Contrast Checker
FreeCheck color contrast against WCAG accessibility standards — entirely in your browser.
Runs entirely in your browser. Nothing you enter is uploaded or stored.
Normal text (16px) — The quick brown fox jumps over the lazy dog.
Large text, regular (24px / 18pt)
Large text, bold (18.66px / 14pt bold)
Color vision simulation
Approximate only — a rough sense of how this pair might look under a color vision deficiency, not a clinically precise simulation.
How it works
What is contrast ratio, and why does it matter?
Contrast ratio measures how different two colors are in relative brightness, expressed as a number from 1:1 (identical, illegible) to 21:1 (pure black on pure white, maximum possible). It matters because text needs enough contrast against its background to be readable — for users with low vision or certain forms of color blindness especially, low-contrast text can be genuinely unreadable, not just harder to read.
What are the actual WCAG thresholds this tool checks?
WCAG 2.1 level AA requires a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text. Level AAA, the stricter standard, requires 7:1 for normal text and 4.5:1 for large text. This tool checks your color pair against all four.
What counts as "large text" for the relaxed threshold?
WCAG defines large text precisely: 18pt (24px) or larger at regular weight, or 14pt (18.66px) or larger at bold weight. Anything smaller than that — including most body text — is held to the stricter "normal text" threshold, regardless of how it looks.
Is my color data sent anywhere?
No. Every calculation — contrast ratio, the pass/fail checks, the color suggestions, the color vision simulation — runs locally in your browser.