WCAG 2.2 AA contrast

WCAG 2.2 Level AA is the legal-baseline contrast standard for most jurisdictions until WCAG 3 ships (≥ 2029). UDTS uses it as an optional, off-by-default cross-check alongside its primary and only required model, APCA — enabling this check doesn't change what ships; APCA's Lc target is the gate.

When to use

• Verifying a foreground / background pair after APCA composition.
• Auditing an existing token catalog or design for legal-baseline compliance.
• Code review on PRs that change color tokens, hover states, or focus indicators.

When NOT to use

• As the primary contrast model when generating new colors. APCACH inverse composition against an APCA Lc target is the generator; this is the cross-check.
• For free-class tokens (illustration, decorative, brand-spot) — they carry no pairing obligation. See apca-contrast for the class system.

The rules