3/9 Colors
Contrast Combinations
Glossary of Terms
- WCAG 2.1
- Web Content Accessibility Guidelines. The current global standard. Calculates contrast using a simple relative luminance ratio ranging from 1:1 to 21:1.
- APCA (WCAG 3.0)
- Advanced Perceptual Contrast Algorithm. The modern standard slated for WCAG 3.0. It uses "polarity-aware" math (distinguishing dark-on-light vs light-on-dark) to produce a Lightness Contrast (Lc) score from 0 to ~108.
- AAA / AA
- Compliance levels. AAA is the gold standard for high accessibility. AA is the acceptable minimum for most legal and professional requirements.
- AA Large
- A passing grade specifically for large typography (typically 18pt+ or 14pt+ bold). These colors lack the contrast for body text but are safe for large headings.