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What is an IMEI number?

Understanding IMEI: The comprehensive guide

The International Mobile Equipment Identity, popularly known as IMEI, is a unique number attributed to every mobile device worldwide. This number is of paramount importance, serving as an identifier for the phone, and holds significant value for both consumers and service providers.

What is an IMEI number?

The IMEI is a 15 to 17 digit number that is universally unique to each mobile device. It is often compared to the VIN (Vehicle Identification Number) of a car, as it serves a similar purpose. This number is used by the GSM (Global System for Mobile Communications) network to identify valid devices. In simpler terms, the IMEI is the identity card of your mobile device, allowing service providers to confirm the device’s authenticity.

Where can I find my IMEI number?

Finding your IMEI number is relatively straightforward. Here are a few methods:

  1. Dial a USSD code
    Dial *#06#, and the IMEI number will appear on your screen.
  2. Check device settings
    Navigate to ‘About Phone’ in your device settings.
  3. Look at physical hardware
    The IMEI number is often printed on the back of the device or beneath the battery.

What is the purpose of an IMEI number?

IMEI numbers are used by mobile network operators (MNOs) to identify and verify a device when it tries to connect to their network. If the IMEI of the device matches an authorised identifier on the global IMEI database, then it will be permitted to traverse data over the network. If it doesn’t match an authorised identifier, then the device will not be granted permission to utilise the network. This is a very common occurrence when it comes to mobile phones as many handsets are locked to specific networks upon purchase.

Why is my IMEI number important?

The IMEI number plays a pivotal role in various situations:

  • Theft or loss
    If your phone is lost or stolen, the IMEI can be used to block the device from being used on any network.
  • Warranty claims & repairs
    Service providers use the IMEI to verify warranty claims and track repairs.
  • Network compatibility
    Certain networks may only support devices with specific IMEI ranges.

The structure of an IMEI number

IMEI numbers are made up of a 15-digit code. It can be split into the following sections…

  • Reporting Body Identifier (RBI)
    A 2-digit code that outlines the GSMA-approved group that allocated the TAC.
  • Type Allocation Code (TAC)
    6-digit code that outlines the model and origin of your device.
  • A serial number (SN)
    6-digit identifier that is unique to your device.
  • Check digit (L)
    This is generated by the Luhn algorithm.

Breaking down IMEI numbers

All IMEI numbers follow the same format:


For example:

35 (RBI) + 012345 (TAC) + 123456 (SN) + 0 (L)

In this example, your device’s IMEI number would be 350123451234560.

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IMEI and it’s role in security

They can also be used to identify devices when they have been lost or stolen. Reporting the IMEI of a missing device to the police can help make sure it is returned to the rightful owner. For this reason, it’s important you make a note of your IMEI numbers and keep them safe. You should never share these device identifier codes with third parties for security reasons.

If your cellular devices are being misused or not adhering to fair usage policies set out by the networks, MNOs have the ability to blacklist IMEI numbers via the global IMEI database. Since all networks can access the database, a blacklisted identifier would prevent your device from being able to operate on any network. It can be a very difficult process to get an IMEI number removed from the blacklist once it has been added.

IMEI and the GSM Association

The GSM Association, a trade body that represents the interests of mobile operators worldwide, assigns the TAC part of the IMEI number. It ensures that each IMEI is unique and corresponds to a specific model and manufacturer.

Mobile Telephones (Re-Programming) Act

Many countries and law enforcement agencies use IMEI numbers to combat cybercrime. In the United Kingdom, the Mobile Telephones (Re-Programming) Act makes it illegal for anyone to own equipment that can change the IMEI number of devices.


Understanding the IMEI number can be of immense value. Not only does it help in identifying your device, but it also plays a crucial role in security, repairs, and network compatibility. Always keep a record of your IMEI number to ensure that you can take appropriate action if your phone is lost or stolen.