Free online WCAG 2.1 color contrast checker - Test AA/AAA compliance with real-time preview
WCAG 2.1 defines two conformance levels: Level AA requires normal text contrast ≥ 4.5:1 and large text (≥18pt or 14pt bold) ≥ 3:1; Level AAA requires normal text ≥ 7:1 and large text ≥ 4.5:1. The ratio is based on relative luminance, where 1:1 is no contrast and 21:1 is maximum (black on white).
Human eyes perceive brightness differently across colors. WCAG uses a relative luminance formula based on the sRGB color space, not simple visual judgment. For example, pure red (#FF0000) on white appears high contrast visually, but its actual ratio is only 4.03:1, failing AA for normal text because red has low luminance.
Level AA is the baseline compliance requirement — most accessibility laws (ADA, Section 508, EN 301 549) use AA as the minimum standard. Level AAA is an enhanced level providing greater accessibility, ideal for audiences with visual impairments. Generally, aim for at least AA compliance, and pursue AAA when possible.
♿ WCAG Contrast Checker has no usage limits — it's free and unlimited. Since processing is done client-side, speed depends on your device. For very large files, we recommend processing in batches for the best experience.
Yes. ♿ WCAG Contrast Checker is fully responsive and works on phones, tablets, and desktops. The interface adapts automatically to your screen size.
No. ♿ WCAG Contrast Checker uses client-side processing — everything runs in your browser. Your data never leaves your device, and the tool works even without an internet connection.
Yes, ♿ WCAG Contrast Checker is completely free to use. No registration or login required — all features are available immediately.
Absolutely. All processing happens locally in your browser. No data is sent to any server, so there's zero risk of data leaks. Your information stays completely under your control.
No. ♿ WCAG Contrast Checker is a web-based tool — just open it in your browser and start using it. No downloads, plugins, or extensions required.