Color Contrast Checker

It is a number describing how different two colours are in brightness, ranging from 1 to 1 for identical colours up to 21 to 1 for black on white. Higher ratios mean text is easier to read against its background.

WCAG AA requires at least 4.5 to 1 for normal text and 3 to 1 for large text. The tool shows whether your colour pair meets these thresholds.

AAA is the stricter standard, needing 7 to 1 for normal text and 4.5 to 1 for large text, while AA is the common baseline at 4.5 to 1 and 3 to 1. The checker reports pass or fail for both levels.

Large text is generally about 18 point or 24 pixels, or 14 point bold, which is roughly 18.66 pixels bold. Larger text is easier to read, so it has a lower contrast requirement.

It compares the relative luminance of the two colours using the WCAG formula, then expresses the difference as a ratio. The tool computes this from the colour values you enter.

No. The calculation runs entirely in your browser, so the colours you test are never uploaded. It works offline once loaded.

Normal text has a higher contrast requirement than large text, so a moderate ratio can clear the large-text bar while missing the normal-text bar. Increasing the contrast or enlarging the text can resolve it.