Dead Pixel Test
Fills the screen with red, green, blue, white and black to reveal dots that stay off (dead pixels), dots that stay on (stuck pixels), and backlight bleed or patches around the edges. The first thing to do the day a new monitor arrives.
Pick a colour and the whole screen fills with it. Get your nose close to the screen and scan for dots of any other colour.
Click or press → for the next colour, Esc to exit. Turn your brightness all the way up — it shows more.
How to read what you see
- Dead pixel — stays black on every colour. That pixel is gone.
- Stuck pixel — a red, green or blue dot lit up on a black screen means a subpixel is stuck. These sometimes free themselves after a few days of use.
- Backlight bleed — a whitish glow at the edges of a black screen is light leaking past the panel. On an LCD, some of this is normal.
- Patches — a broad dark area on the grey screen can mean the panel has been pressed.
Manufacturers set different thresholds for a replacement (how many bad pixels). Check on the day it arrives and take photos.
What this test checks
- Five full-screen solid colours
- Grey gradient (banding)
- Colour bleed and ghosting
- Backlight bleed at the edges
Other device tests
Results depend on your browser and drivers. If something looks wrong here, try the same test in another browser before assuming the hardware is at fault.