Dead pixel test

Fill your whole screen with one colour at a time to find dead pixels (always black), stuck pixels (always one colour) and backlight bleed. Handy for a new Mac or a second-hand display.

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Clacky

Hi! It’s all free 👋Click an app to open it. Drag a window by its top bar.

Clacky Island

It runs right here, on the little Mac. Drag the window, open other apps from the Dock.

How to check for dead pixels

Clean the screen first: dust looks a lot like a dead pixel.
Press Start full-screen test. Click, or press → or space, for the next colour; ← goes back; Esc ends.
Look slowly across the screen on each colour.

What you might see

Dead pixel: a dot that stays black on every colour, easiest to see on white.
Stuck pixel: a dot that stays red, green or blue, easiest to see on black.
Backlight bleed: brighter patches near the edges on black, best seen in a dark room.

Apple and most makers have a policy on pixel faults; check your warranty if you find one on a new display.

Questions

How do I test my MacBook for dead pixels?

Open this test, go full screen and look at each colour, especially white (for dead pixels) and black (for stuck pixels).

What is the difference between a dead and a stuck pixel?

A dead pixel doesn’t light up at all, so it’s black everywhere. A stuck pixel is lit in one colour all the time. Stuck pixels can sometimes recover; dead ones rarely do.

Can a website fix a stuck pixel?

Pixel “fixers” flash colours fast. It sometimes helps a stuck pixel, but fast flashing can be harmful for people sensitive to it, so this test doesn’t flash.