Web Content Accessibility Guidelines 2.0 -- View 3 - Required, Best Practice and Informative

W3C Working Draft 23 Sept. 2003

This version:
Latest version:
Ben Caldwell, Trace R&D Center
Wendy Chisholm, W3C
Gregg Vanderheiden, Trace R&D Center
Jason White, University of Melbourne


This draft is the fourth in a series of reorganization proposals.


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 an editors' copy that has no official standing.

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

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

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

The Working Group welcomes comments on this document at 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


Guideline 1: PERCEIVABLE. Make Content Perceivable by Any User

Core Checkpoints for Guideline 1

1.1 [CORE] All non-text content that can be expressed in words has a text equivalent of the function or information that the non-text content was intended to convey.

Required Success Criteria for Checkpoint 1.1
  1. non-text content that can be expressed in words has a text-equivalent explicitly associated with it.

    • The text equivalent fulfills the same function as the author intended for the non-text content (i.e. it presents all of the intended information and/or achieves the same function of the non-text content).

  2. non-text content that can not be expressed in words has a descriptive label provided as its text-equivalent.

Best Practice Measures for Checkpoint 1.1
  1. non-text content that can not be expressed in words has a text equivalent for all aspects that can be expressed in words.

  2. a text document that merges all audio descriptions and captions into a collated script (that provides dialog, important sounds and important visual information in a single text document) is provided.

Benefits of Checkpoint 1.1 (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 of Checkpoint 1.1 (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."

1.2 [CORE] Synchronized media equivalents are provided for time-dependent presentations.

Editorial Note (06/10/03): There is discussion about moving some of the current success criteria from Required to Best Practice or to an Extended checkpoint. The issue stems from trying to apply the success criteria to every Web cam, newscast, and home broadcast. Another approach is to allow a conformance claim to state, for example, "All pages and applications on this site meet the Core checkpoints of WCAG 2.0 except the Web cam at http://example.org/webcam/."

Required Success Criteria for Checkpoint 1.2
  1. an audio description is provided.

  2. all significant dialogue and sounds are captioned


    If the Web content is real-time and audio-only and not time-sensitive and not interactive a transcript or other non-audio equivalent is sufficient.

    Editorial Note: This exception also applies to item 3.

  3. descriptions and captions are synchronized with the events they represent.

  4. if the Web content is real-time video with audio, real-time captions are provided unless the content:

    • is a music program that is primarily non-vocal

  5. if the Web content is real-time non-interactive video (e.g., a Webcam of ambient conditions), either provide an equivalent that conforms to checkpoint 1.1 (e.g., an ongoing update of weather conditions) or link to an equivalent that conforms to checkpoint 1.1 (e.g., a link to a weather Web site).

  6. if a pure audio or pure video presentation requires a user to respond interactively at specific times in the presentation, then a time-synchronized equivalent (audio, visual or text) presentation is provided.

Best Practice Measures for Checkpoint 1.2
  1. Editorial Note: This whole Checkpoint (1.2) needs reworking. Perhaps move some down from above, or limit the items above to just certain classes of content - and then put the rest of the coverage (for other types of content) here.

  2. captions and audio descriptions are provided for all live broadcasts.

  3. the presentation does not require the user to read captions and the visual presentation simultaneously in order to understand the content.

Benefits of Checkpoint 1.2 (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.


Time-dependent presentations requiring people to use a single sense to follow two or more things at the same time may present significant barriers to some users. Depending on the nature of the 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 may not be available for live broadcasts (e.g. 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 Checkpoint 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 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.

1.3 [CORE] Information, functionality, and structure are separable from presentation.

Required Success Criteria for Checkpoint 1.3
  1. the following can be derived programmatically (i.e. through a markup or data model that is assistive technology compatible) from the content without requiring user interpretation of presentation.

    1. any hierarchical elements and relationships, such as headings, paragraphs and lists

    2. any non-hierarchical relationships between elements such as cross-references and linkages, associations between labels and controls, associations between cells and their headers, etc.

    3. any emphasis

  2. any information presented through color is also available without color (e.g. through context or markup or non-color dependent coding). [I#317]

  3. text content is not presented over a background image or pattern OR the text is easily readable when the page is viewed in black and white (no grayscale).

Best Practice Measures for Checkpoint 1.3
  1. any information presented using color is also available without color and without having to interpret markup.[I#317]

  2. any blinking content can be turned off.[I#325]

Benefits of Checkpoint 1.3 (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.

  • 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 Checkpoint 1.3 (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 4.3)

  • 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.

1.4 [CORE] All text can be decoded into words represented in Unicode.

Required Success Criteria for Checkpoint 1.4

Editorial Note: The CKW reorganization suggested that this checkpoint be combined with checkpoint 3.2. [I#442]

  1. text in the content is provided in Unicode or sufficient information is provided so that it can be automatically mapped back to Unicode.

Best Practice Measures for Checkpoint 1.4
  1. abbreviations and acronyms are clearly identified each time they occur if they collide with a word in the standard language that would also logically appear in the same case (e.g. all caps). (See also checkpoint 3.1) [I#341]

  2. symbols such as diacritic marks that are found in standard usage of the natural language of the content, and that are necessary for unambiguous identification of words, are present or another standard mechanism for disambiguation is provided.

Benefits of Checkpoint 1.4 (Informative)
  • 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 of Checkpoint 1.4 (Informative)
  • 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.

Extended Checkpoints for Guideline 1

1.5 [E1] Structure has been made perceivable through presentation. [I#439]

Required Success Criteria for Checkpoint 1.5
  1. the structural elements present have a different visual appearance or auditory characteristic from each other and from body text.

Best Practice Measures for Checkpoint 1.5
  1. the structural emphases are chosen to be distinct on different major visual display types (e.g. black and white, small display, mono audio playback).

  2. Content is constructed such that users can control the presentation of structural elements or the emphasis on the structure can be varied through alternate presentation formats.

Benefits of Checkpoint 1.5 (Informative)

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 Checkpoint 1.5 (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 only difference might be font size and margin indentation when presented visually, and spoken in a difference voice or preceded by a sound when presented auditorily.

  • Example 2: a data table.

    Groups of rows or columns are labeled with headers.

  • Example 3: 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.

1.6 [E2] Foreground content is easily differentiable from background for visual default presentations.

Required Success Criteria for Checkpoint 1.6
  1. text that is presented over a background color or grayscale has a mechanism that allows the text to be presented in a fashion that has a contrast greater than ______ between text and background color as measured by ______.[I#344]

Best Practice Measures for Checkpoint 1.6
  1. when text content is presented over a background image or pattern, the text is easily readable when the page is viewed in 256 grayscale.

    Editorial Note: this item may be moved or updated if the proposal for adding an extended checkpoint on color is accepted.

  2. this item should read identically to the required item #2, except that it should say "in default presentation mode."

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.

Benefits of Checkpoint 1.6 (Informative)
  • Individuals with low vision can easily make out 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 Checkpoint 1.6 (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.

1.7 [E3] Foreground content is easily differentiable from background for auditory default presentations.

Required Success Criteria for Checkpoint 1.7
  1. audio content does not contain background sounds OR the background sounds are at least 20 db lower than the foreground audio content.


A 20 db difference in sound level is roughly 4 times quieter (or louder).

Benefits of Checkpoint 1.7 (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 Checkpoint 1.7 (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.

  • Example 2: 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 checkpoint 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 people do not need to rely on captions to understand the dialog.

1.8 [E4] [color vision is not required to perceive content (or something like this to allow color-coding issues to exist at extended checkpoint level)]

Required Success Criteria for Checkpoint 1.8
  1. (something to achieve an effect where information can be perceived with common color deficiencies)

Best Practice Measures for Checkpoint 1.8
  1. content can be perceived with no color vision

Benefits of Checkpoint 1.8 (Informative)
Examples of Checkpoint 1.8 (Informative)

Guideline 2: OPERABLE. Ensure that Interface Elements in the Content are Operable by Any User

Core Checkpoints for Guideline 2

2.1 [CORE] All functionality is operable at a minimum through a keyboard or a keyboard interface.

Required Success Criteria for Checkpoint 2.1
  1. all of the functionality of the content, where the functionality or its outcome can be expressed in words, is operable at a minimum through a keyboard or keyboard interface.


    refer to checkpoint 4.3 for information regarding user agent support.

Best Practice Measures for Checkpoint 2.1
  1. wherever a choice between event handlers is available and supported, the more abstract event is used.

Benefits of Checkpoint 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 Checkpoint 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 and 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 checkpoint.)

    • 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.)

2.2 [CORE] Users can control any time limits on their reading, interaction, or responses unless control is not possible due to nature of real-time events or competition.

Required Success Criteria for Checkpoint 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:

    • the user is allowed to deactivate the time limits,

    • or the user is allowed to adjust the time limit over a wide range which is at least ten times or default setting or average user's preference,

    • or the user is warned before time expires and given at least 10 seconds to extend the time limit,

    • or the time limit is due to a real-time event (e.g. auction) and no alternative to the time limit is possible,

    • or the time limit is part of a competitive activity where timing is an essential part of the activity (e.g. competitive gaming or time based testing).

Best Practice Measures for Checkpoint 2.2
  1. any moving content can be frozen using the keyboard[I#325]

Benefits of Checkpoint 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 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 of Checkpoint 2.2 (Informative)
  • Examples of content that requires comprehension or 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.

2.3 [CORE] User can avoid experiencing screen flicker.

Editorial Note (06/10/03): This Checkpoint is currently included in the Core set of Checkpoints because the WCAG WG expects that it will be possible to test content for flicker and the result will be a flicker rate in Hz that can be stored in a machine-readable format. If the assumption regarding a testing tool does not hold at time of final review of these guidelines, this checkpoint will be moved to the Extended set of Checkpoints."

Required Success Criteria for Checkpoint 2.3
  1. At least one of the following is true:

    1. content was not designed to flicker (or flash) in the range of 3 to 49 Hz.

    2. if flicker is unavoidable, the user is warned of the flicker before they go to the page, and as close a version of the content as is possible without flicker is provided.

    Editorial Note:  We would like to include a third criteria here that would state that a test that was conducted and the pages passed. No test or tool exists yet though. We're looking into how such a test and/or tool might be designed.

Best Practice Measures for Checkpoint 2.3
  1. animation or other content does not visibly or purposely flicker between 3 and 49 Hz.

  2. content that might create a problem has been tested [using XYZ tool]; only pages with unavoidable flicker remain and appropriate warnings along with a close alternative presentation have been provided for these pages.

Benefits of Checkpoint 2.3 (Informative)
  • Individuals with photosensitive epilepsy can have seizures triggered by flickering or flashing in the 3 to 49 flashes per second (Hertz) range with a peak sensitivity at 20 flashes per second.

  • Individuals who are easily distracted may not be able to focus on page content with flicker occurring in the same visual field.

Extended Checkpoints for Guideline 2

2.4 [E5] Mechanisms have been added to facilitate orientation and movement in content.

Required Success Criteria for Checkpoint 2.4

Editorial Note: The CKW reorganization proposed that all of the items in required be removed and proposed a rewording of the item in best practice that addressed logical, linear reading order. [I#441]

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

    1. hierarchical structure mark up

    2. Table of contents (or site map)

    3. Alternate display orders (or alternate site navigation mechanisms)

  2. Users are able to skip over large blocks of repetitive material, navigational bars or other blocks of links that are greater than 7 when reading with a synthesizer or navigating using keyboard.[I#323]

Best Practice Measures for Checkpoint 2.4
  1. the content has been reviewed, taking into account the following strategies for facilitating orientation and movement, applying them as appropriate.

    1. breaking up text into logical paragraphs

    2. providing hierarchical sections and titles, particularly for longer documents

    3. revealing important non-hierarchical relationships, such as cross-references, or the correspondence between header and data cells in a table, so that they are represented unambiguously in the markup or data model

    4. dividing very large works into sections and or chapters with logical labels

    5. others?

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

  3. diagrams are constructed in a fashion so that they have structure that can be accessed by the user.

  4. where possible, logical tab order has been created.[I#319]

Benefits of Checkpoint 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 pages for the items.

Examples of Checkpoint 2.4 (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.

2.5 [E6] Methods are provided to minimize error and provide graceful recovery.

Required Success Criteria for Checkpoint 2.5

Editorial Note: The CKW proposal suggested that this required success criterion be combined with one of the best practice items and that another best practice item be moved up. [I#440]

  1. if an error is detected, feedback is provided to the user identifying the error (in an accessible form that meets core checkpoints).

Best Practice Measures for Checkpoint 2.5
  1. where possible, the user is allowed to select from a list of options as well as to generate input text directly

  2. errors are identified specifically and suggestions for correction are provided where possible

  3. checks for misspelled words are applied and correct spellings are suggested when text entry is required.

  4. where consequences are significant and time-response is not important, one of the following is true

    1. actions are reversible

    2. where not reversible, actions are checked for errors in advance

    3. where not reversible, and not checkable, a confirmation is asked before acceptance

Benefits of Checkpoint 2.5 (Informative)
  • Individuals with writing disabilities and people with dyslexia often have difficulty writing text in forms or other places that need text input.

  • Individuals with speech disabilities might not be recognized properly in voice input applications.

Examples of Checkpoint 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.

Guideline 3: UNDERSTANDABLE. Make content and controls understandable to as many users as possible.

Core Checkpoints for Guideline 3

3.1 [CORE] Language of content can be programmatically determined.

Required Success Criteria for Checkpoint 3.1
  1. passages or fragments of text occurring within the content that are written in a language other than the primary natural language of the content as a whole, are identified, including specification of the language of the passage or fragment.


    1. Foreign words or phrases that are found in standard unabridged dictionaries for the natural language of the content do not need to be marked.

    2. This success criterion applies only to foreign words, not to imaginary words, dialect abbreviations and other words that may not be found in an unabridged dictionary of the primary language but that are not foreign words.

  2. [???] document attributes identify the natural language of the document.

Editorial Note: In techniques discussion, it has been argued that language attributes for documents are as important as identifying changes in language within documents. Moving it up here for future discussion.

Best Practice Measures for Checkpoint 3.1
Benefits of Checkpoint 3.1 (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.

Examples of Checkpoint 3.1 (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.

Extended Checkpoints for Guideline 3

3.2 [E7] The definition of abbreviations and acronyms can be unambiguously determined.

Editorial Note: The CKW reorganization suggested that this checkpoint be combined with checkpoint 1.4. [I#442]

Required Success Criteria for Checkpoint 3.2
  1. acronyms and abbreviations do not appear first in standard unabridged dictionaries for the language or define the first time the first time they appear or are available in a glossary on the site.[I#330]

Editorial Note:  If a standard format for doing it can be achieved, we might require that linkages to glossaries for all abbreviations and acronyms that are created by the author or site be provided.  We could also recommend that linkages to any abbreviations, acronyms, etc. used by the authors also be provided.  We could also have a weaker recommendation for acronyms and abbreviations appearing on the site that linkages to glossaries explaining all abbreviations acronyms, etc. that appear in any documents on the site be provided.   

Best Practice Measures for Checkpoint 3.2
  1. a list is provided on the page or home page of URIs to cascading dictionaries that can or should be used to define abbreviations or acronyms.[I#350]

  2. the content has been reviewed, taking into account the following strategies for determining the definition of abbreviations and acronyms, applying them as appropriate.

    1. provide a definition or link (with the first occurrence) of phrases, words, acronyms, and abbreviations specific to a particular community.

    2. provide a summary for relationships that may not be obvious from analyzing the structure of a table but that may be apparent in a visual rendering of the table.

    3. if contracted forms of words are used such that they are ambiguous, provide semantic markup to make words unique and interpretable.

Benefits of Checkpoint 3.2 (Informative)
  • 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.

3.3 [E8] Content is no more complex than is necessary and/or is supplemented with simpler forms of the content.  

Required Success Criteria for Checkpoint 3.3
  1. the content has been reviewed, taking into account the following strategies for evaluating the complexity of the content, applying them as appropriate.

    1. familiarity of terms and language structure

    2. reasonableness of length and complexity of sentences

    3. coherence of paragraphs (and sensibility in length)

    4. clarity of headings and linked text when read out of context

    5. accuracy and uniqueness of page titles

    6. care in the use of all-capital letters where normal sentence case might increase comprehension

    7. inclusion of non-text content to supplement text for key pages or sections of the site where they felt it was appropriate.

Best Practice Measures for Checkpoint 3.3
  1. the content has been reviewed, taking into account the strategies for evaluating the complexity of the content, applying them as appropriate.

Benefits of Checkpoint 3.3 (Informative)
  • All users, especially those with cognitive, learning, and/or reading disabilities benefit from the use of clear and simple writing. This should not discourage you from expressing complex or technical ideas.

  • Using clear and simple language also benefits people whose first language differs from your own, including those people who communicate primarily in sign language.

  • 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.

  • 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.


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 of Checkpoint 3.3 (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.

3.4 [E9] Layout and behavior of content is consistent or predictable, but not identical.  

Required Success Criteria for Checkpoint 3.4
  1. key orientation and navigational elements (such as navigation bars) are generally found in one or two consistent locations or their locations are otherwise predictable.

  2. where inconsistent or unpredictable responses are essential to the function of the content (e.g. mystery games, adventure games, tests, etc.) the user is warned in advance of encountering them.

  3. wherever there are extreme changes in context, one of the following is true:

    1. an easy to find setting, that persists for the site visit, is provided for the user to deactivate processes or features that cause extreme changes in context or

    2. extreme changes in context are identified before they occur so the user can determine if they wish to proceed or so they can be prepared for the change

Best Practice Measures for Checkpoint 3.4
  1. user can select a different location for navigation elements in the layout of the page.[I#352]

  2. the content has been reviewed, taking into account common ideas for making content consistent and predictable, applying them as appropriate.

Benefits of Checkpoint 3.4 (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.


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 of Checkpoint 3.4 (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.

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

Guideline 4: ROBUST. Use Web technologies that maximize the ability of the content to work with current and future accessibility technologies and user agents.

Core Checkpoints for Guideline 4

4.1 [CORE] Technologies are used according to specification.

Required Success Criteria for Checkpoint 4.1
  1. for markup, except where the site has documented that a specification was violated for backward compatibility, the markup has:

    1. passed validity tests of the language (whether it be conforming to a schema, Document Type Definition (DTD), or other tests described in the specification)

    2. structural elements and attributes are used as defined in the specification

    3. accessibility features are used

    4. deprecated features are avoided

    Editorial Note: The following two success criteria seem to overlap with checkpoint 4.3. There is an open question about whether they should be deleted since checkpoint 4.3 covers programmatic interfaces.

Best Practice Measures for Checkpoint 4.1
  1. Same as item #1 above, without the exception for backward compatibility.

Benefits of Checkpoint 4.1 (Informative)
  • This checkpoint further emphasizes that following specifications increases the likelihood of accessible content. While other checkpoints refers to individual pieces of content, this checkpoint takes a step back to look at the broad picture. It also exists to help cover future technologies or issues that we did not anticipate at the time of writing this checkpoint. Thus, the benefits of following specifications are primarily that assistive technologies and user agents can render the content according to spec.

Examples of Checkpoint 4.1 (Informative)
  • Example 1: structural elements.

    Throughout a Web site, structural elements are not used for purposes of presentation. Likewise, presentational elements are not used for purposes of structure.

  • Example 2: accessible API's.

    A Java applet uses the accessibility API defined by the language. Refer to the IBM Guidelines for Writing Accessible Applications Using 100% Pure Java.

4.2 [CORE] Programmatic user interfaces are accessible or alternative, accessible versions are provided

Required Success Criteria for Checkpoint 4.2
  1. any custom user interface elements of the content conform to at least Level A of the User Agent Accessibility Guidelines 1.0. If the custom user interfaces cannot be made accessible, an alternative solution is provided that meets WCAG 2.0 (including this provision) to the level claimed.

    Editorial Note: This checkpoint includes a slightly reworded version of the suggestions from CKW reorganization. However, the following elements appeared to be redundant with the first sentence. Can they be removed?

    1. If the application renders visual text, it should conform to the VisualText checkpoints.

    2. If the application renders images, it should conform to the Image checkpoints.

    3. If the application renders animations, it should conform to the Animation checkpoints.

    4. If the application renders video, it should conform to the Video checkpoints.

    5. If the application renders audio, it should conform to the Audio checkpoints.

    6. If the application performs its own event handling, it should conform to the Events checkpoints.

    7. If the application implements a selection mechanism, it should conform to the Selection checkpoints.

    8. The application should support keyboard access per UAAG 1.0 checkpoints 1.1 and 6.7.

    9. If the application implements voice or pointer input, it should conform to the Input Modality checkpoints.

    10. accessibility conventions of the markup or programming language (API's or specific markup) are used (@@in UAAG somewhere?)

  2. plug-ins required to access the content conform to at least Level A of UAAG 1.0. If required plug-ins are not accessible, an alternative solution is provided that conforms to WCAG 2.0.

Best Practice Measures for Checkpoint 4.2
  1. accessibility conventions of the markup or programming language (API's or specific markup) are used [I#331]

  2. the interface has been tested using a variety of assistive technologies and preferably real people with disabilities who use assistive technologies to determine that those assistive technologies are able to access all information on the page or hidden within the page.

Benefits of Checkpoint 4.2 (Informative)
  • Editorial Note: This section needs to be updated to reflect above changes in checkpoint and success criteria.

    Authors who utilize technologies designed to support accessibility will:

    • encounter fewer challenges when implementing these guidelines

    • avoid the need to create custom solutions and workarounds to address accessibility concerns

    • avoid the need to provide accessible alternate versions for content rendered in a technology that does not fully address these guidelines

  • Individuals who rely on assistive technologies to access the Web will be able interact with the content.

  • Individuals who access the Web with older technologies or alternative browsing devices such as PDAs and cell phones also benefit from the inclusion of accessible alternatives to custom user interfaces.

Extended Checkpoints for Guideline 4

4.3 [E10] Technologies that are relied upon by the content are declared and widely available.

Required Success Criteria for Checkpoint 4.3
  1. the Web resource includes a list of the technologies (other than standard HTML) users must have in order for its content to work as intended. Users who do not have one or more of these technologies can still access and use the resource, though the experience may be degraded.


    When determining your list of technological requirements, consider that assistive hardware and software is often slow to adapt to technological advances, and the availability of assistive technology varies across natural languages. Verify that assistive technology compatible with the technologies you choose is available in the natural language(s) of your content.

Editorial Note: This checkpoint is currently in the set of extended checkpoints. The implications of this are that there is no core checkpoint that says content must transform gracefully or that it must be backwards compatible. However, if the set of core checkpoints is designed well, core conformance would result in content that transforms gracefully. This checkpoint might be too subjective or difficult to test and may be deleted.

Best Practice Measures for Checkpoint 4.3
  1. a list of technologies and features, support for which is required in order for the content to be operable, has been determined and is documented in metadata and / or a policy statement associated with the content.

  2. technologies and features on the required list are available in at least two independently-developed implementations. (it is preferable that the technologies used for the implementations have been supported for at least one prior version of the software)

Editorial Note: A definition of "widely available" should be added here to include something which is low cost and available in many?/most? countries/languages.

Benefits of Checkpoint 4.3 (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 of Checkpoint 4.3 (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 (Non-Normative)

Editorial Note: The WCAG WG has not tackled the definitions of the terms that we are using and acknowledges that we sometimes use terms inconsistently. We need to coordinate our terms and definitions with the WAI Glossary and are working on proposals for a variety of definitions. We have been looking at the UAAG 1.0 glossary and other glossaries within the W3C.

ability to be expressed in words

content that can be expressed accurately and unambiguously in a reasonable number of words (for example, diagrams, charts, illustrations, etc.) Content such as a musical performance or visual artwork is considered "content that can not be expressed in words," since this type of content relies heavily on the visual (or auditory) experience.[I#320]

audio description

An audio description is a verbal description of all significant visual information in scenes, actions, and events that cannot be perceived from the sound track alone to the extent possible given the constraints posed by the existing audio track and limitations on freezing the audio visual program to insert additional auditory description.


When adding audio description to existing materials, the amount of information conveyed through audio description is constrained by the amount of space available in the existing audio track unless the audio/video program is periodically frozen to insert audio description. However, it is often impossible or inappropriate to freeze the audio/visual program to insert additional audio description.

audio descriptions

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.


Captions are text equivalents of auditory information from speech, sound effects, and ambient sounds that are synchronized with the multimedia presentation.

collated script

Editorial Note: @@ that provides dialog, important sounds and important visual information in a single text document

competitive activity

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.

complex content

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.



Editorial Note: We need to include a definition for content here.

controlled languages

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


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.


Functionality is the purpose or intended effect of the content. This may include presentation of information , data collection, securing a response from the user, providing user experience, linking to other content, testing, confirmation, purchasing, etc.

keyboard interface

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

mechanisms that cause extreme changes in context

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 (auditorily 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.

media equivalents

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

natural languages

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

non-text content

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 addressed in checkpoint 4.3.


The term operable includes the concept of efficiency. That is, it implies that the device can be operated from the keyboard in a reasonably efficient fashion. Using MouseKeys or having to tab dozens of times to move through a small section of a document or page, or other unreasonably inefficient keyboard access would not qualify. If a document has a very large number of links, some mechanism other than tabbing through them one at a time needs to be provided. This might include provision of headers (for header navigation), the use of skip navigation, links, etc.[I#346]


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

real-time events

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.

site navigation mechanism

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

  • A home page with hyperlinks on it and subsequent pages that link to the other pages at the site

  • site map(s)

  • search engine(s)

  • expanding outline(s)

  • dynamic fisheye views showing all linked pages or topics related to any page.

  • 3-D virtual representations of site content


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

  1. A book is divided into chapters, paragraphs, lists, etc. Chapter titles help the reader anticipate the meaning of the following paragraphs. Lists clearly indicate separate, yet related ideas. All of these divisions help the reader anticipate changes in context.

  2. A bicycle is divided into wheels and a frame. Further, a wheel is divided into a tire and a rim. In an image of the bicycle, one group of circles and lines becomes "wheel" while another group becomes "frame."


A technology is a

  • markup or programming language

  • application Programming Interface (API)

  • or communication protocol

text equivalent

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.


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.

time-dependent presentation

A time-dependent presentation is a presentation that

  • 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.

unfamiliar content

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.

widely available

Editorial Note: definition of "widely available" should be added here to include something which is low cost and available in many?/most? countries/languages.

Appendix B Contributors (Non-Normative)

Participants in the WCAG Working Group

Appendix C The differences between WCAG 1.0 and WCAG 2.0 (Non-Normative)

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

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

C.1 Improvements in WCAG 2.0

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

  1. Ensure that requirements may be applied across technologies

  2. Ensure that the conformance requirements are clear

  3. Ensure that the deliverables are easy to use

  4. Write to a more diverse audience

  5. Clearly identify who benefits from accessible content

  6. Ensure that the revision is "backward compatible" with WCAG 1.0

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

Appendix D References (Non-Normative)

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