ScreenTail is a set of free browser tools for testing and using screens.
Everything here runs in your browser. There is no account to create, nothing to install, no email to hand over, and no file leaves your machine. Open a page, use the tool, close the tab.
Where it came from
The site began with a broken monitor and a search that went nowhere. Checking for dead pixels should take thirty seconds: fill the screen with one colour at a time and look at it. Instead the results were a mix of pages that wanted an app installed, pages buried under advertising, and pages that showed a colour but nothing else — no way to step through a sequence, no guidance on what a fault actually looks like, no next step once you found one.
That gap turned out to be the whole idea. The individual tools are simple by nature. What was missing was somewhere that had all of them, that loaded instantly, and that told you what to do next.
There are now 43 tools across 9 areas: solid colour screens, display diagnostics, lighting for video calls, screensavers, focus timers and ambient noise, colour utilities, wallpaper generation, screen information, and a set of prank screens. The diagnostics are the ones the site is really built around — dead pixel and stuck pixel tests, backlight bleed, screen uniformity, OLED burn-in, and a guided walkthrough that runs them in sequence for anyone who is not sure where to start.
Three things guide how it is built
It should be fast
Pages carry no framework, no web fonts, and a strict limit on how much code each one may ship — measured in bytes and enforced automatically on every change. A tool that renders a coloured rectangle should not take a second to arrive.
It should be honest about its limits
A browser cannot measure the light coming off your panel, and a web page cannot tell you whether a fault is covered by your warranty. Where a tool can only show you something rather than measure it, the page says so.
It should be safe to use
The stuck pixel tool flashes rapidly, so it sits behind a warning that has to be dismissed deliberately, every time, and it cannot start if that step is skipped. The audio tools start quietly, fade in, and will not play at full volume however the controls are set. None of this is visible when it works, which is rather the point.
How it is paid for
The site is run by one person and paid for by nothing at present. In time there will be advertising on the written guides and, where a tool leads naturally to a purchase, links that may earn a commission. Neither will appear inside a tool while it is being used, and neither will change what the tools tell you.
If something is broken, missing, or wrong, there is a contact address on the contact page. Reports of tools behaving oddly on unusual hardware are especially welcome — that is exactly the thing one person with two monitors cannot test alone.