How to check your screen properly
- Clean the screen first. Half of all "dead pixels" are dust. A microfiber wipe saves you a support ticket.
- Start the test and look over the whole panel on each color, corners included. On a big monitor, lean in — a single pixel at arm's length is smaller than you think.
- Advance with a click, tap, Space, or the arrow keys. Go back with ←. Leave with Esc.
- Note where any spot appears and which colors make it visible — that combination tells you what kind of defect it is.
What each color reveals
| You see | On which screen | What it is |
|---|---|---|
| A black dot | White, and every bright color | Dead pixel — the pixel gets no power or signal. Permanent in almost all cases. |
| A red, green, or blue dot | Black, and colors that should exclude it (a red dot on a pure blue screen, say) | Stuck subpixel — one of the three subpixels is frozen on. Sometimes recoverable. |
| A white dot | Black | Hot pixel — all three subpixels stuck on. Rarer; occasionally recoverable. |
| A dark smudge larger than a pixel | White or gray | Dust behind the glass, pressure damage, or a panel defect — not a pixel fault. Worth photographing before a warranty claim. |
Can it be fixed?
Honest answer: dead pixels, no. Stuck pixels, sometimes. A stuck subpixel is a liquid-crystal cell that stopped responding, and rapid color cycling on that spot occasionally unsticks it. Reports of success are real but anecdotal — nobody has published a controlled study, and manufacturers make no promises. Gentle pressure with a soft cloth while the pixel cycles is the other folk remedy; be careful, since pressing hard can create the very damage you're trying to fix. If a stuck pixel survives a few cycling sessions across a couple of days, it's staying.
Whether a defect qualifies for warranty replacement depends on the maker's pixel policy — most allow a few defective pixels before they'll swap a panel, and the rules differ between dead and stuck. We've collected the policies in Dead vs stuck vs hot pixels — and what warranties cover.
Buying a used device?
This test needs no install and no account, which makes it the right tool to run during the handover, before money moves. Open the site on the device itself, run the colors, then check the gradient test for banding and the refresh rate against the listing's claims. The full checklist is in How to test a used phone or monitor before buying.
Panel healthy? Then it's worth setting up properly — the by-eye calibration takes ten minutes, and the ghosting test shows how it handles motion.