As the world moved from feature phones to smartphones over the last few decades, a tiny detail called an IMEI number has remained a constant. But why is it significant, and what does its existence mean for you?

The IMEI or International Mobile Equipment Identity number is a unique identifier assigned to cellular or mobile devices worldwide. It plays a vital role in a mobile device’s functionality and security. The GSMA (Global System for Mobile Communications Association) is a global body responsible for managing and overseeing the IMEI system.

An IMEI number is primarily used by mobile phones. However, other devices that have a built-in cellular modem, including tablets, mobile hotspots, smartwatches, IoT, and smart home products, also have an IMEI number.

The manufacturer assigns it during a device’s production. However, the manufacturer isn’t solely responsible for it, as part of it is generated by reporting bodies present in different regions, which the GSMA has appointed.

The primary role of the IMEI number is to help cell carriers identify mobile devices on their networks. Carriers use IMEI numbers to recognize and authenticate devices, and manufacturers sometimes use IMEI to identify devices for warranty and after-sales support.

Typically, IMEI is a 15-digit code. This 15-digit identifier comprises three main components – a Type Allocation Code (TAC), a Serial Number (SNR), and a Check Digit (CD).

The TAC is the first eight digits of an IMEI number. It includes two main components: the Reporting Body (RB) identifier and the Type Identifier (TI). The TAC is generated by the reporting bodies for specific device models and primarily includes identifiers about the device model, brand owner, and OEM manufacturer.

The SNR is six digits long and comes after the TAC. It’s the unique serial number assigned by the device manufacturer. The manufacturer calculates the 15th digit, or CD, using the Luhn algorithm and uses it to verify the validity and accuracy of the entire IMEI number.

Device manufacturers also use an extension of IMEI called IMEISV, which has 16 digits. It skips the CD and includes two digits about the device’s software version at the end.

The IMEI number was introduced in the late 1980s or early 1990s, but the exact year of its introduction is unclear. Its initial composition included six digits as TAC and two digits as a final assembly code (FAC). The FAC was phased out around 2003, and the TAC was expanded to eight digits. Since then, the same composition has been used.

Although several organizations have contributed to IMEI’s current state, the GSM Association (GSMA) has been responsible for its management since 2000 and maintains the IMEI database.