Web Content Accessibility Guidelines (WCAG) 2.0 covers a wide range of recommendations for making Web content more accessible. Following these guidelines will make content accessible to a wider range of people with disabilities, including blindness and low vision, deafness and hearing loss, learning disabilities, cognitive limitations, limited movement, speech disabilities, photosensitivity and combinations of these. Following these guidelines will also often make your Web content more usable to users in general.
WCAG 2.0 success criteria are written as testable statements that are not technology-specific. Guidance about satisfying the success criteria in specific technologies, as well as general information about interpreting the success criteria, is provided in separate documents. See
WCAG 2.0 succeeds
This is the Web Content Accessibility Guidelines (WCAG) 2.0
This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.
WCAG 2.0 is supported by the associated non-normative
documents,
The Working Group requests that any comments be made using the provided
This document has been produced as part of the W3C
This document was produced by a group operating under the
This section is
Web Content Accessibility Guidelines (WCAG) 2.0 defines how to make Web content more accessible to people with disabilities. Accessibility involves a wide range of disabilities, including visual, auditory, physical, speech, cognitive, language, learning, and neurological disabilities. Although these guidelines cover a wide range of issues, they are not able to address the needs of people with all types, degrees, and combinations of disability. These guidelines also make Web content more usable by older individuals with changing abilities due to aging and often improve usability for users in general.
WCAG 2.0 is developed through the
Web accessibility depends not only on accessible content but also on accessible Web browsers and other user agents. Authoring tools also have an important role in Web accessibility. For an overview of how these components of Web development and interaction work together, see:
The individuals and organizations that use WCAG vary widely and include Web designers and developers, policy makers, purchasing agents, teachers, and students. In order to meet the varying needs of this audience, several layers of guidance are provided including overall
All of these layers of guidance (principles, guidelines, success criteria, and sufficient and advisory techniques) work together to provide guidance on how to make content more accessible. Authors are encouraged to view and apply all layers that they are able to, including the advisory techniques, in order to best address the needs of the widest possible range of users.
Note that even content that conforms at the highest level (AAA) will not be accessible to individuals with all types, degrees, or combinations of disability, particularly in the
The WCAG 2.0 document is designed to meet the needs of those who need a stable, referenceable technical standard. Other documents, called supporting documents, are based on the WCAG 2.0 document and address other important purposes, including the ability to be updated to describe how WCAG would be applied with new technologies. Supporting documents include:
See
WCAG 2.0 includes three important terms that are different from WCAG 1.0. Each of these is introduced briefly below and defined more fully in the glossary.
It is important to note that, in this standard, the term "
Several success criteria require that content (or certain aspects of content) can be "
Using a technology in a way that is accessibility supported means that it works with assistive technologies (AT) and the accessibility features of operating systems, browsers, and other user agents. Technology features can only be
The definition of "accessibility supported" is provided in the
This section is
All
For
An
Where pauses in foreground audio are insufficient to allow
An
An
Information,
When the sequence in which content is presented affects its meaning, a
Instructions provided for understanding and operating content do not rely solely on sensory characteristics of components such as shape, size, visual location, orientation, or sound.
For requirements related to color, refer to
Color is not used as the only visual means of conveying information, indicating an action, prompting a response, or distinguishing a visual element.
This success criterion addresses color perception specifically. Other forms of perception are covered in
If any audio on a Web page plays automatically for more than 3 seconds, either a
Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether or not it is used to meet other success criteria) must meet this success criterion. See
Except for
If the technologies being used can achieve the visual presentation,
Logotypes (text that is part of a logo or brand name) are considered essential.
For
Per the definition of "decibel," background sound that meets this requirement will be approximately four times quieter than the foreground speech content.
For the visual presentation of
Foreground and background colors can be selected by the user.
Width is no more than 80 characters or glyphs (40 if CJK).
Text is not justified (aligned to both the left and the right margins).
Line spacing (leading) is at least space-and-a-half within paragraphs, and paragraph spacing is at least 1.5 times larger than the line spacing.
Text can be resized without assistive technology up to 200 percent in a way that does not require the user to scroll horizontally to read a line of text
Logotypes (text that is part of a logo or brand name) are considered essential.
All
This exception relates to the underlying function, not the input technique. For example, if using handwriting to enter text, the input technique (handwriting) requires path-dependent input but the underlying function (text input) does not.
This does not forbid and should not discourage providing mouse input or other input methods in addition to keyboard operation.
If keyboard focus can be moved to a component of the page using a
Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See
All
For each time limit that is set by the content, at least one of the following is true:
This success criterion helps ensure that users can complete tasks without unexpected changes in content or context that are a result of a time limit. This success criterion should be considered in conjunction with
For moving,
For requirements related to flickering or flashing content, refer to
Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See
Content that is updated periodically by software or that is streamed to the user agent is not required to preserve or present information that is generated or received between the initiation of the pause and resuming presentation, as this may not be technically possible, and in many situations could be misleading to do so.
An animation that occurs as part of a preload phase or similar situation can be considered essential if interaction cannot occur during that phase for all users and if not indicating progress could confuse users or cause them to think that content was frozen or broken.
Timing is not an
Interruptions can be postponed or suppressed by the user, except interruptions involving an
When an authenticated session expires, the user can continue the activity without loss of data after re-authenticating.
Since any content that does not meet this success criterion can interfere with a user's ability to use the whole page, all content on the Web page (whether it is used to meet other success criteria or not) must meet this success criterion. See
A
If a
The
More than one way is available to locate a
Headings and
Any keyboard operable user interface has a mode of operation where the keyboard focus indicator is visible.
Information about the user's location within a
A
"Heading" is used in its general sense and includes titles and other ways to add a heading to different types of content.
This success criterion covers sections within writing, not
The default
The
A
A
When text requires reading ability more advanced than the
A
When any component receives focus, it does not
initiate a
Changing the setting of any
Navigational mechanisms that are repeated on multiple
Components that have the
If an
If an
For
For
In content implemented using markup languages, elements have complete start and end tags, elements are nested according to their specifications, elements do not contain duplicate attributes, and any IDs are unique, except where the specifications allow these features.
Start and end tags that are missing a critical character in their formation, such as a closing angle bracket or a mismatched attribute value quotation mark are not complete.
For all
This success criterion is primarily for Web authors who develop or script their own user interface components. For example, standard HTML controls already meet this success criterion when used according to specification.
This section is
This section lists requirements for
In order for a Web page to conform to WCAG 2.0, all of the following conformance requirements must be satisfied:
One of the following levels of conformance is met in full.
Although conformance can only be achieved at the stated levels, authors are encouraged to report (in their claim) any progress toward meeting success criteria from all levels beyond the achieved level of conformance.
It is not recommended that Level AAA conformance be required as a general policy for entire sites because it is not possible to satisfy all Level AAA Success Criteria for some content.
For the purpose of determining conformance, alternatives to part of a page's content are considered part of the page when the alternatives can be obtained directly from the page, e.g., a long description or an alternative presentation of a video.
Authors of Web pages that cannot conform due to content outside of the author's control may consider a
When a
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) conform in order for any page that is part of the process to conform.
Only
If
when any technology that is not
when any technology that is not relied upon is turned off in a user agent, and
when any technology that is not relied upon is not supported by a user agent
In addition, the following success criteria apply to all content on the page, including content that is not otherwise relied upon to meet conformance, because failure to meet them could interfere with any use of the page:
If a page cannot conform (for example, a conformance test page or an example page), it cannot be included in the scope of conformance or in a conformance claim.
For more information, including examples, see
Conformance is defined only for
Conformance claims are
The Web pages may be described by list or by an expression that describes all of the URIs included in the claim.
Web-based products that do not have a URI prior to installation on the customer's Web site may have a statement that the product would conform when installed.
A list of the
If a conformance logo is used, it would constitute a claim and must be accompanied by the required components of a conformance claim listed above.
In addition to the required components of a conformance claim above, consider providing additional information to assist users. Recommended additional information includes:
A list of success criteria beyond the level of conformance claimed that have been met. This information should be provided in a form that users can use, preferably machine-readable metadata.
A list of the specific technologies that are "
A list of user agents, including assistive technologies that were used to test the content.
Information about any additional steps taken that go beyond the success criteria to enhance accessibility.
A machine-readable metadata version of the list of specific technologies that are
A machine-readable metadata version of the conformance claim.
Refer to
Refer to
Sometimes, Web pages are created that will later have additional content added to them. For example, an email program, a blog, an article that allows users to add comments, or applications supporting user-contributed content. Another example would be a page, such as a portal or news site, composed of content aggregated from multiple contributors, or sites that automatically insert content from other sources over time, such as when advertisements are inserted dynamically.
In these cases, it is not possible to know at the time of original posting what the uncontrolled content of the pages will be. It is important to note that the uncontrolled content can affect the accessibility of the controlled content as well. Two options are available:
A determination of conformance can be made based on best knowledge. If a page of this type is monitored and repaired (non-conforming content is removed or brought into conformance) within two business days, then a determination or claim of conformance can be made since, except for errors in externally contributed content which are corrected or removed when encountered, the page conforms. No conformance claim can be made if it is not possible to monitor or correct non-conforming content;
A "statement of partial conformance" may be made that the page does not conform, but could conform if certain parts were removed. The form of that statement would be, "This page does not conform, but would conform to WCAG 2.0 at level X if the following parts from uncontrolled sources were removed." In addition, the following would also be true of uncontrolled content that is described in the statement of partial conformance:
It is not content that is under the author's control.
It is described in a way that users can identify (e.g., they cannot be described as "all parts that we do not control" unless they are clearly marked as such.)
A "statement of partial conformance due to language" may be made when the page does not conform, but would conform if
This section is
shortened form of a word, phrase, or name where the abbreviation has not become part of the language
This includes initialisms and acronyms where:
Not defined in all languages.
SNCF is a French initialism that contains the initial letters of the
ESP is an initialism for extrasensory perception.
NOAA is an acronym made from the initial letters of the National Oceanic and Atmospheric Administration in the United States.
Some companies have adopted what used to be an initialism as their company name. In these cases, the new name of the company is the letters (for example, Ecma) and the word is no longer considered an abbreviation.
supported by users'
To qualify as an accessibility-supported use of a Web content technology (or feature of a technology), both 1 and 2 must be satisfied for a Web content technology (or feature):
The technology is supported natively in widely-distributed user agents that are also accessibility supported (such as HTML and CSS);
The technology is supported in a widely-distributed plug-in that is also accessibility supported;
The content is available in a closed environment, such as a university or corporate network, where the user agent required by the technology and used by the organization is also accessibility supported;
The user agent(s) that support the technology are accessibility supported and are available for download or purchase in a way that:
does not cost a person with a disability any more than a person without a disability
is as easy to find and obtain for a person with a disability as it is for a person without disabilities.
The WCAG Working group and the W3C do not specify which or how much support by assistive technologies there must be for a particular use of a Web technology in order for it to be classified as accessibility supported. (See
Web technologies can be used in ways that are not accessibility supported as long as they are not
When a
When citing Web content technologies that have multiple versions, the version(s) supported should be specified.
One way for authors to locate uses of a technology that are accessibility supported would be to consult compilations of uses that are documented to be accessibility supported. (See
document including correctly sequenced text descriptions of time-based visual and auditory information and providing a means for achieving the outcomes of any time-based interaction
A screenplay used to create the synchronized media content would meet this definition only if it was corrected to accurately represent the final synchronized media after editing.
the purpose cannot be determined from the link and all information of the Web page presented to the user simultaneously with the link (i.e., readers without disabilities would not know what a link would do until they activated it)
The word guava in the following sentence "One of the notable exports is guava" is a link. The link could lead to a definition of guava, a chart listing the quantity of guava exported or a photograph of people harvesting guava. Until the link is activated, all readers are unsure and the person with a disability is not at any disadvantage.
picture created by a spatial arrangement of characters or glyphs (typically from the 95 printable characters defined by ASCII).
hardware and/or software that acts as a
functionality provided by assistive technology includes alternative presentations (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).
Assistive technologies often communicate data and messages with mainstream user agents by using and monitoring APIs.
The distinction between mainstream user agents and assistive technologies is not absolute. Many mainstream user agents provide some features to assist individuals with disabilities. The basic difference is that mainstream user agents target broad and diverse audiences that usually include people with and without disabilities. Assistive technologies target narrowly defined populations of users with specific disabilities. The assistance provided by an assistive technology is more specific and appropriate to the needs of its target users. The mainstream user agent may provide important functionality to assistive technologies like retrieving Web content from program objects or parsing markup into identifiable bundles.
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 to improve the visual readability of rendered text and images;
screen readers, which are used by people who are blind to read textual information through synthesized speech or braille;
text-to-speech software, which is used by some people with cognitive, language, and learning disabilities to convert text into synthetic speech;
speech 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 (including alternate keyboards that use head pointers, single switches, sip/puff and other special input devices.);
alternative pointing devices, which are used by people with certain physical disabilities to simulate mouse pointing and button activations.
the technology of sound reproduction
Audio can be created synthetically (including speech synthesis), recorded from real world sounds, or both.
narration added to the soundtrack to describe important visual details that cannot be understood from the main soundtrack alone
Audio description of
In standard audio description, narration is added during existing pauses in dialogue. (See also
Where all of the
Also called "video description" and "descriptive narration."
a time-based presentation that contains only
switch back and forth between two visual states in a way that is meant to draw attention
See also
more than one sentence of text
initialism for "Completely Automated Public Turing test to tell Computers and Humans Apart"
CAPTCHA tests often involve asking the user to type in text that is displayed in an obscured image or audio file.
A Turing test is any system of tests designed to differentiate a human from a computer. It is named after famed computer scientist Alan Turing. The term was coined by researchers at Carnegie Mellon University.
synchronized visual and/or
Captions are similar to dialogue-only subtitles except captions convey not only the content of spoken dialogue, but also equivalents for non-dialogue audio information needed to understand the program content, including sound effects, music, laughter, speaker identification and location.
Closed Captions are equivalents that can be turned on and off with some players.
Open Captions are any captions that cannot be turned off. For example, if the captions are visual equivalent
Captions should not obscure or obstruct relevant information in the video.
In some countries, captions are called subtitles.
major changes in the content of the
Changes in context include changes of:
focus;
A change of content is not always a change of context. Changes in content, such as an expanding outline, dynamic menu, or a tab control do not necessarily change the context, unless they also change one of the above (e.g., focus).
Opening a new window, moving focus to a different component, going to a new page (including anything that would look to a user as if they had moved to a new page) or significantly re-arranging the content of a page are examples of changes of context.
satisfying all the requirements of a given standard, guideline or specification
version that
conforms at the designated level, and
provides all of the same information and
is as up to date as the non-conforming content, and
for which at least one of the following is true:
the conforming version can be reached from the non-conforming page via an
the non-conforming version can only be reached from the conforming version, or
the non-conforming version can only be reached from a conforming page that also provides a mechanism to reach the conforming version
In this definition, "can only be reached" means that there is some mechanism, such as a conditional redirect, that prevents a user from "reaching" (loading) the non-conforming page unless the user had just come from the conforming version.
The alternate version does not need to be matched page for page with the original (e.g., the conforming alternate version may consist of multiple pages).
If multiple language versions are available, then conforming alternate versions are required for each language offered.
Alternate versions may be provided to accommodate different technology environments or user groups. Each version should be as conformant as possible. One version would need to be fully conformant in order to meet
The conforming alternative version does not need to reside within the scope of conformance, or even on the same Web site, as long as it is as freely available as the non-conforming version.
Alternate versions should not be confused with
Setting user preferences within the content to produce a conforming version is an acceptable mechanism for reaching another version as long as the method used to set the preferences is accessibility supported.
See
information and sensory experience to be communicated to the user by means of a
help text that provides information related to the function currently being performed
Clear labels can act as context-sensitive help.
(L1 + 0.05) / (L2 + 0.05), where
L1 is the
L2 is the
Contrast ratios can range from 1 to 21 (commonly written 1:1 to 21:1).
Because authors do not have control over user settings as to how text is rendered (for example font smoothing or anti-aliasing), the contrast ratio for text can be evaluated with anti-aliasing turned off.
For the purpose of Success Criteria 1.4.3 and 1.4.6, contrast is measured with respect to the specified background over which the text is rendered in normal usage. If no background color is specified, then white is assumed.
Background color is the specified color of content over which the text is to be rendered in normal usage. It is a failure if no background color is specified when the text color is specified, because the user's default background color is unknown and cannot be evaluated for sufficient contrast. For the same reason, it is a failure if no text color is specified when a background color is specified.
When there is a border around the letter, the border can add contrast and would be used in calculating the contrast between the letter and its background. A narrow border around the letter would be used as the letter. A wide border around the letter that fills in the inner details of the letters acts as a halo and would be considered background.
WCAG conformance should be evaluated for color pairs specified in the content that an author would expect to appear adjacent in typical presentation. Authors need not consider unusual presentations, such as color changes made by the user agent, except where caused by authors' code.
any sequence where words and paragraphs are presented in an order that does not change the meaning of the content
a sudden, unexpected situation or occurrence that requires immediate action to preserve health, safety, or property
if removed, would fundamentally change the information or functionality of the content,
audio description that is added to an audiovisual presentation by pausing the
This technique is only used when the sense of the
a pair of opposing changes in
See
See also
a
there are no more than three
the combined area of flashes occurring concurrently occupies no more than a total of .006 steradians within any 10 degree visual field on the screen (25% of any 10 degree visual field on the screen) at typical viewing distance
where:
A
A
For general software or Web content, using a 341 x 256 pixel rectangle anywhere on the displayed screen area when the content is viewed at 1024 x 768 pixels will provide a good estimate of a 10 degree visual field for standard screen sizes and viewing distances (e.g., 15-17 inch screen at 22-26 inches). (Higher resolutions displays showing the same rendering of the content yield smaller and safer images so it is lower resolutions that are used to define the thresholds.)
A transition is the change in relative luminance (or relative luminance/color for red flashing) between adjacent peaks and valleys in a plot of relative luminance (or relative luminance/color for red flashing) measurement against time. A flash consists of two opposing transitions.
The current working definition in the field for
Tools are available that will carry out analysis from video screen capture. However, no tool is necessary to evaluate for this condition if flashing is less than or equal to 3 flashes in any one second. Content automatically passes (see #1 and #2 above).
language that is spoken, written or signed (through visual or tactile means) to communicate with humans
See also
phrase whose meaning cannot be deduced from the meaning of the individual words and the specific words cannot be changed without losing the meaning
idioms cannot be translated directly, word for word, without losing their (cultural or language-dependent) meaning.
In English, "spilling the beans" means "revealing a secret." However, "knocking over the beans" or "spilling the vegetables" does not mean the same thing.
In Japanese, the phrase "
In Dutch, "
text that has been rendered in a non-text form (e.g., an image) in order to achieve a particular visual effect
This does not include
A person's name on a nametag in a photograph.
for information purposes and not required for conformance
Content required for
information provided by the user that is not accepted
This includes:
Information that is required by the
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
The word StickyKeys is jargon from the field of assistive technology/accessibility.
interface used by software to obtain keystroke input
A keyboard interface allows users to provide keystroke input to programs even if the native technology does not contain a keyboard.
A touchscreen 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.
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.
A label is presented to all users whereas the
The term label is not limited to the label element in HTML.
with at least 18 point or 14 point bold or font size that would yield equivalent size for Chinese, Japanese and Korean (CJK) fonts
Fonts with extraordinarily thin strokes or unusual features and characteristics that reduce the familiarity of their letter forms are harder to read, especially at lower contrast levels.
Font size is the size when the content is delivered. It does not include resizing that may be done by a user.
The actual size of the character that a user sees is dependent both on the author-defined size and the user's display or user-agent settings. For many mainstream body text fonts, 14 and 18 point is roughly equivalent to 1.2 and 1.5 em or to 120% or 150% of the default size for body text (assuming that the body font is 100%), but authors would need to check this for the particular fonts in use. When fonts are defined in relative units, the actual point size is calculated by the user agent for display. The point size should be obtained from the user agent, or calculated based on font metrics as the user agent does, when evaluating this success criterion. Users who have low vision would be responsible for choosing appropriate settings.
When using text without specifying the font size, the smallest font size used on major browsers for unspecified text would be a reasonable size to assume for the font. If a level 1 heading is rendered in 14pt bold or higher on major browsers, then it would be reasonable to assume it is large text. Relative scaling can be calculated from the default sizes in a similar fashion.
The 18 and 14 point sizes for roman texts are taken from the minimum size for large print (14pt) and the larger standard font size (18pt). For other fonts such as CJK languages, the "equivalent" sizes would be the minimum large print size used for those languages and the next larger standard large print size.
transactions where the person incurs a legally binding obligation or benefit
A marriage license, a stock trade (financial and legal), a will, a loan, adoption, signing up for the army, a contract of any type, etc.
nature of the result obtained by activating a hyperlink
information captured from a real-world event and transmitted to the receiver with no more than a broadcast delay
A broadcast delay is a short (usually automated) delay, for example used in order to give the broadcaster time to queue or censor the audio (or video) feed, but not sufficient to allow significant editing.
If information is completely computer generated, it is not live.
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
This definition is based on the International Standard Classification of Education
The mechanism may be explicitly provided in the content, or may be
The mechanism needs to meet all success criteria for the conformance level claimed.
media that presents no more information than is already presented in text (directly or via text alternatives)
A media alternative for text is provided for those who benefit from alternate representations of text. Media alternatives for text may be audio-only, video-only (including sign-language video), or audio-video.
text by which software can identify a component within Web content to the user
The name may be hidden and only exposed by assistive technology, whereas a
This is unrelated to the name attribute in HTML.
navigated in the order defined for advancing focus (from one element to the next) using a
any content that is not a sequence of characters that can be
This includes
required for conformance
One may conform in a variety of well-defined ways to this document.
Content identified as "
on the most common sized desktop/laptop display with the viewport maximized
Since people generally keep their computers for several years, it is best not to rely on the latest desktop/laptop display resolutions but to consider the common desktop/laptop display resolutions over the course of several years when making this evaluation.
stopped by user request and not resumed until requested by user
information that is not
rendering of the
six year time period that begins between the ages of five and seven, possibly without any previous education
This definition is based on the International Standard Classification of Education
series of user actions where each action is required in order to complete an activity
Successful use of a series of Web pages on a shopping site requires users to view alternative products, prices and offers, select products, submit an order, provide shipping information and provide payment information.
An account registration page requires successful completion of a Turing test before the registration form can be accessed.
determined by software from author-supplied data provided in a
way that different
Determined in a markup language from elements and attributes that are accessed directly by commonly available assistive technology.
Determined from technology-specific data structures in a non-markup language and exposed to assistive technology via an accessibility API that is supported by commonly available assistive technology.
additional information that can be
In HTML, information that is programmatically determinable from a link in English includes text that is in the same 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.
Since screen readers interpret punctuation, they can also provide the context from the current sentence, when the focus is on a link in that sentence.
set by software using methods that are supported by user agents, including assistive technologies
serving only an aesthetic purpose, providing no information, and having no functionality
Text is only purely decorative if the words can be rearranged or substituted without changing their purpose.
The cover page of a dictionary has random words in very light text in the background.
event that a) occurs at the same time as the viewing and b) is not completely generated by the content
A Webcast of a live performance (occurs at the same time as the viewing and is not prerecorded).
An on-line auction with people bidding (occurs at the same time as the viewing).
Live humans interacting in a virtual world using avatars (is not completely generated by the content and occurs at the same time as the viewing).
meaningful associations between distinct pieces of content
the relative brightness of any point in a colorspace, normalized to 0 for darkest black and 1 for lightest white
For the sRGB colorspace, the relative luminance of a color is defined as L = 0.2126 *
if RsRGB <= 0.03928 then
if GsRGB <= 0.03928 then
if BsRGB <= 0.03928 then
and RsRGB, GsRGB, and BsRGB are defined as:
RsRGB = R8bit/255
GsRGB = G8bit/255
BsRGB = B8bit/255
The "^" character is the exponentiation operator. (Formula taken from
Almost all systems used today to view Web content assume sRGB encoding. Unless it is known that another color space will be used to process and display the content, authors should evaluate using sRGB colorspace. If using other color spaces, see
If dithering occurs after delivery, then the source color value is used. For colors that are dithered at the source, the average values of the colors that are dithered should be used (average R, average G, and average B).
Tools are available that automatically do the calculations when testing contrast and flash.
A
the content would not
text or number by which software can identify the function of a component within Web content
A number that indicates whether an image functions as a hyperlink, command button, or check box.
same result when used
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 position relative to other items
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.
the success criterion does not evaluate to 'false' when applied to the page
A self-contained portion of written content that deals with one or more related topics or thoughts
A section may consist of one or more paragraphs and include graphics, tables, lists and sub-sections.
collection of
Different language versions would be considered different sets of Web pages.
a language using combinations of movements of the hands and arms, facial expressions, or body positions to convey meaning
translation of one language, generally a spoken language, into a
True sign languages are independent languages that are unrelated to the spoken language(s) of the same country or region.
a sensory experience that is not purely decorative and does not primarily convey important information or perform a function
Examples include a performance of a flute solo, works of visual art etc.
The way the parts of a
The way a collection of
additional
An audio version of a
An illustration of a complex
A paragraph summarizing the major outcomes and recommendations made in a research study.
As used in these guidelines "Web Technology" and the word "technology" (when used alone) both refer to Web Content Technologies.
Web content technologies may include markup languages, data formats, or programming languages that authors may use alone or in combination to create end-user experiences that range from static Web pages to synchronized media presentations to dynamic Web applications.
Some common examples of Web content technologies include HTML, CSS, SVG, PNG, PDF, Flash, and JavaScript.
sequence of characters that can be
An image of a chart is described in text in the paragraph after the chart. The short text alternative for the chart indicates that a description follows.
Refer to
words used in such a way that requires users to know exactly which definition to apply in order to understand the content correctly
The term "gig" means something different if it occurs in a discussion of music concerts than it does in article about computer hard drive space, 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.
any software that retrieves and presents Web content for users
Web browsers, media players, plug-ins, and other programs — including
data that is intended to be accessed by users
This does not refer to such things as Internet logs and search engine monitoring data.
Name and address fields for a user's account.
a part of the content that is perceived by users as a single control for a distinct function
Multiple user interface components may be implemented as a single programmatic element. Components here is not tied to programming techniques, but rather to what the user perceives as separate controls.
User interface components include form elements and links as well as components generated by scripts.
An applet has a "control" that can be used to move through content by line or page or random access. Since each of these would need to have a name and be settable independently, they would each be a "user interface component."
the technology of moving or sequenced pictures or images
Video can be made up of animated or photographic images, or both.
a time-based presentation that contains only
object in which the user agent presents content
The
This definition is based on
the font, size, color, and background can be set
a non-embedded resource
obtained from a single URI using HTTP plus any other resources that are used in the rendering or intended to be rendered together with it by a
Although any "other resources" would be rendered together with the primary resource, they would not necessarily be rendered simultaneously with each other.
For the purposes of conformance with these guidelines, a resource must be "non-embedded" within the scope of conformance to be considered a Web page.
A Web resource including all embedded images and media.
A Web mail program built using Asynchronous JavaScript and XML (AJAX). The program lives entirely at http://example.com/mail, but includes an inbox, a contacts area and a calendar. Links or buttons are provided that cause the inbox, contacts, or calendar to display, but do not change the URI of the page as a whole.
A customizable portal site, where users can choose content to display from a set of different content modules.
When you enter "http://shopping.example.com/" in your browser, you enter a movie-like interactive shopping environment where you visually move around in a store dragging products off of the shelves around you and into a visual shopping cart in front of you. Clicking on a product causes it to be demonstrated with a specification sheet floating alongside. This might be a single-page Web site or just one page within a Web site.
This section is
This publication has been funded in part with Federal funds from the U.S. Department of Education, National Institute on Disability and Rehabilitation Research (NIDRR) under contract number ED05CO0039. The content of this publication does not necessarily reflect the views or policies of the U.S. Department of Education, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.
Additional information about participation in the Web Content Accessibility Guidelines Working Group (WCAG WG) can be found on the
Bruce Bailey (U.S. Access Board)
Frederick Boland (NIST)
Ben Caldwell (Trace R&D Center, University of Wisconsin)
Sofia Celic (W3C Invited Expert)
Michael Cooper (W3C)
Roberto Ellero (International Webmasters Association / HTML Writers Guild)
Bengt Farre (Rigab)
Loretta Guarino Reid (Google)
Katie Haritos-Shea
Andrew Kirkpatrick (Adobe)
Drew LaHart (IBM)
Alex Li (SAP AG)
David MacDonald (E-Ramp Inc.)
Roberto Scano (International Webmasters Association / HTML Writers Guild)
Cynthia Shelly (Microsoft)
Andi Snow-Weaver (IBM)
Christophe Strobbe (DocArch, K.U.Leuven)
Gregg Vanderheiden (Trace R&D Center, University of Wisconsin)
Shadi Abou-Zahra, Jim Allan, Jenae Andershonis, Avi Arditti, Aries Arditi, Mike Barta, Sandy Bartell, Kynn Bartlett, Marco Bertoni, Harvey Bingham, Chris Blouch, Paul Bohman, Patrice Bourlon, Judy Brewer, Andy Brown, Dick Brown, Doyle Burnett, Raven Calais, Tomas Caspers, Roberto Castaldo, Sambhavi Chandrashekar, Mike Cherim, Jonathan Chetwynd, Wendy Chisholm, Alan Chuter, David M Clark, Joe Clark, James Coltham, James Craig, Tom Croucher, Nir Dagan, Daniel Dardailler, Geoff Deering, Pete DeVasto, Don Evans, Neal Ewers, Steve Faulkner, Lainey Feingold, Alan J. Flavell, Nikolaos Floratos, Kentarou Fukuda, Miguel Garcia, P.J. Gardner, Greg Gay, Becky Gibson, Al Gilman, Kerstin Goldsmith, Michael Grade, Jon Gunderson, Emmanuelle Gutiérrez y Restrepo, Brian Hardy, Eric Hansen, Sean Hayes, Shawn Henry, Hans Hillen, Donovan Hipke, Bjoern Hoehrmann, Chris Hofstader, Yvette Hoitink, Carlos Iglesias, Ian Jacobs, Phill Jenkins, Jyotsna Kaki, Leonard R. Kasday, Kazuhito Kidachi, Ken Kipness, Marja-Riitta Koivunen, Preety Kumar, Gez Lemon, Chuck Letourneau, Scott Luebking, Tim Lacy, Jim Ley, William Loughborough, Greg Lowney, Luca Mascaro, Liam McGee, Jens Meiert, Niqui Merret, Alessandro Miele, Mathew J Mirabella, Charles McCathieNevile , Matt May, Marti McCuller, Sorcha Moore, Charles F. Munat, Robert Neff, Bruno von Niman, Tim Noonan, Sebastiano Nutarelli, Graham Oliver, Sean B. Palmer, Sailesh Panchang, Nigel Peck, Anne Pemberton, David Poehlman, Adam Victor Reed, Bob Regan, Chris Ridpath, Lee Roberts, Gregory J. Rosmaita, Matthew Ross, Sharron Rush, Gian Sampson-Wild, Joel Sanda, Gordon Schantz, Lisa Seeman, John Slatin, Becky Smith, Jared Smith, Neil Soiffer, Jeanne Spellman, Mike Squillace, Michael Stenitzer, Jim Thatcher, Terry Thompson, Justin Thorp, Makoto Ueki, Eric Velleman, Dena Wainwright, Paul Walsch, Takayuki Watanabe, Jason White.
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