WCAG 2.0 Conformance Proposals for 04 January 2007

Updated 18 January based on survey comments and meeting resolutions.

The following is a set of draft revisions for the conformance section of WCAG 2.0. It includes an updated version of the conformance and glossary sections. For the most up-to-date version of WCAG 2.0, please refer to the latest internal working draft.

Table of Contents



This section is normative.

Conformance means that Web content satisfies the success criteria defined in this document. This section outlines the conformance scheme used throughout this document.

WCAG 2.0 success criteria are organized into three levels of conformance. Understanding levels.

The word "levels" does not mean that some success criteria are more important than others. Each success criterion in WCAG 2.0 is essential to some users, and the levels build upon each other. However, even content that conforms at AAA (triple-A) may not be fully accessible to every person with a disability.

All WCAG 2.0 success criteria are written to be testable [LC-900] . While some can be tested by computer programs, others require human testers for part or all of the test. When people who understand WCAG 2.0 and how people with different types of disabilities use the Web test the same content using the same success criteria, the same results should be obtained with a high level of confidence. [LC-1267]

For each success criterion, there is a list of techniques deemed by the Working Group to be sufficient to meet the requirement. For each sufficient technique, there is a test to determine whether the technique has been successfully implemented. If the test(s) for a "sufficient" technique (or combination of techniques) are passed, then that success criterion has been met. Passing all tests for all techniques is not necessary. It is also not necessary to meet a success criterion using one of the sufficient techniques. There may be other techniques which are not documented by the working group that would also meet the success criterion. [LC-1245]

In addition to the success criteria, which are all testable, there are a number of techniques that may enhance accessibility that are not testable or are not always appropriate. These are listed as "Advisory Techniques" in Understanding WCAG 2.0. Authors are encouraged to use these techniques where appropriate, although using them does not affect conformance.

User agents, technology-independence and "relied upon" technologies

Technology independence

WCAG 2.0 defines accessibility guidelines (goals) and success criteria (testable criteria for conformance at different levels of accessibility). The guidelines and success criteria are described in a technology-independent way in order to allow conformance using any Web technology that is enabled for accessibility. WCAG 2.0, therefore, does not require or prohibit the use of any specific technology. It is possible to conform to WCAG 2.0 using both W3C and non-W3C technologies, as long as the technologies are supported by user agents, including assistive technologies.

Note: Although assistive technologies are a type of user agent, they depend upon support from host users agents. To reinforce the need to enable assistive technologies, several success criteria that require user agent support explicitly require support for assistive technologies, too.

Choosing accessibility-enabled Web technologies (AeWT)

In choosing Web technologies (HTML, scripting, etc.) that will be used when creating content, authors must use technologies that will work with existing user agents, including assistive technologies, that are available to the users of their content who have disabilities. These technologies are referred to as accessibility-enabled Web technologies (AeWT).

Accessibility-enabled Web technologies are defined as technologies that include accessibility features needed to create content that can conform to WCAG 2.0 where both of the following are true:

  1. The technologies are supported by assistive technology (AT) available to almost all users

    This means that at least one of the following is true:

    1. The technology implements accessibility APIs that are supported by a wide range of assistive technology including assistive technology that is available to almost all users.

    2. The technology has been tested for interoperability with commonly-used assistive technology in the natural language(s) of the content including assistive technology that is available to almost all users.

  2. The technologies are available to the intended audience

    This means that at least one of the following is true:

    1. The technology is supported natively in widely-distributed user agents. Examples: HTML, frames, CSS, JavaScript

    2. The technology is supported in a widely distributed plug-in. Examples: PDF, Flash, QuickTime, Media Player

    3. The content is available in a closed environment, such as a university or corporate network, where the software required by the technology is installed on all the machines.

    4. The user agent(s) that support the technology are available for download or purchase in a way that does not disadvantage people with disabilities.

      Note: Using a technology that isn't widely distributed isn't necessarily an accessibility issue as long as the process for getting the technology does not disadvantage users with disabilities. For example, if you require users to download a plug-in in order to view content the plug-in would meet this option as long as the download can be completed with assistive technology, the plug-in is as easy to locate as any non-accessibility-enabled version, and the plug-in interoperates with assistive technology.

Editorial Note: A subgroup is working on a reogranization of this section.

Established lists of accessibility-enabled Web technologies

To make it easier for authors who may not be familiar with assistive technologies, established lists of accessibility-enabled Web technologies will be available from WAI and other sources. (See Established lists of accessibility-enabled Web technologies in Understanding Conformance). The use of established lists of accessibility-enabled Web technologies from credible sources can be used instead of individual authors creating and validating their own set.

Correct use of non accessibility-enabled Web technologies

Authors may use technologies that are not accessibility-enabled Web technologies provided that the authors do not rely upon those technologies for conveying any information or functionality. That is, the information and functionality provided through the non-qualifying technology is also provided using accessibility-enabled Web technologies. In addition, the presence of the non-AeWT must not block the ability of the users to access the content via the accessible technologies. Specifically, the following must be true:

  1. All content and functionality are available using only accessibility-enabled Web technologies.

  2. Other (non-accessibility-enabled) Web technologies do not interfere with (break or block access to) the conforming content

    1. when used with user agents that only support the accessibility-enabled Web technologies

    2. when used with user agents that support both the accessibility-enabled Web technologies and the non-AeWT

Conformance requirements

All conformance is based on Web page(s). Conformance claims provide a description of the URIs where the conforming pages can be found.

In order to conform to WCAG 2.0 all of the following conformance criteria must be true for each Web page:

  1. Conformance Levels: All of the Success criteria for the level claimed must be met. Understanding Conformance Criterion 2

    • Content that conforms at Single-A (A) meets all Level 1 success criteria.

    • Content that conforms at Double-A (AA) meets all Level 1 and all Level 2 success criteria.

    • Content that conforms at Triple-A (AAA) meets all Level 1, all Level 2 and all Level 3 success criteria.

  2. Minimum Conformance: At a minimum, all of the Level 1 success criteria have been met. Understanding Conformance Criterion 2

  3. Only AeWT: Only documented accessibility-enabled Web technologies are relied upon to meet WCAG 2.0 success criteria. Understanding Conformance Criterion 1

  4. Alternate Versions: If a Web page within the scope of a claim does not meet all of the required WCAG 2.0 success criteria at the level claimed, then the page provides a mechanism to obtain an alternate version that does, and that mechanism meets all success criteria at the level claimed. Understanding Conformance Criterion 5

    Note: The alternative version does not need to be matched page for page with the original (e.g. the alternative to a page may consist of multiple pages).

  5. Content negotiation: If multiple representations can be retrieved from a URI through content negotiation, then the conformance claim would be for the Web page that is returned when no negotiation is conducted. This version does not need to conform itself, but an alternate version must be available from that Web page in a manner that fully conforms to WCAG 2.0 at the level claimed. [LC-534] Understanding Conformance Criterion 6

    Note: If multiple language versions can be negotiated, then conformant versions are required for each language offered. [LC-939]

    Editorial Note: This conformance criterion is still being explored in its entirety.

  6. Full pages: Conformance is claimed for full Web page(s) only. Understanding Conformance Criterion 7

    Note: Conformance can not be achieved if part of a Web page is excluded. For example, conformance can not apply to a set of pages, but exclude a part of the page or a particular type of content (for example, images or scripts) since doing so would allow exclusion of individual success criteria.

  7. Complete processes: If a Web page that is part of a process does not conform at some level, then no conformance claim is made at that level for any Web pages in that process. Understanding Conformance Criterion 8

    Example: An online store has a series of pages that are used to select and purchase products. All pages in the series from start to finish (checkout) must conform in order to claim conformance for any page that is part of the sequence.

    Editorial Note: This clause pending definition of process.

  8. Non-Interference: Use of any technologies that are not accessibility-enabled Web technologies does not interfere with use of the accessibility-enabled Web technologies used to conform to these guidelines. Specifically, content meets the following criteria even if the content uses a non-accessibility-enabled Web technologies: Understanding Conformance Criterion ? (previously HTM 4.2.2)

    1. No Keyboard Trap: If focus can be moved to non-AeWT content using a keyboard interface, then focus can be moved away from that content using only a keyboard interface, and the method for doing so is described before the content is encountered and in a way that meets all Level 1 success criteria.

    2. Flash Threshold: To minimize the risk of seizures due to photosensitivity, any non-AeWT content does not violate the To minimize the risk of seizures due to photosensitivity, content does not violate the general flash threshold or the red flash threshold (see Success Criterion 2.3.1). [LC-716]

Conformance exceptions

The following exceptions are provided:

  1. Non-commercial user-submitted exception

    Non-commercial user-submitted content is not required to conform as long as the submitted content is limited to text-only, or the tools and instructions for submitting content that conforms are provided to users who are submitting the content. Understanding the non-commercial user-submitted content exception

    Editorial Note: Consider requiring ATAG conformance for the tools section above.

  2. Demonstration/example exception

    If the page contains non-conforming material as a demonstration or example of non-conforming content, the content can be part of a conforming range of URIs if it is identified as such in a conformant manner. The page should also be accompanied by a conforming version if possible (e.g. it is not a test or an example of a page where it is not known how to make the content conform). Understanding the demonstration/example exception

Conformance notes Understanding Conformance Notes

  1. Dynamic content: Web pages include a wide range of content including dynamic content and even immersive interactive environments that are found at a single URI.

  2. Non-conforming Content: It is recommended that even non-conforming content conform to the extent possible.

  3. Aggregated content: Sometimes, a Web page is assembled ("aggregated") from subcomponents from multiple sources. We encourage providers of such subcomponent pieces to follow the success criteria that apply to their content and report these to aggregators in order to help aggregators choose content that will enable them to conform to the guidelines. However, conformance is the responsibility of the aggregator and the conformance level is based upon the entire Web page after it is assembled. Since aggregated content may be compiled in realtime it may not be possible to check it each time it changes. Policies and periodic checks can be used instead.

  4. Automatic conformance to success criteria: If a success criterion relates to a feature, component or type of content that is not used in the content then that success criterion is satisfied automatically.

    Example: Success Criterion 1.2.1 is satisfied automatically for content which does not contain multimedia because all multimedia (which is none) does have captions. If multimedia is later added, then it would have to be captioned.

  5. Supplemental Information: A conforming alternative to part of a page's content is considered part of the page for the purpose of determining the page's conformance.

Conformance claims Understanding Conformance Claims

Conformance claims apply to Web pages, and sets of Web pages.

Note: Web pages often take the form of a traditional HTML page, but can also take the form of a fully interactive and immersive environment.

Required components of a conformance claim

Conformance claims are not required. However, if a conformance claim is made, then the conformance claim must include the following assertions:

  1. The date of the claim

  2. The guidelines title/version: "Web Content Accessibility Guidelines 2.0"

  3. The URI of the guidelines: http://www.w3.org/TR/2006/REC-WCAG20-YYYYMMDD/

    Note: The correct date will replace "YYYYMMDD" when WCAG 2.0 is published as a W3C Recommendation.

  4. The conformance level satisfied: (Level A, AA or AAA)

  5. A list of the specific technologies relied upon by the content, or the established list of accessibility-enabled Web technologies that includes all of the technologies relied upon.

    Note: This includes markup languages, style sheet languages, scripting/programming languages, image formats, and multimedia formats.

    1. "Relied upon" means that the content would not meet WCAG 2.0 at the claimed level if that technology is turned off or not supported.

    2. All of the technologies that are "relied upon" must be accessibility-enabled Web technologies.

  6. A description of the URIs that the claim is being made for.

  7. The pages (if any) where the non-commercial user-contributed content exception is applied.

Optional components of a conformance claim

  1. A list of additional success criteria that have been satisfied beyond a standard claim, optimally provided in a form that consumers can use.

  2. A list of the specific technologies that are "used but not relied upon."

    • If a technology is "used but not relied upon," the content would still meet WCAG 2.0 at the stated conformance level even if that technology is turned off or not supported.

  3. A list of user agents, including assistive technologies, that the content has been tested on. [LC-881]

  4. Information about audience assumptions or target audience. This could include language, geographic information, or other pertinent information about the intended audience.

  5. Information about any additional steps taken that go beyond the success criteria to enhance accessibility.

Examples of conformance claims:

Examples of conformance claims are provided in Examples of Conformance Claims.

Content that conforms to WCAG 1.0

The Web Content Accessibility Guidelines Working Group is working to ensure that organizations and individuals who are currently using WCAG 1.0 (which remains stable and normative at this time) will be able to smoothly transition to WCAG 2.0. For more information about transitioning from WCAG 1.0 to 2.0, please refer to "Transitioning from WCAG 1.0 to 2.0". [LC-1277]

Editorial Note: The transition document is being developed by the EOWG WCAG 2.0 Materials Support Task Force. It is not yet available.

Appendix A: Glossary

This section is normative.


shortened form of a word, phrase, or name

Note: Includes initialisms and acronyms.


abbreviated form made from the initial letters or parts of a name or phrase that contains several words and which may be pronounced as a word [LC-1175]

Example: NOAA is an acronym made from the initial letters of the National Oceanic and Atmospheric Administration in the United States.

activity where timing is essential

activity where timing is part of the design of the activity and removal of the time dependency would change the functionality of the content

alternate version

version that provides all of the same information and functionality in the same natural language and is as up to date as any the non-conformant content [LC-940] [LC-1490]

analog, time-dependent input

input whose result is different depending on the rate of the analog movement (such as when line width varies with pen speed or pressure)

Note: Most actions carried out by a pointing device can also be done from the keyboard (for example, clicking, selecting, moving, sizing). However, there is a small class of input that is done with a pointing device that cannot be done from the keyboard in any known fashion. This type of input can be best characterized by the fact that the outcome can only be achieved by moving the pointer in a smooth fashion at a certain rate. For example, in a watercolor program stroke width and transparency may depend on the rate of movement (and/or pressure) of a "brush." Another example would be a real-time helicopter flight simulator. [LC-1164]

Application Programming Interface (API)

definitions of how communication may take place between applications

Note 1: Implementing APIs that are independent of a particular operating environment (as are the W3C DOM Level 2 specifications) may reduce implementation costs for multi-platform user agents and promote the development of multi-platform assistive technologies. Implementing conventional APIs for a particular operating environment may reduce implementation costs for assistive technology developers who wish to interoperate with more than one piece of software running on that operating environment.

Note 2: A "device API" defines how communication may take place with an input or output device such as a keyboard, mouse, or video card.

Note 3: In this document, an "input/output API" defines how applications or devices communicate with a user agent. As used in this document, input and output APIs include, but are not limited to, device APIs. Input and output APIs also include more abstract communication interfaces than those specified by device APIs. A "conventional input/output API" is one that is expected to be implemented by software running on a particular operating environment. For example, the conventional input APIs of the user agent are for the mouse and keyboard. For touch screen devices or mobile devices, conventional input APIs may include stylus, buttons, and voice. The graphical display and sound card are considered conventional output devices for a graphical desktop computer environment, and each has an associated API.

Note 4: This definition is based on User Agent Accessibility Guidelines 1.0 Glossary.


picture created by a spatial arrangement of characters (typically from the 95 printable characters defined by ASCII).

Assistive technology (as used in this document [LC-732] )

a user agent that both:

  1. provides services beyond those offered by the host user agents to meet the requirements of users with disabilities. Such services include alternative renderings (e.g., as synthesized speech or magnified content), alternative input methods (e.g., voice), additional navigation or orientation mechanisms, and content transformations (e.g., to make tables more accessible), and [LC-1178]

  2. relies on services (such as retrieving Web content and parsing markup) provided by one or more other "host" user agents. Assistive technologies communicate data and messages with host user agents by using and monitoring APIs

Note 1: In this definition, the host user agents are user agents in the general sense of the term. That is, any software that retrieves and renders Web content for users. The host user agent may provide important services to assistive technologies like retrieving Web content from program objects or parsing markup into identifiable bundles. [LC-732]

Note 2: Host user agents may also provide services directly that meet the requirements of users with disabilities. [LC-732]

Note 3: This definition is based on User Agent Accessibility Guidelines 1.0 Glossary.

Example: Examples of assistive technologies that are important in the context of this document include the following:

  • screen magnifiers, and other visual reading assistants, which are used by people with visual, perceptual and physical print disabilities to change text font, size, spacing, color, synchronization with speech, etc in order [LC-604] improve the visual readability of rendered text and images;

  • screen readers, which are used by people who are blind or have reading disabilities to read textual information through synthesized speech or braille displays;

  • voice recognition software, which may be used by people who have some physical disabilities;

  • alternative keyboards, which are used by people with certain physical disabilities to simulate the keyboard;

  • alternative pointing devices, which are used by people with certain physical disabilities to simulate mouse pointing and button activations.

audio description

narration added to the soundtrack to describe important visual details that cannot be understood from the main soundtrack alone

Note 1: Audio description of video provides information about actions, characters, scene changes, on-screen text, and other visual content. [LC-845]

Note 2: In standard audio description, narration is added during existing pauses in dialogue. (See also extended audio description.)

authored component

an authored unit intended to be used as a part of another authored unit

authored unit

set of material created as a single body by an author

Example 1: a collection consisting of markup, a style sheet, and an image or audio clip.

Example 2: a set of Web pages intended to be viewed only as a unit or in sequence.

Note: This definition is based on Glossary of Terms for Device Independence.


turn on and off between 0.5 and 3 times per second


text presented and synchronized with multimedia to provide not only the speech, but also non-speech information conveyed through sound, including meaningful sound effects and identification of speakers [LC-846]

Note: In some countries, the term "subtitle" is used to refer to dialogue only and "captions" is used as the term for dialogue plus sounds and speaker identification. In other countries, subtitle (or its translation) is used to refer to both.

changes of context

change of :

  1. user agent;

  2. viewport;

  3. focus;

  4. content that changes the meaning of the Web page.

Note: A change of content is not always a change of context. Small changes in content, such as an expanding outline or dynamic menu, do not change the context.


satisfying all the requirements of a given standard, guideline or specification [LC-999]

content (Web content)

information and sensory experience to be communicated to the user by means of a user agent, as well as code or markup that define the structure, presentation, and interactions associated with those elements [LC-1180]

Note: This includes the code and markup that define the structure, presentation, and interaction, as well as text, images, and sounds that convey information to the end-user.

context-sensitive help

help text that provides information related to the function currently being performed


a sudden, unexpected situation or occurrence that requires immediate action to preserve health, safety, or property

event handler

section of code that responds to an action taken by the user (or user agent)

Note: On Web pages, events are usually user actions such as moving the mouse, typing, etc.

  • An event handler determines the response to that action.

  • A device-specific event handler only responds to an action by one kind of input device.

  • An abstract event handler is one which can be activated by a variety of input devices.

extended audio description

audio description that is added to an audiovisual presentation by pausing the video so that there is time to add additional description

Note: This technique is only used when the sense of the video would be lost without the additional audio description.

full text alternative for multimedia including any interaction [LC-810]

document including correctly sequenced descriptions of all visual settings, actions, and non-speech sounds combined with descriptive transcripts of all dialogue and a means of achieving any outcomes that are achieved using interaction during the multimedia

Note: A screenplay used to create the multimedia content would meet this definition only if it was corrected to accurately represent the final multimedia after editing.


processes and outcomes achievable through user action

general flash threshold
  • A sequence of flashes or rapidly changing image sequences where all three of the following occur:

    1. the combined area of flashes occurring concurrently (but not necessarily contiguously) occupies more than one quarter of any 341 x 256 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 x 768 pixels;

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

    3. the flashing is below 50 Hz.

Note 1: For the general flash threshold, a flash is defined as a pair of opposing changes in brightness of 10% or more of full scale white brightness, where brightness is calculated as 0.2126 * ((R / FS) ^ 2.2) + 0.7152 * ((G / FS) ^ 2.2) + 0.0722 * ((B / FS) ^ 2.2). R, G, and B are the red, green, and blue RGB values of the color; FS is the maximum possible full scale RGB value for R, G, and B (255 for eight bit color channels); and the "^" character is the exponentiation operator. An "opposing change" is an increase followed by a decrease, or a decrease followed by an increase. This applies only when the brightness of the darker image is below .80 of full scale white brightness.

Note 2: Based on Wisconsin Computer Equivalence Algorithm for Flash Pattern Analysis (FPA)


phrase whose meaning cannot be deduced from the meaning of the individual words and the specific words cannot be changed without losing the meaning

Example 1: In English, "kicking the bucket" means "dying," but the phrase cannot be changed to "kicking the buckets" or "kicking the tub" or "booting the bucket" or "knocking over the bucket" without losing its meaning.

Example 2: In English, "spilling the beans" means "revealing a secret." However, "knocking over the beans" or "spilling the vegetables" does not mean the same thing.

Example 3: In Japanese, the phrase "さじを投げる (どうするこ ともできなくなり、あきらめること" literally translates into "he throws a spoon," but it means that there is nothing he can do and finally he gives up. [LC-1240] [LC-1382]

Example 4: In Dutch, "Hij ging met de kippen op stok" literally translates into "He went to roost with the chickens," but it means that he went to bed early.

  1. a message to be sent and received

  2. a collection of facts or data from which inferences may be drawn [LC-905]

information that is conveyed by color differences

information presented in a manner that depends entirely on the ability to perceive color


for information purposes and not required for conformance

Note: Content required for conformance is referred to as "normative."


shortened form of a name or phrase made from the initial letters of words or syllables contained in that name or phrase

Note: Not defined in all languages.

Example 1: SNCF is a French initialism that contains the initial letters of the Sociétè Nationale des Chemins de Fer, the French national railroad.

Example 2: ESP is an initialism for extrasensory perception.

input error

information provided by the user that is not accepted

Note: This includes:

  1. Information that is required by the Web page but omitted by the user

  2. Information that is provided by the user but that falls outside the required data format or values


words used in a particular way by people in a particular field

Example: The word StickyKeys is jargon from the field of assistive technology/accessibility.

keyboard interface

interface used by software to obtain keystroke input

Note 1: Allows users to provide keystroke input to programs even if the native technology does not contain a keyboard.

Example: A touch screen PDA has a keyboard interface built into its operating system as well as a connector for external keyboards. Applications on the PDA can use the interface to obtain keyboard input either from an external keyboard or from other applications that provide simulated keyboard output, such as handwriting interpreters or speech-to-text applications with "keyboard emulation" functionality.

Note 2: Operation of the application (or parts of the application) through a keyboard-operated mouse emulator, such as MouseKeys, does not qualify as operation through a keyboard interface because operation of the program is through its pointing device interface, not through its keyboard interface.


text , image, or sound or other component with a text alternative that is presented to a user to identify a component within Web content

Note: See also name. [LC-847]

legal committments [LC-1471]

transactions where the person incurs a legally binding obligation or benefit

Example: A marriage license, a stock trade (financial and legal), a will, a loan, adoption, signing up for the army, a contract of any type, etcetera.

live audio-only

A time-based live presentation that contains only audio (no video and no interaction).

live video-only

A time-based live presentation that contains only video (no audio and no interaction).

lower secondary education level

the two or three year period of education that begins after completion of six years of school and ends nine years after the beginning of primary education.

Note: This definition is based on [UNESCO].

luminosity contrast ratio

(L1 + 0.05) / (L2 + 0.05), where L1 is the luminosity of the lighter of the text or background colors, and L2 is the luminosity of the darker of the text or background colors.

Note 1: The luminosity of a color is defined as 0.2126 * ((R / FS) ^ 2.2) + 0.7152 * ((G / FS) ^ 2.2) + 0.0722 * ((B / FS) ^ 2.2).

  • R, G, and B are the red, green, and blue RGB values of the color.

  • FS is the maximum possible full scale RGB value for R, G, and B (255 for eight bit color channels).

  • The "^" character is the exponentiation operator.

Note 2: Luminosity values can range from 0 (black) to 1 (white), and luminosity contrast ratios can range from 1 to 21.

Note 3: A MathML version of the luminosity contrast ratio definition is available. [LC-603] [LC-854]


process or technique for achieving a result


audio or video synchronized with another type of media format for presenting information and/or with time-based interactive components [LC-1499]

must be presented in non-text format

would be invalid if presented in text [LC-1506]

Example: Color blindness test, hearing test, vision exercise, spelling test.


text by which software can identify a component within Web content to the user

Note: The name may be hidden and only exposed by assistive technology, whereas a label is presented even without assistive technology. In many (but not all) cases, the label is a display of the name.

natural language

languages whose rules have evolved through usage within human communities and which are used by humans to communicate with one another, including spoken, written, and signed languages languages used by humans to communicate, including spoken, written, and signed languages [LC-1184] [LC-1500]

non-commercial user-contributed content

content from a person/entity who is not compensated for the content that is included automatically in Web content and where the content is not edited except for censorship

non-text content

content that is not represented by a Unicode character or sequence of Unicode characters when rendered in a user agent according to the formal specification of the content type

Note: This includes ASCII Art, which is a pattern of characters and leetspeak, which is character substitution. [LC-796] .


required for conformance

Note 1: One may conform in a variety of well-defined ways to this document.

Note 2: Content identified as "informative" or "non-normative" is never required for conformance.

parsed unambiguously

parsed into only one data structure

Note: Parsing transforms markup or other code into a data structure, usually a tree, which is suitable for later processing and which captures the implied hierarchy of the input.


stopped by user request and not restarted until requested by user


rendering of the content and structure in a form that can be perceived by the user rendering of the content and relationships in a form that can be perceived by the user [LC-490]

primary education level

six year time period that begins between the ages of five and seven, possibly without any previous education

Note: This definition is based on [UNESCO].

programmatically determined

determined by software from data provided in a user-agent-supported manner such that the various user agents including assistive technologies can extract and present this information to users in different modalities [LC-1502]

programmatically determined link context
  1. Additional information that can be programmatically determined from relationships with a link; and

  2. can be extracted, combined with the link text, and presented to users in different modalities. [LC-497]

Example 1: Screen readers provide commands to read the current sentence when focus is on a link.

Example 2: Examples of information that can be extracted, combined with link text, and presented to users in different modalities include text that is in the same sentence, paragraph, list, or table cell as the link or in a table header cell that is associated with the table cell that contains the link.

programmatically set

set by software using methods that are user-agent-supported

pure decoration

serving only an aesthetic purpose, providing no information, and having no functionality.

real-time event

event that a) occurs at the same time as the viewing, b) is not completely generated by the content, and c) is not pre-recorded

Example 1: A Webcast of a live performance (occurs at the same time as the viewing and is not pre-recorded).

Example 2: An on-line auction with people bidding (occurs at the same time as the viewing).

Example 3: Live humans interacting in a fantasy world using avatars (is not completely generated by the content and occurs at the same time as the viewing) [LC-1503] .

red flash threshold
  • transition to or from a saturated red where all three of the following occur:

    1. The combined area of flashes occurring concurrently occupies more than one quarter of any 341 x 256 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 x 768 pixels.

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

    3. The flashing is below 50 Hz.

regular expression

regular expression as defined in XML Schema Part 2: Datatypes, Appendix F. a sequence of characters that describes or matches a pattern of characters [LC-1152]


meaningful associations between distinct pieces of content [LC-1427]


text or a number by which software can identify the function of a component within Web content

Example: A number that indicates whether an image functions as a hyperlink, command button, or check box.

same functionality

identical result when used

Example: A submit "search" button on one Web page and a "find" button on another Web page 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 the same functionality but would not be labeled consistently.

same relative order

same position relative to other items

Note: Items are considered to be in the same relative order even if other items are inserted or removed from the original order. For example, expanding navigation menus may insert an additional level of detail or a secondary navigation section may be inserted into the reading order.

sign language interpretation

translation of spoken words and other audible information into a language that uses a simultaneous combination of handshapes, facial expressions, and orientation and movement of the hands, arms, or body to convey meaning

Note: Although some languages have a signed counterpart, most sign languages are independent languages that are unrelated to the spoken language of the same country or culture.

specific sensory experience

a sensory experience that is not purely decorative and does not primarily convey important information or perform a function

Example: Examples include a performance of a flute solo, works of visual art etc. [LC-1189]

  1. The way the parts of an authored unit are organized in relation to each other; and

  2. The way a collection of Web pages is organized

supplemental content

additional content that users may use in addition to or instead of the default content, thatillustrates or clarifies the primary content [LC-1505]

Example 1: Examples of supplemental content may include text, images and audio. An audio version of a Web page.

Example 2: An illustration of a complex process.

Example 3: A paragraph describing the major outcomes and recommendations made in a research study.


markup language, programming language, style sheet, data format, or API


sequence of characters

Note 1: This definition does not place requirements on the specific encoding of characters. For advice about appropriate character encodings, refer to [I18N-CHAR-ENC]. [LC-849]

Note 2: Characters are those included in the Unicode/ISO/IEC 106464 repertoire.

text alternative

programmatically determined text that is used in place of non-text content, or text that is used in addition to non-text content and referred to from the programmatically determined text


universal character set that defines all the characters needed for writing the majority of living languages in use on computers

Note: For more information, refer to [UNICODE] or [I18N-CHAR-ENC]. [LC-849]

used in an unusual restricted way

words used in such a way that users must know exactly what definition to apply in order to understand the content correctly

Example: The word "representational" means something quite different if it occurs in a discussion of visual art as opposed to a treatise on government, but the appropriate definition can be determined from context. By contrast, the word "text" is used in a very specific way in WCAG 2.0, so a definition is supplied in the glossary.

user agent

any software that retrieves and renders Web content for users

Example: Web browsers, media players, plug-ins, and other programs — including assistive technologies — that help in retrieving and rendering Web content.


implemented by user agents including assistive technologies [LC-1509]

Note: One of the factors that should be considered before adding a technology to a baseline is the availability of affordable user agents and assistive technologies which support the technology.

variations in presentation of text

changes in the visual appearance or sound of the text; or, if auditory presentation is specified in the content, changes in the sound of text such as voice. , such as changing to a different font or a different voice [LC-852]


the technology of moving pictures or images

Note: Video can be made up of animated or photographic images, or both.


object in which the user agent renders content [LC-1127]

Note 1: The user agent renders content through one or more viewports. Viewports include windows, frames, loudspeakers, and virtual magnifying glasses. A viewport may contain another viewport (e.g., nested frames). User agent user interface controls such as prompts, menus, and alerts are not viewports.

Note 2: This definition is based on User Agent Accessibility Guidelines 1.0 Glossary.

Web page

a primary resource referenced by a URI and any other resources that are rendered simultaneously with it with the understanding that different sub elements or resources may be rendered simultaneously with the primary resource at different points in time.

Note: This definition is based on the definition of Web page in the Web Characterization Terminology & Definitions Sheet.

Example 1: An interactive movie-like shopping environment where the user navigates about and activates products to have them demonstrated, and moves them to a cart to buy them.

Example 2: A Web resource including all embedded images and media.

Wisconsin Computer Equivalence Algorithm for Flash Pattern Analysis (FPA)

a method developed at the University of Wisconsin, working in conjunction with Dr. Graham Harding and Cambridge Research Associates, for applying the United Kingdom's "Ofcom Guidance Note on Flashing Images and Regular Patterns in Television (Re-issued as Ofcom Notes 25 July 2005)" to content displayed on a computer screen, such as Web pages and other computer content

Note: The Ofcom Guidance Document [OFCOM] is based on the assumption that the television screen occupies the central ten degrees of vision. This is not accurate for a screen which is located in front of a person. The Wisconsin algorithm basically carries out the same analysis as the Ofcom Guidelines except that is does it on every possible ten degree window for a prototypical computer display.