# What is an IMEI?

> IMEI (International Mobile Equipment Identity) is the 15-digit serial number that identifies a physical handset, not the subscriber. Where the IMSI identifies the SIM and the MSISDN is the phone number, the IMEI identifies the device itself. Operators use it to block stolen handsets through the EIR (Equipment Identity Register) and to enforce device-based policy. It plays no direct role in SMS routing but often appears alongside the IMSI in fraud analysis.

- Canonical URL: https://www.broadnet.me/answers/what-is-imei
- Language: en
- Last reviewed: 2026-07-22
- Publisher: BroadNet (https://www.broadnet.me)

## IMEI vs IMSI vs MSISDN — three identities

One handset (IMEI) holds one SIM (IMSI) that carries one number (MSISDN) — but each can change independently. Swap the SIM and the IMSI and MSISDN change while the IMEI stays; port the number and the MSISDN moves while the IMSI stays. Keeping the three distinct is essential when reading network or fraud logs. See /answers/what-is-imsi and /answers/what-is-msisdn.

## Where IMEI matters in messaging fraud

SIM-box fraud operations rack up dozens of consumer SIMs behind a small number of physical modems — so a fixed set of IMEIs cycling through many IMSIs is a strong SIM-box fingerprint. Operators blocklist offending IMEIs in the EIR, and SMS firewalls correlate IMEI/IMSI patterns to detect the farms. See /answers/what-is-sim-box-fraud.

## Related

- [All answers](https://www.broadnet.me/answers)
- [Glossary](https://www.broadnet.me/answers)
- [What is an IMSI?](https://www.broadnet.me/answers/what-is-imsi)
- [What is an MSISDN?](https://www.broadnet.me/answers/what-is-msisdn)
- [What is SIM box fraud?](https://www.broadnet.me/answers/what-is-sim-box-fraud)
- [SMS Firewall (operators)](https://www.broadnet.me/operators/sms-firewall)