05 // Unicode, Symbol & Encoding WorkbenchCONTRAST-CHECKER
WCAG 2.1 AA / AAA Color Contrast Ratio & Luminance Workbench
Computes exact sRGB linearized relative luminance `L = 0.2126·R + 0.7152·G + 0.0722·B` and WCAG 2.1 contrast ratio (1:1 to 21:1) for accessible UI typography.
Contrast 17.06 : 1
The quick brown fox jumps over 0123456789.
CONTRAST RATIO
17.06 : 1
WCAG AA NORMAL (≥4.5)
PASS
WCAG AAA NORMAL (≥7.0)
PASS
WCAG AA LARGE (≥3.0)
PASS
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Reference Table
- 01WCAG AA requires `≥ 4.5:1` for normal body text (`< 18pt` or `< 14pt bold`) and `≥ 3.0:1` for large text and interactive UI borders/icons.
- 02WCAG AAA enhanced contrast requires `≥ 7.0:1` for normal text and `≥ 4.5:1` for large text.
Frequently Asked Questions
How is sRGB linearized before computing WCAG luminance?+
For each 8-bit channel `c = C/255`: if `c ≤ 0.04045`, linear `v = c / 12.92`; otherwise `v = ((c + 0.055) / 1.055)^2.4`.
Why does green carry a 0.7152 weight while blue carries only 0.0722?+
Human photopic cone sensitivity peaks in the yellow-green spectrum (~555 nm), making green appear ~10× brighter per watt than pure blue.
What is the maximum possible WCAG contrast ratio?+
Pure black (`#000000`, `L = 0`) against pure white (`#FFFFFF`, `L = 1`) yields `(1 + 0.05) / (0 + 0.05) = 21.00 : 1`.