How to Check Your Smartphone for Dead Pixels (iPhone &...

How to Check Your Smartphone for Dead Pixels (iPhone & Android)

Phones pack hundreds of pixels per inch, which makes defects microscopic and easy to miss—until the return window closes. Use this guide to test any phone (iPhone or Android) quickly and safely. Start with our dead pixel tester in fullscreen to get a clean read.

Why It’s Harder on Mobile

High PPI: 400–500+ PPI on modern phones makes a single pixel ~0.05 mm wide.
Oleophobic coatings and smudges can mask defects.
Notches/holes and UI overlays can hide pixels—test in fullscreen.

Prep Before Testing

Clean with a microfiber cloth; remove screen protectors only if you suspect trapped dust.
Set brightness to 100% (you can lower later).
Disable True Tone/Night Shift/Blue light filters to avoid tinting.
Toggle auto-rotate off so the UI stays stable while you scan.

Method 1: Browser Test (Universal, No App)

Open the dead pixel tester in Safari/Chrome.
Add to Home Screen (optional) for a cleaner fullscreen.
Enter fullscreen; hide the address bar if possible.
Swipe through White, Black, Red, Green, Blue, Cyan, Magenta, Yellow, Gray.
Look for:
- Black dots on White (dead pixels).
- Bright dots on Black (stuck pixels).
- Shadows/ghosts on Gray (burn-in/retention on OLED).

Method 2: Android Built-in Tests (Faster, Hardware-Level)

Samsung: Dial *#0*# → tap Red/Green/Blue/Gray/Black.
Xiaomi: Settings → About Phone → tap Kernel Version 5 times → Hardware tests → display.
Sony Xperia: Dial *#*#7378423#*#* → Service tests → display.
Pixel/OnePlus (varies): Some models lack secret codes; use the browser test instead. Tip: If a dot appears in both the browser test and secret-code test, it’s hardware, not an app artifact.

Method 3: iPhone Tricks to Isolate Pixels

Turn on AssistiveTouch (Settings > Accessibility > Touch > AssistiveTouch). Drag the floating white button over the suspected spot; if the spot sits on top of the button, it’s in the panel, not the UI.
Disable True Tone and Night Shift to remove color shifts while testing.
On OLED iPhones, test on 50% Gray and Dark Red to reveal burn-in/retention.

Reading the Results

Dead pixel: Black dot on White. Rarely fixable; document and return if new.
Stuck pixel: Bright dot on Black; may recover with flashing.
Cluster: Multiple adjacent defects suggest panel or impact damage.
Ghost shapes: Likely OLED retention/burn-in—seen on gray/dark red.

Safety and Comfort

Keep tests short at max brightness to avoid eye strain.
If using a flasher later, don’t stare; set it, look away.

What to Do If You Find a Defect

Day 1–14 return windows: Act immediately; most premium phones have near-zero tolerance early on.
Carrier/retailer swaps: Often easier than manufacturer warranty in the first days.
Photos: Shoot on White and Black; note location (e.g., “2 mm left of the notch”). Turn off HDR to avoid smoothing.

Can You Fix a Stuck Pixel on a Phone?

Possible but lower success than monitors due to high PPI and touch layers.
Use a small flashing box (web tools) over the spot for 10–30 minutes. Don’t press the glass hard; you risk damage.

Common False Positives

Dust under a screen protector. Remove/re-seat if the dot moves.
Notch/punch-hole artifacts—compare against screenshots to rule out UI.
Image retention (temporary) on OLED after static content—rest the phone 10–30 minutes and retest on gray.

When to Walk Away (Used Phones)

Any center-screen defect on OLED.
Multiple dots or a clear ghost image of a status bar/logo.
Seller refusing a quick test with the dead pixel tester.

Quick Checklist (1 minute)

White: any black dots?
Black: any bright dots?
Gray/Dark Red: any ghost shapes?
If yes, document and return; don’t wait past the retailer window.

Next steps: Open the Screen Test in fullscreen on your phone and save white/black/gray screenshots. If you see a bright dot, try the stuck pixel fixer. If it stays black, check Is 1 Dead Pixel Acceptable? Understanding Monitor Warranties.