Understanding WCAG 2.0

Intent of this success criterion

The intent of this success criterion is to make information conveyed by non-text content such as charts, diagrams, audio recordings, pictures, and animations available in a form that can be rendered through any modality (for example, visual, auditory or tactile). Providing text alternatives allows the information to be rendered in a variety of ways by a variety of user agents. For example, a person who cannot see a picture can have the text alternative read aloud to them using synthesized speech. A person who cannot hear an audio file can have the text alternative displayed so that he or she can read it.

Labeling multimedia presentations allows users to determine whether or not they want to play it. (Since conforming multimedia has built-in audio descriptions and captions, a full text alternative is not necessary).

Techniques for Addressing Success Criterion 1.1.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.1.1.

Benefits: How Success Criterion 1.1.1 helps people with disabilities

• People who are blind, have low vision, or have cognitive disabilities can have text alternatives read aloud to them by assistive technology.

• People who have trouble reading text may use tools that both read text aloud and highlight the words as they are read. In some cases, it may be difficult for someone to recognize visual information and the text alternative may help him or her understand the purpose of the non-text content.

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

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

• Additionally, text alternatives support the ability to search for non-text content and to repurpose content in a variety of ways.

Examples of Success Criterion 1.1.1

In the examples below, a single piece of non-text content is used in different contexts that require different text alternatives.

1. A data chart

   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, provides a high-level summary of the data comparable to that available from the chart, and provides the data in a table.

2. An audio recording of a speech (no video)

   The link to an audio clip says, "Chairman's speech to the assembly." A link to a text transcript is provided immediately after the link to the audio clip.

3. An animation that illustrates how a car engine works

   An animation shows how a car engine works. There is no audio and the animation is part of a tutorial that describes how an engine works. All that is needed is a description of the image. From "How car engines work: Internal combustion"

4. A traffic Web camera

   A Web site allows end-users to select from a variety of Web cameras positioned throughout a major city. After a camera is selected, the image updates every two minutes. A short text alternative identifies the Web camera as, "traffic Web camera." The site also provides a table of travel times for each of the routes covered by the Web cameras. The table is also updated every two minutes.

5. A photograph of an historic event in a news story

   A photograph of two world leaders shaking hands accompanies a news story about an international summit meeting. The text alternative says, "President X of Country X shakes hands with Prime Minister Y of country Y."

6. A photograph of a historic event in content discussing diplomatic relationships

   The same image used in a different context intended to explain nuances in diplomatic encounters. The image of the president shaking hands with the prime minister appears on a Web site discussing intricate diplomatic relationships. The first text alternative reads, "President X of country X shakes hands with Prime Minister Y of country Y on January 2, 2009." An additional text alternative describes the room where the leaders are standing, the expressions on the leaders' faces, and identifies the other people in the room. The additional description might be included on the same page as the photograph or in a separate file associated with the image through a link or other standard programmatic mechanism.

7. An audio recording

   The Web page described in the previous example includes a link to an audio recording of the leaders' press conference. The page also links to a text transcript of the press conference. The transcript includes a verbatim record of everything the speakers say. It identifies who is speaking as well as noting other significant sounds that are part of the recording, such as applause, laughter, questions from the audience, and so on.

Related resources

• Excerpts from the NBA Tape Recording Manual, Third Edition. Information on describing complex images to people who are blind.

Intent of this success criterion

This success criterion is designed to make audio visual material available to individuals whose vision is too poor to reliably read captions and whose hearing is too poor to reliably hear dialogue and audio descriptions. This is done by providing a single text document that consists of a combination of the captions (see SC 1.2.1) and a text transcript of the audio descriptions (see SC 1.2.2).

Techniques for Addressing Success Criterion 1.1.2

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.1.2.

Benefits: How Success Criterion 1.1.2 helps people with disabilities

• People who cannot see well or at all and who also cannot hear well or at all can get access to information in audio-visual presentations.

Examples of Success Criterion 1.1.2

• A text description of a movie.

  An author takes a recording of a movie with descriptions and transcribes both the text and the audio description. She then watches the movie, picking up any additional information that is in the captions such as sounds or speaker identification and adds it to the transcription. The result is posted on the Web with a link to it immediately next to the movie's link.

Related resources

Intent of this success criterion

The intent of this success criterion is to enable people who are deaf or hard of hearing to watch multimedia presentations. Captions provide the part of the content available via the audio track. Captions not only include dialog, but identify who is speaking and note important sounds.

Techniques for Addressing Success Criterion 1.2.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.2.1.

Benefits: How Success Criterion 1.2.1 helps people with disabilities

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

Examples of Success Criterion 1.2.1

• A captioned tutorial

  A video clip shows how to tie a knot. The captions read,

  "(music)

  Using rope to tie knots was an important skill

  for the likes of sailors, soldiers and woodsmen.."

  From Sample Transcript Formatting by Whit Anderson.

Related resources

Intent of this success criterion

The intent of this success criterion is to provide people who are blind or visually impaired access to the visual information in a multimedia presentation. The audio description augments the audio portion of the presentation with the information needed when the video portion is not available. During naturally-occurring pauses in dialog, audio descriptions provide information about actions, characters, scene changes and on-screen text which are important and are not described or spoken in the main sound track.

Techniques for Addressing Success Criterion 1.2.3

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.2.3.

Benefits: How Success Criterion 1.2.3 helps people with disabilities

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

Examples of Success Criterion 1.2.3

• A movie with audio description.

  Describer: A title, "Teaching Evolution Case Studies. Bonnie Chen." A teacher shows photographs of birds with long, thin beaks.

  Bonnie Chen: "These photos were all taken at the Everglades."

  Describer: The teacher hands each student two flat, thin wooden sticks.

  Bonnie Chen: "Today you will pretend to be a species of wading bird that has a beak like this."

  Describer: The teacher holds two of the sticks to her mouth making the shape of a beak.

  Transcript of audio based on the first few minutes of, "Teaching Evolution Case Studies, Bonnie Chen" (copyright WGBH and Clear Blue Sky Productions, Inc.)

Related resources

• NCAM Rich Media Accessibility, Accessible SMIL Templates.

• Standard Techniques in Audio Descriptions.

• How to Provide Audio Descriptions.

• Synchronized Multimedia Integration Language (SMIL) 1.0.

• Synchronized Multimedia Integration Language (SMIL 2.0).

• Accessibility Features of SMIL.

Intent of this success criterion

The intent of this success criterion is to enable people who are deaf or hard of hearing to watch real-time presentations. Captions provide the part of the content available via the audio track. Captions not only include dialog, but also identify who is speaking and notate sound effects and other significant audio.

Techniques for Addressing Success Criterion 1.2.4

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.2.4.

Benefits: How Success Criterion 1.2.4 helps people with disabilities

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

Examples of Success Criterion 1.2.4

• A Web cast

  A news organization provides a live, captioned Web cast.

Related resources

See How to Meet Success Criterion 1.2.1 .

Intent of this success criterion

The intent of this success criterion is to enable people who are deaf or hard of hearing and who are fluent in the sign language to watch multimedia presentations. Many people find it easier to follow sign language than to read the text of captions, since the captions are often a second language to them.

Techniques for Addressing Success Criterion 1.2.5

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.2.5.

Benefits: How Success Criterion 1.2.5 helps people with disabilities

• There is a segment of the population that is able to communicate in sign language, but may have weak reading skills. These individuals may not be able to read and comprehend the captions and thus require a sign language interpretation to gain access to the multimedia content.

• Some people who communicate using sign language and are proficient readers may have impaired vision which may make it difficult to read the captions on the screen. A sign language interpretation may be easier to view.

Examples of Success Criterion 1.2.5

• Example 1. A corporation is making an important announcement to all of its employees. The meeting will be held in the main headquarters and streamed to the Web. A sign language interpreter is provided at the meeting location. The live video includes a full view of the sign language interpreter as well as the person presenting.

• Example 2.The same announcement as Example 1 is also Webcast to remote employees. Since there is only one display available for this, the sign language interpreter is shown in the corner of the display.

• Example 3.A university is providing an on-line version of a particular lecture by creating a multimedia presentation of the professor delivering the lecture. The presentation includes video of the professor speaking and demonstrating a science experiment. A sign language interpretation of the lecture is created and presented on the Web with the multimedia version.

Related resources

• Synchronized Multimedia Integration Language (SMIL) 1.0.

• Synchronized Multimedia Integration Language (SMIL 2.0).

• Accessibility Features of SMIL.

• NCAM Rich Media Accessibility, Accessible SMIL Templates.

• National Center on Deafness list of interpreter links.

• National Institute on Deafness and other Communication Disorders: Information on American Sign Language.

• Techniques for filming sign language interpreters.

• eSign Avatar Signing Plugin for Internet Explorer.

• Royal National Institute for Deaf People (RNID).

Intent of this success criterion

The intent of this success criterion is to provide people who are blind or vision impaired access to a multimedia presentation beyond that which can be provided by standard audio descriptions.

Techniques for Addressing Success Criterion 1.2.6

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.2.6.

Benefits: How Success Criterion 1.2.6 helps people with disabilities

• People who are blind, people with low vision who cannot see the screen, as well as those with cognitive disabilities who have difficulty interpreting visually, often use audio descriptions of the visual information. However, if there is too much dialog - the audio descriptions are insufficient. Extended audio descriptions can provide the additional information they need to really understand the video.

Examples of Success Criterion 1.2.6

(none documented at this time)

Related resources

• Synchronized Multimedia Integration Language (SMIL) 1.0.

• Synchronized Multimedia Integration Language (SMIL) 2.0.

• Accessibility Features of SMIL.

• NCAM Rich Media Accessibility, Accessible SMIL Templates.

• Standard Techniques in Audio Descriptions.

Intent of this success criterion

The intent of this success criterion is to enable assistive technology to render Web content in an alternative presentation such as synthesized speech or using larger fonts or different colors while preserving the important structural relationships in the content.

Web content developers add structure to information in order to organize it in a way that makes it easier to understand. Sighted users perceive the structure through various visual cues — headings are often in a larger, bold font and are separated from paragraphs by blank lines; list items are preceded by a bullet and perhaps indented; paragraphs are separated by a blank line; items that share a common characteristic are organized into tabular rows and columns; form fields may be positioned as groups that share text labels.

The purpose of this success criterion is to ensure that any structure that is perceivable to one set of users can be made to be perceivable to all.

Techniques for Addressing Success Criterion 1.3.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.3.1.

Benefits: How Success Criterion 1.3.1 helps people with disabilities

• Providing the ability to programmatically determine structure allows Web content to be presented differently to meet the needs and constraints of people with visual, hearing, and cognitive disabilities. In order for the information to be presented differently, it is necessary for the assistive technology to be able to understand the type of information. For example, if tables of information are programmatically identified as tables, a screen reader can unambiguously determine the contents of each table cell. If tables are instead created simply by positioning content in vertical columns, screen readers will only be able to read each line of text. If the "visual cells" contain more than one line of information, the user will not be able to understand it because the lines of each cell will get intermixed with the corresponding lines in the other cells. The screen reader will read the first line of each cell, then the next line of each cell, and so on.

Examples of Success Criterion 1.3.1

• A form that uses color and an asterisk to indicated required fields

  A form contains both required and optional fields. Instructions at the top of the form explain that required fields are labeled with red text and also with an asterisk. Both the red text and the asterisk are programmatically associated with the appropriate form fields so that assistive technology users can determine the required fields.

• A bus schedule table where the headers for each cell can be programmatically determined

  A bus schedule consists of a table with the bus stops listed vertically in the first column and the different buses listed horizontally across the first row. Each cell contains the time when the bus will be at that bus stop. The bus stop and bus cells are identified as headers for their corresponding row or column so that an assistive technology can programmatically determine which bus and which bus stop are associated with the time in each cell.

• A form where the labels for the checkboxes can be programmatically determined

  In a form, the labels for each checkbox can be programmatically determined by an assistive technology.

• A text document

  A simple text document is formatted with double blank lines before titles, asterisks for bullets and other standard formatting conventions so that its structure can be programmatically determined.

Intent of this success criterion

The intent of this success criterion is to ensure that all users can access information that is conveyed by color. If the information is conveyed through color in an image (or other non-text format), the color cannot be programmatically determined by assistive technology. In this case, providing the information conveyed with color through another means ensures that assistive technology users who cannot see the color can still perceive the information.

Color is an important asset in design of Web content, enhancing its aesthetic appeal, its usability, and its accessibility. However, some users have difficulty perceiving color. People with partial sight often experience limited color vision, and many older users do not see color well. In addition, people using text-only, limited-color or monochrome displays and browsers will be unable to access information that is presented only in color.

When color is essential to understanding content, making sure the color can be programmatically determined allows assistive technologies to inform the user about the color so they can access the information conveyed by the color. Alternately, the information conveyed by color could be made accessible by also conveying it in a non-color dependent way.

Techniques for Addressing Success Criterion 1.3.2

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.3.2.

Benefits: How Success Criterion 1.3.2 helps people with disabilities

• User with visual disabilities.

  • Users with partial sight often experience limited color vision.

  • Users who are blind (using a text-only reader) and need to determine information based on color.

  • Some older users may not be able to see color well.

  • Users who have color-blindness.

  • Users with hearing and visual disabilities.

  • Users who are deaf-blind using braille (text) refreshable displays may be unable to access color-dependent information.

  • People using text-only, limited color or monochrome displays may be unable to access color-dependent information.

  • Users with a handheld device which renders information but with no color context.

  • People using text-only, limited color or monochrome browsers (user agents) may be unable to access color-dependent information.

Examples of Success Criterion 1.3.2

• A form that uses color and an asterisk to indicated required fields

  A form contains both required and optional fields. Instructions at the top of the form explain that required fields are labeled with red text and also with an asterisk. Both the red text and the asterisk are programmatically associated with the appropriate form fields so that assistive technology users can determine the required fields.

• An examination.

  Students view an SVG image of a chemical compound and identify the chemical elements present based on the colors used in the diagram. The text alternatives associated with each element name the color of the element and indicate the element's position in the diagram. Students who cannot perceive color have the same information about the compound as their classmates. (This technique also satisfies Guideline 1.1 Level 1.)

Related resources

Intent of this success criterion

The intent of this success criterion is to enable an assistive technology to provide an alternative presentation of content while preserving the reading order needed to perceive meaning. The order of words in sentences and sentences in paragraphs, for instance, is always critical to meaning. However, if a page contains two independent articles, the relative order of the articles may not affect their meaning, as long as they are not interleaved. It must be possible to programmatically determine at least one sequence of the content that makes sense.

Techniques for Addressing Success Criterion 1.3.3

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.3.3.

Benefits: How Success Criterion 1.3.3 helps people with disabilities

• This success criterion benefits users with visual, hearing, and cognitive disabilities that rely on an alternative, linear presentation of the content. The meaning evident in the sequencing of the information in the default presentation will be the same when they access the information in the linear presentation. When this success criterion is not satisfied, users may be confused or disoriented when the information is presented in an order that makes no sense.

Examples of Success Criterion 1.3.3

• Example 1: In a multi-column document, the linear presentation of the content flows from the top of a column to the bottom of the column, then to the top of the next column.

• Example 2: CSS is used to position a navigation bar, the main story on a page, and a side story. The visual presentation of the sections does not match the programmatically determined order, but the meaning of the page does not depend on the order of the sections.

Intent of this success criterion

The intent of this success criterion is to make information conveyed by varying the presentation of text available even if the information is presented in an alternative modality or if the person cannot perceive the text variations.

On a visual medium, examples of variations in the presentational of text would include:

• emphasizing some words by bolding, italicizing or underlining them;

• indicating content headings by increased font size and bolding font;

• emphasizing words or indicating that they have special status (such as a key term) by changing the font family used to present them;

• emphasizing words by raising them above centerline in a line of text.

Techniques for Addressing Success Criterion 1.3.4

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.3.4.

Benefits: How Success Criterion 1.3.4 helps people with disabilities

• Users of screen readers or refreshable braille displays may be unable to access information conveyed by the formatting of text.

• People with decreased visual perception, including some older users, may not see text formatting well.

Examples of Success Criterion 1.3.4

(none provided at this time)

Intent of this success criterion

The intent of this success criterion is to ensure that all users can access instructions for using the content, even when users cannot perceive shapes, size or use information about spatial location or orientation. Some content relies on knowledge of the shape or position of objects that are not available from the structure of the content (for example, "round button" or "button to the right"). Some users with disabilities are not able to perceive shape or position due to the nature of the assistive technologies they use. This success criterion requires that additional information be provided to clarify anything that is dependent on this kind of information.

Providing information using shape and/or location, however, is an effective method for many users including those with cognitive disability. This provision should not discourage those types of cues as long as the information is also provided in other ways.

Techniques for Addressing Success Criterion 1.3.5

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.3.5.

Benefits: How Success Criterion 1.3.5 helps people with disabilities

• People who are blind and people who have low vision may not be able to understand information if it is conveyed by shape and/or location alone. Providing additional information other than shape and/or location will allow them to understand the information conveyed by shape and/or alone.

Examples of Success Criterion 1.3.5

Intent of this success criterion

The purpose of this success criterion is to provide enough contrast between text and its background so that it can be easily read by people with low vision. The contrast is calculated in such a way that color is not a key factor so that people who also have a color vision deficit will also see a contrast between the text and the background.

The .05 offset is included to compensate for ratio effects that occur when one value is at or near zero and for ambient light effects.

The Gamma correction (^2.2) and the RGB constants are from the sRGB definition.

This success criterion uses the term luminosity contrast ratio rather than luminance to reflect the fact that Web content does not emit light itself. Luminosity contrast ratio gives a measure of the relative luminance that would result when displayed. (Because it is a ratio, it is dimensionless.)

Techniques for Addressing Success Criterion 1.4.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.4.1.

Benefits: How Success Criterion 1.4.1 helps people with disabilities

People with low vision often have difficulty reading text that does not contrast with its background. This can be exacerbated if the person has a color vision deficiency that lowers the contrast even further. Providing a minimum luminance contrast ratio between the text and its background can make the text more readable even if the person does not see the full range of colors. It also works for the rare individuals who see no color.

Examples of Success Criterion 1.4.1

Intent of this success criterion

Individuals who use screen reading software can find it hard to understand the speech output if there is other audio playing at the same time. This is exacerbated when the screen reader's speech output is software based (as most are today) and is controlled via the same volume control as the sound. The purpose of the success criterion is to provide a means to turn it off. Since the screen reader user must use the screen reader to access any controls on the screen, the means to turn it off should be easy to operate and not masked completely by loud music.

Techniques for Addressing Success Criterion 1.4.2

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.4.2.

Benefits: How Success Criterion 1.4.2 helps people with disabilities

Individuals who use screen reading technologies can hear the screen reader without other sounds playing. This is especially important for those who are hard of hearing and for those whose screen readers use the system volume (so they cannot turn sound down and screen reader up).

It also benefits those who have attention deficit disorders that prevent them from ignoring sounds and focusing on the Web content.

Examples of Success Criterion 1.4.2

• An audio file begins playing automatically when a page is opened, however it can be stopped by the user by selecting a "silent" link at the top of the page.

Intent of this success criterion

The purpose of this success criterion is to provide enough contrast between text and its background so that it can be easily read by people with low vision. The contrast is calculated in such a way that color is not a key factor so that people who also have a color vision deficit will also see a contrast between the text and the background. This differs from 1.4.1, the Level 2 success criterion, in that it requires a higher level of contrast.

The .05 offset is included to compensate for ratio effects that occur when one value is at or near zero and for ambient light effects.

The Gamma correction (^2.2) and the RGB constants are from the sRGB definition.

Techniques for Addressing Success Criterion 1.4.3

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.4.3.

Benefits: How Success Criterion 1.4.3 helps people with disabilities

People with low vision often have difficulty reading text that does not contrast with its background. This can be exacerbated if the person has a color vision deficiency that lowers the contrast even further. Providing a minimum luminance contrast ratio between the text and its background can make the text more readable even if the person does not see the full range of colors. It also works for the rare individuals who see no color.

Examples of Success Criterion 1.4.3

Intent of this success criterion

Individuals who are hard of hearing have difficulty separating speech from background sounds or other noise. The purpose of this success criterion is to ensure that the non-speech sounds are low enough that a user can understand the speech. A 20 decibel difference in sound level is roughly 4 times quieter (or louder). Non-speech sound that meets this requirement will be approximately four times (4x) quieter than the speech content.

Techniques for Addressing Success Criterion 1.4.4

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 1.4.4.

Benefits: How Success Criterion 1.4.4 helps people with disabilities

People who are hard of hearing often have great difficulty separating speech from background sound.

Examples of Success Criterion 1.4.4

The following audio tracks provide examples of speech over background sounds.

In the first example the voice (foreground) is recorded at -17.52 decibels and the music (background) is at -37.52 decibels, which makes the foreground 20 decibels louder than the background.

In the second example the voice (foreground) is at -18 decibels and the music (background) is at about -16 decibels making the foreground only 2 decibels louder than the background.

http://www.eramp.com/david/audio_contrast.htm.

Related resources

• About Decibels by Gregg Vanderheiden

Intent of this Success Criterion

The purpose of this success criterion is to ensure that, wherever possible, content can be operated through a keyboard or keyboard interface. When content can be operated through a keyboard or alternate keyboard, it is operable by people with no vision (who cannot use devices such as mice that require eye-hand coordination) as well as by people who must use alternate keyboards or input devices that act as keyboard emulators. Keyboard emulators include speech input software, sip and puff software, on-screen keyboards, scanning software and a variety of assistive technologies and alternate keyboards. Individuals with low vision also may have trouble tracking a pointer and find use of software much easier (or only possible) if they can control it from the keyboard.

Some types of Web content functionality however cannot be controlled from the keyboard. A watercolor application for example where the stroke is defined by the movement and speed of movement and/or pressure is one example. The phrase "except where the task requires analog, time-dependent input" is included to separate those things that cannot reasonably be controlled from a keyboard.

Techniques for Addressing Success Criterion 2.1.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.1.1.

Benefits: How Success Criterion 2.1.1 helps people with disabilities

• People who are blind (who cannot user devices such as mice that require eye-hand coordination).

• People with low vision (who may have trouble finding a tracking a pointer indicator on screen).

Examples of Success Criterion 2.1.1

• Example 1: A drawing Program

  A drawing program allows users to create, size, position and rotate objects from the keyboard.

• Example 2: A drag and Drop Feature

  An application that uses drag and drop also supports 'cut' and 'paste' or form controls to move objects.

• Example 3: Association or discreet line

  A connect-the-dots program allows the user to move between dots on screen and use the spacebar to connect the current dot to the previous one.

• Example 4: Exception - Painting Program

  A watercolor painting program passes as an exception because the brush strokes vary depending on the speed and duration of the movements.

• Example 5: Exception - Model helicopter flight training simulator

  A model helicopter flight training simulator passes as an exception because the nature of the simulator is to teach real-time behavior of a model helicopter.

Intent of this success criterion

This is the same as the success criterion 2.1.1, but no exceptions are allowed: all content is operable from the keyboard.

Intent of this success criterion

The purpose of this success criterion is to ensure that whenever, possible users with disabilities are given adequate time to interact with Web content. People with disabilities such as blindness, dexterity impairments, and cognitive disabilities may require more time to perform functions such as filling out on-line forms. If Web functions are time-dependent, it will be difficult for some users to perform the required action before a timeout occurs. This may render the service inaccessible to them. Designing functions that are not time-dependent will help people with disabilities succeed at completing these functions. Providing options to disable timeouts, customize the length of timeouts, or request more time before a timeout occurs helps those users who require more time than expected to successfully complete forms.

In some cases, however, it is not possible to change the timeout (for example, for an auction or other real-time event) and exceptions are therefore provided for those cases.

Notes Regarding Server Timeouts

• Timed server redirects can be found below under Common Failures.

• Server timeouts like login expiration are dealt with in success criterion 2.2.6.

• Non-timed server redirects (e.g. 3xx response codes) are not applicable because there is no timeout: they work instantly.

Techniques for Addressing Success Criterion 2.2.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.2.1.

Benefits: How Success Criterion 2.2.1 helps people with disabilities

• People with physical disabilities often need more time to react, to type and to complete activities. People with low vision need more time to locate things on screen and to read. People who are blind and using screen readers may need more time to understand screen layouts, to find information and to operate controls. People who have cognitive or language problems need more time to read and to understand. People who are deaf and communicate in sign language may need more time to read information printed in text (which may be a second language for some).

• In circumstances where a sign-language interpreter may be relating audio content to a user who is deaf, control over time limits is also important.

Examples of Success Criterion 2.2.1

Related resources

Intent of this success criterion

The intent of this success criterion is to avoid distracting the user during their interaction with a delivery unit. Certain groups, particularly those with attention deficit disorders, find blinking content distracting, making it difficult for them to concentrate on other parts of the delivery unit. Three seconds was chosen because it is long enough to get a user's attention, but not so long that a user can't wait it out if they need to in order to use the page.

Techniques for Addressing Success Criterion 2.2.2

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.2.2.

Benefits: How Success Criterion 2.2.2 helps people with disabilities

• One use of content that blinks is to draw the visitor's attention to that content. Although this is an effective technique for all users with vision, it can be a problem for some users if it persists. For certain groups, including people with low literacy, reading and intellectual disabilities, and people with attention deficit disorders, content that blinks may result in it being difficult to impossible to interact with the rest of the delivery unit. Providing content that stops blinking after 3 seconds or providing a mechanism for users to stop blinking content allows people in these groups to interact with the delivery unit.

Examples of Success Criterion 2.2.2

• Example 1: A Web advertisement blinks to get viewers attention but stops after 3 seconds

• Example 2: A form blinks an arrow near the submit button if a user finishes filling out the form but does not activate the submit button. The blinking stops after 3 seconds.

• Example 3: An animation runs in the upper portion of the page but has a "freeze animation" button near the bottom of the animation.

Related resources

Intent of this success criterion

The intent of this success criterion is to give the option to temporarily stop content from advancing or updating at a rate beyond the user's ability to read and/or understand the content as it changes.

"Moving" refers to content in which the visible content conveys a sense of motion. Common examples include motion pictures, multimedia presentations, animations, real-time games, and scrolling stock tickers.

"Time-based" refers to content that updates or disappears based on preset time interval. Common time-based content includes audio, automatically updated weather information, news, and stock price updates, and auto-advancing presentations and messages.

Techniques for Addressing Success Criterion 2.2.3

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.2.3.

Benefits: How Success Criterion 2.2.3 helps people with disabilities

• People with reading disabilities, cognitive disabilities, and learning disabilities who may need more time to read or comprehend information can have additional time to read the information by pausing the content.

• In circumstances where a sign-language interpreter may be relating audio content to a user who is deaf, control over time limits is also important.

Examples of Success Criterion 2.2.3

• An essential animation can be paused without effecting the activity

  A Web site helps readers understand 'how things work' through animations that demonstrate processes. Animations have "pause" and "restart" buttons.

• A stock ticker.

  A stock ticker has "pause" and "restart" buttons. Pausing the ticker causes it to pause on the current stock. Restarting causes the ticker to jump ahead to the current stock - stocks that were displayed during the pause will not be displayed. Alternatively, the stock ticker could restart where paused but it would be behind unless the user reloaded the content to jump ahead to the real-time display or unless the ticker "fast-forwarded" until it caught up with the current stock.

• A game is designed so that users take turns rather than competing in real-time

  One party can pause the game without invalidating the competitive aspect of it.

• An auction.

  Users cannot pause the timing because of the nature of the activity. Instead the user is allowed to prepare their bid and hold it - so that a single keystroke submits it.

Related resources

Intent of this success criterion

The purpose of this success criterion is to minimize the occurrence of content that requires timed interaction. This enables people with blindness, low vision, cognitive disabilities, or motor impairments to interact with content. This differs from the Level 1 success criterion in that the only exception is for real-time events.

Techniques for Addressing Success Criterion 2.2.4

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.2.4.

Benefits: How Success Criterion 2.2.4 helps people with disabilities

• People with physical disabilities often need more time to react, to type and to complete activities. People with low vision need more time to locate things on screen and to read. People who are blind and using screen readers may need more time to understand screen layouts, to find information and to operate controls. People who have cognitive or language problems need more time to read and to understand. People who are deaf and communicate in sign language may need more time to read information printed in text (which may be a second language for some).

• In circumstances where a sign-language interpreter may be relating audio content to a user who is deaf, control over time limits is also important.

Examples of Success Criterion 2.2.4

• A test is designed so that time to complete the test does not effect the scoring

  Example will be provided.

• A game is designed so that users take turns rather than competing in real-time

  One party can pause the game without invalidating the competitive aspect of it.

Related resources

Intent of this success criterion

The intent of this success criterion is to allow users to turn off updates from the author/server except in emergencies. Emergencies would include civil emergency alert messages or any other messages that would warn of data loss, loss of connection etcetera.

This allows access by people with cognitive disabilities or attention problems to be able to focus on the content. It also allows users who are blind or have low vision to keep their "viewing" focus on the content they are currently reading.

Techniques for Addressing Success Criterion 2.2.5

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.2.5.

Benefits: How Success Criterion 2.2.5 helps people with disabilities

• Individuals with attention deficit disorders can focus on content without distraction.

• Individuals with low vision or who use screen readers will not have content updated while they are viewing it (which can lead to discontinuity and misunderstanding if they start reading in one topic and finish in another).

Examples of Success Criterion 2.2.5

• (None currently documented.)

Related resources

Intent of this success criterion

The intent is to allow all users to complete authenticated transactions that have inactivity timeouts. For security reasons, many sites implement an authentication timeout after a certain period of inactivity. These timeouts may cause problems for persons with disabilities because it may take longer for them to complete the activity. These users must be given the ability to re-authenticate and continue with the transaction without the loss of any data already entered.

Techniques for Addressing Success Criterion 2.2.6

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.2.6.

Benefits: How Success Criterion 2.2.6 helps people with disabilities

• This success criterion benefits people who may require additional time to complete an activity. People with cognitive disabilities may read slowly and require additionally time to read and respond to a questionnaire. Users interacting via a screen reader may need extra time to navigate and complete a complicated form. A person with motor impairments or who navigates with an alternative input device may require additional time to navigate through or complete input within a form.

• In circumstances where a sign-language interpreter may be relating audio content to a user who is deaf, control over time limits is also important.

Examples of Success Criterion 2.2.6

• A shopping site checkout

  A user is logged into a shopping site. While performing the checkout process, the user is distracted for a long period of time and the session times out. When the user returns to the checkout process and submits the form, the site returns a login screen to re-authenticate. After the user logs in, the check out process is restored with the same information and at the same stage. The user did not lose any data because the server had temporarily accepted and stored the submission even though the session had timed out and restored the user to the same state after re-authentication was completed.

• Authentication in an email program

  An email program has an authentication timeout after 30 minutes. The program prompts the user several minutes before the timeout occurs and provides a link to open a new window in order to re-authenticate. The original window with the in-progress email remains intact and, after re-authentication, the user may send that data.

• A questionnaire with a timeout

  A long questionnaire provided within a single delivery unit has information at the beginning that indicates that the session will time out after 15 minutes. The user is also informed that the questionnaire can be saved at any point and completed at a later time. Within the delivery unit there are several buttons provided to save the partially completed form. In addition, with JavaScript in the baseline, the user can elect to be alerted via a pop-up if the session is close to timing out.

Related resources

Intent of this success criterion

The purpose of this success criterion is to allow users to access the full content of a site without inducing seizures due to photosensitivity.

Individuals who have photosensitive seizure disorders can have a seizure triggered by content that flashes at certain frequencies for more than a few flashes. People are even more sensitive to red flashing than to other colors so a special test is provided for saturated red flashing. These guidelines are based on guidelines for broadcast industry as adapted to work for computer screens, where content is viewed from closer distance (larger angle of vision).

This success criterion replaces a much more restrictive criterion in WCAG 1.0 that did not allow any flashing (even of a single pixel) within a broad frequency range (3 to 50 hz). This success criterion is based on existing specifications in use in England and by others for television broadcast and has been adapted for computer display viewing. The 1024 x 768 screen is used as the reference screen size for the evaluation. The 335 x 268 pixel block represents a 10 degree viewport at typical viewing distance. (The 10 degree field is taken from the original specifications and represents the central vision portion of the eye – where one is most susceptible to photo stimuli).

The combined area of flashes occurring concurrently (but not necessarily contiguously) means the total area that is actually flashing at the same time. It is calculated by adding up the all of the areas of the individual flashes on the screen that are occurring at the same time.

Techniques for Addressing Success Criterion 2.3.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.3.1.

Benefits: How Success Criterion 2.3.1 helps people with disabilities

Individuals who have seizures when viewing flashing material will be able to view all of the material on a site without have a seizure and without having to miss the full experience of the content by having to just use text alternatives. This includes those with photosensitive epilepsy as well as other photosensitive seizure disorders.

Examples of Success Criterion 2.3.1

A movie with a scene involving very bright lightning flashes is scripted so that the lightning only flashes 2 times.

Related resources

• Trace Center Photosensitive Epilepsy Analysis Tool (PEAT)

Intent of this success criterion

The intent of this success criterion is to allow people who navigate sequentially through content more direct access to the primary content of the delivery unit. Web pages and applications often have content that appears on other pages or screens. Examples of repeated blocks of content include but are not limited to navigation links, heading graphics, and advertising frames.

This is in contrast to a sighted user's ability to ignore the repeated material either by focusing on the center of the screen (where main content usually appears) or a mouse user's ability to select a link with a single mouse click rather than encountering every link or form control that comes before the item they want.

Techniques for Addressing Success Criterion 2.4.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.4.1.

Benefits: How Success Criterion 2.4.1 helps people with disabilities

When this success criterion is not satisfied, it may be difficult for people with some disabilities to reach the main content of a Web page quickly and easily.

Screen reader users who visit several pages on the same site may have to hear all heading graphics and dozens of navigation links on every page before the main content is spoken.

People who use only the keyboard or a keyboard interface might have to make dozens of keystrokes before reaching a link in the main content area. This can take a long time and may cause severe physical pain for some users.

People who use screen magnifiers can do not have to search through the same headings or other blocks of information to find the other side where the content begins each time then enter a new page.

Examples of Success Criterion 2.4.1

• A news organization's home page contains a main story in the middle of the page, surrounded by lots of blocks and sidebars for advertising, searching, and other services. It contains a link at the top of the page that jumps to the main story. Without using this link, a keyboard user needs to tab through approximately 40 links to reach the main story; the screen reader user has to listen to 200 words; and the screen magnifier user must search around for the location of the main body.

Related resources

Intent of this success criterion

The purpose of this success criterion is to make it possible for users to locate content in a manner that best meets their needs. Users may find one technique easier or more comprehensible to use than another.

Techniques for Addressing Success Criterion 2.4.2

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.4.2.

Benefits: How Success Criterion 2.4.2 helps people with disabilities

Providing an opportunity to navigate sites in more than one manner can help people find information faster. A person with visual impairments may find it easier to navigate to the correct part of the site using a search, rather than scrolling through a large navigation bar using a screen magnifier or screen reader. A person with cognitive disabilities may prefer a table of contents or site map which provides an overview of the site rather than reading and traversing through several delivery units. Some users may prefer to explore the site in a sequential manner, moving from delivery unit to delivery unit in order to best understand the concepts and layout.

Individuals with cognitive disabilities may find it easier to use search features to find content than to attempt to use a hierarchical navigation scheme that they may find difficult to understand.

Examples of Success Criterion 2.4.2

• A search mechanism .

  A large food processing company provides a site containing recipes created using its products. The site provides a search mechanism to search for recipes using a particular ingredient. In addition, it provides a list box which lists several categories of foods. A user may type "soup" in to the search engine or may select "soup" from the list box to be taken to a page with a list of recipes made from the company's soup products

• Links between delivery units

  A local hair salon has created a Web site to promote its services. The site contains only five delivery units. There are links on each delivery unit to sequentially move forward or backward through the delivery units. In addition, each delivery unit contains a list of links to reach each of the other delivery units.

• where content is a result of a process or task - funds transfer confirmation:

  An on-line banking site allows fund transfer between accounts via the Web. There is no other way to locate the confirmation of fund transfer until the account owner completes the transfer.

• where content is a result of a process or task - search engine results:

  A search engine provides the search result based on user input. There is no other way to locate the search results except to perform the search process itself.

Related resources

• Graphic Organizers page at the National Center for Accessible Curriculum provides a useful overview of different kinds of graphic organizers and their uses, plus a summary of relevant research on the effectiveness of graphical organizers for students with learning disabilities.

Intent of this success criterion

Titles help users find content and orient themselves within content. Titles identify the current location without requiring users to read or interpret page content. When titles appear in site maps or lists of search results, users can more quickly identify the content they need.

Techniques for Addressing Success Criterion 2.4.3

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.4.3.

Benefits: How Success Criterion 2.4.3 helps people with disabilities

These techniques benefit all users. They are especially helpful for users with disabilities that make reading slow and for people with limited short-term memory. People who have difficulty using their hands or who experience pain when doing so will benefit from techniques that reduce the number of keystrokes required to reach the content they need.

Examples of Success Criterion 2.4.3

• Example 1: A Web page is titled: "Smallville High School Home Page".

• Example 2: Each frame in an application has a title: "Navigation Bar", "Upcoming Events", "Latest Sports Results"

Related resources

• Guidelines for Accessible and Usable Web Sites: Observing Users Who Work With Screen Readers. Theofanos, M.F., and Redish, J. (2003). Interactions, Volume X, Issue 6, November-December 2003, pages 38-51, http://portal.acm.org/citation.cfm?doid=947226.947227

Intent of this success criterion

The intent of this success criterion is to help users know where a link goes, so they can decide whether they want to navigate there. A good description on a link improves orientation by helping users interpret the destination page.

Techniques for Addressing Success Criterion 2.4.4

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.4.4.

Benefits: How Success Criterion 2.4.4 helps people with disabilities

This success criterion helps people with motion impairment by letting them skip delivery units that they are not interested in, avoiding the keystrokes needed to visit the referenced content and then return to the current content.

People with cognitive impairment will not become disoriented by extra navigation to and from content they are not interested in.

People with visual disabilities will benefit from not losing their place in the content when they return to the original page. The screen reader's list of links is more useful for finding information because the targets of the link are described.

Examples of Success Criterion 2.4.4

• A link is preceded by a text description of the information at that URL.

  "Learn more about the Government of Ireland's Commission on Electronic Voting" appears before the link "Go Vote!"

• metadata that is programmatically associated with a link provides additional information about the target.

  A the text of a link is "Commission on Electronic Voting." Additionally, the description, "Home page of the Government of Ireland's Commission on Electronic Voting" is associated with the link.

• Both an icon and text are included in the same link

  An icon of a voting machine and the text "Government of Ireland's Commission of Electronic Voting" are combined to make a single link.

• A list of book titles

  A list of books is available in 3 formats: HTML, PDF, and mp3 (a recording of a person reading the book). To avoid hearing the title of each book three times (once for each format), the first link for each book is the title of the book, the second link says "PDF" and the third says, "mp3."

Related resources

• Using Link Titles to Help Users Predict Where They Are Going.

• WebAIM Techniques for Hypertext Links.

Intent of this success criterion

The intent of this success criterion is to help users understand what information is contained in delivery units and how that information is organized. When titles and headings are clear and descriptive, users can find the information they seek more easily, and they can understand the relationships between different parts of the content more easily.

Techniques for Addressing Success Criterion 2.4.5

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.4.5.

Benefits: How Success Criterion 2.4.5 helps people with disabilities

Descriptive titles are especially helpful for users who have disabilities that make reading slow and for people with limited short-term memory. These people benefit when section titles make it possible to predict what each section contains.

People who have difficulty using their hands or who experience pain when doing so will benefit from techniques that reduce the number of keystrokes required to reach the content they need.

This success criterion helps people who use screen readers by ensuring that titles and headings are meaningful when read out of context - for example, in a Table of Contents, or when jumping from heading to heading within a page.

This success criterion may also help users with low vision who can see only a few words at a time.

Examples of Success Criterion 2.4.5

• A news site.

  The home page of a news site lists the headlines for the top stories of the hour. Under each heading are the first 35 words of the story and a link to the full article. Each headline gives a clear idea of the article's subject.

• A guide on how to write well

  A guide on writing contains the following section titles: How To Write Well, Cut Out Useless Words, Identifying Unnecessary Words, etc. The section headings are clear and concise, and the structure of the information is reflected in the structure of the headings.

• Example 3: Consistent headings in different articles

  A collection of Web pages contain articles in a common style. The articles use the same headings for some sections, but the title of the Web page makes it easy to tell the topic of the section.

  For example, the Web site may contain papers from a conference. Submissions to the conference are required to have the following organization: Summary, Introduction, ... sections unique to this article ..., Conclusion, Author Biography, Glossary, and Bibliography.

Related resources

• Guidelines for Accessible and Usable Web Sites: Observing Users Who Work With Screen Readers. Theofanos, M.F., and Redish, J. (2003). Interactions, Volume X, Issue 6, November-December 2003, pages 38-51, http://doi.acm.org/10.1145/947226.947227.

• Writing Better Web Page Titles How to write titles for Web pages that will be more effective for use with search engines.

• Methods for Designing Usable Web Sites Methods for collecting, writing, and revising Web content to make it easy to use.

• How Users Read on the Web A study showing that most users scan Web pages rather than reading them word by word.

• Applying Writing Guidelines to Web Pages A report on the effects of making Web sites concise, easy to scan, and objective.

Intent of this success criterion

The intent of this success criterion is to ensure that when users navigate sequentially through content, they encounter information in an order that reflects the logical relationships in the content. This reduces confusion by letting users form a consistent mental model of the content.

Some Web content must support sequential navigation. For example, a person using a keyboard or keyboard interface to complete an on-line form typically uses the tab key to move from one input element to the next item on the form. Each time the user presses the tab key, the another element receives focus (that is, the user's next action will affect the item that has focus). In some cases it may be necessary to specify the sequence in which items will receive focus, because the default sequence is not logical.

Techniques for Addressing Success Criterion 2.4.6

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.4.6.

Benefits: How Success Criterion 2.4.6 helps people with disabilities

These techniques benefit users who navigate documents sequentially and expect the tab order to match the sequential reading order. People with visual impairments or people with disabilities that make reading difficult can become disoriented when tabbing takes focus someplace unexpected.

Examples of Success Criterion 2.4.6

• Example of the results of failure to meet the success criterion: An on-line subscription form.

  A company's Web site includes a form that collects marketing data and allows users to subscribe to several newsletters published by the company. The form includes typical fields such as name, street address, city, state or province, and postal code. It also includes several checkboxes so that users can indicate which newsletters they want to receive. An individual using a screen magnifier enters her name and street address and presses the tab key, expecting that she will next enter the name of her city. But instead the focus moves to a checkbox beside the name of a newsletter. Only part of the newsletter's title is visible because of the screen magnification, and the user does not realize what has happened. She keys in her address and submits the form. She is surprised when she receives an error message telling her that one or more required fields is incomplete.

Related resources

Intent of this success criterion

The intent of this success criterion is to provide the user a way to orient herself within a Web site or Web application and find related information.

Techniques for Addressing Success Criterion 2.4.7

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.4.7.

Benefits: How Success Criterion 2.4.7 helps people with disabilities

This success criterion is helpful for people with a short attention span who may become confused when following a long series of navigation steps to a Web page. It is also helpful when a user follows a link directly to a page deep within a Web site and needs to navigate that Web site to understand the content of that page or to find more related information.

Examples of Success Criterion 2.4.7

• Links to help user determine location in a site

  A research group is part of an educational department at a university. The group's home page links to the department home page and the university's home page.

• A breadcrumb trail

  A portal Web site organizes topics into categories. As the user navigates through categories and subcategories, a breadcrumb trail shows the current location in the categories hierarchy. Each page also contains a link to the Directory Home.

Related resources

• Breadcrumb Navigation: Further Investigation of Usage

Intent of this success criterion

The intent of this success criterion is to provide the user a way to orient herself within a Web site or Web application and find related information.

Techniques for Addressing Success Criterion 2.4.8

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.4.8.

Benefits: How Success Criterion 2.4.8 helps people with disabilities

This success criterion is helpful for people with a short attention span who may become confused when following a long series of navigation steps to a Web page. It is also helpful when a user follows a link directly to a page deep within a Web site and needs to navigate that Web site to understand the content of that page or to find more related information.

Examples of Success Criterion 2.4.8

• Links to help user determine location in a site

  A research group is part of an educational department at a university. The group's home page links to the department home page and the university's home page.

• A breadcrumb trail

  A portal Web site organizes topics into categories. As the user navigates through categories and subcategories, a breadcrumb trail shows the current location in the categories hierarchy. Each page also contains a link to the Directory Home.

Related resources

• Breadcrumb Navigation: Further Investigation of Usage

Intent of this success criterion

The intent of this success criterion is to ensure that users are aware that an error has occurred and can determine what is wrong. In the case of an unsuccessful form submission, redisplaying the form and indicating the fields in error is insufficient for some users to perceive that an error has occurred. Screen reader users, for example, will not know there was an error until they encounter one of the indicators. They may abandon the form altogether before encountering the error indicator, thinking that the page simply isn't functional.

Techniques for Addressing Success Criterion 2.5.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.5.1.

Benefits: How Success Criterion 2.5.1 helps people with disabilities

Providing information about input errors in text allows users who are blind, colorblind, or have learning disabilities to perceive the fact that an error occurred.

Examples of Success Criterion 2.5.1

• Identifying errors in a form submission.

  An airline Web site offers a special promotion on discounted flights. The user is asked to complete a simple form that asks for personal information such as name, address, phone number, seating preference and e-mail address. If any of the fields of the form are either not completed or completed incorrectly, a text message is displayed notifying the user that some of the information provided has not been accepted. The message also specifies that the form will be redisplayed with incorrect fields identified by two asterisks. The user is then presented with the same form, with all previously and correctly entered information still available. The user is asked to make corrections to any form fields marked with two asterisks.

  Note: This success criterion does not mean that color or text styles cannot be used to indicate errors. It simply requires that errors also be identified using text. In this example, two asterisks are used in addition to color.

Related resources

Intent of this success criterion

The intent of this success criterion is to ensure that users receive appropriate suggestions for correction of an input error if it is possible.

Success Criterion 2.5.1 provides for notification of errors. However, persons with cognitive disabilities may find it difficult to understand how to correct the errors. People with visual disabilities may not be able to figure out exactly how to correct the error. In the case of an unsuccessful form submission, users may abandon the form because although they may be aware that an error has occurred, they may be unsure of how to correct the error.

Techniques for Addressing Success Criterion 2.5.2

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.5.2.

Benefits: How Success Criterion 2.5.2 helps people with disabilities

Providing information about how to correct input errors allows users who have learning disabilities to fill in a form successfully. Users who are blind or have impaired vision understand more easily the nature of the input error and how to correct it. People with motion impairment can reduce the number of times they need to change an input value.

Examples of Success Criterion 2.5.2

• Additional Help for Correcting An Input Error

  An example of output from an HTML form that was not successfully submitted (and an image that it uses). It describes an input error that occurred among other "correct" input and offers additional help for the form field that caused the input error.

• Suggestions from a Limited Set of Values

  An input field requires that a month name be entered. If the user enters "12", suggestions for correction may include

  • a list of the acceptable values, e.g. "Choose one of: January, February, March, April, May, June, July, August, September, October, November, December"

  • a description of the set of values, e.g. Please provide the name of the month

  • the conversion of the input data, interpreted as a different month format: do you mean "December"?

Related resources

Intent of this success criterion

The intent of this success criterion is to help users with disabilities avoid serious consequences as the result of a mistake. For example, purchasing non-refundable airline tickets or submitting an order to purchase stock in a brokerage account are financial transactions with serious consequences. If a user has made a mistake on the date of air travel, he or she could end up with a ticket for the wrong day which can't be exchanged. If the user made a mistake on the number of stock shares to be purchased, he or she could end up purchasing more stock than intended. Both of these types of mistakes can be very costly.

Users with disabilities may be more likely to make mistakes. People with learning disabilities may transpose numbers and letters, and those with motor disabilities may hit keys by mistake. Providing the ability to reverse actions allows users to correct a mistake that could result in serious consequences. Providing the ability to review and correct information gives the user an opportunity to detect a mistake before taking an action that has serious consequences.

Techniques for Addressing Success Criterion 2.5.3

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.5.3.

Benefits: How Success Criterion 2.5.3 helps people with disabilities

Providing safeguards to avoid serious consequences resulting from mistakes helps users with all disabilities who may be more likely to make mistakes.

Examples of Success Criterion 2.5.3

• Order confirmation

  A Web retailer offers on-line shopping for customers. When an order is submitted, the order information, including items ordered, quantity of each ordered item, shipping address, and payment method, are displayed allowing the user to inspect the order for correctness. The user can either confirm the order or make changes.

Related resources

Intent of this success criterion

The intent of this success criterion is to help users avoid making mistakes. Some users with disabilities may be more likely to make mistakes than users without disabilities. Using context-sensitive help, users find out how to perform an operation without losing track of what they are doing.

Techniques for Addressing Success Criterion 2.5.4

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 2.5.4.

Benefits: How Success Criterion 2.5.4 helps people with disabilities

Assistance for text input helps individuals with writing disabilities and people with reading and intellectual disabilities who often have difficulty writing text in forms or other places that need text input.

Additionally, these kinds of assistance help people who are aging and have the same difficulty in text input and/or mouse operation.

Examples of Success Criterion 2.5.4

• Online job application

  Some of the questions may be hard for new job seekers to understand. A help link next to each question provides instructions and explanations for each question.

Related resources

Intent of this Success Criterion

The intent of this success criterion is to ensure that content developers provide information in the delivery unit that user agents need to present text and other linguistic content correctly. Both assistive technologies and conventional user agents can render text more accurately when the language of the delivery unit is identified. Screen readers can load the correct pronunciation rules. Visual browsers can display characters and scripts correctly. Media players can show captions correctly. As a result, users with disabilities will be better able to understand the content.

"Language declarations in HTML and XHTML have nothing to do with character encoding or the direction of text. (…) [T]here is not always a one-to-one mapping between language and script, and therefore directionality. For example, Azerbaijani can be written using both right-to-left and left-to-right scripts." (From Relationships with character encoding and directionality.) Therefore, there are separate mechanisms for declaring the language and directionality of text. The default text direction is left-to-right, which means that direction only needs to be specified if it is right-to-left.

Techniques for Addressing Success Criterion 3.1.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 3.1.1.

Benefits: How Success Criterion 3.1.1 helps people with disabilities

This success criterion helps:

• people who Use screen readers or other technologies that convert text into synthetic speech;

• people with learning disabilities and cognitive limitations that make it difficult to recognize (decode) individual words and sentences;

• people who rely on captions for multimedia.

Examples of Success Criterion 3.1.1

Related resources

Intent of this success criterion

The intent of this success criterion is to ensure that user agents can correctly present content written in a language that is different from the primary language of the delivery unit. This applies to graphical browsers as well as screen readers, braille displays, and other voice browsers.

Both assistive technologies and conventional user agents can render text more accurately if changes of language within the delivery unit are identified. Screen readers can switch to the pronunciation rules for the language of the foreign text, then switch back to the pronunciation rules of the primary language at the end of the foreign phrase or passage. Visual browsers can display characters and scripts in appropriate ways. This is especially important when one language reads from left to right and the other reads from right to left, or when the foreign phrase or passage uses a different alphabet than the primary language. Users with disabilities who know the language of the foreign passage or phrase as well as the language of the delivery unit as a whole will be better able to understand the content.

This requirement does not apply to individual words or to phrases that have become part of the primary language of the content. For example, "rendezvous" is a French word that has been adopted in English, appears in English dictionaries, and is properly pronounced by English screen readers.

Techniques for Addressing Success Criterion 3.1.2

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 3.1.2.

Benefits: How Success Criterion 3.1.2 helps people with disabilities

This success criterion helps:

• people who Use screen readers or other technologies that convert text into synthetic speech;

• people with learning disabilities and cognitive limitations that make it difficult to recognize (decode) individual words and sentences;

• people who rely on captions to recognize language changes in the soundtrack of multimedia content.

Examples of Success Criterion 3.1.2

1. a German phrase in an English sentence.

   In the following sentence, "He maintained that the DDR (German Democratic Republic) was just a 'Treppenwitz der Weltgeschichte'.", the German phrase 'Treppenwitz der Weltgeschichte' is marked as German. 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. When a screen reader encounters the German phrase, it changes pronunciation rules from English to German to pronounce the word correctly.

Related resources

• Language tags in HTML and XML - W3C Internationalization Working Group

• HTML 4.0 Block-Level Elements - Liam Quinn (1998)

• HTML 4.0 Inline Elements - Liam Quinn (1998)

Intent of this success criterion

Certain disabilities make it difficult to understand non-literal word usage and specialized words or usage. Certain disabilities make it difficult to understand figurative language or specialized usage.

Techniques for Addressing Success Criterion 3.1.3

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 3.1.3.

Benefits: How Success Criterion 3.1.3 helps people with disabilities

• This success criterion helps people with disabilities that affect their ability to use context to aid understanding. This includes people with certain learning disabilities and cognitive impairments. In addition, people with low vision often lose context when screen magnifiers zoom in on a small area of the screen. This success criterion also helps people who have difficulty recognizing words (decoding) or remembering the meaning of words by limiting the number of dictionary entries they must read in order to find the definition that fits the context.

Examples of Success Criterion 3.1.3

• Text that includes a definition for a word used in an unusual way.

  Organize the list or "cascade" of dictionaries and other resources so that the definition search will find the intended definitions instead of displaying definitions from other sources in the "cascade." (The "cascade" lists the dictionaries and other reference materials in the order most likely to bring up the right definition. This controls the order to follow when searching for definitions.)

• Including definitions in the glossary.

  WCAG 2.0 uses the word "text" in a specific way. Thus, when the word "text" is used within WCAG 2.0 it is linked to the definition of "text" provided in a glossary within the same delivery unit.

• The specific definition of a word is provided at the bottom of the page.

  The internal link from the word to the corresponding definition is also provided within the page.

Related resources

• Free bilingual dictionaries for a number of languages are available from the Freedict.org Web site. The dictionaries are of uneven quality and size, as noted on the site. Retrieved 9 April 2005.

• The WorldStar Free Dictionaries, Translators and Search Engines site provides access to free on-line dictionaries and search engines in many languages. Retrieved 18 November 2005.

• More dictionaries are at your dictionary, freelang.com (in English, Spanish and French!) and many other places.

Intent of this success criterion

The intent of this success criterion is to ensure that users can access the expanded form of abbreviations.

Techniques for Addressing Success Criterion 3.1.4

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 3.1.4.

Benefits: How Success Criterion 3.1.4 helps people with disabilities

This success criterion helps people whose disabilities make reading difficult or impossible. These include:

• People with learning disabilities or cognitive limitations that impair the ability to read.

• People with low vision. Screen magnification may reduce contextual cues.

• People with memory loss

This success criterion also helps people with disabilities that affect their ability to recognize words as well as their ability to use context to aid understanding. Acronyms and abbreviations may confuse these readers in different ways:

• Some abbreviations do not look like normal words and cannot be pronounced according to the usual rules of the language. For example, the English word "room" is abbreviated as "rm," which does not correspond to any English word or phoneme. The user has to know that "rm" is an abbreviation for the word "room" in order to say it correctly.

• Sometimes the same abbreviation means different things in different contexts. For example, in the English sentence "Dr. Johnson lives on Boswell Dr.," the first "Dr." is an abbreviation for "Doctor" and the second instance is an abbreviation for the word "Drive" (a word that means "street"). Users must be able to understand the context in order to know what the abbreviations mean.

• Some acronyms spell common words, but are used in different ways. For example, "JAWS" is an acronym for a screen reader whose full name is "Job Access with Speech." It is also a common English word referring to the part of the mouth that holds the teeth. The acronym is used differently than the common word.

• Some acronyms sound like common words but are spelled differently. For example, the acronym for Synchronized Multimedia Integration Language, S M I L, is pronounced like the English word "smile."

Examples of Success Criterion 3.1.4

• A dictionary search form.

  A Web site includes a search form provided by an on-line acronym service. Users enter an acronym and the form returns a list of possible expansions from the sources that it searched.

• A medical Web site.

  A medical Web site provides information for both doctors and patients. The site includes a set of cascading dictionaries: a very specialized medical dictionary is first, followed by a second medical dictionary for the general public. The cascade also includes a list of acronyms and abbreviations that are unique to the site, and finally there is a standard dictionary as well. The standard dictionary at the end of the list provides definitions for most words in the text. The specialized medical dictionary yields definitions of unusual medical terms. Definitions for words that appear in more than one dictionary are listed in the order of the cascade. The meaning of acronyms and abbreviations is provided by the list of acronyms and abbreviations.

• An abbreviation whose expansion is provided the first time the abbreviation appears in the content.

  The name, "World Wide Web Consortium," appears as the first heading on the organization’s home page. The abbreviation, "W3C," is enclosed in parentheses in the same heading.

Related resources

• Acronym finder - you can search with the exact acronym, the beginning of the acronym, wildcards and reverse lookup.

• The Opaui Guide to Lists of Acronyms, Abbreviations, and Initialisms on the World Wide Web.

• AbbreviationZ - The A to Z of Acronyms & Abbreviations on the Net.

Intent of this success criterion

The intent of this success criterion is:

• To ensure that additional content is available to aid understanding of difficult or complex text;

• to establish a testable measure indicating when such additional content is required.

This success criterion helps people with reading disabilities while also allowing authors to publish difficult or complex Web content. Text difficulty is described in terms of the level of education required to read the text . Education levels are defined according to the International Standard Classification of Education (UNESCO 1975, 1997), which was created to allow international comparison among systems of education.

Difficult or complex text may be appropriate for most members of the intended audience (that is, most of the people for whom the content has been created). But there are people with disabilities, including reading disabilities, even among highly educated users with specialized knowledge of the subject matter. It may be possible to accommodate these users by making the text more readable. If the text cannot be made more readable, then supplemental content is needed.

Supplemental content is required when text demands reading ability more advanced than the lower secondary education level — that is, more than nine years of school. Such text presents severe obstacles to people with reading disabilities, and is considered difficult even for people without disabilities who have completed upper secondary education.

Techniques for Addressing Success Criterion 3.1.5

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 3.1.5.

Benefits: How Success Criterion 3.1.5 helps people with disabilities

This success criterion benefits people with reading disabilities who can understand complex ideas and processes presented in highly readable text or by other means, such as graphics illustrating relationships and processes or through the spoken word.

Reading and intellectual disabilities affect the ability to recognize individual words. Decoding must be automatic in order for people to read fluently. The act of decoding text word by word consumes much of the mental energy that most people are able to use for understanding what they read.

Examples of Success Criterion 3.1.5

1. A scientific journal including readable summaries of complex research articles

   A scientific journal includes articles written in highly technical language aimed at specialists in the field. The journal's Table of Contents page includes a plain-language summary of each article. The summaries are intended for a general audience with eight years of school. The metadata for the journal uses the Dublin Core specification to identify the education level of the articles' intended audience as "advanced"; and the education level of the intended audience for the summaries as "lower secondary education."

2. Medical information for members of the public.

   A medical school operates a Web site that explains recent medical and scientific discoveries. The articles on the site are written for people without medical training. Each article uses the Dublin Core metadata specification to identify the education level of the intended audience as "lower secondary education" and includes the Flesch Reading Ease score for the article. A link on each page displays the education level and other metadata. No supplemental content is required because people who read at the lower secondary education level can read the articles.

3. An e-learning application.

   An on-line course about Spanish cultural history includes a unit on Moorish architecture. The unit includes text written for students with different reading abilities. Photographs and drawings of buildings illustrate architectural concepts and styles. Graphic organizers are used to illustrate complex relationships, and an audio version using synthetic speech is available. The metadata for each version describes the academic level of the content and includes a readability score based on formulas developed for Spanish-language text. The learning application uses this metadata and metadata about the students to provide versions of instructional content that match the needs of individual students.

Related resources

• A Plain Language Audit Tool provides a checklist for determining whether documents can be edited for clarity and "plain language." The checklist includes a readability assessment. Available from the Northwest Territories (Canada) Literacy Council at http://www.nwt.literacy.ca/plainlng/auditool/cover.htm.

• The Plain Language Network Web site provides many useful resources to help writers produce documents that communicate clearly in a variety of cultural and rhetorical contexts. Refer to: http://www.plainlanguagenetwork.org/.

• The US government's plain language Web site provides general information about plain language as well as information about use of plain language in US government documents, including legal requirements

• The Plain English Campaign Web site provides useful information and guidance for authors writing in English.

• Hall, T.,and Strangman, N. CAST: Graphic organizers. Retrieved 5 April 2005. This article illustrates several different kinds of graphic organizers, explains how each type may be useful, and summarizes research findings that graphic organizers support learning, especially among students with learning disabilities.

Intent of this success criterion

The intent of this success criterion is to ensure that functionality is predictable as visitors navigate their way through a document. Any component that is able to trigger an event when it receives focus must not change the context. Examples of changing context when a component receives focus include, but are not limited to:

• forms submitted automatically when a component receives focus;

• new windows launched when a component receives focus;

• focus is changed to another component when that component receives focus;

Techniques for Addressing Success Criterion 3.2.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 3.2.1.

Benefits: How Success Criterion 3.2.1 helps people with disabilities

• People who navigate with a keyboard, including people with visual impairments that may use assistive technologies and people with mobility problems whose motor control makes using a pointing device difficult, may activate a change of context without having an opportunity to make appropriate choices.

• People with cognitive difficulties may be unaware that an implicit action has caused a change of context.

Examples of Success Criterion 3.2.1

Intent of this success criterion

The intent of this success criterion is to ensure that entering data or selecting from a control have predictable effects. Changes in context, such as changing the input fields based on the value of a radio button can confuse users that do not easily perceive the change or are easily distracted by changes. Changes of context should occur only when it is clear that such a change will happen when a field is selected or a button is pressed.

See Benefits.

Techniques for Addressing Success Criterion 3.2.2

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 3.2.2.

Benefits: How Success Criterion 3.2.2 helps people with disabilities

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

• Individuals who are unable to detect changes of 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.

• Some individuals with low vision, with reading and intellectual disabilities, and who have difficulty interpreting visual cues may benefit from additional cues in order to detect changes of context.

Examples of Success Criterion 3.2.2

All of the following techniques violate success criterion 3.2.2.

• The following examples that violate success criterion 3.2.2 are followed by suggested remedies:

  • A form control that automatically takes an action such as submitting a page. Use a separate submit button.

  • A form control that significantly changes the content when selected. A separate button should be use to change the content. Small changes to content such as changing explanations based of the value of the selection or revealing more detail are allowed.

• A form is presented to the user with multiple fields to be filled in. A submit button is used to accept the values and initiate a change of context.

Intent of this success criterion

The intent of this success criterion is to encourage the use of consistent presentation and layout for users who interact with repeated content in a set of delivery units and need to locate specific information or functionality more than once. Individuals with low vision who use screen magnification to display a small portion of the screen at a time often use visual cues and page boundaries to quickly locate repeated content. Presenting repeated content in the same order is also important for visual users who use spatial memory or visual cues within the design to locate repeated content.

It is important to note that the use of the term "same order" in this criterion is not meant to imply that subnavigation menus cannot be used or that blocks of secondary navigation or page structure cannot be used. Instead, this criterion is intended to assist users who interact with repeated content across delivery units to be able to predict the location of the content they are looking for and find it more quickly when they encounter it again.

Techniques for Addressing Success Criterion 3.2.3

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 3.2.3.

Benefits: How Success Criterion 3.2.3 helps people with disabilities

• Ensuring that changes of context can be programmatically determined allows user agents to provide warnings to users that they are about to occur or support settings that allow users to disable them.

• Users expect user agents to change the context (that is, load a new page) whenever they select a link or a submit button. They can be surprised and confused, however, if the context changes when they are simply navigating through the Web page or changing the setting of a form field. The surprise and confusion is more severe for users who are blind or have low vision and can't see that a new page is loading but simply hear their screen reader suddenly start reading an entirely new page. The surprise and confusion can also be more severe for users with learning disabilities. Avoiding these types of unexpected changes in context reduces such surprise and confusion.

• Ensuring that repeated components occur in the same order on each page of a site helps users become comfortable that they will able to predict where they can find things on each page. This helps users with learning disabilities and also those who are blind.

Examples of Success Criterion 3.2.3

• A consistently located control

  A user may recall that a search field is always located at the bottom right corner of a page in a site. After browsing a number of pages within the site and not finding what they were looking for, the user can quickly locate the search function.

• An expanding navigation menu

  A navigation menu includes a list of seven items with links to the main sections of a site. When a user selects one of these items, a list of subnavigation items is inserted into the top-level navigation menu.

• Consistently positioned skip navigation controls

  A "skip navigation" link is included as the first link on every page in a Web site. The link allows users to quickly bypass heading information and navigational content and begin interacting with the main content of a page.

• Skip to navigation link

  A skip to navigation link is provided to navigational content at the end of a page. The link is consistently located at the top of each page so that keyboard users can easily locate it when needed.

Related resources

• Detweiler, M.C. and Omanson, R.C. (1996), Ameritech Web Page User Interface Standards and Design Guidelines.

• Understanding disability issues when designing Web sites.

Intent of this success criterion

The intent of this criterion is to ensure consistent identification of functional components that appear repeatedly within a set of delivery units. A strategy that people who use screen readers use when operating a Web site is to rely heavily on their familiarity with functions that may appear on different delivery units. If identical functions have different labels on different delivery units, the site will be considerably more difficult to use. It may also be confusing and increase the cognitive load for people with cognitive difficulties. Therefore, consistent labeling will help.

This consistency extends to the text alternatives. If icons or other non-text items have the same functionality, then their text alternatives should as well.

See Benefits.

Techniques for Addressing Success Criterion 3.2.4

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 3.2.4.

Benefits: How Success Criterion 3.2.4 helps people with disabilities

• People who figure out functionality on one page on a site can find the desired functions on other pages if they are present.

• People with difficulty reading text or detecting text alternatives can interact with the Web without depending on text alternatives.

• People who depend on text alternatives can have a more predictable experience. They can also search for the button if it has a consistent label on different pages.

Examples of Success Criterion 3.2.4

• Example 1: Document Icon

  A document icon, which is used to indicate document download throughout out a site. Since there may be multiple documents to download, text alternatives are useful to differentiate the documents. In this case, the document icon serves the same function of loading documents. Using different text alternatives identifying document names for different documents is a consistent use of text alternative.

• Example 2: Check Mark

  A check mark icon functions as "approved", on one page but as "included",on another. Since they serve different functions, they have different text alternatives.

• Example 3: Example of a Failure

  A common "save" icon is used through out the site where page save function is provided on multiple delivery units.

• Example 4: Example of a Failure

  A submit "search" button on one delivery unit and a "find" button on another delivery unit may both have a field to enter a term and list topics in the Web site related to the term submitted. In this case they would have same functionality but would not be labeled consistently.

Intent of this success criterion

The intent of this success criterion is to encourage design of Web content that gives users full control of changes of context. This success criterion aims to eliminate potential confusion that may be caused by unexpected changes of context such as automatic launching of new windows, automatic submission of forms after selecting an item from a list, etcetera. Such unexpected changes of context may cause difficulties for people with motor impairments, people with low vision, people who are blind, and people with certain cognitive disabilities.

Further below is a description of who benefits from this success criterion.

Techniques for Addressing Success Criterion 3.2.5

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 3.2.5.

Benefits: How Success Criterion 3.2.5 helps people with disabilities

• Individuals who are unable to detect changes of 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.

• Some individuals with low vision, with reading and intellectual disabilities, and who have difficulty interpreting visual cues may benefit from additional cues in order to detect changes of context.

• People with certain cognitive disabilities do not get confused if automatic redirects are performed by the Web server instead of the browser.

Examples of Success Criterion 3.2.5

• an "update now" button

  Instead of automatically updating the content, the author provides an "Update now" button that requests a refresh of the content.

• An automatic redirection

  A user is automatically redirected from an old page to a new page in such a way that he or she never realizes the redirect has occurred.

Related resources

• Use standard redirects: don't break the back button! (W3C QA Tip).

• HTTP/1.1 Status Code Definitions: Redirection 3xx.

Intent of this success criterion

The purpose is to ensure that user agents (including assistive technology) can accurately interpret parsable content. If it is not unambiguously parsable then different user agents may present it differently or be completely unable to parse it. The fact that it can be parsed (using repair techniques during parsing) by major mainstream user agents does not mean that it can be parsed (or parsed accurately) by special browsers (including assistive technologies) that a user with a disability might need to employ.

Techniques for Addressing Success Criterion 4.1.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 4.1.1.

Benefits: How Success Criterion 4.1.1 helps people with disabilities

• Ensuring that delivery units parse unambiguously helps ensure that assistive technologies can parse the content accurately and without crashing.

Examples of Success Criterion 4.1.1

Related resources

Intent of this success criterion

The intent of this success criterion is to provide information in a form that assistive technology can extract accessibility information about interactive user interface components in order to present them to users in an understandable way. For example, a screen reader may tell a user that the current control is a checkbox and that it is not checked. Checkbox is the "role" and "not checked" is the state. Users are then able to understand that the option represented by the checkbox is selected. A speech recognition program might build an interaction vocabulary using this information.

Techniques for Addressing Success Criterion 4.1.2

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 4.1.2.

Benefits: How Success Criterion 4.1.2 helps people with disabilities

Providing role, state, and value information on all user interface components enables compatibility with assistive technology, such as screen readers, screen magnifiers, and speech recognition software, used by users with disabilities.

Examples of Success Criterion 4.1.2

• Accessible APIs

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

Related resources

• Access Mozilla: Accessible DHTML

• Dynamic Accessible Web Content Roadmap

• Role Taxonomy for Accessible Adaptable Applications

• States and Adaptable Properties Module

• Microsoft Active Accessibility, Version 2.0

• IBM Guidelines for Writing Accessible Applications using 100% Pure Java

• Flash 8 Accessibility

Intent of this success criterion

The intent of this success criterion is to ensure that an accessible version of all content is available. Authors may use inaccessible technologies or formats on their Web sites. But they must also provide all of the information and functionality in an accessible form that is easily obtained. Note that this is a fallback option and is not preferable to making the content itself accessible.

Techniques for Addressing Success Criterion 4.2.1

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 4.2.1.

Benefits: How Success Criterion 4.2.1 helps people with disabilities

The benefits of determining and documenting technology requirements are that 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 cannot access or to automatically filter to the top sites that would be most usable. Documenting technology requirements will cause authors 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. The benefits of ensuring user interface accessibility and providing accessible alternatives are that individuals who must use alternative browsing technologies and devices will be able to access the content. Individuals who cannot 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 Success Criterion 4.2.1

• An on-line store that lists required technologies.

  By documenting minimum user agent requirements, the store makes it possible for people using particular technologies to determine whether they are going to have trouble using the store or its checkout mechanism before they begin shopping. This prevents users from finding that, after they have selected their products and initiated a checkout process, they are unable to complete their transaction. They can, therefore, choose alternatives where they can be assured greater success.

• An intranet site with multiple versions.

  A large company was concerned that the use of emerging Web technologies on an intranet site might limit their ability to address the needs of individuals at many diverse office locations that have different technology bases and who use a wide variety of user agents and assistive technologies. To address these concerns, the company created an alternative version of the content that met all Level 1 success criteria using a more limited baseline. The requirements for each version were carefully documented, and both versions were available from the same URI, making it easy for each location to choose the version best suited to their needs.

• An informational site ensuring backward compatibility.

  An information site covers a wide variety of subjects and wants to enable their visitors to quickly find the topics they're looking for. To do this, they have implemented an interactive menu system that is only supported in the most recent version of two popular user agents. To ensure that their visitors who do not use these specific user agents are still able to effectively use the site, a navigation mechanism that does not depend on the interactive menu system they are using is presented to user agents that do not support the newer technology.

Related resources

(none currently documented)

Intent of this success criterion

The intent of this SC is to ensure that content does not include components that actively interfere with the accessibility of the remaining content. These include:

• components that would trap keyboard users within inaccessible content.

The baseline is the set of technologies that must be supported for the Web site's content and functionality to be available to the user. All content implemented in technologies in the baseline must conform to WCAG for the claim of conformance for the site to be valid. Content may be implemented in technologies that are not in the baseline, however, if accessible alternatives are provided using technologies that are in the baseline, or if the content is accessible from a user agent that supports only the technologies in the baseline. It is vital that there be no characteristics of any of the content that actively interfere with its accessibility. This is because user agents that support the technology could be present and create accessibility problems even though the technology is not part of the baseline.

The requirement that content that can be entered via the keyboard can be exited via the keyboard refers to "keyboard trapping", a common situation in which the keyboard focus can become stuck in inaccessible plugins, leaving a keyboard-only user with no way to return to the accessible content.

Techniques for Addressing Success Criterion 4.2.2

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 4.2.2.

Benefits: How Success Criterion 4.2.2 helps people with disabilities

This success criterion ensures that accessible content in the baseline is not unintentionally rendered inaccessible by simultaneously displayed content in technologies outside of the baseline. It describes "active inaccessibility" cases that must be avoided even for technologies outside of the baseline and the scope of the WCAG conformance claim.

Examples of Success Criterion 4.2.2

1. Non-baseline content contains a link to information about how to move focus back to the baseline content via the keyboard.

2. The Help information available from the non-baseline content documents how to move focus back to the baseline content via the keyboard, and the Help information can be accessed via the keyboard.

3. (Advisory) The Help information available for the delivery unit documents how to move focus from the non-baseline content to the baseline content via the keyboard, and the Help information can be accessed via the keyboard.

Related resources

(none currently documented)

Intent of this success criterion

The intent of this success criterion is to ensure that an accessible version of all content is available. Authors may use inaccessible technologies or formats on their Web sites. But they must also provide all of the information and functionality in an accessible form that is easily obtained. Note that this is a fallback option and is not preferable to making the content itself accessible.

Techniques for Addressing Success Criterion 4.2.3

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 4.2.3.

Benefits: How Success Criterion 4.2.3 helps people with disabilities

The benefits of determining and documenting technology requirements are that 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 cannot access or to automatically filter to the top sites that would be most usable. Documenting technology requirements will cause authors 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. The benefits of ensuring user interface accessibility and providing accessible alternatives are that individuals who must use alternative browsing technologies and devices will be able to access the content. Individuals who cannot 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 Success Criterion 4.2.3

• An on-line store that lists required technologies.

  By documenting minimum user agent requirements, the store makes it possible for people using particular technologies to determine whether they are going to have trouble using the store or its checkout mechanism before they begin shopping. This prevents users from finding that, after they have selected their products and initiated a checkout process, they are unable to complete their transaction. They can, therefore, choose alternatives where they can be assured greater success.

• An intranet site that transforms gracefully.

  A large company was concerned about the ability to address individuals at many diverse office locations that have different technology bases. To address the problem, they created two versions of their content and documented the requirements for each, making it easy for individual locations to determine which version would work best for their technologies.

• An informational site ensuring backward compatibility.

  An information site covers a wide variety of subjects and wants to enable their visitors to quickly find the topics they're looking for. To do this, they have implemented an interactive menu system that is only supported in the most recent version of two popular user agents. To ensure that their visitors who do not use these specific user agents are still able to effectively use the site, a navigation mechanism that does not depend on the interactive menu system they are using is presented to user agents that do not support the newer technology.

Related resources

(none currently documented)

Intent of this success criterion

At Level 1 and 2, WCAG conformance is only required for technologies inside the baseline. Technologies outside the baseline need not conform, although accessible alternatives using technologies inside the baseline must be provided. This success criterion takes accessibility requirements at Level 3 further and states that any accessibility features supported by technologies outside the baseline must be used, even though accessible alternatives are also provided.

This requires that any accessibility features supported by technologies outside the chosen baseline be used, even though accessible alternatives are also provided. Some technologies do not provide features capable of meeting all WCAG requirements, and therefore content in those technologies cannot meet WCAG requirements alone. For that reason, this success criterion does not require that content in technologies outside the baseline meet all WCAG requirements.

Techniques for Addressing Success Criterion 4.2.4

The following combinations of techniques are deemed to be sufficient by the WCAG Working Group for meeting success criterion 4.2.4.

Benefits: How Success Criterion 4.2.4 helps people with disabilities

Although by definition content in technologies outside the baseline need not be accessible in order to conform to WCAG, because accessible alternatives are provided, accessibility features should nevertheless be provided. This permits users with disabilities who have user agents that do support the technology to use that content, rather than be forced to rely on the accessible alternative. It also future-proofs the site: should the baseline be extended to include a technology that is currently outside the baseline, the content already meets WCAG requirements. This is good practice and always desirable, but is only required for WCAG conformance at Level 3 by this success criterion.

Examples of Success Criterion 4.2.4

• A Web site is developed for a baseline that contains HTML and Script, but does not support Flash. An interactive Flash movie provides video clips and responses to user input. The information provided is also available in HTML with Script support, but the experience is not as rich. The Flash movie provides text alternatives, keyboard support, appropriate tab order, etc. to help make it directly accessible so users who wish can access the richer content directly instead of the accessible alternative.

• At a Web site developed for a baseline that contains HTML but not PDF, a PDF version of a print book is provided with an HTML alternative. Although all the content is available in the HTML version, it cannot be printed in a manner that is true to the design of the original book, and it is much harder to keep track of pagination for references. The PDF version is structured with a logical reading order, text alternatives for images, etc. so it can be viewed directly by users who prefer to access that version and use the features of the PDF reader.

• Prerecorded video is provided on the site. Although the video format supports text tracks for captioning and alternate audio tracks for described video, user agent support for these features is known to be imperfect. Therefore it is decided to leave the video format out of the baseline, and provide a text transcript and text descriptions as an accessible alternative. Nevertheless, captions and audio descriptions are also provided in the video so users who wish can access them while the video is playing.

• An HTML page provides "menu bar"-style navigation with the aid of ECMAScript to display and hide menu options. Because the site is designed to be used by users who have browsers that do not support script, the baseline only includes HTML and does not mandate the use of script. Accordingly, the navigation menus are designed so that if scripts are not supported, links take users to alternate navigation pages so they can navigate the site if the menu options are not shown. The script is designed to be accessible for user agents that do support script, including providing keyboard operability, not preventing keyboard and mouse commands from working, and displaying/hiding content instead of generating/removing content to ensure that users can access the menus as they appear.

Related resources

• IBM Software Accessibility Checklist

• IBM Java Accessibility Checklist

• Sun Java Accessibility Documentation

• Macromedia Flash Accessibility Guidelines

• Adobe PDF Accessibility Guidelines

• NCAM Rich Media Resource Suite