Dead Pixel Test

Checking a brand-new monitor before the return window closes, inspecting a second-hand phone, or hunting a suspicious dot on your laptop? A dead pixel test takes minutes: fill the screen with a series of solid colors and look closely — a healthy panel shows a perfectly uniform field, while defective pixels stand out as dots that refuse to match their surroundings.

Each color exposes a different defect. On white, dead pixels appear as dark specks (and so does dust — wipe the screen first). On black, stuck pixels glow as tiny colored or white points, and LCD backlight bleed becomes visible in a dark room. Red, green and blue light up one subpixel channel at a time, so you can tell exactly which subpixel is stuck or gone. Click or use the arrow keys to cycle colors, and press Esc to finish.

The second mode is a stuck-pixel fixer: a small draggable square rapidly flashes red, green, blue, white and black — one color per screen refresh. A stuck pixel is a subpixel frozen in one state, and forcing fast state changes for 10–15 minutes sometimes unsticks it. Results are genuinely mixed, so treat it as worth trying, not guaranteed. A dead pixel — one that stays black on every color — gets no power at all, and no software can fix that; check your manufacturer's pixel policy instead, because many panels qualify for warranty replacement.

Everything runs locally with standard browser APIs: the Fullscreen API paints the test panels and requestAnimationFrame drives the fixer. Nothing is uploaded, nothing is installed, and the test works the same on monitors, laptops, phones and tablets.