How to test a used monitor for dead pixels before you buy
Buying a used monitor, laptop, or phone? A five-minute pixel test can save you from a screen with permanent dots you'll notice forever. Here's how to check, and what actually counts as a problem.
Dead vs. stuck pixels
- Dead pixel — a pixel that gets no power and stays black on every color. Usually permanent.
- Stuck pixel — a pixel stuck showing one color (red, green, blue, or white) because a sub-pixel is jammed "on." Sometimes fixable.
The difference matters: a stuck pixel can occasionally be revived; a truly dead one generally can't.
How to test in under a minute
The trick is to fill the whole screen with solid colors, one at a time — pure red, green, blue, white, and black — and look closely across the entire surface.
- On a black screen, a stuck pixel shows up as a bright dot.
- On white and each solid color, a dead pixel shows up as a black dot, and a stuck one shows the wrong color.
- Check the corners and edges too, not just the center.
Do it in a dimly lit room so faults stand out, and clean the screen first so you don't mistake dust for a dead pixel.
What's normal vs. a deal-breaker
Manufacturers actually allow a small number of dead pixels under warranty (their "pixel policy"), so one tiny dot isn't necessarily a defect on a new panel — but on a used purchase it's leverage to negotiate or walk away. A dead pixel dead-center, or several clustered together, is a genuine deal-breaker. One faint dot in a corner is a judgment call.
Try reviving a stuck pixel
Stuck (not dead) pixels sometimes recover by rapidly cycling colors in that area, or with gentle pressure while the screen redraws. It doesn't always work, but it's worth a try before giving up.