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Device Monitor

How to check for dead pixels on your iPhone

Open Device Monitor, go to Diagnostics > Screen & Display and start the Dead Pixel Test. Run this before a used-phone purchase: the screen turns solid red, green, blue, white and black in turn, a dark dot on the bright colours is a dead pixel, a coloured dot on black is a stuck one.

3 min read · Updated 2026-10-06

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When should you test for dead pixels?

Run it the day a new phone arrives, before you hand over money for a used one, and again after any screen replacement. Return windows close fast, and a single faulty pixel hides in normal use until the one day you finally notice it - and by then the warranty is gone.

Photos and apps are a weak test, the colours never sit still long enough. A fault only stands out against one flat colour filling the whole screen, which is exactly what this test gives you and nothing else does.

How to run the dead pixel test on iPhone

  1. Turn screen brightness all the way up and wipe the glass with a dry cloth.
  2. Open Diagnostics and tap Screen & Display.
  3. Tap Dead Pixel Test. The screen fills with red and the status bar vanishes - the test names stay in English in every language, by the way.
  4. Scan slowly, corners and edges included, and don't skip the area around the camera cut-out. The hint reads Look for any pixel that doesn't match.
  5. Tap anywhere for the next colour. A counter at the bottom runs from 1/5 to 5/5 next to Tap to cycle colors.
  6. Black is the fifth colour; a tap there closes the test. Run it twice if the room light was bad the first time.

What do dead pixels look like on iPhone?

Each colour exposes a different kind of fault. Keep the table open while you tap through.

What to look for on each of the five colours
ScreenWhat a fault looks likeWhat it usually means
1/5 RedA black or bright dot that is not redDead pixel, or a pixel stuck on another colour
2/5 GreenA black or differently coloured dotDead or stuck pixel
3/5 BlueA black or differently coloured dotDead or stuck pixel
4/5 WhiteA dark dot, or a coloured tint in one spotDead pixel, or a sub-pixel that no longer lights
5/5 BlackA dot that glows red, green, blue or whiteStuck pixel (stays on when it should be off)

Dead pixel, stuck pixel or dust?

  • Dead pixel: never lights, period. A tiny dark point on every bright colour, sharpest against white.
  • Stuck pixel: stays lit in one colour no matter what's underneath. Easiest to catch on black, where everything else is off.
  • Dust or a mark: soft-edged, moves when you tilt the phone, wipes away. Dust under a screen protector fools people the same way - peel a corner if you're not sure.

Tips for a reliable check

  • Test in a dim room - stuck pixels on black hide behind reflections otherwise.
  • Check straight on, then from an angle; a few faults only show at one angle and nowhere else.
  • Found something? Take a close photo with another phone. It's worth more than your word for a return or a warranty claim.
  • The free version may show an ad right after you close the test - let it finish before running it again.

Can the app fix a stuck pixel?

No, it can't. Device Monitor shows you the fault; fixing it is somebody else's job. Some stuck pixels come back to life on their own, most don't. A dead pixel is a hardware problem, full stop - a warranty claim or a shop replacing the screen is the actual remedy.

And it won't find anything automatically either. There's no camera inside the phone pointed at its own screen, so any app claiming to scan for you is really just asking you to look - same as this one.

Questions and answers

Is the dead pixel test free?
Yes. The five-colour Dead Pixel Test is in the free version; only burn-in, touch response and colour gradient need Pro.
How many dead pixels are acceptable on an iPhone?
That's down to the seller or the manufacturer's policy, not the app. On a new phone, report any pixel fault while the return window is still open.
Does the test work on iPad?
Yes, same five colours filling the whole iPad screen, one tap per colour.
Why does the test close after black?
Black is the last of the five, so tapping there ends the test. Reopen it from Screen & Display for another pass.

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