The Web Content Accessibility Guidelines (WCAG) were created to help define how to make web content more accessible with the goal of providing a single shared standard.
The most recent version is WCAG 2.2.
WCAG 2.2 extends Web Content Accessibility Guidelines 2.1 (2018).
WCAG 2.2 success criteria are written as testable statements that are not technology-specific.
Guidance about satisfying the success criteria in specific technologies, as well as general information about interpreting the success criteria, is provided in separate documents.
WCAG are the most widely-accepted set of recommendations and the Revised 508 Standards are based on WCAG 2.0.
The W3C also encourages use of the most current version of WCAG when developing or updating Web accessibility policies.
When WCAG guidelines are followed they improve usability for everyone.
WCAG 1.0 focused heavily on the techniques for accomplishing accessibility, especially as related to HTML.
Subsequent versions of WCAG focused more heavily on the principles of accessibility, making them more flexible, and encourages developers to think through the process of accessibility conceptually.
WCAG 2.0 is based on four main guiding principles of accessibility known by the acronym POUR perceivable, operable, understandable, and robust.
WCAG 2.2 was initiated with the goal to continue the work of WCAG 2.1: Improving accessibility guidance for three major groups: users with cognitive or learning disabilities, users with low vision, and users with disabilities on mobile devices.