I bought a used monitor a while back and did what everyone tells you to do first: pull up an online "dead pixel test" and cycle through some solid colors before deciding whether to keep it. It worked, but afterward I was curious why every single one of these tools looks identical — same handful ...
Source: [Dev.to](https://dev.to/begoodtool/dead-pixel-test-sites-are-just-colored-divs-the-actual-engineering-problem-is-the-fullscreen-api-2a22)