WCAG Color Contrast Checker

Check WCAG 2.1 AA and AAA color contrast ratio between text and background. Live accessibility testing tool.

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主な特徴とプライバシー保証

  • ✓ 100%ブラウザ内完結: データは端末外に出ず、外部サーバーに送信されることはありません。
  • ✓ リアルタイム高速出力: ネットワーク遅延ゼロ、入力と同時に即時反映・高速コピー。
  • ✓ 永久無料＆制限なし: 会員登録不要、課金なし、1日の利用制限も一切ありません。
  • ✓ 標準規格準拠: RFC、ISO、W3Cウェブ標準仕様に厳密に準拠して設計されています。

Test text and background color accessibility contrast

Verify that your website color palette complies with WCAG 2.1 AA and AAA accessibility standards. Get exact contrast ratios and pass/fail indicators for normal and large text.

技術仕様とアーキテクチャ

Execution Environment:
100% Client-Side Browser Sandbox
Data Privacy:
Zero Server Storage / No Tracking
Processing Speed:
Real-time local CPU execution
Cross-Platform:
Works on Windows, macOS, Linux, iOS & Android

Local Processing for CSS Tools

This tool runs within your browser sandbox using modern Web APIs. Inputs are processed on your local device CPU, avoiding network latency and ensuring your data is never stored on external servers or accessible to third parties.

1

Provide Input

Enter, paste, or upload your data into the input field above.

2

Configure & Process

The tool immediately processes your input in real time according to your chosen settings.

3

Copy or Save

Use the Copy button to copy the output to your clipboard, or download the result to your device.

開発者メモ: All operations execute locally in your browser memory for maximum speed and data privacy.

主な利用シーン

  • Audit UI color schemes for Web Accessibility (WCAG 2.1)
  • Ensure button labels and body text remain readable for vision-impaired users
  • Select accessible dark mode and high-contrast theme palettes

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よくある質問

What is the minimum WCAG contrast ratio for normal text?
WCAG 2.1 Level AA requires a contrast ratio of at least 4.5:1 for normal text (under 18pt / 24px) and 3.0:1 for large text.
What ratio is required for Level AAA compliance?
Level AAA requires a contrast ratio of 7.0:1 for normal text and 4.5:1 for large text.
How is contrast ratio calculated?
The contrast ratio is calculated using relative luminance values (L1 + 0.05) / (L2 + 0.05) as defined by the W3C WCAG specification.