Dead pixel and screen test
Seven full-screen colours, one tap each. Every colour shows a different fault: black shows stuck pixels and light leaking at the edges, white shows dead pixels and stains, grey shows burn-in.
Open this page on the phone you want to test. Press Back or the close button to stop at any time.
How to do it
- Turn the brightness all the way up and wipe the screen.
- Tap Start, then tap anywhere to change the colour.
- Look at each colour closely, corners and edges too. Tilt the phone a little.
What the result means
- A tiny black dot on every colour: a dead pixel. It does not come back.
- A dot that stays red, green, blue or white: a stuck pixel. Sometimes it recovers, often not.
- Thin lines across the screen: a damaged panel or a loose screen cable.
- Yellow, pink or dark patches on white: pressure damage or a worn or cheap replacement screen.
- Faint shapes on grey (keyboard, status bar): burn-in, common on older OLED screens.
- Light glowing from the edges on black: backlight bleed on an LCD screen. A little is normal; bright patches are not.
What a browser cannot see: whether the phone is really the model it claims (copies run on a different processor), how worn the battery is, whether the storage is as big as it says, and whether the system was modified. The free Knowfone app for Android checks all of that and every part above in about 7 minutes, then answers: good to buy, buy only at a lower price, or don't buy.
Questions
What is the difference between a dead pixel and a stuck pixel?
A dead pixel gives no light, so it shows as a black dot on every colour. A stuck pixel is lit in one colour all the time, so it shows on the colours that do not match it.
Can dead pixels be fixed?
A dead pixel cannot be fixed; the screen has to be replaced. A stuck pixel sometimes recovers on its own, but when you buy a phone, price it as if it will stay.
How can I tell if a phone has an AMOLED or an LCD screen?
Show the black colour in a dark room at full brightness. An AMOLED screen is completely black; an LCD glows grey because of its backlight. Check which one the model should have before you buy.
More phone tests
Buying a used phone? Read the 14-step checklist or look up the real specs of popular models.