Glossary · Accessibility term
WCAG
Also called: Web Content Accessibility Guidelines, usually said "wuh-cag"
WCAG is the international standard for web accessibility, published by the W3C. It is built in four layers. Four principles at the top, thirteen guidelines under those, then the testable success criteria at three levels of A, AA and AAA, with the technique library underneath as informative guidance. The criteria are the testable part, and a claim rests on them together with the five conformance requirements printed alongside them, at a level that is almost always AA. It is also an ISO standard, which matters more than it sounds, because some national laws cite the ISO number instead of the W3C name. WCAG 2.2 is ISO/IEC 40500:2025 and WCAG 2.0 was 40500:2012, so a procurement form asking for ISO/IEC 40500 is asking for this. In practice, "is this site accessible?" is nearly always being asked as "does it meet WCAG 2.1 or 2.2 Level AA?", and those are not quite the same question.
In practice
What it covers is stated plainly in its own abstract, and so is what it does not. Blindness and low vision, deafness and hearing loss, limited movement, speech disabilities, photosensitivity, combinations of those, and some accommodation for learning disabilities and cognitive limitations. Then the honest sentence. It will not address every need people with those disabilities have. Its stated scope is web content on any kind of device, kiosks included, which surprises people who assume the word web makes it a browser-only standard. Note which half of that sentence is doing the work. It reaches the content, not the machine it is running on.
"WCAG 2" means any version starting with a 2, and that is the standard's own definition rather than a convention. It is the argument to make about a contract naming WCAG 2 with no dot-release attached, and it is a strong one, because W3C also states that meeting 2.2 meets 2.1 and 2.0. What it is not is a ruling. A contract still means what a court or the parties decide it means, so raise the point rather than assuming it closes the question.
It was designed to be tested by a combination of automated testing and human evaluation, and that phrase is inside the standard, describing itself. It is the shortest available answer to anybody selling a scan as a conformance verdict, and it comes from the people who wrote the thing being scanned for.
Level AAA is not a synonym for fully accessible. The standard says content conforming at the highest level still will not be accessible to people with all types, degrees and combinations of disability, and names cognitive, language and learning areas in particular. Anybody writing AAA into a contract as a way of being safe has misread what the top level is.
Why it matters
Because the laws defer to it, WCAG is the thing that actually gets tested, cited in complaints and named in contracts. So "is this accessible?" only becomes answerable once you translate it into a version and a level. The working group's own advice is worth following even when your obligation says otherwise. It recommends adopting 2.2 as the target regardless of what a formal obligation names, both to get the improvements and to be ready when policy catches up, which it has so far always done late.
Reading a citation you were sent
A contract naming ISO/IEC 40500 is naming WCAG, and the year beside it says which version. One naming WCAG 2, with no dot-release attached, is naming any version starting with a 2, by the standard's own definition. Neither citation picks a level for you, so find where the level is stated before you plan anything. Then test to 2.2, because W3C says conforming to it also conforms to 2.1 and 2.0.
Where this shows up on the site
Related terms
- POURPOUR is the field's shorthand for WCAG's four principles, which are Perceivable, Operable, Understandable and Robust.
- Level A, AA, AAALevel A, AA and AAA are WCAG's three conformance levels, and they stack.
- Success criterionA success criterion is a single testable rule in WCAG, and it is the unit everything else is built from.
- GuidelineA guideline is the middle layer of WCAG, and WCAG 2.2 has 13 of them sitting between the four principles and the rules anybody is ever tested against.
- WCAG versions (2.0, 2.1, 2.2)WCAG 2.0 arrived in 2008, WCAG 2.1 in 2018 with rules for mobile, low vision and cognition, and WCAG 2.2 in 2023 with nine more criteria and one removal.
- ConformanceConformance means satisfying all the requirements of a standard, and WCAG has five of them rather than one.
Knowing the word is the easy part.
Find out where your own site stands. The free scan checks 10 pages in a real browser against all 90 supported automated rules, separates 27 best-practice checks from its WCAG findings, and names the rule behind every result.