Dead Pixel Test

Every pixel on an LCD or OLED screen is built from red, green and blue subpixels. When one of them fails, it either stays permanently black (a dead pixel) or permanently lit in one colour (a stuck pixel). Defects like these hide easily on a busy desktop, which is why this test floods your entire screen with pure solid colours — red, green, blue, white, black, gray, cyan, magenta and yellow. A dead pixel shows up as a black dot on every bright colour; a stuck pixel appears as a wrongly-coloured dot on solid backgrounds.

Beyond single pixels, the gradient screens reveal panel-level problems: smooth RGB and grayscale sweeps expose colour banding, a full-hue sweep shows tint shifts, and the checkerboard and pixel-grid patterns make uneven sharpness or scaling artifacts obvious. Sit about 30 cm from a clean screen — a speck of dust is the most common false alarm.

If you find a stuck (not dead) pixel, the built-in exerciser rapidly flashes black and white at 6 to 30 Hz over a small draggable spot or the whole screen. Cycling a stuck subpixel this way for a few minutes can sometimes free it; truly dead pixels are usually permanent hardware faults. A photosensitivity warning is shown before any flashing starts. The whole test runs in your browser with real fullscreen, keyboard shortcuts and tap-to-cycle controls — nothing to download or install.