Dead Pixel Test for Phones
Runs in Safari or Chrome with no app install — which makes it perfect for testing a used phone in your hand before money changes hands. Most modern phones are OLED, so this sequence includes the dark-gray slides where OLED problems live.
9 full-screen colors · click, tap, swipe or press Space to advance · Esc to exit
Free · No download · No sign-up · Runs locally in your browser
Phone-specific tips
- • Tap or swipe to change colors; swipe back to revisit a slide.
- • iPhones don't allow true browser fullscreen — the test still covers the page; scroll the address bar away or add the page to your home screen.
- • Turn brightness up and disable auto-brightness and Night Shift.
- • Rotate the phone to check both orientations.
The 5-minute used-phone screen check
- Wipe the screen — dust and pocket lint are the #1 false alarm.
- Run the color slides above. On the black slide, look for glowing dots (stuck pixels) and, on OLED, for any patch that isn't perfectly black.
- Linger on the dark grays. Banding, blotches and burnt-in keyboard or status-bar ghosts show at 5–20% gray. A faint status bar outline means the panel has real burn-in.
- Run the touch grid. Screen replacements — common in used phones — frequently leave dead touch stripes. Paint every edge.
- Check the result against the price. Minor uniformity issues might be worth a discount; burn-in and dead touch zones only get worse.
Something looks wrong?
A colored dot on the black slide may be recoverable — try the stuck pixel fixer (position the flash area with your finger). A black dot on white is a dead pixel: on a phone under warranty that's a service claim, and on a used purchase it's a negotiation point. Either way, capture it in a screen test report while the evidence is on screen.