[contents]

W3C

Web Content Accessibility Guidelines 2.0

W3C Working Draft 26 July 2004

This version:
http://www.w3.org/WAI/GL/WCAG20/WD-WCAG20-20040726.html
Latest version:
http://www.w3.org/WAI/GL/WCAG20/
Previous version:
http://www.w3.org/WAI/GL/WCAG20/WD-WCAG20-20040602.html
Editors:
Ben Caldwell, Trace R&D Center
Wendy Chisholm, W3C
Gregg Vanderheiden, Trace R&D Center
Jason White, University of Melbourne

Copyright © 2004  W3C ® ( MIT , ERCIM , Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply.

Abstract

The World Wide Web Consortium (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 guidelines. It attempts to apply guidelines to a wider range of technologies and to use wording that may be understood by a more varied audience.

Status of this Document

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

This document is prepared by the Web Content Accessibility Guidelines Working Group (WCAG WG) to show how more generalized (less HTML-specific) WCAG guidelines 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.

Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress. A list of current W3C Recommendations and other technical documents is available.

The Working Group welcomes comments on this document at public-comments-wcag20@w3.org. The archives for this list are publicly available. Archives of the WCAG WG mailing list discussions are also 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

Appendices

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. 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 3 layers to the guidelines information.

1 - Top layer - Overview of Design Principles, Guidelines, Success Criteria

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 4 major principles for accessibility (Perceivable, Operable, Understandable and Robust).

  3. The (non-technology-specific) guidelines (14 in total).

  4. Success criteria (normative), and definitions, benefits and examples (all non-normative) for each guideline

  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.

Editorial Note: These checklists do not yet exist. At the present time, it is not clear if the checklists will be normative or non-normative. If checklists are non-normative, it is easier to update them. If checklists are normative, changes made to them alter the definition of conformance. However, it may be necessary to make checklists normative in order for the guidelines to be testable.

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:

(Items above 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 write the code. 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

These guidelines cover a wide range of issues and recommendations for making Web content more accessible. They include recommendations to make content 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 Working Draft of WCAG 2.0 builds upon WCAG 1.0 and reflects feedback received since the publication of WCAG 1.0 in May 1999. Although the same approaches to accessibility are followed in 1.0 and 2.0, the organization and structure have changed. Where WCAG 1.0 uses guidelines to group checkpoints, this Working Draft of WCAG 2.0 uses guidelines to group success criteria. Where WCAG 1.0 assigns a priority to a checkpoint, this Working Draft of WCAG 2.0 categorizes a success criterion into one of three levels.

In addition, the general design principles have been reworded to apply across a wide range of existing and emerging technologies. The WCAG 2.0 Working Draft does not include technology-specific implementation requirements or techniques, but it will link to technology-specific requirements as well as technology-specific examples and techniques (as soon as those documents are more stable).

The Web Content Accessibility Guidelines Working Group is working to ensure that organizations and individuals who are currently using WCAG 1.0 (which remains stable and referenceable at this time) will be able to smoothly transition to WCAG 2.0. For more information about the similarities and differences between WCAG 1.0 Checkpoints and WCAG 2.0 Guidelines and success criteria, please refer to the (draft) Mapping Between WCAG 1.0 and the WCAG 2.0 Working Draft.

Conformance

Editorial Note: There are several open issues with the proposed conformance scheme. This section outlines the conformance scheme used throughout this document. Feedback, comments, and proposals are encouraged.

Guidelines are divided into three categories of success criteria:

  • Level 1 success criteria:

    1. Achieve a minimum level of accessibility through markup, scripting, or other technologies that interact with user agents, including assistive technologies

    2. Could be reasonably be applied to all Web resources.

  • Level 2 success criteria:

    1. Increase accessibility through either or both of the following:

      1. additional facilitation of user agent based accessibility

      2. content and/or presentation that provides direct accessibility without requiring the user or their user agent to do anything different from users without disabilities

    2. Could be reasonably be applied to all Web resources.

  • Level 3 success criteria:

    1. Go beyond Level 1 and 2 to increase direct and user agent enhanced accessibility

The Working Group believes that all success criteria should be testable. Tests can be done by computer programs or by people who understand these guidelines. Tests done by people who understand the guidelines should get the same results testing the same content for the same success criteria.

Editorial Note: To facilitate discussion related to the levels assigned to each criteria, a square bracket notation is included at the end of each criteria. "[I]" (invisible) indicates that a criterion does not specify how information is presented and "[V]" (visible) indicates that addressing the criterion may require an author to present content in particular ways.

Note:

Some guidelines do not contain level 1 success criteria.

Conformance Requirements

  1. Any conformance with WCAG 2.0 requires that all level 1 success criteria for all guidelines be met.

  2. WCAG 2.0 conformance at level A means that all level 1 success criteria for all guidelines are met.

  3. WCAG 2.0 conformance at level AA means that all level 1 and all level 2 success criteria for all guidelines are met.

  4. WCAG 2.0 conformance at level AAA means that all level 1, level 2 and level 3 success criteria for all guidelines are met.

Conformance Claims

All conformance claims must include at least the following information:

  1. The version of the guidelines to which the conformance claim is made.

  2. The URI of the authored unit for which the claim is being made.

    Editorial Note: There is question by some as to whether the term "authored unit" can be made precise enough.

    Editorial Note: There is some question as to whether URI is specific enough a reference to the material for which the claim is being made.

  3. The level of conformance being claimed.

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."

Editorial Note: In some instances, the WCAG 2.0 Working Draft may be easier to conform to than the WCAG 1.0 Recommendation while other criteria might be harder to meet in WCAG 2.0 than in WCAG 1.0. The WCAG WG will consider the differences between WCAG 1.0 and WCAG 2.0 conformance and offer advice to developers who currently conform to WCAG 1.0. This advice might take the form of a WCAG 1.0 conformance profile to WCAG 2.0 and information about migrating from WCAG 1.0 to WCAG 2.0. This advice is not yet available.

Overview of Design Principles

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

  1. Content must be perceivable.

  2. Interface elements in the content must be operable.

  3. Content and controls must be understandable.

  4. Content must be robust enough to work with current and future technologies.

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 beneficial to a variety of people with and without disabilities. For example, people who are temporarily operating under constrained conditions like operating in a noisy environment where they can not hear well or at all, or driving their car where their eyes are busy would benefit from an accessible site. 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 that 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:

  • Someone who cannot hear well will want a visual representation of information presented via sound.

  • Someone who cannot see well will want to hear or feel (via braille or tactile graphics) an equivalent of the visual information.

  • Someone who does not have the strength to move quickly or easily will want to use as little movement as possible and have as much time as they need when operating Web interfaces.

  • Someone who does not read well may want to hear the information read aloud.

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. There are many tools that 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.

Principle 1: Content must be perceivable.

Guideline 1.1 Provide text alternatives for all non-text content.

Level 1 Success Criteria for Guideline 1.1

  1. Text-alternatives are explicitly associated with non-text content and one of the following is true: [I]

    1. For non-text content that is functional, such as graphical links or buttons, text alternatives identify the purpose or function of the non-text content; or,

    2. For non-text content that is used to convey information, text alternatives convey the same information; or,

    3. For non-text content that is intended to create a specific sensory experience, such as music or visual art, text alternatives identify and describe the non-text content; or,

    4. Multimedia alternatives are provided according to guideline 1.2; or,

    5. Non-text content that does not provide information or functionality is marked such that it can be ignored by assistive technology

Level 2 Success Criteria for Guideline 1.1

  1. No level 2 success criteria for this guideline.

Level 3 Success Criteria for Guideline 1.1

  1. For multimedia content, a text document (similar to a play script) is provided that includes descriptions of all important visual information as well as transcripts of dialogue and other important sounds. [I]

Guideline 1.1 (text-equiv) Issues

Who Benefits from Guideline 1.1 (Informative)

  • People who are blind, have low vision, have cognitive disabilities or have trouble reading text for any reason can have the text read aloud to them by assistive technology.

  • People who are deaf, are hard of hearing, or who are having trouble understanding audio information for any reason can read the text presentation or have it translated and presented as sign language by assistive technology.

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

Examples of Guideline 1.1 (Informative)

  • Example 1: an image used as a button. (short equivalent for function)

    A right arrow icon is used to link to the next slide in a slide show. The text equivalent is "Next Slide," so that a screen reader would read the phrase "Next Slide" and automatically identify it as a link by adding the word link or changing the synthesizer's voice.

  • Example 2: a data chart. (short label + longer description)

    A bar chart compares how many widgets were sold in June, July, and August. The short label says, "Figure one - Sales in June, July and August." The longer description identifies the type of chart or graph, provides a high-level summary of the data comparable to that available from the chart or graph, and provides the data in a table or other accessible format.

  • Example 3: an animation. (short label + longer description)

    An animation shows how to tie a knot. The short label says, "An animation showing how to tie a square knot." The longer explanation describes the hand movements needed to tie the knot.

  • Example 4: an audio file of a speech. (short label + transcript)

    An audio file is embedded in a Web page. The short label says, "Chairman's speech to the assembly." A link to a text transcript is provided immediately after the audio clip.

  • Example 5: an audio file of a symphony. (short label)

    An audio file is embedded in a Web page. The short label says, "Beethoven's 5th Symphony performed by the Vienna Philharmonic Orchestra."

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

Editorial Note: To meet our publication deadline, resolution of issues for this guideline are deferred to our next Working Draft. The primary question is, "How do these success criteria apply to every Webcam, newscast, and home broadcast?" Options we are considering include moving existing success criteria from Level 1 to Level 2 or allowing conformance claims to exclude portions of a site, such as, "All pages and applications on this site meet the Level 1 guidelines of WCAG 2.0 except the Web cam at http://example.org/webcam/."

Level 1 Success Criteria for Guideline 1.2

  1. An audio description of visual events is provided for audio-visual media. [I]
  2. Captions are provided for all significant dialogue and sounds in time-dependent material. [I]
  3. Descriptions and captions are synchronized with the events they represent. [I]

    Exception:

    A text transcript or other non-audio equivalent does not need to be synchronized with the multimedia presentation if all four of the following statements are true:

    1. the content is real-time and

    2. the content is audio-only and

    3. the content is not time-sensitive and

    4. the content is not interactive

    Note:

    This exception applies to both success criteria 2 and 3 above.

  4. If the Web content is real-time video with audio, real-time captions are provided. [I]

    Exception:

    If the content is a music program that is primarily non-vocal, then captions are not required.

  5. If the Web content is real-time, non-interactive video (for example, a Webcam view of surrounding conditions such as weather information), then one of the following is provided: [I]

    • a substitute that conforms to guideline 1.1 (for example, an ongoing text report of weather conditions)

    • a link to a substitute that conforms to guideline 1.1 (for example, a link to a weather Web site that conforms to Guideline 1.1)

  6. If a presentation that contains only audio or only video requires users to respond interactively at specific times during the presentation, then a synchronized equivalent presentation (audio, visual or text) is provided. [I]

Exception:

If content that is rebroadcast from another medium or resource meets accessibility requirements for that medium, then the rebroadcast satisfies this checkpoint if it complies with other applicable sections of WCAG 2.0

Level 2 Success Criteria for Guideline 1.2

  1. Synchronized captions are provided for all real-time broadcasts. [I]

    Editorial Note: There are questions about what is possible and what should be required for real-time audio description since there is no way to know when there will be gaps in audio (when descriptions could be read) and other issues with describing real-time events.

Level 3 Success Criteria for Guideline 1.2

  1. No level 3 success criteria for this guideline.

Guideline 1.2 (media-equiv) Issues

Who Benefits from Guideline 1.2 (Informative)

  • People who are deaf or have a hearing loss can access the auditory information through captions.

  • People who are blind or have low vision as well as those with cognitive disabilities who have difficulty interpreting visually what is happening benefit from audio descriptions of visual information.

People without disabilities also benefit from media equivalents:

  • People in noisy environments or with muted sound often rely on captions.

  • Captions help many people to develop language and reading skills.

  • Audio descriptions provide visual information for people who are temporarily looking away from the video presentation, for example, when following an instructional video and looking at their hands.

  • Captions and text descriptions make it possible to index and search media files.

Note:

Time-dependent presentations that require 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 presentation, it may be possible to avoid scenarios where, for example, a user who is deaf would be required to watch an action on the screen and read the captions at the same time. However, this may not be available for live broadcasts (for example, a football game). Where possible (especially for education and training materials), 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 of Guideline 1.2 (Informative)

  • Example 1: a movie clip with audio description and captions.

    A clip from a movie is published on a Web site. In the clip, a child is trying to attract a puppy to the child's bedroom by laying a trail of crumbs. Since the soundtrack includes only the child's mumbling, the audio description that is heard when the child stops mumbling says "Charlie puts a crumb on each stair leading to his room." The caption that appears as he mumbles reads, "[inaudible mumbling]."

  • Example 2: a video clip of a news story.

    A video clip accompanies a news story about flooding in a major city. The reporter gives a verbal description of the scene. No audio description is necessary. The captions display what the reporter is saying.

  • Example 3: a silent animation.

    An animation shows a pantomime with a white face and black costume climbing an invisible ladder. There is no audio track for this animation. No captions or audio description are required. Instead, a text label and description are provided as required by guideline 1.1.

Guideline 1.3 Ensure that information, functionality, and structure are separable from presentation.

Level 1 Success Criteria for Guideline 1.3

  1. Structures and relationships within the content can be derived programmatically. [I]

    Editorial Note: The concepts of "reliable" and "standard" need to be incorporated into the definition of "programmatically."

  2. Emphasis can be derived programmatically. [I]
  3. Any information presented through color is also available without color (for example, through context or markup or coding that does not depend on color). [I]

Level 2 Success Criteria for Guideline 1.3

  1. Information presented using color is also available without color and without having to interpret markup (for example through context or text coding). [V]

Level 3 Success Criteria for Guideline 1.3

  1. No level 3 success criteria for this guideline.

Guideline 1.3 (content-structure-separation) Issues

Who Benefits from Guideline 1.3 (Informative)

  • Separating content and structure from presentation allows Web content to be presented differently to meet the needs and constraints of different users without losing any of the information or structure. For example, information can be presented via speech or braille (text) that was originally intended to be presented visually.

  • It can also facilitate automatic emphasis of structure or more efficient navigation.

  • All of these can benefit people with cognitive, physical, hearing, and visual disabilities.

Examples of Guideline 1.3 (Informative)

Editorial Note: These examples are improvements on previous drafts, but are HTML-specific. These will be generalized in future drafts.

  • Example 1: A form that mentions in text which required fields are missing.

    When a user submits a form without filling in all the required fields, a message appears that informs the user which fields are missing. The missing fields are also indicated in color to help people with cognitive limitations recognize what fields need attention. Because the message is also available in text, people who cannot see color well will still know which fields they have to correct.

  • Example 2: A bus schedule where the headers have been associated with the cells.

    A bus schedule consists of a table with the bus stops listed vertically and the different trips listed horizontally. Each cell contains the time when that bus will be at that bus stop. Structural markup has been used to associate that cell with both the corresponding bus stop and the corresponding trip.

  • Example 3: A form where the labels for the checkboxes have been associated with the checkboxes.

    In a form where users can select different options using checkboxes, the labels for the checkboxes have been associated with the checkboxes. This benefits different types of users. It allows users who are blind to determine what the checkbox is for. People with limited motor functions can check the checkbox more easily because they can click anywhere on the label instead of just on the checkbox.

Guideline 1.4 In visual presentations, make it easy to distinguish foreground words and images from the background.

Level 1 Success Criteria for Guideline 1.4

  1. Any text that is presented over a background is electronically available so that it could be re-presented in a form that allows the text to be distinguished from the background. [I]

    Note:

    Text that meets guideline 1.1 should satisfy this criterion.

Level 2 Success Criteria for Guideline 1.4

  1. Text that is presented over a background has a contrast greater than ____ between the text and the background as measured by ___ or the resource provides a mechanism to allow the text to meet this criterion. [V]

Editorial Note: The working group is seeking an algorithm that measures contrast in a way that is accurate and testable enough that we could include it in the guidelines. One algorithm, which comes from the Techniques For Accessibility Evaluation And Repair Tools document, is currently under consideration for inclusion in the techniques, but the group has not yet found something that is specific enough to be included at the guidelines level.

Level 3 Success Criteria for Guideline 1.4

  1. Text that is presented over a background has a contrast greater than ____ between the text and the background as measured by ___ in default presentation mode. [V]
  2. Text is not presented over a background image or pattern, or if a background image or pattern is present, the text is easily readable when the content is viewed in grayscale to determine if the background makes it difficult to identify individual characters. [V]

Guideline 1.4 (visual-contrast) Issues

Who Benefits from Guideline 1.4 (Informative)

  • Individuals with low vision can easily read characters in the content even if they don't have the wide field of view or full range of color perception used by fully sighted persons to separate text from background images.

Examples of Guideline 1.4 (Informative)

  • Example 1: a background image on a page.

    A background image and text are arranged so that there is no image behind the text or the image is so faint that the difference between the darkest part of the image and the text (which is dark) meets the standard foreground/background contrast requirements. The image behind the text also does not contain lines that are about the same width as the characters so they do not interfere with character recognition.

Guideline 1.5 In auditory presentations, make it easy to distinguish foreground speech and sounds from background sounds. [level 2 guideline]

Level 1 Success Criteria for Guideline 1.5

  1. No level 1 success criteria for this guideline.

Level 2 Success Criteria for Guideline 1.5

  1. No level 2 success criteria for this guideline.

Level 3 Success Criteria for Guideline 1.5

  1. Audio content does not contain background sounds OR the background sounds are at least 20 decibels lower than the foreground audio content with the exception of occasional short sounds. [V]

Note:

A 20 decibel difference in sound level is roughly 4 times quieter (or louder). Background sound that meets this requirement will be approximately four times (4x) quieter than the foreground audio content.

Guideline 1.5 (audio-contrast) Issues

Who Benefits from Guideline 1.5 (Informative)

  • Individuals with hearing impairments that limit their ability to hear all of the frequencies of speech can make out the words from the sounds they can hear because they are not mixed with residual sounds from the music.

Examples of Guideline 1.5 (Informative)

  • Example 1: speech over background sounds.

    Because speech is often naturally mixed with background sounds (movies, live news etc) and cannot be easily removed or separated, captions are provided (under guideline 1.2) to make dialog understandable. However not all people can see or read the captions. Where speech is mixed or recorded so that it is at least 20 db above any background sounds, most people do not need to rely on captions to understand the dialog.

Principle 2: Interface elements in the content must be operable.

Guideline 2.1 Make all functionality operable via a keyboard or a keyboard interface.

Level 1 Success Criteria for Guideline 2.1

  1. All of the functionality of the content, where the functionality or its outcome can be described in a sentence, is operable through a keyboard or keyboard interface. [I]

    Note:

    This includes author-provided accessibility features.

    Note:

    Other interfaces (such as a mouse) can be provided in addition to keyboard operation.

    Note:

    Refer to guideline 4.2 for information regarding user agent support.

Level 2 Success Criteria for Guideline 2.1

  1. Wherever a choice between input device event handlers is available and supported, the more abstract event is used. [I]

Level 3 Success Criteria for Guideline 2.1

  1. All functionality of the content is designed to be operated through a keyboard or keyboard interface.

Guideline 2.1 (keyboard-operation) Issues

Who Benefits from Guideline 2.1 (Informative)

  • Individuals who are blind (and cannot use pointing devices) can have access to the functionality of the Web content or site.

  • Individuals with severe physical disabilities can use speech input (which simulates keystrokes) to both enter data and operate the interface elements on the page.

Examples of Guideline 2.1 (Informative)

  • Example 1: operation with multiple input devices.

    The content relies only on focus-in, focus-out, and activation events; these are defined in the API of the environment for which the content is written, and are intended to be operable by a variety of input devices, including pointing devices, keyboards and speech input systems.

  • Example 2: examples of Web content that would and would not be operable from a keyboard or keyboard interface

    • If it's written to be operable from a computer keyboard, it conforms. (because it is operable from the keyboard.)

    • If it's written to be used on a device that doesn't usually have a keyboard such as a cell phone, but it can be controlled by an optional keyboard for that device, it conforms. (A person who needs a keyboard - or alternate keyboard - can use it to control the application.)

    • If it's written to be used with a device that doesn't have a keyboard, but it could also be used by similar devices that do and it would work with their keyboard, it conforms. (A person who needs a keyboard would not buy the device without the keyboard. That device may itself not be considered accessible. But the content can be controlled from a device with a keyboard and therefore conforms to this guideline.)

    • If it's written to work with devices that do not have keyboards and it can not be used by any other devices that do have keyboards, then it does not conform. (It cannot be accessed via keyboard.)

Guideline 2.2 Allow users to control time limits on their reading or interaction unless specific real-time events or rules of competition make such control impossible.

Level 1 Success Criteria for Guideline 2.2

  1. Content is designed so that time limits are not an essential part of interaction, or at least one of the following is true for each time limit: [I]

    • the user is allowed to deactivate the time limit or;

    • the user is allowed to adjust the time limit over a wide range which is at least ten times the length of the default setting or;

    • the user is warned before time expires, allowed to extend the time limit with a simple action (for example, "hit any key") and given at least 10 seconds to respond or;

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

    • the time limit is part of an activity where timing is essential (for example, competitive gaming or time-based testing) and time limits can not be extended further without invalidating the activity.

Level 2 Success Criteria for Guideline 2.2

  1. The user is allowed to turn off content that blinks for more than 3 seconds. [I]
  2. The user is allowed to pause and/or permanently stop moving or time-based content. [I]

Level 3 Success Criteria for Guideline 2.2

  1. The content has been designed in a way that any time limits in the content would pass level 1, success criteria 1 for this guideline without exceptions. [V]

    Editorial Note: Real time events would not be allowed with this wording. Do we want to accept them?

  2. Any non-emergency interruptions, such as the availability of updated content, can be postponed and/or suppressed by the user. [V]

Guideline 2.2 (time-limits) Issues

Who Benefits from Guideline 2.2 (Informative)

  • People with reading disabilities, cognitive disabilities, and learning disabilities often need more time than most people to read and comprehend written text.

  • People with physical disabilities can access content that is updated often in cases where content might not be processed and read before being refreshed or when read out of order an assistive technology or voice browser.

Examples of Guideline 2.2 (Informative)

  • Examples of content that must meet the success criteria of this checkpoint:

    • automatic refresh,

    • redirection,

    • blinking or scrolling text,

    • dialog that disappears after a short period,

    • shutdown or deactivation of resource if activity is not received in a set amount of time.

  • Example 1: blinking text.

    Client-side scripting is used to create blinking text. The content provides an option that allows the user to turn off the blinking.

  • Example 2: a news site that is updated regularly.

    A news site causes its front page to be updated every half hour. The front page contains minimal text and primarily consists of links to content. A user who does not wish the page to update selects a checkbox. The checkbox is in the "user preferences" portion of the site which is one of the first links on each page.

Guideline 2.3 Allow users to avoid content that could cause photosensitive epileptic seizures.

Level 1 Success Criteria for Guideline 2.3

  1. Content that violates General Flash Threshold or Red Flash Threshold is marked in way that the user can access prior to its appearance. [V]

Level 2 Success Criteria for Guideline 2.3

  1. Content does not violate the General Flash Threshold or Red Flash Threshold. [V]

Level 3 Success Criteria for Guideline 2.3

  1. Content does not violate any of the Spatial Pattern Thresholds. [V]

General Flash Threshold

  • A sequence of flashes or rapidly changing image sequences is not permitted when both the following occur:

    1. the combined area of flashes occurring concurrently (but not necessarily contiguously) occupies more than one quarter of any 355 x 268 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 by 768 pixels and

    2. there are more than three flashes within any one-second period.

    Note:

    For the general flash threshold, a flash is defined as a pair of opposing changes in luminance (i.e., an increase in luminance followed by a decrease, or a decrease followed by an increase) of 20 candelas per rectangle meter (cd.m-2) or more and where the screen luminance of the darker image is below 160 cd.m-2.

Red Flash Threshold

  • A transition to or from a saturated red at any luminance level is not permitted when both of the following occur:

    1. the combined area of flashes occurring concurrently occupies more than one quarter of any 355 x 268 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 by 768 pixels and

    2. there are more than three flashes within any one-second period.

    Note:

    For the red flash threshold, a flash is defined as any pair of opposing transitions to or from a saturated red at any luminance level . (See notes 1 and 2 below)

Spatial Pattern Thresholds

  • Clearly discernible stripes consisting of more than five light-dark pairs in any orientation are not permitted when the stripes are stationary when the pattern occupies more than 40% of any 355 x 268 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 by 768 pixels.

  • Clearly discernible stripes consisting of more than five light-dark pairs in any orientation that change direction, oscillate, flash, or reverse in contrast are not permitted when the pattern occupies more than 25% of any 355 x 268 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 by 768 pixels.

    1. Clearly discernable stripes are stripes where the screen luminance of the darker bars in the pattern is below 160 cd.m-2 and differs from the lighter bars by 20 cd.m-2 or more (see notes 1 and 2 below).

Guideline 2.3 (flicker) Issues

Notes:

  1. Video waveform luminance is not a direct measure of display screen brightness. Not all display devices have the same gamma characteristic, but a display with a gamma of 2.2 may be assumed for the purpose of determining electrical measurements made to check compliance with these guidelines.

  2. For the purpose of measurements made to check compliance with these guidelines, pictures are assumed to be displayed in accordance with the 'home viewing environment' described in Recommendation ITU-R BT.500 in which peak white corresponds to a screen illumination of 200 cd.m-2.

  3. Thresholds are based on ITC Guidance Note for Licensees on Flashing Images and Regular Patterns in Television (Revised and re-issued July 2001) as modified by the Wisconsin Computer Equivalence Algorithm.

Editorial Note: A free tool will be available from the University of Wisconsin's Trace Center that will carry out the above analysis on Web content. The tool will be available by the second quarter of 2004.

Who Benefits from Guideline 2.3 (Informative)

  • Individuals with photosensitive epilepsy can avoid having seizures triggered by flashing or by spatial patterns.

Guideline 2.4 Facilitate the ability of users to orient themselves and move within the content. [level 2 guideline]

Level 1 Success Criteria for Guideline 2.4

  1. No level 1 success criteria for this guideline.

Level 2 Success Criteria for Guideline 2.4

  1. In documents greater than 50,000 words or sites larger than 50 perceived pages, at least one of the following is provided. [V]

    Editorial Note: What's a perceived page? What if it's a voice XML application? How does it apply to Web applications? Why 50 and 50,000?

    1. hierarchical structure,

    2. table of contents (for pages) or site map (for sites),

    3. alternate display order (for pages) or alternate site navigation mechanisms (for sites).

  2. Large blocks of material that are repeated on multiple pages, such as navigation menus with more than 8 or more links, can be bypassed by people who use screen readers or who navigate via keyboard or keyboard interface. [V]

Level 3 Success Criteria for Guideline 2.4

  1. Information is provided that would indicate at least one logical sequence in which to read a document. [I]
  2. Diagrams are constructed so that they have structure that users can access. [I]
  3. Logical tab order has been created. [I]

    Editorial Note: "logical tab order" may not be testable.

  4. Each page or other resource that can be accessed separately and that supports a title has a title that identifies the subject or purpose of the resource. [I]

    Editorial Note: We need to define "accessed separately" to clarify that what is being titled is a piece of content in its entirety vs. individual elements or portions of the content.

  5. There is a statement associated with the content asserting that items from the following list were considered: [V]

    1. Breaking up text into logical paragraphs,

    2. Dividing documents, especially very long ones, into hierarchical sections and subsections with clear and informative titles,

    3. Revealing important non-hierarchical relationships, such as cross-references so that the relationships are represented unambiguously in the markup or data model.

      Editorial Note: Are there any others?

Guideline 2.4 (navigation-mechanisms) Issues

Who Benefits from Guideline 2.4 (Informative)

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

    • Users with physical disabilities can use structure to more easily jump between paragraphs, chapters, sections etc.

    • Users with cognitive disabilities can use structure (chapter titles, headers, etc.) to provide more context for the text that follows them. They also provide warning of a change in context and reorient the user to the new focus.

    • Users with blindness or low vision can jump from header to header to get an overview or to more quickly "skim" to the section they are interested in.

    • Readers with low vision can sometimes (depending on display technology) change how chapter titles and headers are displayed to make them more visible and easier to use when skimming the document.

    • the content can be presented on a variety of devices because the device software can choose only those elements of the content that it is able to display and display them in the most effective way for that device.

  • Providing different navigation mechanisms can provide a better match between different people's skills, background knowledge, visual vs. text orientation, and the type of information they are seeking at the moment.

  • Individuals with cognitive disabilities may find it easier to ask for what they want than to deduce its location from categorical choices.

  • Individuals with low vision or blindness may find search techniques that fetch everything that relates to a topic of interest to be easier than techniques that require them to scan lists or content for the items.

  • Presentation that emphasizes structure:

    • enables users with cognitive and visual disabilities to orient themselves within the content,

    • enables all users to move quickly through the content and notice major content divisions

    • enables all users, but particularly users with visual or cognitive disabilities to focus on important content,

    • enables all users, but particularly users with visual or cognitive disabilities to distinguish the different types of content.

Examples of Guideline 2.4 (Informative)

  • Example 1: documentation for a product.

    Identifying chapters in the structure of a book is appropriate and accepted use of labeling the structure. Within the chapters, headings identify (label) changes in context and highlight ideas contained in the following text. Subtle differences between the appearance of the chapter title and the section headings helps the user understand the hierarchy and relationship between the title and headings. The difference might be font size and margin indentation when presented visually, and spoken in a different voice or preceded by a sound when presented auditorily.

  • Example 2: a scalable image of a bicycle.

    Lines and a circle (spokes and rim) are grouped into a "wheel." Lines in a triangle that attach to each wheel are grouped into a "frame."

  • Example 3: user interface.

    User interface controls are divided into organized groups.

  • Example 4: a data table.

    Groups of rows or columns are labeled with headers.

  • Example 5: an audio presentation.

    An audio rendering of a document, generated according to a style sheet, uses a different, more formal voice to read titles and headers so the listener can easily identify the words as a title and not part of the running text.

Guideline 2.5 Help users avoid mistakes and make it easy to correct them. [level 2 guideline]

Level 1 Success Criteria for Guideline 2.5

  1. No level 1 success criteria for this guideline.

Level 2 Success Criteria for Guideline 2.5

  1. If a user error is detected, the error is identified and provided to the user in text

  2. If a user error is detected, and suggestions for correction are known and can be provided without jeopardizing security or purpose (for example, test validity), they are provided (in an accessible form that meets Level 1 success criteria).

  3. Where consequences are significant and time-response is not important, one of the following is true:

    1. Actions are reversible.

    2. Where not reversible, actions are checked for errors before going on to the next step in the process.

    3. Where not reversible, and not checkable, the user is able to review and confirm or correct information before submitting it.

Level 3 Success Criteria for Guideline 2.5

  1. Where the input options are known, there are less than 75 of them, and they can be provided without jeopardizing security, test validity, etc, users are allowed to select from a list of options as well as to enter text directly.

  2. Checks for misspelled words are applied and correct spellings are suggested when text entry is required.

Guideline 2.5 (minimize-error) Issues

Who Benefits from Guideline 2.5 (Informative)

  • Identifying typing errors helps individuals with writing disabilities and people with dyslexia who often have difficulty writing text in forms or other places that need text input.

  • Certain disabilities make it more difficult to operate input devices, resulting in more input errors. For example, individuals with limited motor functions are more likely to make errors when they operate a mouse or a keyboard. Speech recognition systems may find it more difficult to recognize the speech of individuals with speech disabilities. Features that assist in recognizing and correcting errors benefit individuals with these types of disabilities.

Examples of Guideline 2.5 (Informative)

  • Example 1: a search engine.

    A search engine is provided with a variety of search options for different skill levels and preferences. It includes a spell checker and offers "best guess" alternatives, query-by-example searches, and similarity searches.

Principle 3: Content and controls must be understandable.

Guideline 3.1 Ensure that the meaning of content can be determined.

Level 1 Success Criteria for Guideline 3.1

  1. The natural language of the document as a whole can be identified by automated tools. [I]
  2. The meaning of abbreviations and acronyms can be programmatically located. [I]

Level 2 Success Criteria for Guideline 3.1

  1. The meanings and pronunciations of all words in the content can be programmatically located. [I]
  2. The meaning of all idioms in the content can be programmatically determined. [I]
  3. For each foreign language passage or phrase in the body of the content, the language is identified through markup or other means. Foreign passages or phrases are passages or phrases that are in a language other than the primary language of the document. [I]

    Note:

    This does not include use of foreign words in text where such usage is a standard extension of the language.

Level 3 Success Criteria for Guideline 3.1

  1. Where a word has multiple meanings and the intended meaning is not the first in the associated dictionary(s), then additional markup or another mechanism is provided for determining the correct meaning. [I]
  2. Section headings and link text are understandable when read by themselves as a group (for example, in a screen reader's list of links or a table of contents). [V]
  3. There is a statement associated with the content asserting that the Strategies for Reducing the Complexity of Content (the following list) were considered. [V]

    Editorial Note: We are still examining methods to make some or all of these testable (which might make them success criteria on their own).

    • In general

      • Organizing material so it is easy to read and use.

      • Using a style manual, dictionary, and other reference materials.

      • Testing documents to learn if potential users understand the material, and including people with cognitive, learning, or reading disabilities in the test group.

      • Developing a single topic or subtopic per paragraph.

    • Vocabulary

      • Using vocabulary that is likely to be familiar to intended readers.

        • If the resource is intended for people who work in a particular technical field, consider using a Controlled Language. For example, a resource designed for aircraft engineers could use a controlled language like the one used by Boeing Aircraft Company.

        • If a technical resource is intended for translation into other languages, consider using a Controlled Language.

        • Avoiding professional jargon, slang, and other terms with a specialized meaning that may not be clear to people outside a specific group when resources are intended for a general audience or for translation into other languages,. It may also be helpful to review the document for plain language, using a checklist like the ones produced by US and Canadian government agencies.

        Editorial Note: Need to add examples from other countries and other languages.

      • Using length and complexity of sentences that are consistent with recommended best practices for the intended audience, such as those found in current textbooks about writing in the audience's field or discipline.

    • Sentences

      • Making sentence-length consistent with common practice in the language of the document or the primary audience for whom the document is intended. Textbooks about writing in that field or related disciplines may be useful when such textbooks are available.

    • Syntax

      • Using the simplest sentence forms consistent with the purpose of the content

        • For example, the simplest sentence-form for English consists of Subject-Verb-Object, as in John hit the ball or The Web site conforms to WCAG 2.0.

      • Using bulleted or numbered lists instead of paragraphs that contain long series of words or phrases separated by commas.

    • Nouns, noun-phrases, and pronouns

      • Using single nouns or short noun-phrases.

      • Making clear pronoun references and references to earlier points in the document

        example of potential ambiguity: The sentence below contains several pronouns whose references are not clear:

        Web developers can't understand those guidelines because they don't speak their language.

        1. It is not clear which guidelines are referred to as "those guidelines" (the guidelines you are reading now would be these guidelines)

        2. It isn't clear whether the pronoun "they" refers to the Web developers or to the guidelines (the rules of English syntax indicate that the reference is to the guidelines, but common usage doesn't always obey those rules)

        3. It isn't clear whether the pronoun "their" refers to the language used by the Web developers or the language in which the guidelines are written.

        The sentence can be rewritten to resolve the ambiguities:

        Web developers can't understand these guidelines because the guidelines are not written in the developers' language.

    • Verbs

    • Voice

      • Using the active voice for documents written in English and some other Western languages, unless there is a specific reason for using passive constructions. Sentences in the active voice are often shorter and easier to understand than those in the passive voice.

        • Active: Many people believe that readers understand sentences in the active voice more easily than sentences in the passive voice.

        • Passive: It is believed by many that sentences in the active voice are more easily understood by readers than sentences in the passive voice.

    • Tenses

      • Using verb tenses consistently.

        For example, do not switch randomly between past and present tense. In the sentences, John left the room. He takes the elevator down to the lobby, the shift from past tense (in the first sentence left the room) to present tense in the second sentence (takes the elevator) might create ambiguity about John's use of the elevator: did he use it in the past or is he using it now?

    • Logic and relationships

      • Indicating logical relationships between phrases, sentences, paragraphs, or sections of the text.

        • In some cases, simple words such as and, however, furthermore, and therefore may be enough to make the logical relationship clear between one sentence and the next. Other cases may require longer phrases or even additional sentences.

    • Instructions and operable content

      • Thoroughly explaining instructions or required actions.

      • Using names and labels consistently.

      • Being clear where the document:

        • 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).

      • Using a goal-action structure for menu prompts.

      • Using default settings (and the ease in re-establishing them)

      • Using two-step, "select and confirm" processes to reduce accidental selections for critical