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ToolWrenCheck whether your text and background colors meet WCAG accessibility contrast requirements, with a live preview.
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Contrast is a free, private online tool that lets you check the WCAG contrast ratio between text and background colors, with AA and AAA pass/fail grades. It runs entirely in your browser, so nothing you enter is uploaded to a server.
Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.
Low contrast between text and its background makes content hard to read, especially for users with low vision. The WCAG accessibility guidelines define minimum contrast ratios that good designs should meet.
WCAG sets thresholds: 4.5:1 for normal text and 3:1 for large text at level AA, and 7:1 (normal) / 4.5:1 (large) at the stricter AAA level. This checker grades your colors against all four.
Enter or pick a text and background color and the tool computes the exact contrast ratio using the official relative-luminance formula, then shows pass/fail for each WCAG level with a live preview.
A contrast checker measures how different a text color is from its background, expressed as a ratio from 1:1 (identical) to 21:1 (black on white). Sufficient contrast is what makes text readable, especially for people with low vision, in bright sunlight, or on poor-quality screens. It is one of the most important and most overlooked aspects of accessible design.
The Web Content Accessibility Guidelines (WCAG) set minimum contrast ratios that good designs should meet. For normal text the thresholds are 4.5:1 for level AA and 7:1 for AAA; large text (roughly 18pt, or 14pt bold) needs only 3:1 for AA and 4.5:1 for AAA. This tool grades your color pair against all of these and shows a clear pass or fail for each.
Contrast is based on relative luminance - a measure of how much light each color emits, weighted for how the human eye perceives red, green and blue (we are most sensitive to green). The ratio compares the lighter and darker luminances using the official WCAG formula. This is why two colors that look similarly bright can still fail: perceived brightness and measured luminance are not the same.
Accessible contrast is not only for users with visual impairments - it helps everyone reading on a phone outdoors, on a dim laptop, or while tired. Many countries also legally require accessible websites, and search and platform guidelines increasingly reward accessibility. Checking contrast early prevents costly redesigns later.
Contrast is necessary but not sufficient for accessibility: also consider font size and weight, line spacing, and never relying on color alone to convey meaning (pair it with text or icons). Use the live preview here to judge real readability, and the AA/AAA grades to confirm you meet the standard. Everything runs in your browser.