Pick a text colour and a background colour and get the official WCAG contrast ratio with pass/fail badges for AA and AAA — the same numbers the accessibility auditors use, computed from the published formula on your device. When a pair fails, the page also finds the nearest colour that passes, so you can fix the design instead of just being scolded.
The quick brown fox jumps over 13 lazy dogs — Aa 0O8B
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Click a swatch under the preview to try it as the text colour; the suggestions blend your text colour toward black or white by the smallest step that reaches the target ratio.
Palette lab — tints & shades
Nine tints (mixed toward white) and nine shades (toward black) of the current text colour.
What the numbers mean
AA is the level most laws and policies require: normal text needs a ratio of 4.5:1, large text (≈18.66px bold or 24px regular and up) needs 3:1. AAA raises those to 7:1 and 4.5:1. The ratio comes from relative luminance — each channel is linearised from sRGB and weighted for how sensitive the human eye is to red, green and blue (0.2126 / 0.7152 / 0.0722), which is exactly why bright yellow on white fails so violently while you can still read it yourself on a good screen. Roughly 1 in 12 men and 1 in 200 women have some colour-vision deficiency, and every user over 40 loses contrast sensitivity — accessibility maths is audience maths, not bureaucracy.
Part of Everyday Tools. Tukuk-OS practices what it checks: pages here ship with a read-aloud engine and this checker exists because we audited ourselves with it.
Tukuk-OS