WCAG 2.1 Contrast Checker
Test accessibility contrast ratio between text color and background, verify AA / AAA compliance for web UI design, support transparent RGBA colors, no data upload to server.
Foreground Text Color
Background Color
Sample Text ABC 123
Contrast Ratio:
21:1
Pass all WCAG AA & AAA standards
Normal Text (≥4.5:1)
PASS
Large Text (≥3:1)
PASS
Graphical Objects / UI Components (≥3:1)
PASS
Final RGBA Values:
text: rgba(0,0,0,1); background: rgba(255,255,255,1)
How to Use This WCAG Contrast Checker
This accessibility checker follows official WCAG 2.1 AA / AAA color contrast standards for website development. All luminance and ratio calculations run locally in your browser without sending any color data to server.
- Pick text foreground and background color via color picker or input HEX code manually
- Adjust alpha transparency to test semi-transparent overlay text effect
- Real-time preview shows actual display effect of text on background
- Tool auto calculates contrast ratio and judges compliance for normal text, large text and UI graphics
- Copy final RGBA color codes for direct use in your CSS stylesheet
WCAG Standard Rules:
- Normal small text: Minimum contrast ratio 4.5:1 (AA standard)
- Large text (18pt / 14pt bold): Minimum contrast ratio 3:1
- UI borders, icons and graphical controls: Minimum 3:1 contrast ratio
Frequently Asked Questions
WCAG 2.1 requires at least 4.5:1 contrast for regular body text to ensure readability for visually impaired users. Large text only needs 3:1 ratio.
Yes, this tool fully supports alpha transparency channel, it blends foreground and background color automatically to compute accurate real-world contrast ratio.
100% free unlimited usage, no login, no sign-up, no hidden fees. All calculations processed offline inside browser, zero data upload.