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Dead pixel test: check a screen for dead and stuck pixels

Fill the screen with solid colours to spot dead, stuck or hot pixels and backlight bleed, with an optional stuck-pixel fixer (opt-in, flashing).

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Dead and stuck pixels are easiest to spot on a screen filled with one flat colour. This test fills the whole display with black, white, red, green, blue, gray or any colour you choose, and you step through them with a click, a tap or the arrow keys. Check a new monitor, laptop or phone within the return period, or a second-hand one before you buy.

On each colour, look slowly across the whole screen from a normal viewing distance. A dead pixel stays black on every colour; a stuck pixel stays one colour (often red, green or blue) and is most visible on black; a hot pixel stays white. The black screen in a dark room also shows backlight bleed and glow along the edges of LCD panels, and the gray screen reveals uneven brightness (clouding or banding).

The optional stuck pixel fixer flashes a small square through red, green, blue, white and black. Leaving it over a stuck pixel for 10 to 30 minutes sometimes frees it; it cannot repair dead pixels or physical damage, and there is no guarantee. Because rapidly flashing colours can trigger seizures in people with photosensitive epilepsy, the fixer only starts after you read a warning and tick an explicit opt-in.

How to use it

  1. Clean the screen, set brightness to normal and, for black, darken the room.
  2. Click "Start full-screen test" (or a colour to start with it).
  3. Click, tap, press Space or → for the next colour and ← to go back; press Esc to exit.
  4. If you find a stuck pixel, read the warning, opt in to the fixer and drag the flashing square over it.

Frequently asked questions

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

A dead pixel gets no power and stays black whatever is shown. A stuck pixel has one or more subpixels (red, green or blue) permanently on, so it shows as a coloured dot. Stuck pixels can sometimes be revived; dead pixels usually cannot.

Does the stuck pixel fixer work?

Sometimes, for recently stuck pixels, by rapidly switching the subpixels on and off. Results vary, it may take 10 to 30 minutes or several sessions, and it does nothing for dead pixels or cracks. Check your warranty's pixel policy first; many manufacturers replace panels with a certain number of defects.

Is the flashing safe?

Not for everyone. Flashing lights can trigger seizures in people with photosensitive epilepsy. The fixer only runs after you opt in, you can stop it with Esc or the Stop button, and you should not look at it directly while it runs.

Does it work on phones and tablets?

Yes. Tap to change colours. Some phone browsers (notably Safari on iPhone) do not allow full screen for web pages, so the colour fills the browser window instead; hide the toolbars by scrolling or use the browser's full-screen mode where available.

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