Contrast Checker

How to use Contrast Checker

1. Open Contrast Checker — it runs entirely in your browser with no setup.
2. Paste or type your input into the text area, or upload a file where supported.
3. Set any options you need. The result appears in the output panel — there is no upload step and no waiting on a server.
4. Review the output instantly; large inputs are handled locally without lag.
5. Copy the result to your clipboard or download it. Your data never leaves the page.

Why use Contrast Checker?

• 100% free with no limits, no sign-up and no watermarks.
• Private by design — your data are processed in your browser and never uploaded to a server.
• Fast and lightweight, with instant results even on a phone or a slow connection.
• Works everywhere — any modern browser on Windows, macOS, Linux, Android or iOS.
• Part of a full color tools suite, so related contrast checker tasks are one click away.

What people use Contrast Checker for

• Checking whether body text passes WCAG AA against its background.
• Testing a brand colour before using it for links or buttons.
• Fixing an accessibility audit failure on text contrast.

Contrast Checker: limits and things worth knowing

• WCAG 2.x requires a contrast ratio of at least 4.5:1 for normal text and 3:1 for large text at AA. AAA raises these to 7:1 and 4.5:1.
• Large text means 18pt (24px) or 14pt (18.66px) bold and above. That threshold is why a heading can pass where the same colour fails in body copy.
• Ratios run from 1:1 (identical) to 21:1 (black on white). The calculation uses relative luminance, not simple brightness, which is why two colours that look equally bright can score very differently.
• Non-text elements — icons, input borders, focus indicators — need 3:1 under WCAG 2.1's 1.4.11, a criterion that is very widely missed.
• WCAG 3.0 proposes APCA, a perceptually different model that accounts for text size and weight. It is still a draft; 2.x remains the standard to conform to.

Sources

• WCAG 2.2 — Contrast (Minimum) 1.4.3
• WCAG 2.2 — Non-text Contrast 1.4.11

Is it private and secure?

Your privacy is built in. Contrast Checker runs completely on your device, so whatever you enter stays in your browser and is never transmitted, logged or stored on any server.

Network activity: none. Nothing is sent and nothing is fetched. This tool makes no network request at all once the page has loaded — which is why it keeps working if your connection drops.

You do not have to take that on trust — our privacy proof page publishes the Content-Security-Policy that enforces it, lists every third party it permits, and shows how to verify the whole claim yourself.

Learn more

Why Browser-Based Tools Are Safer for Your Files — Most online converters upload your files to a server. Client-side tools don't. Here's why that difference matters for privacy.