WCAG 2.1: Every Success Criterion Explained, With an AA Checklist

WCAG 2.1 is a W3C accessibility standard, published in 2018 and updated in 2025, that organizes 78 success criteria under the principles of perceivable, operable, understandable, and robust content. Level AA compliance requires meeting 50 criteria, including 30 Level A and 20 Level AA requirements covering alternatives for non-text content, captions, keyboard operation, readable structure, color contrast, responsive reflow, form errors, consistent navigation, and compatibility with assistive technology. WCAG 2.1 added 17 criteria to WCAG 2.0, with 12 at Levels A or AA addressing mobile orientation, zoom and reflow, non-text contrast, text spacing, touch gestures, motion controls, and screen-reader status messages. The ADA Title II web rule requires US state and local governments to meet WCAG 2.1 AA by April 2027 for larger jurisdictions and April 2028 for smaller or special-district governments, while the standard is also referenced in European accessibility rules and commonly used in private-sector audits. WCAG 2.2 retains nearly all 2.1 requirements, removes Parsing as a requirement, and adds nine criteria, so content that conforms to 2.2 also conforms to 2.1. Effective testing combines automated scans for detectable code issues with manual keyboard, screen-reader, zoom, mobile, and content-quality checks for criteria requiring human judgment.

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