MSISDN: Mobile Station International Subscriber Directory Number
This is the number you dial to reach someone. It is the primary identity used for routing calls and SMS in the PSTN (Public Switched Telephone Network). Crucially, the MSISDN is not stored on the SIM card; it is assigned by the operator's database (HLR).
Structure (E.164 Format)
Identifies the country (e.g., +1 USA, +44 UK, +91 India).
Identifies the network operator within the country (e.g., 404 for Vodafone Idea in India).
Unique identifier for the user within that operator's network.
Interactive Decoder
IMSI Analyzer
IMSI: International Mobile Subscriber Identity
The IMSI is the unique identifier stored inside the SIM card. It is used internally by the network to identify the subscriber. For security, the IMSI is sent over the air as rarely as possible; instead, a TMSI (Temporary Mobile Subscriber Identity) is used.
Structure
3 digits (e.g., 310 for US, 404 for India).
2 or 3 digits identifying the operator (e.g., 01 for Verizon, 10 for Airtel).
9-10 digits uniquely identifying the subscriber within the operator's network.
IMEI: International Mobile Equipment Identity
Unlike MSISDN and IMSI which identify the subscription, the IMEI identifies the physical hardware (the phone itself). It is used for device tracking, blacklisting stolen phones (EIR database), and ensuring device compatibility.
Structure (15 Digits)
TAC (Type Allocation Code)
First 8 digits. Identifies the manufacturer and model. For example, Apple iPhones have specific TACs assigned by GSMA.
SNR (Serial Number)
Next 6 digits. A unique sequence defined by the manufacturer for that specific unit.
CD / SVN (Check Digit)
Last digit. Calculated using the Luhn algorithm to validate the IMEI integrity.
IMEI Validator
Enter an IMEI to check validity using the Luhn Algorithm.
Network Attachment Simulator
Visualize how the MSISDN and IMSI interact during a Location Update (Registration).