Checking the Screen on a Used Smartphone | Steps for Burn-in, Dead Pixels and Touch
Used smartphones and tablets can hide screen faults that photos do not show. OLED burn-in and touch panels with dead spots in particular are often noticed only after you start using the device, when a return may be hard. This guide covers a 10-minute screen check you can do in a shop or when you collect a marketplace purchase, how the precautions differ between LCD and OLED, how to tell whether a screen has been replaced, and tips for sellers sharing their results.
Why the screen check matters on a used phone
The screen is one of the most expensive parts of a smartphone to repair. On top of that, burn-in and dead pixels barely show up in listing photos, and touch faults only appear when you actually use the screen.
- Buying in a shop: if they let you handle it, check before you pay
- Buying online or on a marketplace: check as soon as it arrives, before you confirm receipt
- Warranty and returns: check the shop's warranty period or the marketplace's rules on confirming receipt in advance
You only need to open a screen checker in the browser, so there is no app to install. The whole check takes about 10 minutes, in the order below.
Checking for burn-in with a full-screen grey
On an OLED screen, pixels that show the same image for a long time wear out first and can leave a faint mark. This is burn-in. It appears in the shape of things that always sit in the same place, such as the status bar, keyboard, navigation bar and buttons of frequently used apps.
- 1
Turn brightness to maximum and show 50% grey
Burn-in shows up more clearly on a mid grey than on white or black. Fill the whole screen with grey.
- 2
Look closely at the top and bottom of the screen
Check for faint outlines of text or shapes in the status bar at the top (clock and battery) and where the keyboard sits in the lower half.
- 3
Also look at dark grey and red
On dark grey, burn-in can show as uneven brightness, and on solid red as a colour shift. If you see the same shape in several colours, treat it as burn-in.
A mark that shows for only a few seconds right after switching images may be temporary image retention. If the same shape does not fade after showing grey for a while, it is burn-in. The difference is explained in detail in telling image retention from burn-in.
Different precautions for LCD and OLED
Even on the same kind of phone, the faults to watch for depend on the display type. Find out which type the model you are buying has, and you will know what to focus on.
| Display type | Common faults | Screens to focus on |
|---|---|---|
| OLED | Burn-in, green or purple tint, unevenness in dark areas | 50% grey, dark grey |
| LCD | Uneven backlight, white spots, light bleeding at the edges | White, black |
| Both | Dead pixels, areas that do not respond to touch | Five solid colours, touch test |
Most iPhones from the iPhone X onwards use OLED, while the iPhone XR, iPhone 11 and iPhone SE (2nd and 3rd generation) use LCD. On Android it varies by model, so check the manufacturer's spec sheet for OLED (AMOLED) or LCD.
Then check dead pixels, touch and refresh rate
- Dead pixels: show black, white, red, green and blue in turn and look for dots that stay lit or never light. Tips for spotting them are in how to check for dead pixels.
- Touch response: trace the grid across the whole screen with your finger and check that no area is left unfilled. Be especially careful in the lower half, where the keyboard often appears, and in the four corners. See the touch panel response test for details.
- Multi-touch: place five fingers at once and check that it shows 5 points.
- Refresh rate: on a 120 Hz model, measure it and check that the value is close to the spec. Safari on iPhone may show 60 Hz, so read the notes in how to check your refresh rate as well.
Also check the outside of the screen by eye. Shine a light at an angle and look for the screen lifting (a gap between it and the body), fine cracks and chipped corners. A lifting screen can be a sign that the battery inside is swelling, so take it seriously.
Clues that a screen has been replaced
Some used devices have had their screen replaced with a non-genuine part during repair. A replaced screen may differ from the original in colour, touch sensitivity and brightness.
- iPhone: on models that show Parts and Service History under Settings → General → About, you can see whether the screen has been replaced and whether it is a genuine part.
- Colour and brightness: a white screen that looks very blue or yellow, or a low maximum brightness, can be signs of a replaced screen.
- Screen edges: black borders of different widths on the left and right, or adhesive squeezing out, are also clues.
FAQ
- How do I check a used phone for burn-in?
- Turn brightness to maximum and show 50% grey across the whole screen. Look for faint outlines of text or shapes where the status bar and keyboard sit. If you see the same shape on dark grey or solid red as well, it is burn-in.
- What should I check when I collect a used phone?
- For the screen, check for burn-in, dead pixels, areas that do not respond to touch, the number of simultaneous touch points, the refresh rate, and any lifting or cracks. Opening a screen checker in the browser lets you go through everything in about 10 minutes.
- Can LCD phones get burn-in?
- LCD screens rarely get permanent burn-in like OLED, and any mark is usually temporary image retention that fades. On an LCD, focus on uneven brightness, white spots and light bleeding at the edges.
- Can I tell whether the screen has been replaced?
- On iPhone models that show Parts and Service History under Settings → General → About, you can check. Otherwise, differences in colour and maximum brightness, uneven border widths and adhesive squeezing out are clues.
Tools in this article
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