What Is an IMEI Number? Everything You Need to Know (2026)

Every mobile phone, cellular tablet and cellular smartwatch carries a 15-digit number that works like a fingerprint for its radio: the IMEI. You rarely see it, but networks read it every time the device connects, police use it to trace stolen handsets, and it’s the single most useful number you can have when you buy or sell a used phone.

This guide explains what an IMEI is, what each digit means, what it can (and can’t) reveal, and how to use it to protect yourself.

What does IMEI stand for?

IMEI stands for International Mobile Equipment Identity. It was introduced with GSM networks in the 1990s and is still used on 3G, 4G LTE and 5G today. Each IMEI belongs to the device, not to you and not to your SIM card. Swap the SIM, change the number, reset the phone — the IMEI stays the same.

That makes it different from two numbers people often confuse it with:

• Phone number (MSISDN) — belongs to your subscription and moves with your SIM.
• IMSI — the subscriber identity stored on the SIM or eSIM profile. It identifies your account to the network.
• IMEI — burned into the phone’s modem by the manufacturer. It identifies the hardware.

Phones with two SIM slots, or a SIM plus an eSIM, usually have two IMEIs — one per radio line. We cover that in why your phone has two IMEI numbers.

The structure: what the 15 digits mean

An IMEI isn’t random. It is built from three parts, defined by the 3GPP standards and administered by the GSMA:

• TAC — Type Allocation Code (digits 1–8). Identifies the brand and model. The first two digits are the reporting body that approved the allocation (for example 35 for BABT, 01 for PTCRB in the US, 86 for TAF in China). Read more in what is a TAC code.
• SNR — Serial Number (digits 9–14). A six-digit number the manufacturer assigns to each unit within that TAC.
• CD — Check Digit (digit 15). Calculated from the first 14 digits with the Luhn algorithm. It catches typos and many fake numbers. See how the IMEI check digit works.

You may also see a 16-digit IMEISV in some menus. It is the same TAC and serial followed by a two-digit software version number instead of the check digit. For checks, always use the 15-digit IMEI.

What an IMEI is used for

1. Identifying the device on the network

When your phone registers on a network, it reports its IMEI. Operators use it to apply settings for that model (VoLTE, 5G bands, Wi-Fi calling), and to enforce rules on the hardware.

2. Blocking lost and stolen phones

When an owner reports a phone stolen, the carrier adds the IMEI to its block list and, in most countries, shares it through the GSMA device registry — the “blacklist”. Networks connected to that registry can refuse service to the phone no matter which SIM is inserted. A GSMA blacklist check tells you whether a phone has been reported.

3. Carrier locks and financing

Carriers keep SIM-lock and financing status against the IMEI. That’s why a carrier and SIM-lock check can tell you if a phone is locked to AT&T, Vodafone or another network before you pay — and why US phones with unpaid balances can be barred via the USA blacklist / barred check.

4. Warranty, repairs and records

Manufacturers link the IMEI (and serial number) to warranty, purchase date and repair history. Apple, Samsung and Google support desks will ask for it.

Is the IMEI unique? Can it be changed?

Each IMEI is meant to be unique worldwide. Manufacturers receive TAC ranges from the GSMA and are responsible for never repeating a serial within them. In practice you can occasionally find duplicate IMEIs on cheap counterfeit or uncertified phones that all share one invalid number — another reason to verify before you buy.

Changing an IMEI (sometimes called “IMEI repair” or “flashing”) is illegal in many countries, including the UK, and it’s a common trick used to resell stolen handsets. A phone whose IMEI in Settings doesn’t match *#06#, the SIM tray or the box should be treated as a red flag.

How to find your IMEI

The universal method works on almost every phone: open the dialer and type *#06#. The IMEI (or both IMEIs on dual-SIM phones) appears instantly — no call is made.

• iPhone: Settings › General › About, then scroll to IMEI.
• Android: Settings › About phone (on some models: About phone › Status or IMEI information).
• Box or SIM tray: most boxes carry the IMEI on a barcode label; many iPhones print it on the SIM tray.

Lost the phone itself? There are still several ways to recover the number — see how to find the IMEI number on any phone.

Validate an IMEI in your browser

Before you run paid checks, make sure the number is even possible. The tool below checks the length and the Luhn check digit and splits the IMEI into TAC, serial and check digit. Try the sample 356938035643809, then paste your own:

A valid result only means the number is well-formed. It doesn’t tell you who owns the phone, whether it’s blacklisted, or whether it’s iCloud-locked. For that you need an official record lookup.

What an IMEI check can — and can’t — tell you

An IMEI is not personal data in the sense of exposing the owner, which is why sharing it with a buyer is safe and normal. It’s also why tracking a phone “by IMEI” is something only networks and law enforcement can do — any app that promises to locate a phone from its IMEI alone is a scam.

To see the full picture on a phone you’re about to buy, start with the All-in-one Basic Info report (Apple) or All-in-one by IMEI/serial, and confirm the brand and model with a manufacturer + model check. Our IMEI check page runs them for you.