Color Contrast Checker (WCAG 2.1)
Ensure inclusive, accessible web design by calculating exact relative luminance and WCAG 2.1 contrast ratios between text and background colors in real time.
At a glance
Color Contrast Checker (WCAG 2.1) is a free web tool that tests color contrast ratios according to WCAG 2.1 guidelines. It mathematically calculates relative luminance and precise contrast ratios ranging from 1.00:1 to 21.00:1. Real-time interactive UI preview testing headings, paragraphs, primary filled buttons, outline buttons, and forms. All processing is local: nothing is uploaded, and no account is required.
100% In-Browser WCAG 2.1 Color Contrast Checker
Calculate exact relative luminance and contrast ratios, audit WCAG 2.1 AA/AAA compliance, auto-tweak colors, and simulate color blindness.
Color Selection
WCAG 2.1 Compliance Audit
Design With Clarity & Inclusive Contrast
Web accessibility ensures that all users, including individuals with low vision, aging eyes, or color vision deficiency, can easily consume your content.
WCAG Success Criterion 1.4.3 requires a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text to guarantee readability across all monitors and lighting conditions.
Why Use This Color Contrast Checker (WCAG 2.1)?
How to Use Color Contrast Checker (WCAG 2.1)
Select Text and Background Colors
Use the interactive color pickers or type in 6-digit hex codes for your foreground text and background colors.
Review Contrast Ratio & WCAG Score
Inspect the calculated contrast ratio banner and check the compliance matrix for AA and AAA certification.
Test in UI Playground or Click Auto-Fix
Inspect how your colors render in real buttons and form inputs, or click "Auto-Fix (AA)" to intelligently nudge lightness into compliance.
Worked example: Mid-Gray on White WCAG Verdict (4.54:1)
The engine computes relative luminance with sRGB linearization, derives ratio as (L1+0.05)/(L2+0.05), and gates against WCAG thresholds.
text: #767676 on background: #FFFFFF
Contrast ratio: 4.54:1 - AA normal text: PASS (needs 4.5), AAA: FAIL (needs 7.0); large text: PASS
Technical Specifications & Engine Details
| Specification | Details |
|---|---|
| Supported Formats | HEX, RGB, COLOR → RATIO, WCAG, REPORT, TEXT |
| Execution Mode | 100% Client-Side In-Browser (client) |
| Browser Requirements | Requires modern web browser with ECMAScript 6+ and standard DOM Web APIs. |
| Performance Constraints | Client browser memory limit (typically 1–2 GB RAM); processing speed depends on local device CPU. |
100% Client-Side Privacy Guarantee
All calculations, color parsing, and simulations run entirely in your local browser memory. Zero data is sent to external servers.
Frequently Asked Questions
What is the difference between WCAG AA and AAA contrast requirements?
What qualifies as "Large Text" under WCAG guidelines?
How does the Smart Auto-Fix feature work?
Why should graphical objects and UI components meet 3:1 contrast?
Methodology
Rankings and recommendations here are never paid for.
Last updated .