Buying a used smartphone is an excellent way to save 30–50% off the price of a new device while still getting a flagship from a previous generation. But there's a downside to such a deal: hidden defects, locked devices, water damage, and fakes. To avoid disappointment, you need to know what to look for. We've prepared a checklist of 12 essential checks — go through it before handing over your money.
1. Check the IMEI and serial number
Dial *#06# — the IMEI will appear on the screen. Compare it with the number on the box, in the settings ("About Phone"), and on the SIM card tray. All three values must match. Then "check" the IMEI on the manufacturer's website (e.g., checkcoverage.apple.com for iPhone) or through services like imei.info — this will tell you the model, year of manufacture, warranty status, and if the device is reported stolen.
2. Make sure it's not an iCloud/Google lock
The main pain point of the used market is locked devices. Ask the seller to log out of their Apple ID or Google account right in front of you and perform a factory reset. After the reset, the phone should go through the initial setup without asking for someone else's password. If the seller refuses, walk away.
3. Inspect the body and screen in good lighting
Turn the phone at different angles in bright light. Look for dents, chips on the corners (a sign of drops), scratches on the glass, and signs of tampering (damaged screws, uneven gaps between the body and the screen). Turn on a white background (open a blank page in the browser) and check the screen for dead pixels, spots, yellowing, and lines.
4. Test the touch screen and Force Touch
Open "Notes" or any drawing application and drag your finger across the entire screen — the line should be continuous with no "blind spots." Check all edges: sometimes, after a screen replacement, the touch screen works intermittently around the perimeter.
5. Check the battery health
On iPhone: "Settings" → "Battery" → "Battery Health & Charging." The capacity should be no less than 85% — otherwise, the battery will need to be replaced soon. On Android, use codes (*#*#4636#*#* for some models) or the AccuBattery app: it will show the real capacity after several charging cycles.
6. Test all cameras and the flash
Take several photos and videos with the main, ultrawide, telephoto, and front cameras. Check autofocus, stabilization, flash, and the operation of all modes (portrait, night, slow-motion). The images should be sharp, without spots or dark areas at the edges — this is a sign of a damaged sensor.
7. Check the speakers, microphones, and earpiece
Play some music — the sound should be loud, clear, and without crackling. Record a voice message and listen to it: if the voice is muffled, the microphone is clogged or damaged. Call someone and make sure you can hear the other person through the top earpiece.
8. Test all buttons and ports
Volume buttons, power button, mute switch, Touch ID/Face ID, fingerprint scanner — everything should respond on the first press. Connect the charger and headphones (if there's a jack): check that the device charges steadily and sound travels both ways.
9. Check Wi-Fi, Bluetooth, GPS, and cellular connectivity
Connect to Wi-Fi, download a small file — the speed should match your plan. Pair the phone via Bluetooth with another device. Open "Maps" and make sure GPS quickly finds your location. Insert your SIM card — the phone should register with the network immediately.
10. Make sure Face ID / Touch ID are working
On iPhone, a common problem is that Face ID or Touch ID stop working after non-original repairs. Ask the seller to register your face or fingerprint right in front of you. If the feature is "unavailable" — this is a serious drawback and a reason to negotiate the price or decline the purchase.
11. Check repair history and part originality
On iPhone XS and newer, in "Settings" → "General" → "About" → "Parts and Service History", the system will show if the screen, battery, and camera have been replaced, and if the parts were original. The message "Unknown Part" means that the device was repaired in an unofficial workshop — this affects both the price and the lifespan.
12. Request a receipt, box, and indirectly check water resistance
A receipt or box is not mandatory but increases trust in the seller. Ask directly if the phone has been submerged: even after drying in rice, the device eventually starts to "glitch." Look into the charging port with a flashlight — oxidation or a green film indicates moisture ingress.
What to do after checking
If all 12 points are passed — congratulations, you have a worthy device. If 2-3 points raise doubts, negotiate or look for another option. The most reliable way to avoid risks is to buy refurbished smartphones from trusted sellers with a warranty: each device undergoes diagnostics on dozens of parameters, and in case of problems, it is exchanged or refunded.
At APPTRADE, we only sell verified Apple iPhone, Google Pixel, and Samsung Galaxy smartphones with pre-sale diagnostics and warranty — you don't need to go through the checklist yourself; we've already done it for you. Check out our catalog and choose your next smartphone risk-free.