Contrast Ratio Checker calculates the relative luminance contrast between two colors following the WCAG 2.1 algorithm and reports whether the combination passes AA (4.5:1 for normal text, 3:1 for large text) and AAA (7:1 for normal text, 4.5:1 for large text) requirements. It uses the sRGB to relative luminance conversion with the gamma correction formula defined in the specification. The tool provides real-time preview of text on the background color and suggests the nearest passing color when the current combination fails.
Frontend developers validating accessible designs, UX designers checking color choices, and accessibility auditors reporting WCAG compliance findings. The tool runs entirely in your browser — your data never leaves your device.
Learn more about related topics: WCAG 2.1, Relative luminance, Color accessibility, AA/AAA compliance.
Contrast Ratio Checker is a free, browser-based developer tool on AIDToolStack. Check WCAG color contrast ratios between foreground and background colors. It requires no installation or sign-up and works entirely in your browser.
Yes, completely free. Contrast Ratio Checker has no usage limits, no account requirements, and no hidden fees. Use it as often as you need.
No, all processing happens locally in your browser. Your data never leaves your device and nothing is sent to any server.
Yes, it works in any modern browser on both desktop and mobile devices. No app download required — just open the page and start using it.
AIDToolStack tools run entirely in your browser with no server processing. This means faster results, complete privacy, and zero downtime. There are no ads blocking your workflow, and everything is free with no sign-up required.
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