Contrast Checker

Compute the WCAG contrast ratio between two colors and see which AA / AAA bars you pass. Fully local.

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.