What Is a Color Contrast Checker?
A color contrast checker measures the contrast ratio between two colors to determine if text will be readable against its background. This is essential for meeting WCAG (Web Content Accessibility Guidelines) — the international standard for web accessibility. Poor contrast makes content unreadable for millions of users with low vision or color deficiencies.
This tool calculates the contrast ratio in real time, tells you whether your color combination passes WCAG AA and AAA standards for both normal and large text, and lets you fine-tune colors until they meet accessibility requirements.
WCAG Contrast Requirements
| Level | Normal Text | Large Text |
|---|---|---|
| AA (minimum) | 4.5 : 1 | 3 : 1 |
| AAA (enhanced) | 7 : 1 | 4.5 : 1 |
Tips for Accessible Color Choices
- → Don't rely on color alone. Always pair color with text labels, icons, or patterns so color-blind users can distinguish elements.
- → Test both themes. If your site has light and dark modes, check contrast in both. Colors that pass on white may fail on dark backgrounds.
- → Use our Color Blindness Simulator to see how your palette looks to users with different types of color vision deficiency.
How to Use This Contrast Checker
- Enter your foreground color — Paste the hex code or pick the text color you're using.
- Enter your background color — Paste the hex code or pick the background color behind the text.
- Read the contrast ratio — The tool calculates the WCAG contrast ratio and shows whether your combination passes AA and AAA standards for both normal and large text.
- Adjust until you pass — If your colors fail, adjust the lightness of either color until the ratio meets your target level.
Tips and Best Practices
- → Aim for 4.5:1 minimum. WCAG AA requires 4.5:1 for normal text and 3:1 for large text (18px+ bold or 24px+ regular). AAA requires 7:1 and 4.5:1 respectively.
- → Test all color combinations. Don't just test primary text on the main background. Check link colors, placeholder text, disabled states, error messages, and text over images or gradients.
- → Increase contrast, not just color difference. Two bright colors can have high color difference but low luminance contrast. The contrast ratio measures luminance, which is what actually affects readability.
- → Use our Color Blindness Simulator too. Good contrast doesn't guarantee good color distinction. Users with color vision deficiency need both sufficient contrast AND non-color visual cues. Try our Color Blindness Simulator.
See also: After generating a dark theme, the Dark Mode Generator validates that each colour pair still meets WCAG contrast.
Related tools
- Contrast measures legibility; perceptual difference measures consistency. For QA against brand drift use the Perceptual Color Difference tool with CIEDE2000.
- For auditing an entire palette in one view, the Palette Contrast Matrix generates every possible N-by-N foreground-background pair in a single grid.
Frequently Asked Questions
Built by Derek Giordano · Part of Ultimate Design Tools