How to Test a Used iPhone Before Buying
Buying from eBay, Swappa, Back Market or Facebook Marketplace? Work through this checklist with the phone in your hand before you pay. The first two steps take a minute and protect you from the two faults that make a phone worthless — everything after that runs free in your browser, in about ten minutes total.
-
Check Find My iPhone is switched off
Open Settings, tap the name at the top, then Find My, then Find My iPhone. It must be OFF, and the phone must be signed out of the seller's Apple ID. A phone still linked to their account is activation-locked and permanently unusable to you — no reset, repair shop or Apple Store can unlock it. If the seller cannot sign out on the spot, walk away.
Checked on the phone itself — no tool needed.
-
Verify the IMEI is clean
Dial *#06# to display the IMEI, and check it matches Settings, General, About. Run it through a free IMEI checker to confirm the phone is not reported lost or stolen and is not still tied to a carrier contract. A blacklisted IMEI cannot make calls on any network.
Checked on the phone itself — no tool needed.
-
Check the battery health
Settings, Battery, Battery Health & Charging. Aim for 85% or higher. Below 80% costs roughly the price of a replacement, so use it to negotiate. If Maximum Capacity is missing entirely, the phone has a non-genuine battery — ask what else was replaced.
iPhone battery health guide → -
Read the Parts and Service History
Settings, General, About, then scroll to Parts and Service History. iOS lists any screen, battery or camera it cannot verify as genuine. Replaced parts are not automatically a dealbreaker, but they should match the seller's account of the phone — and they should be reflected in the price.
Checked on the phone itself — no tool needed.
-
Inspect the screen for dead pixels
Fill the screen with solid colours to catch dead or stuck pixels and discolouration. These hide easily against a normal home screen and are impossible to fix afterwards.
Open the dead pixel test → -
Check the OLED screen for burn-in
Check the panel type first: the X, XS, 11 Pro, 12 and every model after use OLED, which can develop permanent ghosting, but the XR, 11 and SE (2nd and 3rd generation) are LCD and cannot burn in. On an OLED model, look for a faint keyboard outline in the lower half or a status-bar shadow along the top, using flat grey at moderate brightness in a dim room.
Open the burn-in test → -
Test the whole touchscreen
Drag across every part of the display to find dead zones. Replacement screens and drop damage often leave a narrow unresponsive strip along one edge that normal use rarely reveals.
Open the touchscreen test → -
Test multi-touch
Place several fingers on the screen at once. Failed multi-touch breaks pinch-to-zoom and typing accuracy, and it is a common fault on cheap aftermarket panels.
Open the multi-touch test → -
Test the cameras
Check the front camera here, then open the Camera app and cycle through every rear lens — ultra-wide, wide and telephoto. Look for dust behind the glass, purple flare and a lens that will not focus.
Open the camera test → -
Test the microphone and speakers
Record and play back to confirm the microphone is clean, then use the audio test for the speakers. Water-damaged iPhones very often sound muffled or crackly here first.
Open the microphone test → -
Check the motion sensors
Rotate the phone to confirm the gyroscope responds. Faulty motion sensors break screen rotation, camera stabilisation and navigation, and they are a classic symptom of a hard drop.
Open the gyroscope test → -
Test the vibration motor
Confirm the Taptic Engine fires. A dead vibration motor means no silent-mode alerts, and on an iPhone it is an awkward, labour-heavy repair.
Open the vibration test →
Red flags — negotiate hard or walk away
- The seller cannot or will not sign out of their Apple ID. Walk away — this is not negotiable.
- The IMEI comes back as lost, stolen or blacklisted.
- Maximum Capacity is missing from Battery Health, indicating a non-genuine battery.
- Several parts flagged as unverified in Parts and Service History, which often points to water or impact damage.
- Dead touch zones along a screen edge.
- Muffled or crackling microphone and speakers — a common sign of water damage.
- The seller will not let you spend ten minutes with the phone before paying.
Frequently Asked Questions
What is the most important thing to check when buying a used iPhone?
Activation Lock. If Find My iPhone is still on and signed in to the seller's Apple ID, the phone is permanently tied to that account and nobody — not a repair shop, not Apple — can unlock it. Make the seller sign out in front of you before any money changes hands.
What battery health is acceptable on a used iPhone?
Aim for 85% or higher. Between 80% and 84% the phone works fine but a replacement is due, so deduct that cost from your offer. Below 80% iOS shows a Service message. A missing Maximum Capacity figure means a non-genuine battery.
How can I tell if a used iPhone is stolen?
Dial *#06# for the IMEI and run it through a free IMEI checker for lost, stolen or blacklisted status. A blacklisted phone cannot connect to any mobile network. Confirm Find My is off as well, since stolen devices are usually still linked to the owner's account.
Does a replaced screen or battery mean I should not buy it?
Not necessarily — a professional repair can be perfectly good, and a new battery is a plus on an older phone. What matters is that it is disclosed and reflected in the price. Be more cautious when several parts are flagged, which often indicates water or impact damage.
How long does the full check take?
About ten minutes. Every browser test runs without installs, so you can do it while meeting the seller. The activation lock and IMEI checks take under a minute and should never be skipped.