WCAG 2.0 and 2.1 guidelines consist of three levels of Accessibility that a website can achieve. It’s recommended that you aim for Level AA at the beginning in order to mitigate litigation risks, and then add to the website in order to achieve a AAA rating if possible:
Level A – Your website is accessible to some users.
Level AA – Your website is accessible to almost all users.
Level AAA – Your website is accessible to all users.