Buying a used phone: the ten-minute inspection that catches the three failures no seller mentions

Used-phone losses come in exactly three families, and the seller's own honesty never predicts which you are buying: a phone that belongs to someone else's account, a phone the networks are going to switch off, and a phone whose damage is cosmetic at the meeting and structural by the month. Fifteen minutes and a fixed sequence catch all three - and the sequence matters because its middle step is the one sellers resent, which is the one most worth insisting on.

Step one: the identity, matched and checked

Dial the IMEI code (the one every phone answers with on the dialer) and make the number match three places - the screen that appears, the box if it exists, and the settings page. Then run that number through the registry your country's operators use for stolen and blocked devices, plus the global device check the GSMA publishes - where the lookup lives changes by country and networks update the services, so ask the seller to stand with you while you open it; a genuine handset survives ten seconds of a public phone's browser. An IMEI that is 'different on the box than the phone' is not paperwork confusion; it is a phone with a transplanted identity, and the walk to the gate takes two minutes.

Step two: the erase in front of you - the step not to trade

Do not accept 'I'll wipe it after you pay.' Factory reset happens in front of you, and then the first minutes of setup tell you the truth: an iPhone must arrive at the welcome screen with activation lock off - if it asks for the previous owner's account, the phone is cuffed to that Apple ID and no price is low enough. Android's equivalent is the factory-reset protection: after your shared erase, if the setup screen demands a stranger's Google account, the sale ends there. While you are in the same menus, look at profiles and device-admin entries on Android and the VPN-and-management pane on iOS - a corporate profile is the signature of a company pool device, and those are more often lost than lost-and-found.

Step three: the damage pass, in daylight

• Battery, the honest ways: iPhones state maximum capacity in the settings - read it, and treat 'health' numbers quoted in listings as claims until the phone agrees. On Android, run the twenty-minute test: full charge, long video call, and a drop that makes the percentage slide like a bored clerk - past a quarter gone with the screen half-active, you are buying a battery job whether the seller agrees or not. And any back that bulges, any screen lifting at one edge: walk; a swollen cell is not a discount item.
• The screen-swap tells: True Tone missing on an iPhone is the manufacturer's own confession that the glass came off. Then the uniformity pages: full white and full grey images show glue lines, bright patches and the ghost of an old crack better than any seller's lighting. Drag an app icon in a slow rectangle hugging every edge - the corners are where a cheap replacement loses touch.
• Water: pop the SIM tray and look at the small sticker inside - pink or red means it was dunked and someone wants you not to know. Corrosion in the charging port and a speaker grille that sounds underwater on the test tone are the same story from further away.

Step four: the two-minute full-body

Every button, both cameras with flash, speaker on max and on call, mic - record a clip and play it back - charging in the port with your own cable, wireless charge if advertised, fingerprint on ten presses, face unlock in shadow. A used phone failing one sensor is a used phone priced as a donor board, whatever the listing's maths say. Then the receipt: names, number, IMEI written on it, both signatures - the paperwork is what separates 'bought cheap' from 'bought stolen' when the question is asked later, and an honest seller is relieved by it, which is its own test.

The verdict, as a rule

Every hesitation is a no: a seller who won't erase in front of you knows which of the three families you're about to discover. A phone that passes all four steps is the market's actual bargain - a flagship's hardware at its second-owner price, with the only risk left being the thing you can plan for: a battery, which this desk's charging pages long advised treating as a service item, not a verdict.