Why this check matters more than any spec
A used iPhone that is still bound to the seller's Apple ID will stop at an Activation Lock screen the moment it is reset, however good the screen or battery is. At that point it is worth parts money only.
Activation Lock cannot be removed by any tool, so the entire value of the purchase hinges on confirming the lock is not present before you hand over money.
The five-minute verification
Do this with the seller present and before any payment. If any step is refused, treat it as a failed inspection rather than a negotiation point.
- 1Ask the seller to factory-reset the iPhone in front of you (Settings → General → Transfer or Reset iPhone → Erase All Content and Settings).
- 2Confirm it drops to the Hello / setup screen rather than an Activation Lock screen.
- 3Watch the seller sign out of iCloud, or verify at icloud.com/find that the device is gone from their account.
- 4Check the IMEI on the box or SIM tray against Settings → General → About before any reset.
- 5Test that a fresh Apple ID of yours can complete setup and reach the Home Screen.
- 6Walk away from any seller who refuses any of these steps — it is the single most reliable red flag.
Reading the IMEI the right way
Find the IMEI in Settings → General → About, on the original box, or in the SIM tray of older models. Cross-check that the number matches in all available places — mismatches are a sign of a swapped chassis or a refurbished device being sold as new.
You can confirm the device is not reported lost or stolen and see its Activation Lock state through Apple's coverage checker and any reputable IMEI check service. A device still signed in to someone's Find My will show as activation-locked.
Red flags that should end the sale
A seller who will not let you reset the phone in person, who 'will remove the account later', who insists you pay first, or who claims Activation Lock is easy to 'unlock with software' is describing a device you cannot safely buy.
That last claim is both false and a reliable tell: no software clears Activation Lock. A seller who repeats it either does not understand the device they are selling or intends to sell you one that will never activate.
FRPB and used-device checks
FRPB is for Android Factory Reset Protection, not iOS Activation Lock, so it plays no part in inspecting an iPhone. Its relevance is to Android purchases, where FRP is the equivalent obstacle and can be cleared for a genuine owner.
Whichever platform you are buying, the principle is identical: verify the device is free of its previous account before paying, because that is the one problem no tool reliably fixes.
Safety, legality and when to stop
FRPB is intended strictly for authorised device owners and licensed repair professionals. You must own the device or hold explicit written permission from its owner. Using an FRP bypass tool on hardware you do not own may defeat an anti-theft control and can be illegal in your jurisdiction.
Stop and reassess if the device reports a bootloader state you did not expect, if the model or chipset FRPB detects does not match the handset in front of you, or if the operation halts mid-way. A mismatched firmware package is the single most common cause of a hard brick — abandoning an operation is always cheaper than recovering from one.