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designVercel

Minimum Contrast

MUST

MUST: Meet contrast—prefer APCA (https://apcacontrast.com/) over WCAG 2

Prefer APCA over WCAG 2 for accurate perceptual contrast

Bad

Good

Why it matters

WCAG 2.x contrast ratios have known issues. APCA (Accessible Perceptual Contrast Algorithm) provides more accurate measurements of readability. Aim for APCA values appropriate to text size and weight. Generally, body text should have Lc 60+ and headings Lc 45+.

References

Built by Gleb Stroganov, design engineer at Evil Martians.

The rules come from other people's skills and guidelines — Vercel, Rauno Freiberg, @Ibelick, impeccable, Emil Kowalski, Tailwind, RAMS — each one credited on the Sources page. The work here is extraction and wiring: every rule is pulled into one corpus, given a good and a bad example you can operate, a MUST/SHOULD/NEVER rule an agent can paste, and a link back to where it came from.