First, here's what the WCAG success criteria don't mean: They're not a measure of accessibility. One person I spoke to hypothesized that for a given problem X, A was the lowest level of accessibility to solve X, AA was the middle of the road level, and AAA was the most accessible. That person wanted to know why I didn't just adopt the A solution for everything so that we could move on. They're also not a measure of audience, although often they correlate with audience size. Pretty much everyone needs you to implement the A-level solitions, and many of the AAA-level solutions are most meaningful to small audiences such as \\"people who are D/deaf and need ASL translations\\". Here's what the success criteria do mean: For the entire set of guidelines, A-level guidelines are the absolute minimum an organization should do ((Accessibility Fundamentals - Disabilities, Guidelines, and Laws at Deque University)) (presumably because they are both achievable and meaningful for a very large audience). AA-level guidelines are the middle, achievable and meaningful, but with not as much effort as AAA guidelines, which are meaningful for a smaller audience but more challenging to achieve ((Accessibility Fundamentals - Disabilities, Guidelines, and Laws at Deque University)). I tell people to think of level A as table stakes. If you're not getting the A guidelines correct, your website, document, or app probably isn't usable by anyone, much less by people with disabilities. Level AA is not only the legal standard in most places (meaning you have to complete both A and AA) it's the most achievable for a reasonable expense. Level AAA is for the times when you know you have a niche audience that you need to ensure has access, but it's also for standing out from the crowd. Some AAA guidelines are actually easy to achieve, especially if there's a matching AA guideline that has exceptions that don't apply to you. When choosing what level to test, I recommend WCAG 2.1 AA, with the understanding that anytime you can pick up a AAA without significant effort, you should do it. Conformance is the floor, not the ceiling.