Millions search "white screen for video call" or "dead pixel test" and end up downloading sketchy apps. ScreenTools fixes that — 96 browser-native tools in one bookmark. Use your display as a video-call key light, monitor diagnostic, classroom timer, fake Windows update prank, DVD screensaver, or OLED sleep soundscape. Everything renders live in your tab. No install, no account, no ads. Open, press F, done. Built because I got tired of single-purpose apps for things a browser tab does better.