Currently, there are two versions of WCAG that are considered stable specifications.
Initially released in 2008, WCAG 2.0 is the basis for many international accessibility rules and regulations, and it remains a stable W3C Recommendation. However, since it was developed when the first smartphones were only just emerging, there is little in the specification to address accessibility through mobile devices. Also, there was little in WCAG 2.0 to address accessibility for people with cognitive disabilities.
On June 5, 2018, WCAG 2.1 was released as a W3C Recommendation. It is intended to extend WCAG 2.0, adding 17 new success criteria and one additional guideline that addresses mobile accessibility, as well as aspects of accessibility for people with cognitive disabilities, among other additions.
A goal in creating WCAG 2.1 has been to ensure that sites that comply with it also continue to comply with WCAG 2.0. This ensures that any obligations to conform with WCAG 2.0 are compatible with WCAG 2.1 conformance, if it is used as the basis for creating accessible web content. Organizations and websites should be aiming to conform with WCAG 2.1 into the future but can continue to conform with WCAG 2.0.
We won’t go into the details and differences between WCAG 2.0 and WCAG 2.1 here, but we will point out the new success criteria, and the one guideline, when we get into the details in the units that follow this one. Look for the following to denote success criteria that fall into.