, and providing explanations for unusual terms can all facilitate understanding.

Checkpoint 4.1 Write clearly.

This checkpoint lists ideas to help you review content for clarity. Plain language specialists around the world promote many of these ideas. The following items are not presented as success criteria, however, or as an attempt to impose editorial style. Rather, they are elements to consider as you review writing. They reflect the idea that accessibility begins with understanding.

Success criteria

Reviewer's Note: Since there has been concern about requirements at the minimum level that would require content to be presented in a particular way, this checkpoint has been worded in a way that requires authors to "consider" a list of criteria and review their content with that list in mind. Is this difference clear in comparison to other checkpoints?

You meet Checkpoint 4.1 at the Minimum Level if you review the content with items such as these in mind:
  1. familiarity of terms and language structure
  2. reasonableness of length and complexity of sentences
  3. coherence of paragraphs (and sensibility in length)
  4. clarity of headings and linked text when read out of context
  5. accuracy and uniqueness of page titles
  6. care in the use of all-capital letters where normal sentence case might increase comprehension
You meet Checkpoint 4.1 at Level 2 if you review the content with items such as these in mind:
  1. use of sentence structures that increase understanding
    • such as active voice in languages where this form helps convey information
  2. length of noun phrases
    • strings of no more than three or four nouns are easiest to understand
  3. clarity of reference with pronouns and anaphoric expressions (these refer back to something already said in the text)
    • example of potential ambiguity: "Scientists study monkeys. They eat bananas."
  4. correct use of conjunction forms and adverbs to make explicit the relationship between phrases or parts of the text
    • such as "and," "but," "furthermore," "not only"
  5. complexity of verb tenses
    • do the tenses used in a document seem overly complicated?
  6. intelligibility of verb phrases
  7. familiarity of idioms or slang
  8. logic in the order and flow of information
  9. consequences of ambiguity or abstraction
  10. improved readability of vertical lists might offer in place of long paragraphs of information
  11. use of summaries to aid understanding
  12. thoroughness in the explanation of instructions or required actions
  13. consistency in the use of names and labels
  14. clarity where the document:
    • addresses users
    • explains choices and options
    • labels options to get more information
    • instructs users how to modify selections in critical functions (such as how to delete an item from a shopping cart)
  15. application of:
    • proper markup to highlight key information
    • goal-action structure for menu prompts
    • default settings (and the ease in re-establishing them)
    • two-step "select and confirm" processes to reduce accidental selections for critical functions
    • calculation assistance to reduce the need to calculate
You meet Checkpoint 4.1 at Level 3 if at least one of the following is true:

Definitions (informative)

Controlled languages use a restricted vocabulary taken from natural language. The purpose is to make texts easier to understand and translate. Standards generally limit words to a single meaning and prescribed part of speech. Complex syntax is avoided. Information about controlled language applications is available on the World Wide Web.

Benefits (informative)

Checkpoint 4.2 Supplement text with non-text content.

Success criteria

You will have successfully met Checkpoint 4.2 at the Minimum Level if:
  1. authors have included non-text content to supplement text for key pages or sections of the site where they felt it was appropriate.
You will have successfully met Checkpoint 4.2 at Level 2 if:
  1. the content has been reviewed and it is believed that text has been supplemented with non-text content to the extent deemed appropriate by the author
You will have successfully met Checkpoint 4.2 at Level 3 if:
  1. non-text content has been added to the site for key pages or sections specifically to make the site more understandable by users who cannot understand the text only version of the site.
The following are additional ideas for enhancing content along this particular dimension:

Note: Supplementing text with non-text (e.g. graphics, sound, smell, etc) is useful for all users. However there are no clear guidelines as it relates to disability. Specific objective criteria that could be applied across all types of content are therefore not possible. Advisory recommendations are, however, listed below to provide guidance in this area. See also the techniques documents for the different technologies.

Reviewer's Note: Do we have any items to add here or do we just include examples below?

Definitions (informative)

Non-text content - includes images, text in raster images, image map regions, animations (e.g., animated GIFs), applets and programmatic objects, ASCII art, scripts, images used as list bullets, spacers, graphical buttons, sounds (played with or without user interaction), stand-alone audio files, audio tracks of video, and video.

Reviewer's Note: Is this definition adequate?

Benefits (informative)

Note: Designers need to be cautious in deciding when to use illustrations. Reading a picture is probably a learned activity that is easier for some than others. Some users skip the pictures; others read only the pictures. Designers must also recognize that visual conventions are not universal and that individuals develop their own mental schema and expectations in interpreting visual information.

Examples (informative)

Checkpoint 4.3 Annotate complex, abbreviated, or unfamiliar information with summaries and definitions.

Success criteria

You will have successfully met Checkpoint 4.3 at the Minimum Level if:
  1. acronyms and abbreviations are defined the first time they appear.
You will have successfully met Checkpoint 4.3 at Level 2 if:
  1. the content has been reviewed, taking into account the additional ideas listed below, and it is believed that complex, abbreviated or unfamiliar information has been annotated appropriately
You will have successfully met Checkpoint 4.3 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:
  1. provide a definition or link (with the first occurrence) of phrases, words, acronyms, and abbreviations specific to a particular community.
  2. provide a summary for relationships that may not be obvious from analyzing the structure of a table but that may be apparent in a visual rendering of the table.
  3. if contracted forms of words are used such that they are ambiguous, provide semantic markup to make words unique and interpretable.

Definitions (informative)

Content is considered complex if the relationships between pieces of information are not easy to figure out. If the presentation of the information is intended to highlight trends or relationships between concepts, these should be explicitly stated in the summary.

Examples of complex information:

Content might be unfamiliar if you are using terms specific to a particular community. For example, many of the terms used in this document are specific to the disability community.

Benefits (informative)


Guideline 5 - Robust.
Use Web technologies that maximize the ability of the content to work with current and future accessibility technologies and user agents.

Checkpoint 5.1 Use technologies according to specification.

Success criteria

You will have successfully met Checkpoint 5.1 at the Minimum Level if:
  1. for markup, except where the site has documented that a specification was violated for backward compatibility, the markup has passed validity tests of the language (whether it be conforming to a schema, Document Type Definition (DTD), or other tests described in the specification), structural elements and attributes are used as defined in the specification, accessibility features are used, and deprecated features are avoided.
    Reviewer's Note:The following two success criteria seem to overlap with checkpoint 5.4. There is an open question about whether they should be deleted since Checkpoint 5.4 covers programmatic interfaces.
  2. for Application Programming Interfaces (API's), programming standards for the language are followed.
  3. accessibility features and API's are used when available.
You will have successfully met Checkpoint 5.1 at Level 2 if:
  1. for markup, the markup has passed validity tests of the language (whether it be conforming to a schema, DTD, or other tests described in the specification), structural elements and attributes are used as defined in the specification, accessibility features are used, and deprecated features are avoided.
You will have successfully met Checkpoint 5.1 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:

Reviewer's Note: Are protocols relevant to this checkpoint? If so, why, and should we require that they be used according to specification? Obviously there are interoperability advantages in doing so, but is this pertinent to accessibility?

Benefits (informative)

Examples (informative)

Checkpoint 5.2 Ensure that technologies relied upon by the content are declared and widely available.

Success criteria

You will have successfully met Checkpoint 5.2 at the Minimum Level if:
  1. a list of technologies and features, support for which is required in order for the content to be operable, has been determined and is documented in metadata and / or a policy statement associated with the content.
    • Note: When determining your list of technological requirements, consider that assistive hardware and software is often slow to adapt to technological advances, and the availability of assistive technology varies across natural languages. Verify that assistive technology compatible with the technologies you choose is available in the natural language(s) of your content.
  2. the content is still usable when features not on the required list (for example, scripting and stylesheets) are turned off or not supported.
You will have successfully met Checkpoint 5.2 at Level 2 if:
  1. Technologies and features on the required list are available in at least two independently-developed implementations.
  2. of at least two such implementations, it is true that the technologies and features on the required list have been supported by at least one prior version of the software.
You will have successfully met Checkpoint 5.2 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:

Definitions (informative)

A technology is a

A feature is a specific component of a technology, for example an element in a markup language or a function call in an Application Programming Interface. Typically, a given feature may only be available in specific versions of the technology, and thus may need to be noted explicitly in the required list.

Benefits (informative)

Benefits of determining and documenting baseline user agent requirements:

Benefits of designing for backward compatibility:

Examples (informative)

Checkpoint 5.3 Choose technologies that are designed to support accessibility.

Success criteria

You will have successfully met Checkpoint 5.3 at the Minimum Level if:
  1. the technology or combination of technologies chosen:
    1. support device independence
    2. include accessibility features
    3. have publicly documented interfaces for interoperability
    4. make use of operating system accessibility features (either directly or via the user agent) supported by assistive technologies in the natural language(s) of the content
    5. are implemented in user agents and/or proxies in the natural language(s) of the content
You will have successfully met Checkpoint 5.3 at Level 2 if:
You will have successfully met Checkpoint 5.3 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:

Benefits (informative)

Checkpoint 5.4 Ensure that user interfaces are accessible or provide an accessible alternative.

Success criteria

You will have successfully met Checkpoint 5.4 at the Minimum Level if:
  1. any applications with custom user interfaces conform to at least Level A of the User Agent Accessibility Guidelines 1.0. If the application cannot be made accessible, an alternative, accessible solution is provided.
You will have successfully met Checkpoint 5.4 at Level 2 if:
  1. the interface has been tested using a variety of assistive technologies and preferably real people with disabilities who use assistive technologies to determine that assistive technologies can access all information on the page or hidden within the page.
    Reviewer's Note:
    It would be possible to comply with the checkpoint without carrying out tests (either with users or with assistive technologies). Conversely, it is possible to conduct tests, but still fail to meet the checkpoint (with respect to assistive technologies that were not tested, for example). Should this success criterion be deleted?
  2. device-independent access to functionality is provided
  3. accessibility conventions of the markup or programming language (API's or specific markup) are used
You will have successfully met Checkpoint 5.4 at Level 3 if:
The following are additional ideas for enhancing content along this particular dimension:

Reviewers Note: There are a number of open issues and questions related to this checkpoint. Some examples include:

  1. How can we provide guidelines related to this checkpoint for interactive content?
  2. How should WCAG 2.0refer to UAAG 1.0?
  3. How do other applications (ex. Java, PDF and Flash) fit into UAAG?

Benefits (informative)


Appendix A: Glossary

The WCAG WG has not tackled the definitions of the terms that we are using and we sometimes use terms inconsistently. We need to coordinate our terms and definitions with the WAI Glossary. We are working on proposals for a variety of definitions. We have been looking at the UAAG 1.0 glossary and other glossaries within the W3C. For now, a simple list of the terms that are defined in this document are included below. Definitions for each term will be included at a later date.

  1. text equivalent
  2. Non-text content
  3. time-dependent presentation
  4. Media equivalents
  5. captions
  6. audio descriptions
  7. Content
  8. Presentation
  9. Structure
  10. Natural languages
  11. keyboard interface
  12. Real-time events
  13. competitive activity
  14. structure
  15. site navigation mechanism
  16. Presentation
  17. Mechanisms that cause extreme changes in context
  18. Controlled languages
  19. Non-text content
  20. complex
  21. unfamiliar
  22. technology
  23. feature

Appendix B: Contributors

Participants in the WCAG Working Group

Appendix C: The differences between WCAG 1.0 and WCAG 2.0

Since the release of WCAG 1.0 in May 1999, the WCAG Working Group has received feedback on priorities of checkpoints, the usability of the set of documents, and requests for clarifications on the meaning of specific checkpoints and what is needed to satisfy them. Thus, it is intended that WCAG 2.0, when it eventually becomes a W3C Recommendation:

For a checkpoint by checkpoint comparison, refer to the Checkpoint Mapping Between WCAG 1.0 and the WCAG 2.0 Working Draft.

Improvements in WCAG 2.0

We hope that WCAG 2.0 will have several improvements over WCAG 1.0. While the primary goal of WCAG 2.0 is the same as WCAG 1.0 (to promote accessibility of Web content) additional goals for WCAG 2.0 include improvements that will:

  1. Ensure that requirements may be applied across technologies
  2. Ensure that the conformance requirements are clear
  3. Ensure that the deliverables are easy to use
  4. Write to a more diverse audience
  5. Clearly identify who benefits from accessible content
  6. Ensure that the revision is "backward compatible" with WCAG 1.0

For more information about the intended improvements in WCAG 2.0 Working Draft, please refer to Requirements for WCAG 2.0.

Appendix D: References

Reviewer's Note: Links within the document will be turned into references and the links to those documents will be listed here as references. They are inline for the time being.