Color Contrast Checker
Check foreground-background color contrast against WCAG 2.1 AA and AAA thresholds for text and UI.
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浏览器内运行这个工具能做什么
Enter two colors and instantly see the WCAG 2.1 contrast ratio plus pass/fail results for normal text, large text, and non-text UI components.
It flags compliance with WCAG 2.1 AA and AAA thresholds for normal text (4.5:1, 7:1), large text (3:1, 4.5:1), and non-text UI (3:1).
这个工具可以完成什么
Color Contrast Checker computes the exact luminance-based contrast ratio between a foreground and background color.
依赖结果前需要检查什么
- Performance and maximum practical input size depend on browser memory, device speed, and the structure of the input.
- Review the generated result before replacing or publishing an original file.
如何使用
- 1
Pick foreground and background colors using the color picker or paste a hex/rgb value.
- 2
Read the ratio and AA/AAA indicators — all thresholds are shown side-by-side.
- 3
Press Swap colors to quickly invert and re-check.
常见问题
What's the difference between AA and AAA?
AA is the baseline required by most accessibility regulations. AAA is a stricter enhanced level. For normal text, AA is 4.5:1 and AAA is 7:1; for large text, AA is 3:1 and AAA is 4.5:1.
What counts as large text?
WCAG defines large text as at least 18pt (24px) regular, or 14pt (18.66px) bold. Anything smaller falls under the normal text thresholds.
How is the ratio calculated?
We follow WCAG 2.1's formula: convert each color to sRGB relative luminance, then compute (L1 + 0.05) / (L2 + 0.05) where L1 is the lighter of the two. The ratio ranges from 1:1 to 21:1.
下一步常用工具
如果还需要校验、转换或复用结果，可以继续打开相近的浏览器本地工具。