Dead Pixel Test
Fill the whole screen with one colour at a time and look for the dots that do not change. Eight fills, and the colour ones are pure: the red really is #FF0000 and not a softened designer red, because a red with a little blue mixed into it is exactly where a stuck blue sub-pixel hides. The control bar fades after a few seconds of stillness so it is not sitting on top of the pixels you came to check, and it comes back the moment you move the mouse, tap the screen or press a key.
White: dead pixels show as black dotsClick a colour, or Space / → to step through. Esc leaves full screen.
The full sweep. Every fault this test can find shows on one of these.
- The sub-pixels get no power, so the dot stays black on every fill, white included. Warranty terms usually count these.
- One sub-pixel is always on, so the dot shows red, green or blue even on black. Stuck pixels sometimes free up; see the note below.
- Not a pixel fault: it moves or disappears when the screen is wiped. Try a soft dry cloth before making a claim.
Look, do not squint. Sit at your normal distance and let each colour hold the screen for a few seconds: a fault is easier to see when you are not hunting for it. A dead pixel stays black on all eight fills and will not recover. A stuck one sometimes frees up after a spell of colour cycling, which is what the every 3 seconds setting does for you, though nothing here can promise it. The pixel count above is the screen’s own report, which is the figure to use when a warranty quotes a threshold per million pixels.
Accuracy. The colours are pure full-screen fills, which is all the test needs. Whether a pixel is dead or stuck is your eye's call; the notes say what each looks like.
Common questions
- What is the difference between a dead pixel and a stuck pixel?
- A dead pixel gets no power, so it is black on every fill, white included. A stuck pixel has one sub-pixel jammed on, so it shows as a red, green or blue dot, and it is most obvious on black. The quickest way to tell them apart is to look at white and then at black: a dot that is dark on white and invisible on black is dead, and a dot that is coloured on black is stuck. A third possibility is neither, which is why the page lists dirt as a case: a mark that moves or disappears when you wipe the screen was never a pixel fault.
- Can a stuck pixel be fixed?
- Sometimes. A sub-pixel that is jammed on will occasionally free up after a long spell of colour changes, and the Advance control here will cycle the fills for you at three seconds each so you can leave it running. It is not reliable and nothing on this page can promise it. A dead pixel is a different matter: it has no power reaching it, and cycling colours does nothing for it.
- How many dead pixels are acceptable before a screen counts as faulty?
- There is no single answer, and anyone quoting you one number is guessing. Manufacturers publish their own thresholds and they differ by brand, by panel class and by where on the screen the fault sits, with several counting a bright stuck pixel more seriously than a dark dead one. Some state the limit as a count, others as a rate per million pixels. Find the display warranty text for your exact model and read the threshold it names. That is why this page reports your screen's own pixel count: it is the number a per-million threshold is measured against, and it is not the resolution most people would quote from memory.
- Does this work on a phone or a tablet?
- Yes. Tap anywhere to move to the next colour, and the control bar reappears with the tap so you can reach Exit. One limit worth knowing: some mobile browsers, iPhone Safari among them, do not give web pages true full screen. When the browser refuses, the test covers the tab instead and says so on screen, which means the strip behind the browser's own bars is not being tested. Everything the fill actually covers is tested the same way it is on a desktop.
- Why does the red look so harsh compared with other dead pixel pages?
- Because it is pure. Pleasant reds are mixtures: a typical interface red has green and blue in it as well, so filling the screen with one leaves every sub-pixel partly lit and a stuck blue pixel has somewhere to hide. Every fill here drives each channel either fully off or fully on, which is the whole point of the test. The one deliberate exception is 50% grey, which is not there to find single pixels at all: it is the fill on which uneven backlighting, clouding and banding show up, and neither pure black nor pure white shows those.
- Does anything about my screen leave my browser?
- No. The fills are drawn by your own browser, the resolution and pixel ratio are read from your own browser and used only to print the Screen line, and nothing is uploaded, stored or sent anywhere. There is no account and no upload step. Close the tab and there is nothing left behind.
The colours are pure full-screen fills, which is all the test needs. Whether a pixel is dead or stuck is your eye's call; the notes say what each looks like.