Dead Pixel Test
Fill your whole screen with solid colours to reveal dead pixels (always black) and stuck pixels (stuck on one colour). A flasher mode can help coax stuck pixels back to life. Everything runs locally in your browser.
Or jump straight to a colour:
In the test: click or → / Space for the next colour · ← for the previous · F toggles the flasher · Esc exits.
How to use the dead pixel test
Clean your screen first — dust and smudges are easy to mistake for pixel faults. Press Start full-screen test and the page fills edge to edge with a solid colour; click or press the right-arrow or space bar to move through red, green, blue, white, black, cyan, magenta, yellow, and grey. On each colour, look closely (a magnifying glass helps) for any point that doesn't match. A dead pixel stays black on every colour because it receives no power. A stuck pixel shows a fixed red, green, or blue point that's most obvious on the opposite colours — for example a stuck red sub-pixel jumps out against green, blue, and black backgrounds.
The flasher mode rapidly alternates black and white over the whole screen. Rapidly exercising a stuck sub-pixel like this sometimes unsticks it after a few minutes — leave it running on the affected area and check again. Press F while testing to toggle the flasher on and off, and Esc to exit at any time. The test uses your browser's fullscreen mode where available; if the browser blocks fullscreen, the colour fill still covers the page.
A quick caution: the flasher rapidly alternates high-contrast black and white, which can be uncomfortable and may affect people with photosensitive epilepsy — skip it if flashing light is a problem for you. Nothing about this test is recorded or sent anywhere; it simply paints colours on your own display.
Found a bad pixel? Read what causes dead pixels and can you fix them for repair odds and warranty thresholds.