International Mobile Equipment Identity (IMEI) is a number that facilitates device validity identification. The IMEI number is unique and typically 15 or 17 digits, which are stored on the battery's backside. The IMEI is strictly used for identification by by Global System for Mobile Communications (GSM), Wideband Code Division Multiple Access (WCDMA) and some satellite devices.
The IMEI number does not have a permanent subscriber relationship. Swapping a Security Information Management (SIM) card cannot prevent phone banning because the IMEI number is stored inside the phone - not the SIM card.
The most common IMEI format is AA-BBBBBB-CCCCCC-D, described as follows:
- AA: Represents the Reporting Body Identifier indicating Type Allocation Code (TAC) by GSMA approval group
- BBBBBB: Represents remaining TAC digits
- CCCCCC: Represents the serial sequence of the model, or mobile phone
- D: Algorithm used to validate the ID number. May be a LUHN check digit for the entire model or 0.
- A check digit is the last IMEI digit and calculated according to the LUHN formula. The check digit is a function of all remaining IMEI digits and guards against potentially incorrect entries in the central equipment identity register (CEIR). Check digit presentation should be in electronic and printed form on both the label and packaging.
Information regarding manufacturer, model type, date and country of approval may be located on mobile phones with known IMEI numbers. The IMEI number's primary purpose is blocking or tracking lost mobile phones via the IMEI database (IMEI DB), which is a central database containing basic IMEI information. This database is used by millions of GSM and #G devices in GSM networks worldwide. When a phone powers on, the IMEI number is transmitted and verified by the IMEI DB in the network's Equipment Identity Register (EIR).
The GSM association provides IMEI DB member access to GSM and 3G operators across the world. Network operators use IMEI DB data to determine customer device types and supported features.