Dead pixel, backlight bleed and burn-in test

When to test the screen

Check the screen when you look at a used device, as soon as you collect a device after a screen replacement, and in the first days of a new device while you can still return it. Dead pixels and tints are hard to spot in everyday use but stand out on a solid colour. Turn the brightness all the way up and look in a slightly dim room.

Common faults and their causes

• Dead or stuck pixels: a manufacturing defect, or damage from pressure or a drop. A tiny dot in a corner may be acceptable on a cheap used device; on a new one, ask for an exchange.
• Yellow or pink tint, blotches: burn-in on an ageing OLED screen (easiest to see on grey), or a low-quality replacement screen.
• Backlight bleed at the edges: an LCD panel pressed unevenly during assembly, or a laptop lid under stress.
• Lines or broken gradients: a loose display cable or a failing display controller. These usually get worse over time.

What to do if you find a fault

• Photograph the screen with another device. A screenshot taken on the device itself won't show hardware faults.
• New device: report it to the shop and exchange it within the return window. Just repaired: tell the shop before you pay. See checking a device after a repair.
• For every screen fault in detail: the screen guide.