The Web Content Accessibility Guidelines, WCAG, are published by the World Wide Web Consortium, the body that sets web standards. They describe what makes web content usable by people with disabilities, in a form that can be tested.
Versions
WCAG 2.0 was published in 2008, 2.1 in 2018 and 2.2 in 2023. Each version keeps everything in the one before and adds to it. This platform tests against 2.1, which is the version most laws and contracts currently name, and reports on the extra 2.2 criteria separately.
Levels
- Level A. The minimum. Failing these makes content impossible for some people to use.
- Level AA. Includes level A, and adds criteria that remove significant barriers. This is the level laws, policies and contracts almost always require.
- Level AAA. The highest level. Not expected across a whole site, because some content cannot meet it.
WCAG 2.1 levels A and AA together contain 49 success criteria that apply to web pages: 29 at level A and 20 at level AA. Those 49 are what your compliance score is built on.
The four principles
| Principle | In plain words | Examples |
|---|---|---|
| 1. Perceivable | People can get the information, whatever senses they use. | Alternative text, captions, contrast, text that can be resized. |
| 2. Operable | People can use every control, however they interact. | Keyboard access, enough time, no flashing, clear focus, meaningful links. |
| 3. Understandable | People can follow the content and the interface. | Page language, predictable behaviour, clear labels and error messages. |
| 4. Robust | Assistive technology can interpret it reliably. | Correct names, roles and states on controls, and status messages. |
One criterion left out
WCAG 2.1 also contains 4.1.1 Parsing. The W3C has since declared it obsolete, because modern browsers and assistive technology no longer depend on it, and it was removed in WCAG 2.2. We do not test or score it.
The law
Many laws and policies around the world point at WCAG 2.1 AA. In the United States, for example, the Department of Justice's ADA Title II rule adopts it for state and local government websites. What applies to you depends on where you operate and who you serve. This is not legal advice; if you have an obligation, confirm it with a legal adviser.