Dead pixel test
Cycle full screen colours to find dead pixels, stuck pixels, backlight bleed and uniformity problems.
Your screen fills with each colour in turn. Look closely for dots that stay the wrong colour. Clean the screen first, since dust looks exactly like a dead pixel.
- White Dead pixels show as black dots
- Black Stuck pixels and backlight bleed
- Grey Uniformity and banding
- Red Failed red subpixels
- Green Failed green subpixels
- Blue Failed blue subpixels
How to run the test properly
Clean the screen first. Dust and dried specks are indistinguishable from a dead pixel at a glance, and most suspected dead pixels turn out to be dirt.
Work in a dimly lit room, sit closer than usual, and move your eyes systematically across the panel rather than looking at it as a whole. Spend the most time on white, which reveals dead pixels, and black, which reveals stuck ones.
What each colour reveals
White
Dead pixels appear as black dots. This is the single most useful screen in the set.
Black
Stuck pixels glow against the black. This screen also shows backlight bleed and clouding, which are panel characteristics rather than pixel faults.
Grey
Uniformity problems, banding and dirty screen effect show up on grey more than anything else. Faint vertical bands are common on cheaper IPS panels.
Red, green and blue
Each pixel is made of three subpixels. A pixel can fail partially, which looks normal on white but shows as a dark dot on one of the primary colours. These screens isolate which subpixel has failed.
If you find a defect on a new screen
Test it and document it immediately. Photograph the defect with the relevant colour on screen, note the date, and raise it inside the return window rather than the warranty period. A return is almost always easier than a warranty claim, and many panel warranties allow a few defective pixels while a retailer return does not have to.
Common questions
What is the difference between a dead pixel and a stuck pixel?
A dead pixel receives no power and stays black on every colour, including white. A stuck pixel is permanently lit in one colour, so it shows up clearly against a black screen. Stuck pixels sometimes recover, dead pixels do not.
Can a stuck pixel be fixed?
Occasionally. Rapidly cycling colours in that area can unstick a subpixel, and gentle pressure with a soft cloth over the spot while the screen is on sometimes works. Neither is reliable, and pressing too hard can damage more pixels. A dead pixel cannot be revived.
How many dead pixels before a warranty replacement?
Most manufacturers use ISO 9241-307 class II, which permits a small number of defective pixels before a panel counts as faulty. The exact threshold varies by brand and panel size, and some premium monitors advertise a zero bright pixel policy. Check your specific warranty.
I see uneven brightness at the edges on black.
That is backlight bleed, and it is a normal characteristic of edge lit LCD panels rather than a pixel fault. It is only a warranty matter if it is severe enough to be visible in ordinary use.
Does this work on a phone or TV?
Yes. Any device with a browser works. For a TV, opening the page on a connected laptop or casting the tab gives you a full screen test at the panel native resolution.
Troubleshooting guides
Test your other hardware
Most hardware faults travel in pairs. If one device is misbehaving, check the rest.