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White Screen
Fills your entire screen with solid white. Cleaning the screen, spotting dust and dark…
Grey Screen
Fills your entire screen with solid grey. The best single colour for judging panel uniformity and for spotting dirty-screen effect on televisions.
Screen Tests
Nothing uploaded
No sign-up
Free, unlimited
Press Fullscreen, then look closely at the whole panel.
In short
A mid grey field is the single best colour for judging panel uniformity, and it is the one professional reviewers use. The reason is that uniformity faults are brightness variations, and the eye judges brightness differences most accurately in the middle of the range — a bright white field saturates the perception and hides small differences, while a dark field is too dim to compare across. Grey sits where the eye is most discriminating. What it reveals is the dirty screen effect: uneven patches and smears across the panel that look like the screen needs cleaning and do not wipe off. It is a manufacturing variation rather than a defect, present to some degree on nearly every large panel, and it is most visible during panning shots in sport, which is where people usually first notice it. Grey is also the best field for spotting OLED image retention, ahead of cyan. Judge it fullscreen, at your normal brightness, in a dimly lit room, and step back a metre or two — uniformity is a whole-panel judgement rather than a close-up one.
How to use the Grey Screen
- The test starts on its own — no button to press and nothing to install.
- Follow the prompt in the test panel and watch the readings update live.
- Press Reset to start over with a clean slate.
About the Grey Screen
The Grey Screen fills your entire screen with solid grey. The best single colour for judging panel uniformity and for spotting dirty-screen effect on televisions. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.
What people use it for
- The best single colour for judging panel uniformity and for spotting dirty-screen effect on televisions.
- Checking a monitor or phone screen before a return window closes.
- Using as a plain backdrop for photography or for cleaning the screen.
Press Fullscreen above before judging anything. A colour patch surrounded by page furniture tells you very little — the panel needs to be filling the whole screen, ideally in a dark room, with any night-light or blue-light filter switched off.
Frequently asked questions
What is the difference between a dead and a stuck pixel?
A dead pixel receives no power and stays black on every colour. A stuck pixel is latched on and shows the same bright red, green or blue dot against every background. Stuck pixels sometimes recover; dead ones never do.
How do I tell a dead pixel from dust?
Dust sits on the outside of the glass and moves or disappears when you wipe the screen with a microfibre cloth. A dead pixel does not move and stays in exactly the same position on every colour.
How many dead pixels before I can return a monitor?
That depends on the manufacturer's policy, which is usually written against the ISO 9241-307 pixel fault classes. Most consumer panels are sold to a standard that tolerates several sub-pixel faults, so check the specific warranty terms — and photograph what you find while the panel is still within the return window.
Is the Grey Screen free, or is there a paid tier?
Free, unlimited, and no email address required. You can use it a hundred times a day and nothing changes.
Does anything I enter leave my computer?
No. The Grey Screen runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
What problem does the Grey Screen solve?
The jobs it is built for: the best single colour for judging panel uniformity and for spotting dirty-screen effect on televisions. Checking a monitor or phone screen before a return window closes. Using as a plain backdrop for photography or for cleaning the screen. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Is there a catch?
Press Fullscreen above before judging anything. A colour patch surrounded by page furniture tells you very little — the panel needs to be filling the whole screen, ideally in a dark room, with any night-light or blue-light filter switched off.
Why does the test start on its own?
No installation, no extension and no driver. The Grey Screen uses the browser's own device APIs and begins as soon as the page loads, so there is nothing to press first. Press Reset at any point to start over with a clean slate.
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