PixelCheck: Dead Pixel Test
iPhone & iPad · iOS 17.0 or later
Check a screen before you pay for it.
PixelCheck fills your screen with solid colors so dead and stuck pixels have nowhere to hide, then tests touch response, backlight bleed and OLED burn-in. Buying a used iPhone, or just had a screen repaired? Run the guided check and share the result.
01 — Dead pixel test
Dead pixel or stuck pixel? Which color shows which.
A dead pixel stays permanently dark: you see a tiny black dot on a bright color. A stuck pixel stays permanently lit, often red, green or blue: you see it on a dark screen. PixelCheck cycles through 11 full-screen colors. Tap or swipe to change color, and scan the whole screen slowly on each one, especially the edges and the center.
White, yellow, cyan, light gray
Bright screens. A dead pixel is a black dot.
Black, dark gray, gray
Dark and mid-gray screens. A stuck pixel is a lit dot, often red, green or blue.
Red, green, blue, magenta
One color at a time. A pixel that cannot show that color stands out as a dark or off-color dot.
Full brightness, nothing in the way
The status bar is hidden, the screen stays awake and brightness goes to maximum for the test. It goes back to your setting when you leave.
02 — The six tests
Everything a screen check needs, in one app
Dead Pixel Test
11 solid colors from white to dark gray. Swipe or tap to move on, and a row of dots shows where you are.
Pixel Fixer
Flashes red, green, blue, white and black quickly to try to revive a stuck pixel. A timer counts the minutes.
Photosensitivity warning: rapid flashing. Not for anyone sensitive to flashing lights.
Backlight Bleed Test
A pure black screen for a dark room. Look at the corners and edges for light leaking through. Most relevant on LCD screens.
Touch Screen Test
An 8 × 16 grid of 128 zones that light up as you touch them. Multi-touch, a percentage counter and a reset button.
Burn-in Test
A drifting gray block or a uniform gray screen, with a gray level from 10 to 90 percent, to reveal ghost images and uneven brightness.
Screen Info
Model name and identifier, iOS version, display type, logical and physical resolution, scale factor, current brightness and maximum frame rate.
03 — Guided Screen Check
Four tests in a row, then a report you can send
The guided check runs the dead pixel, backlight bleed, touch and burn-in tests one after another. Each starts with a short briefing on what to look for. When it is over you answer Pass, Fail or Skip. At the end you get a summary, “No issues found” or how many tests need attention, and a report card you can share as an image: device model, iOS version, date and the result of each test.
The verdicts are yours. The app gives you clean screens and keeps count; it does not judge the screen for you.
PixelCheck Report
Device model · iOS version · date
Dead Pixel Test Pass
Backlight Bleed Test Pass
Touch Screen Test Pass
Burn-in Test Pass
No issues found (layout shown for illustration)
- Ask to run it before you pay. It takes a few minutes and works offline, so the shop's Wi-Fi does not matter.
- Dim the room for the backlight and burn-in tests, and look at the edges, not only the middle.
- Open Screen Info and check that the model matches the one you are being sold.
- Share the report with the seller, or keep it as a record of how the screen looked on the day.
04 — Support
Questions people actually ask
What is the difference between a dead pixel and a stuck pixel?
A dead pixel stays dark. It shows up as a tiny black dot on bright colors such as white or yellow. A stuck pixel stays lit, often red, green or blue, and shows up on dark screens such as black or dark gray.
Does PixelCheck find dead pixels by itself?
No. A phone cannot see its own screen, so the app does the part that is hard to do by hand: it fills every pixel with one clean color at full brightness and keeps everything else out of the way. You look, and you decide. In the guided check you answer Pass, Fail or Skip after each test.
Can PixelCheck repair a dead pixel?
Not a dead one. The Pixel Fixer flashes red, green, blue, white and black quickly, which can sometimes wake up a stuck pixel. It is not guaranteed to work, and a pixel that is truly dead stays dead. The app suggests leaving it running for at least ten minutes with the stuck pixel in view; a timer shows how long it has been going.
Photosensitivity warning: the Pixel Fixer flashes bright colors rapidly. Do not use it if you are sensitive to flashing lights. The app shows the same warning before it starts.
Why does the screen get so bright, and why does it stay on?
The dead pixel, backlight bleed and Pixel Fixer screens set the screen to full brightness so faults are easy to see, and every full-screen test keeps the screen from locking while you look. When you leave a test, PixelCheck puts your brightness back to where it was.
What does the Touch Screen Test check?
The screen is divided into a grid of 8 by 16 zones, 128 in all. Each zone lights up the first time a finger touches it, and a counter shows how much of the screen you have covered. It reads several fingers at once, so you can sweep the screen quickly. At 100 percent it says “All zones tested!”. A zone that never lights up is a touch dead zone. The reset button clears the grid.
When is the backlight bleed test useful?
Backlight bleed is light leaking around the edges of an LCD screen. Show the black screen in a dark room and look at the corners and edges for a glow. OLED screens switch pixels off completely, so they are not expected to show bleed.
What are the two burn-in modes?
Burn-in is a faint, permanent ghost of an image that was on screen for a long time, mostly an OLED issue. The test shows either a gray block that drifts slowly across black, or a uniform gray screen, with a slider from 10 to 90 percent. Subtle burn-in is easiest to see at a medium gray. Look for shadows of the status bar, keyboard or navigation bar.
Is the “Display Type” on the Screen Info page measured?
No. It is looked up from the device's model identifier (for example OLED, LCD or mini-LED), not measured from the screen. A model the app does not know yet is shown by its identifier instead of a name. If it matters, check the display type against Apple's specifications for your model.
Which iPhones and iPads does it run on?
iPhone and iPad with iOS or iPadOS 17.0 or later. It is a paid app with a single purchase: no subscription, no in-app purchases and no ads.
Which languages is it in?
English, German, Spanish, French, Japanese, Korean, Norwegian, Portuguese (Brazil) and Chinese (Simplified).
Does it need the internet or collect data?
No. It makes no network connections and has no analytics, ads or third-party code, so it works in airplane mode and in the shop. The details are in the privacy policy.
05 — Still stuck?
Write to a human
Say which iPhone or iPad you have, the iOS version, and what happened. A screenshot helps.