WCAG conformance levels

Every success criterion in the Web Content Accessibility Guidelines carries a level: A, AA or AAA. The letters are not a quality grade. They record how essential a criterion is and how broadly it can be achieved across all kinds of content. Level A removes barriers that stop people using content at all. Level AA addresses barriers that make content difficult for large groups of people. Level AAA gathers criteria that are valuable but cannot be satisfied by every kind of content, which is why the guidelines themselves advise against adopting full AAA as a site-wide policy. A criterion is not necessarily harder to implement because it sits at the highest level, and several are straightforward for one kind of content while being impossible for another.

AA is what regulation, procurement and contracts almost always name, and conformance is cumulative: claiming AA means every level A criterion and every level AA criterion is satisfied, across whole pages and across complete processes. That last part is where most claims quietly fall over. Passing on a landing page while the checkout contains an unlabelled field means the process does not conform, and a statement covering only the pages somebody remembered to test is not a conformance statement at all.

What a conformance claim has to state

• The version it was tested against, since 2.0, 2.1 and 2.2 are different documents with different criteria in them.
• The level claimed, and the fact that it is met in full rather than mostly, because the guidelines allow no partial credit.
• The scope: which pages and which end-to-end processes were assessed, described precisely enough that a reader can tell what was left out.
• The date and the technologies relied upon, because a claim describes a particular build of a product on a particular day.

There is no partial conformance in these guidelines: a page either meets a level or it does not, and AA with two exceptions is a progress report rather than a claim.