Are my files uploaded?

No. This tool runs entirely in your browser tab. Files are read from your disk into memory and the result is generated locally.

Is it free? Are there limits or watermarks?

Free and open source (MIT). There are no file-size caps, daily quotas, accounts or watermarks.

Does it work offline?

Yes, once the page (and any engine it needs) has loaded, it keeps working without a connection thanks to the service worker cache.

Home / Design / Colour Contrast Checker

Colour Contrast Checker

Check the WCAG contrast ratio of two colours for AA and AAA text.

Free, no uploads, no sign-up. Runs 100% in your browser.

How Colour Contrast Checker works

Relative luminance is computed for both colours and the ratio is compared with the WCAG limits: 4.5 for normal text and 3 for large text at level AA, 7 and 4.5 at AAA.

Input: Text. Output: Text.

How to use Colour Contrast Checker

Paste or open your text.
Adjust the options.
Copy or download the result.

Tips

Generated CSS works in every modern browser.
Exports are produced locally, so you can work offline.

Colour Contrast Checker FAQ

Are my files uploaded?: No. This tool runs entirely in your browser tab. Files are read from your disk into memory and the result is generated locally.
Is it free? Are there limits or watermarks?: Free and open source (MIT). There are no file-size caps, daily quotas, accounts or watermarks.
Does it work offline?: Yes, once the page (and any engine it needs) has loaded, it keeps working without a connection thanks to the service worker cache.

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