Check colour contrast against WCAG AA/AAA, with a live text preview.
Check the contrast ratio between a text colour and its background against WCAG 2.1 AA and AAA thresholds, for normal and large text. Live ratio, pass/fail grid, and a real text preview. Accepts hex, rgb(), and named colours. Runs entirely in your browser.
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WCAG AA requires 4.5:1 for normal text and 3:1 for large text — 18pt, or 14pt bold and above. AAA raises that to 7:1 and 4.5:1. Interface components and meaningful graphics need 3:1. AA is the level most legislation and procurement requirements reference.
Light grey body text is the single most common failure, and it usually comes from a designer choosing it on a bright calibrated monitor. Something like #999 on white lands near 2.8:1 — comfortably below AA. Darkening to roughly #767676 clears the threshold while still reading as grey rather than black.
It is necessary, not sufficient. Contrast covers legibility, but you also need to avoid relying on colour alone to convey meaning — a red border marking an invalid field is invisible to many colour-blind users without an icon or text. Treat the ratio as a floor, then check the design without colour.
Yes, WCAG Contrast Checker is completely free. No signup, no account, and no watermark on outputs. A Pro tier is available for 100 AI ops/day and larger file sizes.
WCAG Contrast Checker runs entirely in your browser. Your file is never uploaded — it is read, processed and saved locally, so it never reaches our servers or anyone else's. You can disconnect from the internet after the page loads and it still works.
Large text sample
Normal body text sample — the quick brown fox jumps over the lazy dog.
What it measures: The contrast ratio between text and its background, from 1:1 (no contrast) to 21:1 (black on white), using the official WCAG relative-luminance formula.
The thresholds: WCAG AA requires 4.5:1 for normal text and 3:1 for large text (18pt, or 14pt bold). AAA requires 7:1 and 4.5:1. Meeting AA is the common legal and design baseline.
Why it matters: Low contrast is one of the most common accessibility failures, making text hard to read for people with low vision or on glary screens.
Privacy: Everything is computed locally in your browser. Nothing is sent to a server.