Color Contrast Checker
Check whether your text and background colors meet WCAG 2.1 accessibility contrast requirements. Enter any two hex colors (or pick them visually) to get the exact contrast ratio and instant pass/fail results for AA and AAA levels at both normal and large text sizes, with a live preview of the color pairing. Essential for accessible, readable web design — computed entirely in your browser.
How to Use Color Contrast Checker Online (Free & Client-Side)
Color Contrast Checker runs 100% locally in your web browser. Follow these 3 simple steps to process your files or data in seconds without uploading to external servers.
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Step 1: Input Data or File
Drop your file, paste text, or set parameters into the Color Contrast Checker interface above. Files are read directly from local memory.
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Step 2: Instant Local Execution
Hardware-accelerated WebAssembly processes your input instantly with zero network delay and zero server queue waiting.
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Step 3: Export & Download
Instantly download or copy your processed result. No watermarks, no registration, and no file size paywalls.
Zevylo vs Legacy Online Tools Comparison
See why privacy-conscious professionals choose Zevylo over legacy cloud-upload sites:
| Comparison Factor | Zevylo (Color Contrast Checker) | Legacy Competitors (Ezgif, iLovePDF, CloudConvert) |
|---|---|---|
| Data Storage & Privacy | 100% In-Browser (0 bytes uploaded) | Transferred to external cloud servers |
| Processing Speed | Instant (No network upload wait) | Throttled by internet upload speeds |
| File Size Limits | Unlimited (Device RAM capacity) | Capped (often 25MB - 100MB max) |
| Cost & Paywalls | 100% Free & Unlimited | Daily quotas, wait timers, or paid subscriptions |
| Ad Clutter & CLS | Zero disruptive banner popups (CLS = 0) | 5-8 intrusive ads, video overlays & layout shifts |
| International Accessibility | Worldwide multi-language support (12 languages) | Limited language options or paid localization |
Learn the Working Mechanisms & RFC Web Standards Behind Color Contrast Checker
Read our dedicated technical article covering algorithms, browser privacy, specifications, and advanced workflows.
Frequently Asked Questions
QWhat contrast ratio do I need?
WCAG AA requires at least 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.
QWhat counts as "large text"?
Text that is at least 24px regular weight, or at least 18.66px (14pt) bold.
QHow is the ratio calculated?
It uses the official WCAG 2.1 formula: relative luminance of each color is computed, then the ratio is (lighter + 0.05) / (darker + 0.05).
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