Web Content Accessibility Guidelines 2.0

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.

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.

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

Introduction

Purpose

This document outlines design principles for creating accessible Web sites. 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:

An introduction
The 5 major Guidelines for accessibility (Perceivable, Operable, Navigable, Understandable and Robust).
The (non-technology-specific) checkpoints for each guideline (21 in total).
Success criteria (normative), and definitions, benefits and examples (all non-normative) for each checkpoint
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:

Hypertext Markup Language (HTML) and Extensible Hypertext Markup Language (XHTML™) Techniques
Cascading Style Sheets (CSS) Techniques
Server-side scripting Techniques
Client-side scripting Techniques
Scalable Vector Graphics (SVG) Techniques
Synchronized Multimedia Integration Language (SMIL) Techniques
Extensible Markup Language (XML) Techniques

(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

In order to claim any conformance to the guidelines it is necessary to satisfy the "MINIMUM" success criteria of every checkpoint. The minimum criteria represent those aspects of the checkpoint requirements which, in the absence of a full implementation, will nonetheless offer substantial benefit to people with disabilities by removing barriers that would otherwise make it difficult or impossible to access the content. The Level 2 and Level 3 criteria build upon this functionality, making the content accessible to people who would not be able to access it, or could do so only with substantial difficulty, if only the minimum criteria had been met.A full discussion of the underlying rationale of the conformance scheme, including the three levels of conformance, is presented in Appendix B.

Sites which go beyond the Minimum level of conformance can claim conformance at higher levels in several ways.

If they meet all of the criteria for Level 2 or Level 3 they can claim conformance at those levels.
If they meet some but not all of the criteria for Level 2 then can claim conformance at Level 1+.
If they meet all of the criteria for level 2 and some but not all of the criteria for Level 3 then can claim conformance at Level 2+.
It is possible and recommended that sites report specifically which criteria they have met within each of the guidelines and checkpoints. This can be done using [Reviewer's Note: method not yet defined].

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.

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.
Operable. Ensure that the interface elements in the content are operable by any user.
Navigable. Facilitate content orientation and navigation
Understandable. Make it as easy as possible to understand the content and controls.
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:

Someone who cannot hear will want to see the information normally presented via sound.
Someone who cannot see will want to hear or read through braille information that is usually presented visually.
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. 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.

Definitions (informative)

A text equivalent

serves the same function as the non-text content was intended to serve.
communicates the same information as the non-text content was intended to convey.
may contain structured content or metadata.

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)

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

Examples (informative)

Example 1: an image used as a button. (short description of 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 what is read by a screen reader would be "link: Next Slide."
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 lists the data themselves.
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 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."

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:

an audio description is provided of all visual information in scenes, actions and events (that can't be perceived from the sound track).
- The audio description should 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).
all significant dialogue and sounds are captioned
exception: if the Web content is real-time audio-only, if not time-sensitive (news, emergency, etc.), and not interactive, a transcript or other non-audio equivalent is sufficient.
descriptions and captions are synchronized with the events they represent.
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
if the Web content is real-time non-interactive video (e.g. a Webcam of ambient conditions), an accessible alternative is provided that achieves the purpose of the video. If the author's purpose is to provide real-time information, a media equivalent is provided that conforms to checkpoint 1.1, or a link is provided to content elsewhere which conforms to checkpoint 1.1 (e.g. a link to a weather Web site).
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:

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).
captions and Audio descriptions are provided for all live broadcasts that are professionally produced.
if Web content is an interactive audio-only presentation, the user is provided with the ability to view only the captions, the captions with the audio, or both together.

You will have successfully met Checkpoint 1.2 at Level 3 if:

a text document (a "script") that includes all audio and visual information is provided.
captions and Audio descriptions are provided for all live broadcasts which provide the same information.

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

(presently no additional criteria for this level.)

Definitions (informative)

A time-dependent presentation is a presentation which

is composed of synchronized audio and visual tracks (e.g., a movie), OR
requires the user to respond interactively at specific times in the presentation.

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

captions are text equivalents of auditory information from speech, sound effects, and ambient sounds that are synchronized with the multimedia presentation.
audio descriptions are equivalents of visual information from actions, body language, graphics, and scene changes that are voiced (either by a human or a speech synthesizer) and synchronized with the multimedia presentation.

Benefits (informative)

People who are deaf or have a hearing loss can access the auditory information through the 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 the audio descriptions of the visual information.

People without disabilities also benefit from the media equivalents.

People in noisy environments or with muted sound often use captions.
Captions are used by many to develop language and reading skills.
Audio descriptions also provide visual information for people who are temporarily looking away from the video presentation such as when following an instructional video and looking at their hands.
Captions and text descriptions can also be used to index and search media files.

Note: Time-dependent presentations that require dual, simultaneous attention with a single sense can 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 dual, simultaneous attention or so that it gives the user the ability to effectively control/pause different media signals.

Examples (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 lure a puppy to the child's bedroom by laying a trail of crumbs. The child mumbles inaudibly to himself as he lays the trail. When not watching the video, it is not obvious that he is laying a trail of crumbs since all you hear is the mumbling. The audio description that is interspersed with the child's mumbling says "Charlie lays a crumb on each stair leading to his room." The caption that appears as he mumbles is, "[inaudible mumbling]."
Example 2: a video clip of a news story.
A video clip accompanies a news story about the recent flooding in a major city. The reporter describes what is seen, for everyone. No audio description is necessary. The captions display what the reporter is saying.
Example 3: a silent animation.
An animation shows a pantomime climbing a ladder. There is no audio track for this animation. No captions or audio description are required. Instead, a text equivalent is provided as described in checkpoint 1.1.

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)

Separating content and structure from presentation allows Web pages 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.

Examples (informative)

Example 1: a multi-column document.
A document is marked up with headings, paragraphs and other structural features. It is presented visually in three columns. The markup that creates the columns is separate from the markup that specifies the logical structure of the document.
Example 2: a scrolling list of stock prices.
Current stock quotes are scrolled horizontally across the screen. The data are separate from the methods used to scroll the text across the page.
Example 3: a 3-dimensional site map.
A custom user interface renders 3D visualizations of the pages on a site and how they relate to one another from a data source. Any hierarchical relationships, groupings, cross-references, etc. would originate in the data source so that alternate interfaces could be rendered (from the same source) that expose the structure of the site in an accessible form. (See also checkpoint 5.4)
Example 4: a list that allows users to sort information on a page according to preference.
A script allows a user to rearrange a categorical listing of music files by date, artist, genre, or file size. The script updates both the structure and the presentation accordingly when generating alternate views.

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:

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:

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:

content is constructed such that users can control the presentation of the structural elements.
alternate presentation formats are available to vary the emphasis of the structure.

The following are additional ideas for enhancing a site 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.

for visual presentations, use font variations, styles, size and white space to emphasize structure.
use color and graphics to emphasize structure.
for auditory presentations, use different voice characteristics and/sounds for major headings, sections and other structural elements.
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.
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.

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:

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:

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.
abbreviations and acronyms are clearly identified where they occur. (See also checkpoint 4.3.)
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:

the primary natural language of the content is identified at the page level.

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

(presently no additional criteria for this level.)

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)

Phrases from various languages, acronyms and abbreviations are often interspersed in writing. When these phrases are identified, a speech synthesizer can voice text with the appropriate accent and pronunciation. When they are not identified, the speech synthesizer will use the default accent and pronunciation of the language on the rest of the page, which can make the phrase unintelligible. Identifying changes in language and marking abbreviations and acronyms as such will also allow a tool to ask for automatic translations of that content. When editing content, authoring tools can switch between appropriate spelling dictionaries.
Facilitating unambiguous decoding of characters and words in content is also helpful for individuals who are learning to read or learning a second language.

Examples (informative)

Example 1: a French phrase in an English sentence.
In the following sentence, "And with a certain je ne sais quoi, she entered both the room, and his life, forever." the French phrase "je ne sais quoi" is marked as French. Depending on the markup language, English may either be marked as the language for the entire document except where specified, or marked at the paragraph level.
Example 2: an acronym in a page title.
In the following heading, "People of the W3C." the acronym "W3C" is marked as an acronym. Because it has been marked appropriately, the user agent would be able to speak the letters of the acronym one at a time rather than attempting to pronounce it as though it were a word.

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.

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:

automatic refresh,
redirection,
blinking or scrolling text
dialog that disappears after a short period
shutdown or deactivation of page 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 user can deactivate the use of scripting in his or her browser or override the use of scripts with a user style sheet.
Example 2: a news site that is updated regularly.
A news site causes its front page to be updated every 1/2 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.

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

Checkpoint 3.1 Provide structure within content.

Success criteria

You will have successfully met Checkpoint 3.1at the Minimum Level if:

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:

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:

information is provided that would allow an assistive technology to determine at least one logical, linear reading order
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 a site 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.

break up text into logical paragraphs.
provide hierarchical sections and titles, particularly for longer documents
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.
divide very large works into sections and or chapters with logical labels.
others?

Definitions (informative)

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

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.
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,

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.

Examples (informative)

Example 1: a physics dissertation.
A dissertation contains well-defined sections such as "Abstract," "Table of Contents," "Chapter 1," etc. The pieces in each section (paragraphs, subheadings, quotes) are denoted with structural markup.
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.

Definitions (informative)

Mechanisms that cause extreme changes in context include:

opening a new browser window unexpectedly and without any nonvisual cue (back button suddenly appears nonfunctional)
in an auditory presentation, the speaker changes with no visual cue and no notation in captions.
captions that do not identify a change in speaker

Common user actions include:

mouse movements
key activation
link selection
use of browser navigation buttons (e.g. back and forward)
opening new browser windows

Common responses to user actions include:

loading a new page
exposing/concealing content based on mouse position or keyboard focus
displaying the contents of a menu (auditorally or visually)
displaying pop-up menus or windows
submitting a form

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)

Individuals who are unable to detect extreme changes in context or may not realize that the context has changed are less likely to become disoriented while navigating a site. This applies to people in the following ways:
- Individuals who are blind or have low vision may have difficulty knowing when a visual context change, such as a new window popping up, has occurred. In this case, warning users of context changes in advance minimizes confusion when the user discovers that the back button no longer behaves as expected.
- Using captions to note changes in speaker is beneficial for individuals who are deaf or hard of hearing and who may be unable to discern changes in speaker for audio-only presentations.
Some individuals with low vision, with dyslexia and who have difficulty interpreting visual cues may benefit from additional cues in order to detect extreme changes in context.

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)

Example 1: a form to deactivate pop-up windows.
A checkbox is provided on a page of links to let the user select whether they want the resultant pages to appear in new windows or not.
Example 2: a warning given before a pop-up window.
At the end of a news story, several links are provided for more information. At the beginning of each link is an icon of an arrow with the text equivalent, "Link will open in new window."
Example 3: frames that do not track history making the back button behave unexpectedly.
Example 4: forms.

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

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 as clearly and simply as is [appropriate / possible] for the purpose of the content.

Reviewer's Note: This item is under discussion. There is consensus for the existence of the checkpoint but not for the form of the success criteria. We do not therefore have something for the draft at this time. There is a list below of items that are being explored for inclusion either as success criteria or as Advisory Recommendations. We are also compiling a longer list (approx 50 items) of different ideas that relate to this checkpoint.

This checkpoint is very difficult and the group is wrestling with a number of problems. Among them:

It is very difficult to determine what makes writing clear and simple for all topics.
Some content is derived from other sources and is copyrighted so it cannot be altered.
Some materials or topics cannot be communicated accurately in simple language.
There are some cases where the form is specific to the intent, (poetry, exposition )
Since some people can not understand the content no matter how simply it is written, it is not possible to make any content accessible to everyone. Therefore, we are having difficulty finding specific objective criteria that could be applied across all types of content and sites.

Comments, suggestions and contributions to the discussion and work on this topic are also solicited. Refer to the issues list for more information.

Success criteria

You will have successfully met Checkpoint 4.1 at the Minimum Level if:

(still under construction.)

You will have successfully met Checkpoint 4.1 at Level 2 if:

(still under construction.)

You will have successfully met Checkpoint 4.1 at Level 3 if:

(still under construction.)

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

(still under construction.)

Partial list of items being explored for inclusion as success criteria or advisory recommendations

content under site control is written as clearly and simply as the author feels [appropriate / possible] for the purpose of the content.
the content has been reviewed and is believed to be written as clearly and simply as is [appropriate / possible] for its intended purpose
summaries and/or simpler forms are provided for key pages or sections of the content.
provide an outline or a summary for your document.
break up long paragraphs into shorter ones, with one idea per paragraph.
break up long sentences into shorter ones.
provide accurate unique page titles.
ensure that headings and link text are unique and that they make sense when read out of context.
provide definitions for any jargon or specialized terminology used in your document.
provide explanations of figurative, metaphorical, or idiomatic uses of language (for example, 'haven't seen you in a coons age' or 'the sight tore my heart out').
language should be used that your intended audience ought to be familiar with.
when introducing new concepts or terms, they should be defined or annotated in language that the audience is expected to be familiar with, or definitions or explanations should be linked to that might be easier to understand.

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)

Sounds, graphics, videos and animations can help make concepts presented in a Web site easier to understand, especially for people with cognitive, reading, or learning disabilities or those who are unfamiliar with the language of the text of the site.

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)

Example 1: a description of a process.
A page describes how to learn to play soccer. Each step in learning the fundamentals of the game is illustrated with a photograph of a player doing what is described in the text.
Example 2: a concrete concept.
The primary concept on a page is concrete. It is discussing Mt. Pinatubo. It includes both a description of the 1991 eruption as well as photos of the eruption and the aftermath. It links to another site that contains video and another site that contains a 3D simulation of what happened underneath the crust and within the volcano during the eruption.
Example 3: child's report of school trip.
A child went with her school on a trip to a bicycle manufacturing plant. She wrote a report for her family and friends to post to the Web. In the report, she includes the company logo as well as a picture of a bicycle on the assembly line. She links to the company Web site for more information. She includes photos she took of the plant.
Example 4: stock trading data.
A news site is comparing the performance of the economy from 3rd quarter of this year with 3rd quarter from the last 3 years. They compare prices of the most popular stocks. They present the data in a bar graph with a link to the raw data they used to create the bar graph.
Example 5: history of music.
A grandfather's hobby is listening to and playing music. He creates a Web site that includes examples of many different types of music and musical instruments. When describing specific types of music, he links to a short sound clip.

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:

data tables,
concepts that are esoteric or difficult to understand,
content that involves several layers.

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)

Summarizing information that is difficult to understand helps people who do not read well.
Providing a summary of the visual cues that show relationships between complex information helps people who do not use visual cues or who have difficulty using visual cues. For example, people who are completely blind do not use any visual cues, while people with dyslexia or with low vision might have difficulty interpreting visual cues.
Defining key terms and specialized language will help people who are not familiar with the topic.
Providing the expansion of abbreviations and acronyms not only helps people who are not familiar with the abbreviation or acronym but can clarify which meaning of an abbreviation or acronym is appropriate to use. For example, the acronym "ADA" stands for both the American with Disabilities Act as well as the American Dental Association.

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

Definitions (informative)

A technology is a

markup or programming language
application Programming Interface (API)
or communication protocol

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:

Individuals can identify (either through site documentation or automatically through metadata) whether or not they are likely to be able to use a site. In conjunction with a search engine or a proxy server, this could be used to automatically filter out sites a user can not access or to automatically filter to the top sites that would be most usable.
Requiring sites to document their baseline will cause them to evaluate assumptions about user agents and will minimize the number of sites that are inadvertently inaccessible because they are unaware of backward compatibility issues.

Benefits of designing for backward compatibility:

Individuals who must use alternative browsing technologies and devices will be able to access the content.
Individuals who can not afford or otherwise do not have access to newer technologies also benefit from backward compatibility in that they will not need to purchase upgrades or equipment as often.

Examples (informative)

Example 1: an online store.
By documenting minimum user agent requirements, the store makes it possible for people using particular technologies to determine if they are going to have trouble using the store or its checkout mechanism without having to go through the entire process of shopping and checkout only to find out that they are unable to complete their transaction at the end. They can, therefore, shop at stores they can be successful at.
Example 2: an Intranet site.
A large company was concerned about the ability to address individuals at many diverse sites that have different technology bases. They have, therefore, created two versions of their content and documented the requirements for each, making it easy for individual sites to determine which version would work for their technologies.

Appendix A: Glossary

Reviewer's Note: Should we include only the definitions of terms appearing in the guidelines or is there some subset of key terms from the glossary that should also be included? We also need to make sure that the glossary definitions are the same as the definitions which appear in the guidelines themselves. 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.

Appendix B: Explanation of Conformance Levels and Success Criteria

The Three Levels of Conformance

The effect of the three levels of conformance defined in these guidelines may be characterized as follows.

If Web content satisfies a checkpoint at the first conformance level (i.e., "minimum"), then the barriers to access which the checkpoint was designed to address will have been minimally overcome for at least some people with disabilities. The quality of access thus provided is not necessarily high, and there may well be people with disabilities to whom the content remains inaccessible due to issues relevant to the checkpoint, despite the attainment of minimal conformance.

At level 2, a more demanding standard of access is achieved. Often, this is assured by requiring, in success criteria at this level, that the access-related features of the content be reviewed for quality and completeness. In undertaking such reviews, it is recommended, though not required for purposes of conformance, that consistent processes be followed and that, if possible, these should include evaluation of the content by users with disabilities, for example as part of a testing procedure. To guide designers and evaluators in developing content and reviewing it for accessibility, the additional ideas section that appears under most checkpoints, lists various factors which greatly enhance the level of access provided. These factors are not in themselves testable (see below), but they should be taken into account in designing content and assessing its quality, as required by the success criteria at level 2 of the guidelines.

At level 3, the highest possible standard of access is attained along the dimension identified in the checkpoint. The purpose of implementing a checkpoint at level 3 is typically to optimize the content for use by people with specific requirements or expectations. For this reason, there may be particular types of content for which conformance to a given checkpoint, at level 3, is not feasible. Nevertheless, implementors are strongly encouraged to meet level 3 success criteria wherever possible. Moreover, there are some people with disabilities who may only be able to access the content if it conforms to level 3 of one or more particular checkpoints. [Perhaps we need an example here?]

Testability

All success criteria in these guidelines are testable, according to the following definition. A success criterion is considered testable if:

There nonetheless exist requirements, or factors of importance to accessibility, which are not testable according to the above definition. These have been placed in the additional ideas sections of relevant checkpoints, and should be taken into account not only in developing Web content, but also, as noted above, in evaluating its degree of accessibility to people with disabilities.

Appendix C: Contributors

Appendix D: 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:

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:

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

Appendix E: 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.

Web Content Accessibility Guidelines 2.0

W3C Working Draft 8 January 2003