Signal & Syntax · Networks, HLR and porting

What Is an IMSI?

The IMSI (International Mobile Subscriber Identity) is the up-to-15-digit code on a SIM. The IMSI names the subscription inside the network.

Also calledInternational Mobile Subscriber Identity

Example

234 15 1234567890 MCC MNC MSIN

IMSI in Practice

An IMSI starts with the MCC and MNC of the issuing network, followed by the MSIN. The HLR maps each IMSI to an MSISDN. A new SIM brings a new IMSI while the MSISDN stays the same. Networks send a temporary code over the air in place of the IMSI.

Related Terms

MSISDN MSISDN stands for Mobile Station International Subscriber Directory Number. MCC and MNC The MCC (mobile country code) names a country in three digits. HLR The HLR (Home Location Register) is the subscriber database in a mobile operator's core network. VLR The VLR (Visitor Location Register) is a temporary database attached to a mobile switching center.

Read the Guide

Guide

HLR Lookup vs eHLR

Two ways to check whether a number is in use. Read the guide →

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