Check a background and text color pair against WCAG 2.1 contrast requirements. Get the exact ratio and a pass/fail for AA and AAA.
WCAG (Web Content Accessibility Guidelines) defines a minimum contrast ratio between text and its background so people with low vision or color blindness can still read it. The ratio ranges from 1:1 (no contrast) to 21:1 (pure black on pure white).
| Level | Normal text | Large text (18px+ bold, or 24px+) |
|---|---|---|
| AA (minimum) | 4.5 : 1 | 3 : 1 |
| AAA (enhanced) | 7 : 1 | 4.5 : 1 |
Most organizations only need to meet AA — it's the level referenced by most accessibility laws, including the European Accessibility Act (EAA), which took effect for many digital products and services in mid-2025. AAA is a stricter bar mainly used by government sites or products specifically designed for low-vision users.
Usually not. AA is the standard most legal and industry guidelines require. AAA is optional unless your product specifically targets accessibility-sensitive audiences (e.g. government, healthcare, or assistive-tech products).
Contrast ratio is calculated from relative luminance, not how different two hues look to the eye. Two colors can look visually distinct but still have low luminance contrast — for example, a mid-tone orange on a mid-tone blue often fails even though the hues are clearly different.
Large text (18.66px bold or larger, or 24px+ regular) has a lower required ratio — 3:1 for AA — because bigger text is easier to read at lower contrast. This tool checks against the normal-text thresholds; for large-text-only content, a 3:1 AA pass is generally enough.