Check relative luminance and brightness of any color to predict contrast on light or dark backgrounds. The Color Luminance Checker is one of 900+ free developer tools on Toolblip - all open to use without a signup.

Open the Color Luminance Checker on this page, paste or upload your input, and the result updates as you type. Use the copy button to grab the output, or adjust options to tune the result. Nothing you enter leaves your browser.

Yes. The Color Luminance Checker is a free online tool on Toolblip - no signup, no account, no hidden usage limits. It runs in your browser and works on desktop and mobile.

Yes. The Color Luminance Checker processes your data entirely client-side, so nothing you paste is uploaded or stored on any server. It's safe to use with internal snippets, private keys for debugging, or any other sensitive content you'd rather not send to a remote service.

The Color Luminance Checker works with the formats web developers reach for every day - HEX, RGB / RGBA, and HSL. You can copy any value with one click for use in CSS, design tools, or code.

Once the page has loaded, the Color Luminance Checker continues to work without an internet connection. Bookmark this page and return to it anytime - all logic runs locally.