What a black screen is good for
- Backlight bleed and IPS glow. In a dark room, a black screen shows light leaking at the edges of LCD monitors.
- Stuck pixels. A pixel that stays lit shows as a bright red, green, blue or white dot on black.
- OLED check. A good OLED screen is fully black, with no grey glow at all.
- Darkness without turning off. Keep a screen dark during a presentation, a film night or a long download, while the computer keeps running.
How to check for backlight bleed
- Darken the room and set the monitor to the brightness you normally use.
- Open the black screen in full screen.
- Look straight at the screen from your normal sitting distance. Bright patches at the edges or corners are backlight bleed. A glow that changes when you move your head is IPS glow, which is normal for IPS panels.
A little bleed is normal for LCD screens. Bleed you can see during a dark film scene at normal brightness is worth reporting under warranty.
For a full pixel check, use the dead pixel test. It cycles through black, white and the main colours.
Frequently asked questions
Short answers to the questions people ask most about this test.
How do I make my screen black?
Click Full screen on this page and your whole display turns black. Press Esc or double-click to exit.
What is the difference between backlight bleed and IPS glow?
Backlight bleed stays in the same place when you move your head, usually at the edges. IPS glow shifts and changes with your viewing angle and is a normal trait of IPS panels.
Does a black screen save power?
On OLED screens, yes, because black pixels are switched off. On LCD screens the backlight stays on, so the saving is small.