What IMEI Stands For
IMEI means International Mobile Equipment Identity. It is a 15-digit number assigned to cellular devices and used by mobile networks to identify the physical hardware connecting to them. Unlike your phone number or SIM card, the IMEI is tied to the device itself — it does not change when you swap carriers or SIM cards.
IMEI Structure: TAC, SNR, and Check Digit
The 15 digits of an IMEI are divided into three functional segments:
- TAC (Type Allocation Code) — digits 1–8: Identifies the device model and manufacturer. The first two digits indicate the reporting body (for example, 35 means allocated by the GSMA through the UK). The TAC is how a carrier instantly knows which phone model is connecting without you telling them.
- SNR (Serial Number) — digits 9–14: A unique serial number assigned by the manufacturer that distinguishes individual units of the same model.
- Check digit — digit 15: Calculated using the Luhn algorithm, the same checksum method used on credit card numbers. It validates that the preceding 14 digits form a structurally legitimate IMEI and catches simple transcription errors.
The Luhn check works by doubling every other digit from right to left, summing the result, and confirming the total is divisible by 10. If a digit is entered incorrectly, the check fails and the IMEI is rejected as invalid before any network query is made.
IMEI vs MEID vs EID
| Identifier | Length | Used By | Purpose |
|---|---|---|---|
| IMEI | 15 digits (decimal) | GSM/LTE/5G devices globally | Identifies the device on the network |
| MEID | 14 hex digits | Legacy CDMA devices (older Verizon, Sprint) | Same concept as IMEI for CDMA equipment |
| EID (eSIM ID) | 32 hex digits | Devices with embedded SIM | Identifies the eSIM chip, not the device's radio identity |
Modern 5G phones use IMEI. Older CDMA-era devices used MEID, which is a 56-bit hexadecimal identifier. The EID is separate from both — it identifies the physical eSIM chip soldered into the device and is used during eSIM profile provisioning, not for network registration.
IMEI vs SIM vs ICCID vs Phone Number
| Identifier | Identifies | Used For |
|---|---|---|
| IMEI | The phone hardware | Compatibility checks, blacklist, warranty, activation |
| SIM / eSIM profile | Your carrier subscription credentials | Authenticating your line on the network |
| ICCID | The SIM card or eSIM profile number | SIM activation and support reference |
| EID | The embedded eSIM chip | eSIM provisioning by SM-DP+ server |
| Phone number (MSISDN) | Your reachable line | Calls, SMS, account identity |
Where to Find Your IMEI
- Dial *#06#: Works on virtually every phone regardless of OS. The IMEI appears on screen immediately.
- iPhone: Settings > General > About. Scroll to IMEI. Also printed on the physical SIM tray on most models and on the original box.
- Android: Settings > About Phone (exact wording varies by manufacturer). Also accessible via Settings > About > Status > IMEI Information on many Samsung devices.
- SIM tray: On many iPhone models, the IMEI is laser-etched on the SIM card tray itself.
- Original box or receipt: Printed on the retail packaging barcode label.
- Carrier account: Most carrier apps and websites list IMEI under device details.
How Carriers Use IMEI
- Checking whether the phone model supports their network bands and VoLTE requirements.
- Confirming whether the device is unlocked and eligible for activation on their network.
- Blocking devices reported lost, stolen, or associated with unpaid financing contracts.
- Matching eSIM profile downloads to the correct physical device via EID cross-reference.
- Supporting warranty validation, insurance claims, and device trade-in eligibility.
IMEI Blacklisting
A carrier or operator can report an IMEI to the GSMA Device Check database or national equivalent (in the US, the CTIA Stolen Phone Checker uses industry-shared blacklists). Once an IMEI is blacklisted, any carrier checking the list will refuse to activate service on that device. Reasons for blacklisting include: the owner reported the phone lost or stolen, the device financing contract was not paid, or the device was involved in a fraud or insurance claim. A blacklisted phone may still connect to emergency services but will be barred from normal voice, data, and SMS activation.
Blacklisting is separate from carrier locking. An unlocked phone can still be blacklisted, and a locked phone is not necessarily blacklisted.
Buying a Used Phone: How to Check IMEI Status
Before purchasing a used phone, always check the IMEI status. Services like the GSMA Device Check, CTIA Stolen Phone Checker, or carrier-specific IMEI checkers (available on T-Mobile, AT&T, and Verizon websites) can tell you whether the device is clean, reported stolen, or still associated with an active financing agreement. A phone with a financed balance that was never paid can be blacklisted by the original carrier even if the current seller presents a clean receipt. Check the IMEI, not just the seller's story.
Dual-SIM Phones and Two IMEIs
A phone with two hardware cellular radios — or a single radio with dual-SIM capability — is assigned two IMEI numbers, one per SIM slot. Both IMEIs appear when you dial *#06# on a dual-SIM device. Each IMEI can be checked and blacklisted independently. When a carrier activates a dual-SIM phone, they typically record both IMEIs in their system.
Why You Should Treat IMEI as Sensitive
An IMEI is not a secret in the same way a password is, but it is device identity information. Share it with carriers, repair providers, insurers, and legitimate trade-in services. Avoid posting it publicly in marketplace listings or screenshots, since a bad actor with your IMEI could theoretically report the device as lost or use it for social engineering attacks on carrier support lines.
Frequently Asked Questions
What does IMEI identify?
IMEI identifies the mobile device hardware. It is different from your phone number, SIM card number, account number, and eSIM profile.
How do I find my IMEI?
On most phones, dial *#06# or look in Settings under About Phone or General > About. Dual SIM phones may show two IMEI numbers.
Can an IMEI be blocked?
Yes. Carriers can blacklist an IMEI when a phone is reported lost, stolen, financed and unpaid, or involved in fraud. A blacklisted phone may fail activation even with a valid SIM.