How to test for dead pixels
A dead pixel is a sub-pixel that never lights up. A stuck pixel is one that never turns off. They look similar at a glance and are fixed in completely different ways — so the first job is telling them apart.
The difference in one line
A dead pixel stays black no matter what the screen displays, because its transistor has failed and it receives no power. A stuck pixel is permanently powered, so it shows as a bright red, green, blue or white dot. Dead pixels are effectively permanent. Stuck pixels can often be recovered.
The test
Run the screen through solid colours and look closely at each one. You need white, black, red, green and blue at minimum — a single colour will hide half the faults.
- Clean the screen first. A speck of dust looks exactly like a dead pixel and you will waste an hour chasing it.
- Go fullscreen so no browser chrome is visible.
- On white, look for black dots. That is a dead pixel or a dead sub-pixel.
- On black, look for bright dots. That is a stuck pixel.
- On red, green and blue, look for dots of the wrong colour. This catches a single failed sub-pixel inside an otherwise working pixel.
- Sit at your normal viewing distance first, then move closer. A fault you can only see with your nose against the glass is not a fault worth returning a panel over.
Do this in a dimly lit room. Ambient light reflecting off the panel hides low-contrast defects, and backlight bleed is invisible in a bright room.
What counts as a fault worth claiming
Almost every manufacturer publishes a dead-pixel policy, and almost none of them replace a panel for a single dead sub-pixel. Typical thresholds run from three to six defective sub-pixels, often with tighter limits for defects in the centre of the screen than at the edges. Premium and professional monitor lines frequently advertise a zero-bright-dot warranty, which is exactly the kind of thing worth paying for if you do colour work.
Before you contact support, photograph the defect with the solid-colour background behind it and note roughly where it sits on the panel. A support agent who can see the fault immediately is a support agent who escalates faster.
Trying to revive a stuck pixel
Two approaches are worth a try, in this order.
Rapid colour cycling
Flashing the pixel between colours at speed can knock a stuck sub-pixel back into normal operation. Run a fast colour cycle over the affected area for ten to thirty minutes. This works often enough to be worth doing and cannot damage anything.
Gentle pressure
Switch the display off. Wrap a finger in a soft microfibre cloth, apply light pressure directly over the stuck pixel, and switch the display back on while still pressing. Release. The idea is to reseat liquid crystal that has settled wrong. Use genuinely light pressure — pushing hard on an LCD can create permanent pressure marks, and on an OLED it can destroy the panel.
If neither works after a few attempts, the pixel is not coming back.
When it is not a pixel at all
Not every dot is a pixel fault. Dust or an oil smudge moves when you wipe it. A dark patch that changes shape as you shift your head is usually a pressure mark or delamination. A dot that appears only in one application is a rendering bug, not hardware — check it against a solid colour in a different app before you blame the screen.