Luma / Brightness Checker

Check text contrast against backgrounds for WCAG accessibility compliance

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About This Tool

The Luma / Brightness Checker calculates the contrast ratio between a text color and background color (or image) to verify WCAG accessibility compliance. See instant pass/fail results for WCAG AA and AAA standards.

How to Use

  1. Select Background Type: Solid Color or Image.
  2. If using a solid color, pick a Background Color with the color picker. If using an image, upload an image file.
  3. Pick a Foreground (Text) Color using the text color picker.
  4. Click Check Contrast to see the contrast ratio and WCAG AA/AAA pass/fail status.

Why Choose OmniTools?

⚡ Instant Results

Zero server lag. All calculations run locally on your device for maximum speed.

🛡️ 100% Private

Your data never leaves your device. No uploads, no servers, no tracking.

Frequently Asked Questions

What is WCAG contrast ratio?

WCAG (Web Content Accessibility Guidelines) requires a minimum contrast ratio of 4.5:1 for normal text (AA) and 7:1 for enhanced accessibility (AAA). Large text requires 3:1 for AA.

What's the difference between AA and AAA?

WCAG AA is the standard compliance level required by most accessibility laws. AAA is the enhanced level providing better readability for users with visual impairments.

How is luminance calculated?

Relative luminance is calculated using the WCAG formula which applies gamma correction to RGB values and weights them by human perception (R: 0.2126, G: 0.7152, B: 0.0722).

Is this tool free?

Yes, completely free with no sign-up required. All processing runs in your browser.

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