Dead Pixel Test
You just unboxed a monitor, or you are about to buy a used one. Step through eleven full screen colours and spot dead and stuck pixels with your own eyes. No install, no extension, runs in the browser.
This tool is built for computer monitors. It opens on phones too, but a single pixel is almost impossible to judge on a small screen. Use a desktop display.
Before you start
These five steps change the outcome of the test. Mistaking a speck of dust for a dead pixel on a dirty screen is the most common error.
- Clean the screen
Microfibre cloth and a small amount of screen cleaner. Never wipe dry, dust leaves scratches. This is the only way to tell dust apart from a dead pixel.
- Darken the room
Close the curtains and switch off the ceiling light. With no reflections, a single bad dot stands out immediately.
- Warm the monitor up
Wait ten minutes after switching the display on. Some stuck pixels only appear once the panel has warmed up.
- Use the native resolution
Pick the panel's own resolution in your display settings. Scaled output blurs pixel boundaries.
- Look close, then step back
Get about 30 cm from the screen and sweep the surface section by section. Then return to normal distance and decide whether it actually bothers you.
What each colour reveals
Every pixel is made of three subpixels: red, green and blue. On a solid colour screen, dots whose subpixel is not working appear black, while dots stuck permanently on appear bright against other colours. That is why you need to step through all of them.
| Colour | What to look for | Why it matters |
|---|
Trying to revive a stuck pixel
A stuck pixel is a dot whose subpixel is locked on one colour. Driving that area with rapid colour changes can get the liquid crystal moving again. It does not always work, but it costs nothing and does not harm the panel.
Read this first. The fixer shows a small square that changes colour rapidly. Do not use it if you have photosensitive epilepsy, or if someone nearby does. Place the square over the faulty dot only, not across the whole screen. It stops automatically when the timer runs out.
Open the fixer, then drag the square onto the stuck pixel. Run it for ten minutes, close it and check. If nothing changed, try once more at twenty minutes.
Some stuck pixels recover this way, some do not. A dead pixel never will, because there is no circuit receiving power there. Pressing and massaging the screen can damage the panel permanently.
A revived pixel can get stuck again later. If the same dot keeps failing two or three times, starting a warranty claim makes more sense.
Dead pixel or stuck pixel?
The two get mixed up, but the difference is large. A correct diagnosis stops you running the fixer for nothing, and stops you delaying a warranty claim.
Always black
The pixel gets no power at all. It sits as a black dot on a white screen and disappears on black. It never changes colour and cannot be recovered in software. Warranty or panel replacement is the only route.
Fixed colour
The pixel has power but is locked on one colour. On a black screen you see a bright red, green, blue or white dot. The fixer has a real chance here.
Always white
All three subpixels are permanently on. It shows as a white dot on a black screen. Technically a stuck pixel, and the same methods apply.
| Symptom | On black | On white | Diagnosis |
|---|---|---|---|
| Nothing visible | Invisible | Black dot | Dead pixel |
| Coloured dot | Glowing red, green or blue | Invisible | Stuck pixel |
| White dot | Glowing white | Invisible | Hot pixel |
| Smudge that moves | Blurry shadow | Blurry shadow | Dust or a fingerprint, clean the screen |
| Wide dark area | Invisible | Grey patch | Panel pressure or a backlight fault |
How many dead pixels are covered?
Manufacturers set this against the pixel fault classes in the ISO 9241 standard. Most consumer monitors ship as Class II, meaning a small number of faulty pixels counts as production tolerance and may not justify a replacement on its own. The table below shows the faults per million pixels the standard allows.
| Class | Fully dead (Type 1) | Always on (Type 2) | Subpixel fault (Type 3) | Typical use |
|---|---|---|---|---|
| Class 0 | 0 | 0 | 0 | Zero fault guaranteed specialist panels |
| Class I | 1 | 1 | 2 | Professional and medical displays |
| Class II | 2 | 2 | 5 | Consumer monitors and laptop panels |
| Class III | 5 | 15 | 50 | Low cost panels |
The numbers are per million pixels and represent the upper limit the standard permits. Individual brands can be more generous, and some advertise a zero dead pixel guarantee. Read the pixel clause in the warranty document before you buy. Recording the unboxing makes a claim easier to argue.
Frequently asked
How do I run a dead pixel test?
Clean the screen, darken the room and leave the monitor on for ten minutes. Then start the full screen test on this page. Step through red, green, blue, white and black one at a time and sweep the surface section by section on each colour. Any fixed dot that differs from its surroundings is a faulty pixel.
Can a dead pixel be fixed?
A genuinely dead pixel cannot, because the transistor at that point receives no power. A stuck pixel is a working pixel locked on one colour, and the fixer that drives rapid colour changes can revive it. Identify which one you have first: a dot glowing on a black screen is stuck, a black dot remaining on a white screen is dead.
How long should I run the stuck pixel fixer?
Ten minutes is enough for a first attempt. If nothing changes, make sure the square sits directly over the pixel and run it for twenty minutes. There is no demonstrated benefit to running it longer than thirty minutes.
How many dead pixels count as normal?
Under ISO 9241, consumer monitors are usually treated as Class II, which allows up to two fully dead pixels per million as production tolerance. This is not the same across brands, and some manufacturers replace a panel over a single dead pixel. The pixel clause in your warranty document is the text that binds.
Does the dead pixel test work on a phone?
The page opens on a phone and shows the colours full screen, but this tool was designed for computer monitors. Pixel density on a phone is so high that telling a single faulty dot apart with the naked eye is close to impossible. Use a desktop or laptop display when it matters.
What should I check when buying a used monitor?
When you meet the seller, connect the display to a computer and open this page. Step through the colours, then look for a permanent shadow on a white screen. A shadow means the panel has image retention, which is a more serious problem than a dead pixel. Also check the corners for backlight bleed on a black screen.
Can the dead pixel test damage my screen?
No. Full screen colours are no different from ordinary output, and the fixer only changes colours without touching the panel physically. The methods that do cause damage are the ones circulating online: pressing on the screen and rubbing it with a cloth wrapped pen. Do not use those.
Does the dead pixel test apply to OLED screens?
The colour test works on OLED panels and reveals faulty dots the same way. On OLED, though, the real risk is permanent image retention rather than individual pixels. Do not leave a solid white screen up for long, a few seconds is enough to check.