How to Check a Used iPhone Before You Buy It

App detail screen showing verified iPhone and carrier code information
See the app on the App Store: Secret Codes: IMEI & Carrier

Secret Codes: IMEI & Carrier app icon

Buying a used iPhone can be a great way to save money, but a quick inspection is essential. Before you pay, check the IMEI, carrier lock, Activation Lock, battery, display, cameras, speakers, and cellular connection. This checklist helps you identify problems while you are still with the seller.

1. Check the IMEI and model

Open Settings > General > About and compare the IMEI with the seller's documentation or original box. You can also dial *#06# in the Phone app to display supported device identifiers. Do not post an IMEI publicly; share it only with a carrier or trusted seller when necessary.

2. Confirm Carrier Lock

In the About screen, look for Carrier Lock. “No SIM restrictions” generally means the iPhone is unlocked. If the phone is locked, ask the original carrier whether it can be unlocked before you buy it. An unlocked device is especially important if you plan to travel or switch to an MVNO.

3. Check Activation Lock

The seller should erase the iPhone in front of you and remove it from their Apple Account. Do not buy a device that asks for the previous owner's Apple Account during setup. This is different from a carrier lock and can prevent you from using the phone.

4. Test the hardware

Check Battery Health, storage, touch input, display pixels, cameras, microphone, speaker, Face ID, charging, Wi-Fi, Bluetooth, and cellular data. A short call and a mobile-data test can reveal problems that are not obvious from the outside.

Use a verified iPhone checklist

Secret Codes: IMEI & Carrier on the App Store brings IMEI, carrier-lock, SIM, eSIM, carrier compatibility, and device diagnostic checks together in one utility. It is useful when you need a clear checklist at the seller's location, and the app does not upload your saved notes or scan results.

Final decision

Walk away if the seller refuses the checks, the IMEI details do not match, Activation Lock remains enabled, or the carrier cannot confirm compatibility. A few minutes of testing can prevent an expensive mistake.

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