WCAG Color Contrast Checker (AA / AAA)

Check text/background contrast against WCAG 2.1 AA and AAA - live preview

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注意: 下記のツールインターフェースは現時点で英語のみに対応しています。UI の翻訳は順次進めています。 このツールを英語で見る →
The quick brown fox jumps over the lazy dog - 0123456789
14.33:1
Contrast ratio · Normal text
AA (normal ≥ 4.5)PASS
AA large (≥ 3)PASS
AAA (normal ≥ 7)PASS
AAA large (≥ 4.5)PASS

Uses the WCAG 2.1 sRGB relative-luminance formula. “Large text” is 24px (18pt) regular or 18.66px (14pt) bold.

使い方

  1. 1
    Pick foreground and background

    Type HEX or use the color pickers. Alpha is supported and blended over the background.

  2. 2
    Read the ratio

    The exact contrast ratio appears with AA / AAA pass/fail badges for normal and large text.

  3. 3
    Nudge until it passes

    Sliders adjust lightness in tiny steps so you can find the closest passing shade.

WCAG Color Contrast Checker (AA / AAA) について

Free WCAG color contrast checker. Pick foreground and background colors to see the exact contrast ratio (per WCAG 2.1 relative luminance) and pass/fail badges for AA, AA Large, AAA, and AAA Large. Live preview of real text at the actual colors. Runs entirely in your browser. 712 Tools の WCAG Color Contrast Checker (AA / AAA) はモダンな JavaScript API を使って完全にブラウザ内で動作します - サーバーがあなたのデータを見ることは一切ありません。つまり、即時の結果、完全なプライバシー、アップロード制限なしです。

デバッグ、簡単な確認、あるいは本番のインシデント対応まで - このツールは何度でも無料で使えます。ウォーターマークなし、サインアップなし、ツール内広告なし。

よくある質問

What ratios does WCAG require?

AA needs 4.5:1 for normal text and 3:1 for large. AAA needs 7:1 for normal and 4.5:1 for large. 'Large' is 18pt (24px) regular or 14pt (18.66px) bold.

Which luminance formula is used?

The WCAG 2.1 sRGB relative-luminance formula - the same one webaim.org and axe use. Results match to the fourth decimal.

What about APCA?

APCA (the proposed WCAG 3 algorithm) isn't included yet - it's still in draft. This tool sticks to the current WCAG 2.1 formula that accessibility auditors and lawyers actually cite.

続きを読む

5 分で読了

The WCAG color contrast checklist every designer should bookmark

AA vs AAA, the math behind the ratios, why gray-on-gray fails on retina screens, and the two-line HTML that makes a color contrast test run in seconds.

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