Open color lab
A small studio for color

Contrast,
clearly.

Pick two colors, preview text and check readability. A little tool for designers, makers and curious minds.

Color contrast checker

WCAG 2.x relative luminance ratio

Use the color pickers or type a six-digit hex code. Results update as you edit.

Designed to be read.
Readable text makes better everyday experiences. The quick brown fox jumps over the lazy dog.
Contrast ratio—Scale from 1:1 to 21:1
Normal text / AA—Minimum 4.5:1
Large text / AA—Minimum 3:1

This checker implements the WCAG relative luminance formula for sRGB colors. The ratio alone does not confirm full accessibility: font size, weight, context, user settings and other requirements also matter. Calculations happen entirely inside your browser.