Checking a Used Phone Before You Buy
Six checks that cover the parts of a phone most likely to be quietly broken, all of them runnable in the phone's own browser.
Phones hide their faults better than laptops, because the screen and the digitiser are the same component and both are the parts most likely to have been repaired. A replaced screen is not automatically a problem, but an aftermarket panel can have a narrower colour range, worse brightness, or a digitiser that misses touches in a band near one edge. None of that is visible from the home screen.
The other reason to check carefully is that phone repairs are disproportionately expensive relative to secondhand value. A screen and digitiser assembly on a mid-range handset can cost a substantial share of what the whole phone is worth used. Unlike a laptop, you also cannot work around a bad touchscreen with an external peripheral — if the digitiser has a dead band, the phone is compromised for everything.
Run these on the phone you are buying, in its own browser, not on yours. That sounds obvious but it is the single most common mistake: people check the seller's listing photos and then test their own device out of habit. Every step below works in mobile Safari or Chrome with nothing installed.
The checklist
Tick each step as you go. Run them on the handset you are buying rather than your own, and keep the brightness up throughout — several of these checks depend on it.