It evaluates the contrast on all elements of the page considering their computed style for the color and background-color CSS properties. In case of these colors are defined with RGBA values, it also considers the opacity to deduce the real color that finally is show. The tool also includes two fields in which the colors can be introduced manually to be tested. Finally, it auto-refreshes when DOM
![WCAG Contrast checker – Get this Extension for 🦊 Firefox (en-US)](https://cdn-ak-scissors.b.st-hatena.com/image/square/96f90dafaf6a2bcc6957c89f96541badb2d7d033/height=288;version=1;width=512/https%3A%2F%2Faddons.mozilla.org%2Fuser-media%2Fpreviews%2Ffull%2F198%2F198920.png%3Fmodified%3D1622132253)