How to run a dead pixel test
- Clean the screen with a dry microfibre cloth so dust does not fool you.
- Set the brightness to normal or high and turn off Night Light, Night Shift, f.lux or True Tone, which tint the white.
- Press Start full screen test. On a phone, turn it sideways first.
- On each colour, scan the screen in rows from about 50 cm away, then check the corners and edges up close.
- When you see a suspect dot, long-press it (touch) or right-click it (mouse). A circle marks it without covering the pixel.
- Step through all six colours. A pixel can look fine on black and wrong on white.
Every colour fills each physical pixel, whatever your display scaling is, so even a 4K panel at 150% is fully covered.
Dead, stuck or hot: what you are looking at
| Fault | How it looks | Best colour to spot it | Can it recover? |
|---|---|---|---|
| Dead pixel | Always black | White, gray | Rarely |
| Stuck pixel | Always red, green, blue or a mix | Black, and the other two primaries | Sometimes |
| Hot pixel | Always white | Black | Rarely |
| Stuck subpixel | One colour missing, so white looks tinted at one dot | White, red, green, blue | Sometimes |
Each pixel on an LCD or OLED is made of three subpixels: red, green and blue. A dead pixel gets no signal, so it stays dark. A stuck pixel has one or more subpixels that stay on, so it glows one colour on black. A hot pixel has all three stuck on, so it is a white dot on black. On OLED screens, a whole pixel that stays dark is usually a failed emitter and will not come back.
Not every dot is a pixel fault
Dust on the glass wipes off. Dust trapped inside a laptop panel looks soft and grey, usually bigger than a single pixel, and is easiest to see on the white screen. Bright patches at the edges on black are backlight bleed, which you can check on the black screen.
Making a defect map for a return
Most return and warranty desks ask where the faults are. After marking, set the Type for each one, add the model and serial number in Notes, and press Download defect map. You get a PNG with the screen outline, numbered circles, pixel positions and your notes. In full screen the positions are real screen pixels from the top-left corner. Attach a close photo of the screen as well: set your phone camera to a low exposure, show the colour where the fault is clearest, and hold the phone close and square to the screen.
Your marks are saved in this browser only, so you can close the page and come back. Clear marks removes them.
How many dead pixels are allowed?
The old ISO 13406-2 standard set four pixel fault classes. Class II, which most monitors used, allowed per million pixels up to 2 always-lit pixels, 2 always-dark pixels and 5 faulty subpixels. A 2560 x 1440 monitor has about 3.7 million pixels, so it could pass with 7 bright and 7 dark pixels. ISO 9241-307 replaced that standard in 2008 and keeps a similar class idea, but makers rarely quote it now. What counts in practice is your brand's own pixel policy and the shop's return window. Some premium lines promise replacement for a single bright pixel, and a shop return within the first weeks is usually easier than a warranty claim, so test a new screen on the day it arrives.
Can a stuck pixel be fixed?
Sometimes. A stuck subpixel can free up after the liquid crystal around it is driven on and off quickly, which is what the fixer does. Place the flashing square over the marked pixel and let it run for 10 to 20 minutes, then test again. It does not help a dead pixel, and success reports are anecdotal. Avoid pressing hard on the panel or rubbing it with a pen: it can make things worse and may void the warranty.
More screen checks
Measure your monitor's refresh rate with the refresh rate test, and see the webcam test if you are setting up a laptop.
Questions
How do I check my monitor for dead pixels?
Press "Start full screen test", then click or press the right arrow to step through black, white, red, green, blue and gray. Look over the whole screen on each colour from about 50 cm away. A dot that stays black, or stays one colour, is a faulty pixel.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel stays black on every colour because it gets no power. A stuck pixel stays red, green or blue, or a mix, because one or more of its subpixels is stuck on. A hot pixel stays white on every colour. Stuck pixels can sometimes recover; dead pixels almost never do.
Can a dead pixel fix itself?
A truly dead pixel rarely comes back. A stuck pixel sometimes clears after hours of use, or after running the pixel fixer over it for 10 to 20 minutes. Results vary and nobody can promise it works, so mark the pixel and keep your proof first.
How many dead pixels are acceptable?
It depends on the maker. Under the old ISO 13406-2 Class II rules, used by most monitors, a 1920 x 1080 screen could have about 4 always-lit and 4 always-dark pixels before it counted as faulty. Many brands now publish their own, stricter policy, and some replace a screen for a single bright pixel.
Is it a dead pixel or dust?
A pixel fault is sharp and exactly one dot, and it stays put when you move your head. Dust on the surface wipes off. Dust inside a laptop panel looks soft and blurry, usually larger than a pixel, and shows best on the white screen.
How do I prove dead pixels for a return?
Mark each faulty pixel with a long-press or right-click, add a note, and press "Download defect map". Then photograph the screen showing the colour where the pixel is easiest to see, with your phone close to the screen. Send both with your return or warranty claim.
Does the dead pixel test work on phones and TVs?
Yes. On an Android phone, tablet or TV browser the test fills the screen. iPhones do not allow full screen for web pages, so the test fills the browser window; turn the phone sideways and the bars shrink. Check the edges separately.
Is the pixel fixer safe?
It cannot damage a screen; it only changes colours quickly. It is not safe for people with photosensitive epilepsy, because it flashes bright colours many times a second. That is why it never starts on its own, needs a tick in the box, and stops on any key.
More tests
Black screenA full black screen, one clickWhite screenA full white screen, one clickRefresh rate testYour monitor Hz, measured in the browser
Mouse testCheck every button, side buttons and the scroll wheel
Keyboard testPress every key, with ISO, AZERTY and QWERTZ layouts
Controller testButtons, sticks, triggers and vibration for any gamepad