Color Contrast Checker

This accessibility compliance tool evaluates color contrast ratios between foreground text and background colors, determining whether combinations meet WCAG (Web Content Accessibility Guidelines) standards for readability by users with visual impairments. The checker calculates relative luminance for each color, applies the WCAG contrast ratio formula: (L1 + 0.05) / (L2 + 0.05) where L1 is lighter color and L2 is darker, then compares results against minimum thresholds: 4.5:1 for normal text AA compliance, 7:1 for AAA compliance, and reduced requirements for large text over 18pt or bold 14pt.

Luminance calculation converts RGB values through gamma correction and weighted channel summation reflecting human eye sensitivity where green contributes most to perceived brightness: L = 0.2126×R + 0.7152×G + 0.0722×B, with RGB values first linearized from sRGB's gamma-encoded representation. The mathematical rigor ensures objective accessibility measurement matching how visually impaired users experience contrast, particularly those with low vision, cataracts, or age-related contrast sensitivity loss.

The interface accepts colors via hex codes, RGB values, or color picker inputs, immediately calculating contrast ratios and displaying pass/fail indicators for each WCAG level (A, AA, AAA) across normal and large text categories. Visual previews render sample text in foreground/background combinations enabling subjective verification alongside numerical compliance. Recommendations suggest alternative colors maintaining aesthetic intent while improving ratios when failures occur. Common applications include auditing website accessibility before launch, comparing marketing materials for inclusivity, validating UI component libraries against accessibility standards, or designing presentations ensuring projection visibility. Advanced features support batch checking entire color palettes against background options, generating accessible color variations, or exporting compliance reports documenting accessibility due diligence. All calculations execute client-side, maintaining privacy for proprietary brand colors under development.