The 4 principles of the Web Content Accessibility Guidelines (WCAG) 2.1 are expanded into 13 guidelines providing a framework for designers to design applications that are more accessible to all users.
For each guideline, the WCAG provide a set of testable success criteria that can be used to assess how well your application conforms to the guideline. Unlike the guidelines, the success criteria are testable and therefore form the basis for accessibility audits.
There are three levels of conformance: A (lowest), AA and AAA. Requiring AAA conformance is considered an unsuitable policy in most cases, but AA conformance is both achievable and helpful.
Each success criterion has an associated conformance level. To achieve a certain level of conformance all success criteria at that level and below must be met. E.g. to achieve AA conformance, all the level A and level AA success criteria must be met.
There is also a collection of techniques you can use to help you fulfil these success criteria. Techniques are either:
- sufficient techniques that fulfil the testable criteria, or
- advisory techniques that address accessibility barriers that are not covered by the testable success criteria.
It's important to design with accessibility in mind. You should apply all the techniques that you are able to, including the advisory techniques, in order to best address the needs of the widest possible range of users.