WCAG 2.2 · APCA
Red on White contrast
#FF0000 text on a #FFFFFF background has a WCAG contrast ratio of 3.99:1 and APCA Lc 64. It passes AA only for large text and UI components.
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Large text, 24px: The quick brown fox jumps over the lazy dog
Normal text, 16px: Pack my box with five dozen liquor jugs. How vexingly quick daft zebras jump.
Small text, 13px: Sphinx of black quartz, judge my vow.
WCAG 2.2 contrast ratio
3.99:1
| Level | Needs | Result |
|---|---|---|
| AA · normal text | 4.5:1 | ✗ Fail |
| AAA · normal text | 7:1 | ✗ Fail |
| AA · large text (24px, or 18.66px bold) | 3:1 | ✓ Pass |
| AAA · large text | 4.5:1 | ✗ Fail |
| AA · UI components & graphics | 3:1 | ✓ Pass |
Ratios are truncated, never rounded up, so a displayed value never claims more than the pair delivers.
APCA lightness contrast
Lc 64
Body text
Lc ≥ 75
✗ Fail
Content text
Lc ≥ 60
✓ Pass
Large text & UI
Lc ≥ 45
✓ Pass
APCA is polarity-aware: #FFFFFF text on #FF0000 gives a different Lc. Read the WCAG vs APCA guide.
Suggested fix for WCAG AA (4.5:1)
Keep the background #FFFFFF, change the text
#EE0000 · 4.53:1
OKLCH lightness −0.031 (hue kept)
Keep the text #FF0000, change the background
#161616 · 4.52:1
OKLCH lightness −0.798 (hue kept)
Found by changing only OKLCH lightness (hue kept, chroma reduced only to stay inside sRGB) by the smallest amount that reaches 4.5:1.