Dead Pixel Test

Fills a monitor, laptop or phone screen with solid colours such as black, white, red, green and blue so you can find dead pixels, stuck pixels and backlight bleed. Use it when a new monitor arrives or before you buy a used device.

How to use

1. Choose the first colour under "Start with" and press "Start"; the screen switches to full screen.
2. Click, or press Space or →, for the next colour. Press ← or click the left side of the screen to go back.
3. Scan each colour area by area and look for dots of a different colour. Turn on "Advance automatically" to change colour at the chosen "Advance every" interval.
4. Press Esc or "Exit" when you are done.

How it works

• There are 8 solid colours, grey at 25, 50 and 75%, grey steps, a gradient, a checkerboard and a grid. The gradient and grey steps show banding and uniformity problems.
• The screen changes only when you press something, or every 3 seconds or more when advancing automatically. Rapid flashing screens sold as stuck-pixel fixers are left out because they can trigger photosensitive seizures.
• The last screen you viewed and the automatic advance settings are remembered in this browser.

Questions and answers

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

A dark dot on a white or bright screen is a dead pixel. A bright dot on black, or a dot that stays one colour on every screen, is a stuck pixel.

How do I check a monitor for backlight bleed?

Darken the room, show the "Black" screen and look at the edges and corners. Light spreading in from the edges is backlight bleed.

How can I tell a dead pixel from dust?

Wipe the screen and look again. Dust disappears or moves when wiped, while a faulty pixel stays in the same place. Look from 30 to 50 cm away, straight on.