Color Contrast Checker

What is a Color Contrast Checker?

A color contrast checker measures the visual contrast between two colors — typically text and its background — and determines whether the combination meets accessibility standards set by the Web Content Accessibility Guidelines (WCAG). The contrast ratio is a mathematical calculation based on the relative luminance of each color, producing a number between 1:1 (no contrast) and 21:1 (maximum contrast, black on white or vice versa).

WCAG 2.1 defines specific contrast thresholds that ensure text is readable for people with normal vision and people with low vision or color vision deficiency. The two primary levels are AA (minimum) and AAA (enhanced). For normal text (under 18pt or 14pt bold), the AA minimum is 4.5:1 and AAA is 7:1. For large text (18pt+ or 14pt+ bold), the AA minimum is 3:1 and AAA is 4.5:1.

When Should You Check Color Contrast?

Color contrast checking should be part of every design and development workflow. Web designers testing color palettes for accessibility compliance. Frontend developers verifying that UI text meets WCAG standards before launch. Content creators ensuring blog and article text is readable. Marketing teams checking that promotional material is accessible to all audiences.

UX designers building inclusive interfaces test button text, form labels, error messages, and inactive text against their backgrounds. Product managers reviewing designs for accessibility before sprint planning. QA testers verifying accessibility requirements are met. Anyone creating digital content should verify contrast ratios.

How It Works

The checker converts your foreground and background colors to relative luminance values using the sRGB color space, then calculates the contrast ratio using the WCAG formula. It compares the ratio against the four WCAG thresholds (AA normal, AA large, AAA normal, AAA large) and shows pass/fail for each. The live preview shows your text on the background color in real time.

Limitations

This tool checks color contrast only — it does not test font size, weight, or rendering quality, which also affect readability. The contrast calculation uses the sRGB color space, which is standard for web content but may not match print or wide-gamut displays. Some edge cases with very dark or very light colors may produce unexpected ratios due to floating-point precision. The tool does not test non-text elements like icons, borders, or focus indicators.

Tips for Best Results

Aim for AAA compliance whenever possible — it provides a better experience for all users, not just those with accessibility needs. Test all interactive elements: buttons, links, form inputs, and focus states. Remember that contrast applies to all text, including default text in form fields and disabled button text. Use this tool alongside a color blindness simulator to ensure your palette works for all users.