Atreyee Poddar
Buying a second-hand phone feels a little like online dating. The photos look great, the description is glowing, and you really want to believe it's ‘gently used’. But just like dating, a little due diligence goes a long way before you commit.
Every phone has a unique ID number — its IMEI — and it is the single most important thing to check. Dial *#06# on the phone or find it in Settings, then plug it into a free checker like IMEI.info or your carrier's own lookup tool. This tells you instantly if the phone has been reported lost, stolen, or blacklisted. Skip this step and you could end up with an expensive brick the moment you try to activate it.
Batteries degrade, and replacing one isn't free. Check Settings > Battery > Battery Health on iPhone, or use an app like AccuBattery on Android. Anything under 80% health means you'll likely be buying a new battery sooner rather than later — factor that into your offer.
This is the fun (slightly awkward) part where you test everything in front of the seller: volume rocker, power button, charging port (bring your own cable!), Face ID or fingerprint sensor, and the vibration motor. If something feels sticky or unresponsive, that's leverage — or a dealbreaker.
On iPhone, confirm there's no Apple ID signed in and Find My iPhone is off. On Android, make sure the previous Google account is removed and Factory Reset Protection (FRP) is cleared. If the seller can't or won't do this, walk away.
Hidden inside the SIM card tray (and sometimes elsewhere) are tiny liquid contact indicators — usually white stickers that turn red or pink if the phone has taken a swim. A phone can look pristine and still have failed this test.