Test 05
Dead pixel test
Nine full-screen fills that make faults obvious. Click or press the arrow keys to move through them.
Clean the screen first. Dust looks exactly like a dead pixel and is the most common false alarm.
Stuck pixel fixer
A stuck pixel is lit but showing the wrong color. Cycling colors rapidly over it sometimes restores it. This is different from a dead pixel, which receives no power and cannot be revived.
Warning: this flashes colors rapidly. Do not use it if you have photosensitive epilepsy or are sensitive to flashing light.
Checking a screen before you buy it
Run white and black first, since between them they catch almost everything. Then work through red, green, and blue, which isolate individual subpixels and expose faults that a white screen hides. Finish on gray in a dark room to judge backlight uniformity. The whole sequence takes under a minute and is worth doing before money changes hands.
Common questions
How do I test for dead pixels?
Clean the screen, then run each full-screen color in turn and look closely for dots that stay the wrong color. White reveals dead pixels as black dots, and black reveals stuck pixels as bright ones.
What is the difference between a dead pixel and a stuck pixel?
A dead pixel receives no power and stays black on every color. A stuck pixel is lit but frozen on one color, so it shows up as a red, green, or blue dot. Stuck pixels can sometimes be recovered, dead ones cannot.
Can a dead pixel be fixed?
Not by software. A dead pixel has no power reaching it, so nothing displayed on screen can change it. Only a stuck pixel has any chance of recovery, and even then it is far from guaranteed.
How many dead pixels before a warranty claim?
Manufacturers set their own thresholds and most tolerate a small number before replacing a panel. Check your specific warranty terms, since the limits vary widely between brands and between consumer and professional monitors.
Why does the gray screen look uneven at the edges?
That is usually backlight bleed or IPS glow rather than a pixel fault. It is most visible on a dark screen in a dark room and is common on LCD panels, though severe cases can be grounds for a return.