To test a monitor for dead pixels, fill the screen with solid red, green, blue, white and black in turn, and scan each one for a dot that is the wrong colour. A pixel that stays black on every colour is dead; one stuck on a single colour shows up against the others. The free monitor test cycles these full-screen patterns so faults stand out.
That is the method. The detail below helps you tell a real fault from dust, and decide whether it is worth acting on.
Dead versus stuck
These two terms get used interchangeably but mean different things, and the difference decides whether you can fix it.
A dead pixel receives no power at all, so it stays black no matter what the screen displays. It is most visible against a white or bright background, where it appears as a tiny black dot. Dead pixels almost never recover.
A stuck pixel is locked on one colour, usually full red, green or blue, because one of its sub-pixels is jammed on. It shows up brightest against a black screen. Stuck pixels sometimes free themselves over hours or days, and can occasionally be coaxed back with gentle methods.
How to test for dead pixels
Step 1: Clean the screen first
Wipe the display with a soft, dry cloth. A speck of dust looks exactly like a stuck pixel until you try to wipe it away, and you do not want to return a perfectly good monitor over a crumb.
Step 2: Go full screen and cycle the colours
Open the monitor test, go full screen, and step through red, green, blue, white and black. On each colour, scan the whole screen slowly, including the corners where faults hide. A pixel that is the wrong colour on a solid background is the thing you are hunting.
Step 3: Check gradients and bands
The gradient and colour-band patterns reveal problems that solid colours miss: banding, where smooth gradients show visible steps, and backlight unevenness. These matter more on TVs and projectors than on phones.
What to do about a fault
- A stuck pixel. Try leaving the colour-band or rapidly changing pattern running for a while, which can sometimes unstick it. Gentle, careful pressure on the spot with a soft cloth helps in some cases, though it carries its own small risk.
- A dead pixel. These rarely recover. The question becomes whether it breaches the maker’s warranty, which usually allows a small number before they will replace the panel.
- Several faults at once. Worth a warranty claim or a return, especially on a new screen, where most policies are strictest while the return window is open.
Test before the window closes
The single most useful time to run this is the day a new or used screen arrives, while you can still return or exchange it. A dead pixel you spot in week one is the shop’s problem; the same pixel found in month three is yours. Five minutes now can save a frustrating fault you cannot unsee later.
While you are checking your setup, a webcam test and a quick internet speed test round out a new-machine shakedown.