What it takes for a page to conform to WCAG

The target comes from whatever binds the site: a law, a contract or an organisation's policy. Each names a version and a level, and the three standards below all set AA:

Understanding Conformance calls the choice of level "fundamentally a policy decision". WCAG 2.2 §5.2.1, Note 2, advises against requiring AAA for whole sites, because some content can't meet every AAA criterion, and Note 1 encourages reporting progress on criteria above the level reached. W3C intends content that conforms to 2.2 to conform to 2.0 and 2.1 too; a policy that names an older version may still ask for 4.1.1, as what in WCAG is required, and what is only advice explains.

WCAG 2.2 §5.2: "In order for a web page to conform to WCAG 2.2, all of the following conformance requirements must be satisfied." Each conformance requirement applies to a web page, not a site:

A long description or another presentation of a video, reached directly from the page, counts as part of that page. What makes a way of using a technology accessibility supported is in whether a technique works in the screen readers people use.

Under non-interference, a page may use a technology in a way that isn't accessibility supported, or in a way that doesn't conform, as long as the information is also available in a way that does and the rest of the page stays usable. The page must also keep meeting the requirements when a technology it doesn't rely on is turned on, turned off, or not supported. And four 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":

Understanding Conformance gives the reason with an example: content in a technology that isn't relied upon, because its information is also given in HTML, still traps keyboard focus and flashes, so keyboard users can't reach the rest of the page and some people may have seizures. Requirement 5 is there to stop that. A page that can't conform at all, such as a test page or an example page, can't be in the scope of conformance or of a claim.

Requirement 1 lets a page that doesn't conform stay in scope when a conforming alternate version is provided. WCAG 2.2's definition sets four conditions. The alternate version:

1. conforms at the designated level;
2. provides all of the same information and functionality, in the same human language;
3. is as up to date as the content that doesn't conform;
4. can be reached in at least one of these ways: from the page that doesn't conform, by an accessibility-supported mechanism; or the page that doesn't conform can only be reached from the conforming version; or only from a conforming page that also leads to the conforming version.

Its notes add that the alternate needn't match page for page, that each language offered needs its own, that it can be on another site if it is as freely available, and that a user preference that switches to it is acceptable if setting it is accessibility supported. Understanding Conformance says people must be told the alternate exists, for example by a clearly named link, and calls it "a fallback option": "the preferred method of conformance is to make all content directly accessible." Failure F19 is a page with no way to find its alternate version. Scanned and untagged PDFs that screen readers can't read uses an HTML page beside the PDF as one.

"Conformance is defined only for web pages", says WCAG 2.2 §5.3, though a claim may cover one page, a series of pages, or multiple related pages. A conformance claim is optional: "Authors can conform to WCAG 2.2 without making a claim." A claim that is made must include:

A conformance logo is a claim and needs the same parts. The optional parts include criteria met above the level, the technologies used but not relied upon, and the browsers and assistive technology used to test.

A claim covers pages that each conform. WCAG-EM 2.0 says claims "cannot be made for entire websites based upon the evaluation of a selected sub-set of web pages and functionality alone", since untested pages may fail. What a sample supports is an evaluation statement: the date, the WCAG version, the level, the scope, the technologies relied upon, and the accessibility support baseline. How to choose and test the sample is in testing a whole site against WCAG, and standing behind the result.

For content the author doesn't control, WCAG 2.2 §5.4 gives two options. A page that is monitored and repaired "within two business days" can still be claimed to conform. Otherwise, a statement of partial conformance says: "This page does not conform, but would conform to WCAG 2.2 at level X if the following parts from uncontrolled sources were removed." The parts must be out of the author's control and described so users can identify them. Understanding Conformance stresses that this "is a statement of non-conformance". §5.5 gives the same form for a language that assistive technology doesn't support.

Three documents are easily confused:

W3C's guidance on statements says they "are not technical assessments or declarations of conformity", though they ideally refer to one. What a statement says is in accessibility statements that are missing or say nothing; reading a VPAT is in reading a vendor's VPAT before you buy, and what to ask next.