Short answer: our screen tools run in your browser, so they can show you what your screen does with solid colors and moving patterns. They can’t measure color accuracy or brightness, and we say so on each tool. Our fix guides are based on manufacturer documentation and established fixes, not hands-on hardware testing.
How the screen tools work
Take the dead pixel test. It fills the screen with one solid color at a time (nine in total, including black, white, red, green and blue) using your browser’s full-screen mode. You step through with a tap, the arrow keys or the space bar, or let it cycle every 4 seconds. Black shows stuck pixels best. White shows dead ones.
Nothing leaves your device. The page reads your screen resolution and pixel ratio so it can tell you how many physical pixels you’re checking, and that’s it.
The stuck pixel fixer flashes a small square of rapidly changing colors. It works on some stuck pixels and never on dead ones. Because it flashes, it carries a photosensitivity warning and won’t start until you press the button.
What the tools can’t do
A browser can only draw what your system sends it. So the tools can’t see HDR-only problems, faults above your current refresh rate, or issues in the monitor’s own scaler. Phones may add their own color processing. And none of this replaces a colorimeter for calibration. We don’t own one, so we don’t make calibration claims.
How we check the tools
Before a tool goes live, we open it on the devices and browsers we have and confirm the colors fill the screen, the controls work, and full-screen mode behaves. Known quirks get written on the page. Safari on iPhone can’t hide its address bar, for example, so the dead pixel test tells you to scroll to check the edges.
We check the tools in current Chrome, Edge, Safari and Firefox on desktop and phone.
Where fix guides come from
We haven’t hands-on tested monitors, laptops, phones, TVs or GPUs for our guides. Fix steps are based on manufacturer documentation and established fixes, and guides link the manufacturer or other named source where they use one. We don’t publish test results we haven’t produced.
We don’t run a lab. We don’t get review units from brands, and we don’t score or rank monitors we haven’t used.
Products we mention
Product suggestions are based on published specs, manufacturer documentation and named reviews. They show up only when a replacement makes sense, after the free fixes and warranty options.
Questions about a test or a result that doesn’t match yours? Tell us. Reports like that help us fix the tools.
