What is the difference between WCAG 2.0, 2.1, and 2.2?

WCAG 2.0 (2008) established 61 success criteria under the four POUR principles and is still the version Section 508 references. WCAG 2.1 (2018) added 17 more criteria for mobile, low-vision, and cognitive accessibility, and it's the version the DOJ codified for ADA Title II in its 2024 rule. WCAG 2.2 (2023) added 9 more criteria — including focus appearance, dragging movements, and accessible authentication — and removed one (4.1.1 Parsing), bringing the Level A + AA total to 56. Each version is backward-compatible, so meeting 2.2 AA automatically satisfies 2.1 AA and 2.0 AA.