Dead Pixel Checker
Wipe your screen first: most “dead pixels” are dust. A pixel dark on white is dead; a pixel lit on black is stuck. The single colors isolate each subpixel so you can tell which channel failed.
How it works
仕組みA dead pixel stays dark no matter what; a stuck pixel glows one color forever. Both hide easily in busy images and jump out instantly on a solid field. This checker floods your screen with pure white, black, the three primaries, their complements, and a 50% gray, one fullscreen panel at a time, so you can sweep the whole display in under a minute. It's worth doing while any new monitor or phone is still inside its return window.
On white, a dead pixel appears as a dark dot. On black, a stuck subpixel glows. Pure red, green, and blue isolate each subpixel so you can tell exactly which channel died, and the gray panel reveals backlight clouding rather than pixel faults.
Clean the screen first; most candidates are dust. If it persists, photograph it on the color that shows it best and check your manufacturer's dead-pixel policy; many replace panels above a small threshold, especially for bright stuck pixels.
Sometimes. Stuck (lit) pixels occasionally recover after cycling colors rapidly over the area or gentle massage with a soft cloth; dead (dark) ones almost never do. Attempt anything physical at your own risk.