What is IMEI

IMEI IMEI (International Mobile Equipment Identity) is a unique 15-digit identifier assigned to every mobile device during manufacturing. It's like a fingerprint: no two devices share the same IMEI.

IMEI is used by mobile carriers to identify devices on the network, by law enforcement to track stolen phones, and by buyers to check a device's history before purchasing. The IMEI standard is defined by the GSMA and used worldwide.

IMEI is embedded in the device's cellular module at the factory and does not change after reflashing, factory reset, or SIM card swap. Changing an IMEI is illegal in most countries.

TAC TAC (Type Allocation Code) - the first 8 digits. They identify the manufacturer and device model. For example, TAC 35345678 uniquely identifies a specific iPhone model with a particular configuration (storage, color, region).

Serial Number Serial Number - the next 6 digits. A unique serial number for the device within its TAC group. This part makes every IMEI unique.

Check Digit Check Digit - the last digit. A checksum calculated using the Luhn algorithm. It verifies the IMEI's correctness - if someone makes a typo, the checksum won't match.

Starting with iPhone XS / XR (2018), all iPhones support two cellular lines - physical SIM + eSIM, or dual eSIM. Each line has its own IMEI:

IMEI 1 - the main physical SIM card (or the first eSIM on models without a SIM slot, starting with iPhone 14 US).

IMEI 2 - eSIM (or the second physical SIM on China models with dual SIM slots).

To check a device in iSpy, you can use either IMEI - both are linked to the same device and will give identical results for iCloud, Blacklist, and other checks. However, Carrier Lock may differ: one line may be locked to a carrier while the other is not.

For a pre-purchase check, IMEI is preferred - it covers more checks (Blacklist, Carrier Lock, iCloud, MDM). Serial number is useful for checking warranty and GSX reports. iSpy accepts both identifiers. warranty and GSX reports. iSpy