imei

The International Mobile Equipment Identity (IMEI) is a unique identifier assigned to mobile devices that connect to cellular networks. It is used by network operators, manufacturers, and authorities to identify valid devices, prevent theft, and manage access to networks.

The standard IMEI number is 15 digits long. It consists of a Type Allocation Code (TAC) of the first 8 digits, a Serial Number (SNR) of the next 6 digits, and a final check digit. The check digit is calculated with the Luhn algorithm to verify the number’s integrity. The TAC identifies the device model and configuration, while the SNR uniquely identifies an individual device within that model family.

IMEI numbers are allocated by manufacturers and registered in global databases maintained by the GSMA and national regulators. Operators may blacklist devices by IMEI, rendering stolen or unauthorized phones unusable on the network. The IMEI is distinct from the IMSI, which identifies the subscriber’s SIM card rather than the device.

IMEI Software Version (IMEISV) adds two digits to indicate the device’s software version, producing a 16-digit number used in some networks and devices.

Because the IMEI is a persistent device identifier, it is treated as sensitive information in many jurisdictions. In most places, changing or falsifying an IMEI is illegal. Users can typically view their device’s IMEI by dialing *#06# on many phones or by checking device information menus.

Related identifiers include the MEID, used in certain CDMA networks.