Understanding Color Contrast
Color contrast is fundamental to web accessibility. When text doesn't have enough contrast against its background, it becomes difficult or impossible for many people to read — including those with low vision, color blindness, or anyone using a screen in bright sunlight.
WCAG Contrast Requirements
The Web Content Accessibility Guidelines (WCAG) 2.1 specify minimum contrast ratios for text:
| Level | Normal Text | Large Text |
|---|---|---|
| AA (Minimum) | 4.5:1 | 3:1 |
| AAA (Enhanced) | 7:1 | 4.5:1 |
What is Large Text?
Large text has relaxed contrast requirements because bigger characters are easier to distinguish:
- Regular weight: 18pt (24px) or larger
- Bold weight: 14pt (18.5px) or larger
Beyond Text: UI Components
WCAG 2.1 also requires a minimum 3:1 contrast ratio for:
- User interface components (buttons, form fields, focus indicators)
- Graphical objects (icons, charts, infographics)
Tips for Better Contrast
- Test early: Check contrast during the design phase, not after development
- Consider context: Text over images may need a semi-transparent overlay
- Don't rely on color alone: Use icons, underlines, or other visual cues alongside color
- Test with real users: Automated tools catch many issues, but user testing reveals more
Frequently Asked Questions
What is color contrast ratio?
Color contrast ratio measures the difference in luminance (brightness) between two colors. It's expressed as a ratio like 4.5:1, where higher numbers indicate greater contrast. The maximum possible ratio is 21:1 (black on white), and the minimum is 1:1 (identical colors).
What are WCAG AA and AAA standards?
WCAG (Web Content Accessibility Guidelines) defines two conformance levels for color contrast. AA requires 4.5:1 for normal text and 3:1 for large text. AAA requires 7:1 for normal text and 4.5:1 for large text. AA is the standard requirement for most websites, while AAA provides enhanced accessibility.
What counts as large text?
Large text is defined as 18pt (24px) or larger for regular weight, or 14pt (approximately 18.5px) or larger for bold text. Large text has lower contrast requirements because larger characters are easier to read.
Why is color contrast important?
Good color contrast ensures that text is readable by people with low vision, color blindness, or those viewing screens in bright environments. Poor contrast can make content inaccessible to millions of users and may violate accessibility laws like the ADA or Section 508.
Does this tool work offline?
Yes! This tool runs entirely in your browser with no server required. Once loaded, it works without an internet connection and your color choices are never sent anywhere.
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