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How to check a used Android phone before you buy it

Updated September 26, 2026

Used Android phones (Samsung, Pixel, Xiaomi, OnePlus, Motorola…) come in endless variations, which makes it easy for a seller to overstate the specs or condition. The good news is that Android shows more information than an iPhone, and most brands include a hardware test menu. Here is a sensible order for checking one.

Tip: open soimay.com in Chrome on the phone you are about to buy. There is nothing to install on the seller's phone.

1. Google account lock (FRP)

Android has Factory Reset Protection (FRP): if the previous owner's Google account is still on the phone, after a factory reset it will ask for that exact account before it can be used.

  • Go to Settings › Accounts (or Passwords & accounts): no Google account of the seller's may remain.
  • Samsung phones also have a Samsung account with a reactivation lock: it must be signed out too.
  • Best: have the seller remove the accounts and factory reset in front of you, then sign in with your own account.

2. IMEI and region

Dial *#06# in the Phone app to see the IMEI and compare it with Settings › About phone and the box. In many countries you can check the IMEI against a stolen or blacklisted phone register. Phones made for the Chinese market may lack Google services: open Google Play and Gmail to make sure they work.

3. The right model and specs

The seller says 12 GB of RAM and a recent Snapdragon chip? Check. The device info test reads the model code (for example SM-S918B), Android version, CPU threads, GPU and screen resolution. Compare with Settings › About phone too. A model code that doesn't match the advertised name points to an older model or a rebuilt phone.

Check device specsSee the model, operating system, CPU threads, GPU, RAM and screen resolution of a phone or laptop in the browser, and compare them with what the seller claims.

4. The maker's built-in test menu

  • Samsung: dial *#0*# in the Phone app for a test menu (screen colours, touch, speaker, sensors, vibration). The Samsung Members › Diagnostics app also checks each component.
  • Xiaomi, Redmi, POCO: dial *#*#6484#*#* to open the CIT hardware test menu.
  • Other brands often have a diagnostics section in their support or service app.

The maker's menu and the tests on soimay.com complement each other: do both and little will slip through.

5. OLED screens: burn-in, lines, dead pixels

Most mid-range and flagship Android phones use OLED screens, which look great but are prone to burn-in: a faint ghost of the navigation bar, keyboard or status bar. Fill the screen with grey and look closely. Some older Galaxy models also develop vertical green lines.

Dead pixel, backlight bleed and burn-in testFind dead or stuck pixels, backlight bleed, burn-in and lines on a phone or laptop screen. Eight full-screen colours, free, no app to install.

Cheap replacement screens are often dimmer, tinted, and lose the in-display fingerprint sensor. More in how to check a used phone screen.

6. Touch and fingerprint

Swipe to fill the grid and find dead zones, then go to Settings › Security › Fingerprint and add your own fingerprint. In-display fingerprint sensors often fail after a non-genuine screen replacement.

Touch screen test: dead zones and ghost touchesSwipe to fill a grid of cells and spot dead touch zones or ghost touches on a phone or tablet. Runs full screen, free.

7. Sensors, vibration, auto-rotate

The gyroscope, accelerometer and compass matter for games, maps and screen rotation. Tilt the phone and watch the numbers change, turn off rotation lock and turn the phone sideways, and test the vibration.

Sensor and vibration testCheck the accelerometer, gyroscope, compass, auto-rotate and vibration motor of a phone right in the browser.

8. Battery and charging port

  • Samsung: Samsung Members › Diagnostics › Battery status.
  • Recent Pixels and many Android 14+ phones: Settings › Battery › Battery health.
  • Others: run something heavy for a few minutes and watch how fast the battery drops.

Plug and unplug a few times and gently wiggle the cable to test the USB-C port. The battery test reacts instantly to each plug event and measures the drain rate.

Battery and charging port testSee the battery level, detect plugging and unplugging to test a loose charging port, and watch how fast the battery drains. Plus how to read battery health on iPhone, Android and laptops.

9. Cameras, speakers, microphones

Open every camera in the Camera app (ultra-wide, main, telephoto, macro), photograph something close to test focus and record a video with sound. Use the camera, speaker and microphone tests to check each part closely.

10. Rooted or unlocked bootloader?

Restart the phone: if the boot screen shows a warning that the bootloader is unlocked, the software has been tampered with. Such phones may refuse to run banking and payment apps. Ask the seller, or walk away.

11. Calls, mobile data, body

Put your SIM in and make a call, browse over mobile data, and try both SIM slots. Look along the frame: a raised screen or a back cover coming away is a sign of a swollen battery.

Wrapping up

Save your results as a PDF or a report link on the soimay.com Results page. Things to check by hand (accounts, battery, IMEI) are in the manual checklist.

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