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How to check a used iPhone before you buy it

Updated September 26, 2026

A used iPhone can save you a lot of money, but it can also come with an Activation Lock, a carrier lock, or a cheap replacement screen or battery. This guide follows the order that works best when you have the phone in your hands: rule out the problems that can't be fixed first, then check the hardware.

Tip: open soimay.com in Safari on the iPhone you are about to buy. The tests run right in the browser, so there is nothing to install or sign in to on the seller's phone.

1. Activation Lock: check this first

If the previous owner's Apple Account is still on the phone, it will hit Activation Lock after a reset and becomes almost useless. This is the one problem with no legitimate fix, so check it before anything else.

  • Open Settings: the top row (the account name) must be empty and just say "Sign in to your iPhone".
  • Find My iPhone must be off (Settings › [name] › Find My).
  • Safest of all: ask the seller to go to Settings › General › Transfer or Reset iPhone › Erase All Content and Settings in front of you, then set the phone up with your own Apple Account.

If the seller refuses to sign out or erase the phone, walk away, however good the price.

2. Carrier lock

A phone locked to a carrier only works with that carrier's SIM. Go to Settings › General › About and find Carrier Lock: an unlocked iPhone says "No SIM restrictions".

3. IMEI and serial number

Dial *#06# in the Phone app to show the IMEI, then compare it with the IMEI in Settings › General › About, on the SIM tray and on the box. They must all match. Enter the serial number on Apple's coverage check page to confirm the exact model and activation date. In many countries you can also check the IMEI against a stolen-phone register.

On the same About screen, the first letter of the Model Number tells you where the phone came from: M is a new retail unit, F is Apple refurbished, N is a warranty replacement and P is a personalised (engraved) unit.

4. Replaced parts

Since iOS 15.2 an iPhone reports replaced parts itself. Go to Settings › General › About › Parts and Service History (it only appears if something was replaced):

  • Genuine Apple Part: replaced with an original part, which is acceptable.
  • Unknown Part: the screen, battery or camera is non-genuine. Negotiate hard or walk away.

Other signs: stripped screws next to the charging port, glue showing around the screen, and True Tone missing from Control Center (common after a non-genuine screen replacement).

5. Battery health

Go to Settings › Battery › Battery Health & Charging:

  • 85% or more: good. 80–85%: fine, but worth a lower price. Under 80%, or a "Service" message: the battery needs replacing soon.
  • iPhone 15 and later also show the cycle count in Settings › General › About.
  • A battery shown as "Unknown Part" is a third-party replacement.

More detail in how to check battery health.

6. Screen: dead pixels, burn-in, bleed

Turn brightness all the way up and fill the screen with one colour at a time. Grey reveals burn-in on OLED screens, black shows bright pixels and white shows yellow stains. On iPhone the test has a full-screen video mode where colours change by themselves every few seconds.

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.

7. Touch

Swipe to fill a grid covering the whole screen. An area that never fills is a dead zone; cells that fill without being touched are ghost touches, common with cheap replacement screens.

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.

8. Face ID / Touch ID

The most reliable check: go to Settings › Face ID & Passcode, tap Set Up an Alternate Appearance (or add a fingerprint) and scan your own face. If it works, the sensor is fine. "Face ID is not available" means the front camera module is broken or has been tampered with.

Fingerprint and Face ID testCheck the fingerprint sensor, Face ID, Touch ID or Windows Hello through the browser, with an animated step-by-step guide.

9. Speakers, microphones, cameras

  • Speakers: play the top and bottom speakers separately and sweep the frequencies to hear crackling. Use the speaker test.
  • Microphones: iPhones have several; record and play back with the microphone test, and record a video with sound.
  • Cameras: open each lens (0.5x, 1x, 3x/5x) in the Camera app, photograph something close to test focus, and point at a bright sky to find dust spots. The camera test shows the real resolution of each camera.

10. Buttons, vibration, charging port

Press power, volume up and down, and the ring switch or Action button: they should click firmly. Plug in a charger and gently wiggle the cable: if charging cuts in and out, the Lightning or USB-C port is loose or dirty.

11. Calls and signal

Put your own SIM in and make a call: the earpiece is clear, the other side hears you, and speakerphone works. Turn off WiFi and load a few pages over mobile data.

12. Body and water damage

Look along the frame under a light: a gap between the screen and the frame, or a slightly raised screen, is a sign of a swollen battery. Pull the SIM tray and look into the slot: a liquid indicator that has turned red means the phone has been in water.

After the checks

On soimay.com the Results page lets you save a PDF or create a report link as a record of the phone's condition when you bought it. Any faults you found are also a fair reason to negotiate. Things the browser can't read (IMEI, iCloud, battery) are covered by the manual checklist.

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