A used laptop usually arrives by post and you get days with it. A used phone gets handed to you across a table, and you have about ten minutes.
So the order matters. Deal with what cannot be undone first. A dead pixel is annoying; a handset with someone else’s account still attached is a paperweight.
If you’re reading this on the phone in question, that helps. Every check below runs in this browser.
Buying a used phone, the three things that can’t be fixed later
The account lock, which you cannot check online
Skip this one and the phone can end up unusable.
On an iPhone, Activation Lock ties the handset to the previous owner’s Apple Account. Erasing it doesn’t help: setup will demand their password. Apple documents what triggers it and how the seller removes it.
The catch is that there is no official way to check it in advance. Apple withdrew the serial-number lookup that did this in January 2017. Any site now offering an “iCloud lock check” by IMEI is not Apple, and you are trusting an unknown third party with the handset’s identifiers.
That leaves one reliable method: at the meeting, have the phone erased and take setup all the way to the home screen. If a lock remains, setup stops and asks for an account you don’t have. A seller unwilling to do this has told you something.
Android works the same way. Factory Reset Protection keeps the previous Google Account attached (Google’s explanation), and the test is identical: erase, then reach the home screen.
It takes a few minutes, so ask the seller to bring the phone already erased.
Whether it’s been reported lost or stolen
A blocked IMEI means no network will activate it. Cheap becomes worthless.
Get the IMEI before you meet — dialling *#06# displays it — and run it through whichever blocklist service covers your country. These are national rather than global, usually run by a carrier association or a police-linked register, so search for the one operating where the phone will be used rather than trusting a generic checker. A result is a snapshot: a handset reported an hour ago won’t show yet.
Check it before the meeting. Walking away is much easier over a message than across a table.
Outstanding finance and network lock
A phone bought on an instalment plan leaves the finance agreement in the seller’s name. Changing who holds the handset doesn’t move the contract. What a carrier can do about arrears varies by contract and country, which is a good reason to buy one that is already paid off rather than find out.
Ask to see the balance screen in their carrier app, and confirm the phone isn’t locked to a network you don’t use.
Then the checks that run in the browser
From here you can use the phone in your hand. A minute or two each.
Whether the touchscreen responds everywhere
This is the fault that hides best. A replaced screen or a bad drop leaves patches that don’t register, or areas that register touches nobody made.
Opening a few apps won’t find it, because you only ever touch the same familiar places. The touch test above lays out twenty cells, four across and five down, and leaves the ones you haven’t reached unfilled.
The grid is a panel on the page rather than the whole display, so it can’t cover every corner. Turning the phone landscape and running it again puts the grid over a different band of the screen.
Pay attention to the edges and corners — that’s where a replacement panel usually shows its seams. Touchscreen problems covers telling dead zones from ghost touch.
What the screen looks like under a flat color
The dead pixel test fills the display with one color at a time. Bright app screens in a bright room hide all of this.
- Black dot on white → dead pixel
- Bright dot on black → stuck pixel
- A pattern on gray → burn-in. A status bar or keyboard outline means heavy use
Most phones are OLED now, so burn-in is a real risk rather than a theoretical one. See image retention and burn-in for the shapes to look for, and dead pixels for single points.
If you’re meeting somewhere bright, cupping your hands around part of the screen helps.
Speakers and microphone
The speaker test drives each side separately. Phones split their speakers between the earpiece and the bottom edge, so one dead side disappears entirely when music is playing.
The mic test just needs the input level to move while you talk. Some handsets use different microphones for calls and recording, so an actual phone call is the more complete check.
What a browser can’t tell you
Battery health. On iPhone it’s in Settings → Battery → Battery Health, shown as a maximum capacity percentage. Android varies by manufacturer and some don’t show it at all. Either way you have to ask the seller to open it in front of you.
Charging and the port. Plug it in and confirm it actually charges. If wiggling the cable interrupts it, the port is worn.
Cameras. Open the stock camera app and cycle through rear, front, and ultra-wide. Watch for focus hunting and for haze or specks in the frame.
Physical condition. Screws with tool marks, an uneven gap between frame and glass, a display whose color is slightly off — all signs of past repair. Liquid contact indicators sit in different places on different models.
The same evening
One more thing once you’re home: sign in with your own accounts and confirm the erase was genuine. A leftover account belonging to the previous owner can lock the phone remotely later. Walk through the accounts listed in settings.
Going the other way, if you’re the one selling, remove your accounts before wiping. Reversed, the buyer inherits the same problem. Wiping a device before you hand it on has the order.
The short version
Run the IMEI before you meet. At the table, erase the phone and take setup to the home screen — that is the only reliable account-lock check there is. Then sweep the touchscreen, put a flat color up, and test both speakers. Ten minutes.
Laptops need a different list: what to check when buying a used laptop. If something sold as new looks like it wasn’t, was it really new? covers the counters that can’t be reset.