Contrast Checker

About

Contrast Checker is a no-nonsense WCAG 2.1 contrast calculator that lives in your toolbar. Pick a foreground and a background — via the native color pickers or by typing a hex — and see the contrast ratio update in real time, alongside four pass/fail badges:

- Normal text · AA  (≥ 4.5:1)
- Normal text · AAA (≥ 7:1)
- Large text · AA   (≥ 3:1)
- Large text · AAA  (≥ 4.5:1)

Key features:
- Real-time ratio update as you type or pick
- Native browser color pickers for both foreground and background
- Live preview pane that actually applies the colors so you see what your users would see
- Swap-colors button for quickly auditing both directions
- Your last-used colors are remembered locally
- Pure WCAG 2.1 math (sRGB → linear → relative luminance → ratio) — no fancy "perceptual" tweaks

Zero host permissions. Zero analytics. Zero remote code. The whole calculator ships inside the extension package.