What is IMEI? Complete Guide to International Mobile Equipment Identity

What Is IMEI?

IMEI (International Mobile Equipment Identity) is a unique 15-digit number that identifies every mobile device worldwide, including smartphones, tablets, cellular-enabled smartwatches, and mobile hotspots.

IMEI numbers are assigned and managed by the GSMA (Global System for Mobile Communications Association). Each phone is programmed with a one-of-a-kind IMEI at the factory, and this number is tied to the device hardware, meaning it cannot normally be changed. You can think of the IMEI as the "ID card" of your phone, because carriers, manufacturers, and law enforcement use it to identify, track, and verify every single device.

As of 2026, more than 5 billion mobile devices are in active use around the world, and each one carries at least one IMEI. Dual-SIM phones have two IMEI numbers, one for each SIM slot, so a single device can be identified on two cellular networks independently.

If you want to verify a phone before buying it second-hand, the fastest way is to check its IMEI through a service such as IMEICheck, which returns the model, warranty status, carrier lock, and blacklist status in seconds.

The 15-Digit IMEI Structure

An IMEI is not a random string of numbers. It follows a strict structure defined by the 3GPP standard, and the 15 digits are split into three sections:

1. TAC (Type Allocation Code) — First 8 digits

The TAC is the "Type Allocation Code" and it identifies the brand and exact model of the device. The first 2 digits are the Reporting Body Identifier, for example 01 for the CTIA in the United States and 35 for the BABT in the United Kingdom. The remaining 6 digits are allocated by the GSMA to a specific device model. An iPhone 15 Pro Max and a Samsung Galaxy S25 Ultra carry completely different TAC codes.

From the TAC alone it is possible to reverse-lookup the brand, model, storage capacity, and even the color of a device. The GSMA maintains a database of more than 290,000 TAC records, and IMEICheck uses this database to identify a device model from its IMEI.

2. SNR (Serial Number) — Middle 6 digits

The SNR is the serial number of the device, assigned by the manufacturer to differentiate individual units that share the same TAC. In other words, every phone of the same model has the same TAC but a different SNR.

3. Check Digit — Last 1 digit

The 15th digit is a check digit calculated from the first 14 digits using the Luhn algorithm. Its purpose is to validate the IMEI: if you mistype a single digit, the check digit will not match and the IMEI will be rejected, preventing incorrect lookups.

What Is IMEI Used For?

The IMEI number has several important real-world uses:

1. Anti-theft and Blacklisting

When a phone is stolen or lost, the owner can contact their carrier to have the IMEI added to the GSMA blacklist. Once blacklisted, the device cannot connect to any cellular network to make calls or use mobile data, even if the thief inserts a new SIM card. This is the single most powerful anti-theft function of the IMEI.

Before buying a used phone, always run an IMEI check to confirm the device is not blacklisted, so you do not end up with a stolen or unpaid phone.

2. Warranty Verification

Manufacturers use the IMEI to look up a device activation date and warranty status. For example, Samsung phones can be verified by IMEI to confirm whether they are still under warranty and how many days of coverage remain. Apple devices are usually checked by serial number, which serves the same purpose.

3. Carrier Lock Detection

Carriers use the IMEI to identify whether a device is SIM-locked (also called "network locked" or "carrier locked"). If you bought a phone on contract from a carrier, the device may be locked to that carrier. An IMEI check reveals the lock status and whether the phone is eligible to be unlocked.

4. Used Phone Verification

When buying a second-hand phone, an IMEI check verifies:

• Whether the model matches what the seller claims
• Whether the activation date matches the stated purchase time
• Whether the device is refurbished or a clone
• Whether iCloud Activation Lock is on (for iPhones)
• Whether the device is blacklisted

5. Device Tracking

Although the IMEI itself does not provide GPS location, carriers can see which cell tower a device connects to and use the IMEI to roughly estimate its location. Law enforcement agencies use IMEI-based tracking when investigating phone theft cases.

IMEI vs MEID vs Serial Number

Many people confuse IMEI, MEID, and the serial number. They are related but distinct concepts:

Modern phones (post-2020) almost all use IMEI, while MEID is mainly found on older CDMA devices. Apple devices usually have both an IMEI and a serial number, and the serial number typically returns more detailed information when checked.

How to Find Your Phone IMEI

There are several ways to find an IMEI, depending on your situation:

Method 1: Dial code (fastest)

Open the phone dialer and enter *#06#. The IMEI appears on screen instantly. This works on essentially every phone brand.

Method 2: Check in Settings

iPhone: Settings > General > About > scroll down to IMEI

Android: Settings > About phone > Status information > IMEI information

Method 3: Physical labels

The IMEI is usually printed in these locations:

• On the barcode label of the original phone box
• On the back of the SIM tray (on some models)
• On the back of the phone (on some older models)
• On the purchase receipt or e-warranty card

Method 4: If the phone is lost

If the phone is already lost, you can still recover the IMEI:

• Google Dashboard (Android): visit google.com/android/find
• iCloud (iPhone): sign in at icloud.com and check the device list
• The original phone box
• The purchase receipt or order confirmation email

Frequently Asked Questions

Conclusion

IMEI is the unique identifier of every mobile phone, a 15-digit number that encodes the device model, serial number, and a validation check digit. It plays a critical role in anti-theft blocking, warranty verification, carrier lock detection, and used phone verification. Understanding what an IMEI is and how to use it helps you protect your device rights and avoid scams when buying a second-hand phone.

If you need to check a phone IMEI right now, use the IMEICheck free lookup tool. Enter the 15-digit IMEI to instantly receive a full report covering model, warranty status, carrier lock, and blacklist status.