Black Screen Test
A pure black, full-screen display — the single best way to spot backlight bleed, light leaks around the edges of a panel, and any pixel that's stuck showing a bright color when it should be off.
Why use a black screen test
Spotting backlight bleed and light leaks
Backlight bleed shows up as patches of grayish or yellowish light glowing through an otherwise black screen, usually along the edges or corners. It's a common issue on LCD monitors and laptops, and a full black screen in a dim room is the most reliable way to see how bad it is before deciding whether a display is acceptable.
Finding stuck pixels that show color
A pixel stuck on red, green, or blue is easy to miss against busy content but stands out immediately against solid black. If you spot a tiny colored dot that doesn't move or disappear, it's very likely a stuck (not dead) pixel — see the dead pixel test page for how to tell the two apart.
Using black as an OLED power-saver or presentation background
On OLED and AMOLED screens, true black pixels are switched off entirely, so a full black screen can help save battery briefly or serve as a clean, distraction-free background for presenting, screen recording, or covering a webcam light.