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.
The success criteria for each guideline are organized into three (3) levels of conformance.
Level 1 success criteria:
Achieve a minimum level of accessibility through markup, scripting, or other technologies that interact with or enable access through user agents, including assistive technologies.
Can reasonably be applied to all Web resources.
Level 2 success criteria:
Achieve an enhanced level of accessibility through one or both of the following:
markup, scripting, or other technologies that interact with or enable access through user agents, including assistive technologies
the design of the content and presentation
Can reasonably be applied to all Web resources.
Level 3 success criteria:
Achieve additional accessibility enhancements for people with disabilities.
Are not applicable to all Web resources.
Note: Some guidelines do not contain success criteria at every level.
This method of grouping success criteria differs in important ways from the approach taken in WCAG 1.0. In WCAG 1.0, each checkpoint is assigned a "priority" according to its impact on accessibility for users. Thus Priority 3 checkpoints appear to be less important than Priority 1 checkpoints. The Working Group now believes that all success criteria of WCAG 2.0 are essential for some people. Thus, the system of checkpoints and priorities used in WCAG 1.0 has been replaced by success criteria grouped under Levels 1, 2, and 3 as described above.
The Working Group believes that all success criteria should be testable. Tests can be done by computer programs or by people who understand this document. When multiple people who understand WCAG 2.0 test the same content using the same success criteria, the same results should be obtained.
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 supports 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 they are supported by accessible user agents.
WCAG 2.0 uses the term user agent to mean: Any software that retrieves and renders Web content for users. This may include Web browsers, media players, plug-ins, and other programs - including assistive technologies - that help in retrieving and rendering Web content. .
It is important to note that assistive technologies are included in this definition. (Assistive technologies include screen readers, screen magnifiers, on screen and alternative keyboards, single switches, voice recognition and a wide variety of input and output devices that meet the needs of people with disabilities.)
In choosing technologies to rely upon, developers need to know what technologies they can assume are supported by, and active in, accessible user agents. A set of such technologies is called a baseline. Developers must ensure that all information and functionality comprising the Web content conform to WCAG 2.0 assuming (a) that user agents support only the technologies in the baseline specified for the content and (b) that those technologies are active.
Baselines are defined outside the WCAG 2.0 guidelines as part of a more comprehensive accessibility policy. Baseline considerations will be significantly different if the entity defining the baseline can guarantee the availability of specific user agents.
Example 1: A government site that provides information to the public
A government agency publishes information intended for the general public. The specified baseline includes only technologies that have been widely supported by more than one accessible and affordable user agent for more than one release.
Example 2: A government adopts a guideline for use with accessible user agents in use by its citizens
A government periodically changes the baseline it requires for developers of public sites to reflect the increasing ability of affordable user agents (including assistive technology) to work with newer technologies.
Example 3: A government provides accessible user agents to all citizens
A government provides all citizens with user agents that support newer technologies. The government specifies a baseline that includes newer technologies that are supported in the user agents provided by that government.
Example 4: A private intranet
A company or government agency provides its employees with the information technology tools they need to do their jobs. The baseline for intranet sites used only by employees includes newer technologies that are supported only in the user agent which the organization provides for its employees. Because the company controls the user agents that will view its internal content - the author has very accurate knowledge of the technologies that those user agents support.
(Note that in example 4, the author is not specifying the baseline in terms of a user agent. The organization had specified the user agent to be used by organization employees in advance. The author just has knowledge that only that agent is used so the author has very good knowledge of the technologies the user agent supports and creates a baseline based on those technologies. Care must be taken here however since that agent would have to be cross-disability accessible or else the author's assumptions may be bad because users with disabilities may have to use other user agents to access the content.)
Developers may also use technologies that are not in the specified baseline provided that the following are true:
All content and functionality must be available using only the technologies in the specified baseline.
The non-baseline technologies must not interfere with (break or block access to) the content
when used with user agents that only support the baseline technologies
when used with user agents that support both the baseline and the additional technologies.
Additional information can be found on the baseline at Questions and Answers about Baseline and WCAG 2.0.
WCAG 2.0 conformance at level A means that all Level 1 success criteria in the guidelines are met assuming user agent support for only the technologies in the chosen baseline.
WCAG 2.0 conformance at level Double-A means that all Level 1 and all Level 2 success criteria in the guidelines are met assuming user agent support for only the technologies in the chosen baseline.
WCAG 2.0 conformance at level Triple-A means that all Level 1, Level 2 and Level 3 success criteria in the guidelines are met assuming user agent support for only the technologies in the chosen baseline.
Editorial Note: The working group is looking at AAA conformance as being an indication that the content goes beyond AA conformance in a major way but do no necessarily require conformance to all Level 3 success criteria. Some Level 3 success criteria cannot be applied to all web content and some are not necessary in certain circumstances. We are considering different criteria for claiming AAA conformance. Comments and suggestions are invited.
Conformance claims apply to delivery units and sets of delivery units. (In many cases, a "delivery unit" is the same as a "page." In other cases, however, such as Web applications, the term "page" may be inappropriate, so the Working Group has adopted the term "delivery unit" from the Device Independence Working Group.)
The date of the claim
The guidelines title/version: "Web Content Accessibility Guidelines 2.0"
The URI of the guidelines: http://www.w3.org/TR/2005/REC-WCAG20-YYYYMMDD/
The conformance level satisfied: (Level A, AA or AAA)
The Baseline used to make the conformance claim. (If baseline is a published baseline it can be named along with a URI that points to it. The baseline technologies can also be spelled out individually in the conformance claim. )
Scope of the claim (a URI, list of URI's or a regular expression)
A list of the specific technologies "relied upon" to create the content for which the claim is being made. (This includes markup languages, style sheet languages, scripting/programming languages, image formats, and multimedia formats.)
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)
the set of "Relied Upon" technologies must be a proper subset of the Baseline.
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.
A list of user agents that the content has been tested on. This should include assistive technologies.
Information about audience assumptions or target audience. This could include language, geographic information. It CANNOT specify physical, sensory or cognitive requirements.
Example 1: On 13 March 2005, www.johnpointer.com conforms to W3C's WCAG 2.0, Conformance Level 1.The baseline for this claim is XHTML 1.0. The specification that this content *relies upon* is: XHTML 1.0. The specifications that this content *uses* are: CSS2, Real Video, Real Audio, MP3, and gif. This content was tested using the following user agents and assistive technologies: Firefox 1.01 (Windows, Linux), IE 3.0 and 6.0 (Windows, Mac), Jaws 3.7 and Jaws 6.0 (windows), Safari 1.2 (Mac), Opera 7.5 (OSX).
Example 2: On 1 August 2006, "S5: An Introduction" http://meyerweb.com/eric/tools/s5/s5-intro.html conforms to W3C's WCAG 2.0. Conformance Level 1. The baseline for this claim is UDBaseline#1-2006 at http://UDLabs.org/Baseline#1-2006.html. The specification that this content *relies upon* is: XHTML 1.0 (Strict). The specifications that this content *uses* are: JavaScript 1.2, CSS2, png, and jpg.
Example 3: On 1 July 2005, "Photo gallery application" http://example.com/photos conforms to W3C's WCAG 2.0, Conformance Level 1. The baseline is ISA-Baseline#2-2005 at http://ISA.gov/Baselines/BL2-2005. The specifications that this content *relies upon* are: XHTML 1.0 (Strict), CSS2, JavaScript 1.2, jpg. The specification that this content *uses* is: gif. The techniques profile that this content uses is, "HTML/ECMAScript for latest browsers."
A delivery unit conforms to WCAG 2.0 at a given conformance level only if all content provided by that delivery unit conforms at that level.
Note: If multiple representations can be retrieved from a URI through content negotiation, then the conformance claim would be for the delivery unit that is returned when no negotiation is conducted (unless the server returns an error for that condition, in which case one of the negotiated forms must comply).
Editorial Note: There is some question as to whether URI is specific enough a reference to the material for which the claim is being made.
Editorial Note: A question has been raised as to whether the information required in items 1-3 above should all be transmitted in the HTTP header or in some other way.
Editorial Note: The working group is considering adding the following note to the conformance section to differentiate Web Content from standard stand alone software and other products that are downloaded over the Internet and not used via a user agent.. Note: If data, software or other materials are downloaded over the internet but are not used via a user agent then they are not considered Web content and are not covered by these guidelines.
Sometimes a delivery unit is assembled ("aggregated") from multiple sources that each have their own level of conformance. These sources are called authored units. The conformance level for a delivery unit that contains authored units is equal to the lowest conformance level claimed for the delivery unit content and any of the authored units it contains - including claims of aggregated units.
A delivery unit referred to by a URI conforms to WCAG 2.0 at a given conformance level only if all content provided by that delivery unit conforms at that level. For example, if the delivery unit provides information retrieved from a database in response to users' queries, all delivery units containing such information must satisfy the success criteria of WCAG 2.0 to the level at which conformance is claimed. In the case of content negotiation, WCAG 2.0 conformance is not required if the user agent requests a version of the content that does not meet WCAG 2.0 at the specified conformance level.
Editorial Note: We are currently looking at how to handle unknown or community-contributed, authored units that are created using an aggregator supplied tool. We are currently considering whether aggregated content would be judged to conform to WCAG if the aggregator supplied tool can conform to the Authoring Tool Accessibility Guidelines (ATAG) 2.0.
Conformance claims can be limited, or "scoped," to pertain to only some parts of a Web site. All conformance claims, however, must be directed to a URI or a range of URIs. Scoping to exclude a particular type of content (for example, images or scripts) from a site is not allowed since it would allow exclusion of individual success criteria. Scoping by URI to exclude sections of a site is allowed so that authors can make claims for just some parts of a site.
This Working Draft of WCAG 2.0 builds upon WCAG 1.0 and reflects feedback received since the publication of WCAG 1.0 in May 1999.
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 the similarities and differences between WCAG 1.0 Checkpoints and WCAG 2.0 Guidelines and success criteria, please refer to the (draft) Mapping between WCAG 1.0 and the WCAG 2.0 Working Draft.
Authors whose content currently conforms to WCAG 1.0 may wish to capitalize on past accessibility efforts when making the transition to WCAG 2.0. A qualified conformance statement could allow them this flexibility. For example, a conformance claim might include the following statement: "Materials created or modified before 31 December 2005 conform to WCAG 1.0. Materials created or modified on or after 31 December 2005 conform to WCAG 2.0."
Editorial Note: In some instances, the WCAG 2.0 Working Draft may be easier to conform to than the WCAG 1.0 Recommendation while other criteria might be harder to meet in WCAG 2.0 than in WCAG 1.0. The WCAG WG will consider the differences between WCAG 1.0 and WCAG 2.0 conformance and offer advice to developers who currently conform to WCAG 1.0. This advice might take the form of a WCAG 1.0 conformance profile to WCAG 2.0 and information about migrating from WCAG 1.0 to WCAG 2.0. This advice is not yet available.