WCAG 2.1 Success Criteria
WCAG 2.1 is the technical standard cited in nearly every ADA web lawsuit and demand letter in the United States. It defines what an accessible website actually is — broken into four principles (Perceivable, Operable, Understandable, Robust), each with concrete success criteria at three conformance levels (A, AA, AAA).
The pages below explain each criterion in plain English, show what failing examples look like in real code, and walk through the fix. Level AA is the de-facto US compliance target — that's the level you should be targeting unless a specific contract or jurisdiction requires AAA.
Perceivable
Information must be presented in ways users can perceive — text alternatives for images, captions for video, content that adapts to assistive tech.
- 1.1.1Non-text ContentLevel A
- 1.2.1Audio-only and Video-onlyLevel A
- 1.2.2Captions (Prerecorded)Level A
- 1.2.3Audio Description or Media AlternativeLevel A
- 1.2.4Captions (Live)Level AA
- 1.2.5Audio Description (Prerecorded)Level AA
- 1.3.1Info and RelationshipsLevel A
- 1.3.2Meaningful SequenceLevel A
- 1.3.3Sensory CharacteristicsLevel A
- 1.3.4OrientationLevel AA
- 1.3.5Identify Input PurposeLevel AA
- 1.4.1Use of ColorLevel A
- 1.4.2Audio ControlLevel A
- 1.4.3Contrast (Minimum)Level AA
- 1.4.4Resize TextLevel AA
- 1.4.5Images of TextLevel AA
- 1.4.10ReflowLevel AA
- 1.4.11Non-text ContrastLevel AA
- 1.4.12Text SpacingLevel AA
- 1.4.13Content on Hover or FocusLevel AA
Operable
All functionality must work via keyboard, give users enough time, avoid seizure triggers, and help users navigate.
- 2.1.1KeyboardLevel A
- 2.1.2No Keyboard TrapLevel A
- 2.1.4Character Key ShortcutsLevel A
- 2.2.1Timing AdjustableLevel A
- 2.2.2Pause, Stop, HideLevel A
- 2.3.1Three Flashes or Below ThresholdLevel A
- 2.4.1Bypass BlocksLevel A
- 2.4.2Page TitledLevel A
- 2.4.3Focus OrderLevel A
- 2.4.4Link Purpose (In Context)Level A
- 2.4.5Multiple WaysLevel AA
- 2.4.6Headings and LabelsLevel AA
- 2.4.7Focus VisibleLevel AA
- 2.5.1Pointer GesturesLevel A
- 2.5.2Pointer CancellationLevel A
- 2.5.3Label in NameLevel A
- 2.5.4Motion ActuationLevel A
Understandable
Text must be readable, pages must behave predictably, and forms must help users avoid and correct mistakes.
- 3.1.1Language of PageLevel A
- 3.1.2Language of PartsLevel AA
- 3.2.1On FocusLevel A
- 3.2.2On InputLevel A
- 3.2.3Consistent NavigationLevel AA
- 3.2.4Consistent IdentificationLevel AA
- 3.3.1Error IdentificationLevel A
- 3.3.2Labels or InstructionsLevel A
- 3.3.3Error SuggestionLevel AA
- 3.3.4Error Prevention (Legal, Financial, Data)Level AA
Robust
Content must remain accessible as user agents and assistive tech evolve — valid markup, proper ARIA, name/role/value exposed.
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