What is an IMSI number?
An IMSI (International Mobile Subscriber Identity) is a unique 15-digit number that identifies a mobile subscriber within a cellular network. It is stored on the SIM card and is distinct from the phone number — the IMSI identifies the subscriber to the network, while the phone number (MSISDN) is what others dial.
IMSI structure
- MCC (Mobile Country Code) — 3 digits identifying the country. For example: 310 for the US, 404/405 for India, 234 for the UK, 505 for Australia.
- MNC (Mobile Network Code) — 2–3 digits identifying the specific network operator. For example: 260 for T-Mobile US, 840 for Reliance Jio India, 30 for EE UK.
- MSIN (Mobile Subscription Identification Number) — The remaining digits (up to 10) uniquely identifying the subscriber within that operator's network.
MCC-MNC pairs used
- AT&T US: 310-410 · T-Mobile US: 310-260 · Verizon US: 311-480
- Airtel India: 404-20 / 404-45 · Reliance Jio India: 405-840
- EE UK: 234-30 · Three UK: 234-20
- Telstra Australia: 505-01
API access
Generate IMSIs via API: GET /api/v1/network/imsi?country=IN&count=20
What is the difference between IMSI and IMEI? +
An IMEI identifies the physical handset (the device), while an IMSI identifies the subscriber (the SIM card / user account). If you put a different SIM in the same phone, the IMEI stays the same but the IMSI changes. Both are 15 digits, but only IMEI uses the Luhn checksum.
What is the difference between IMSI and MSISDN? +
The MSISDN is the phone number people dial (e.g. +91 9876543210). The IMSI is an internal network identifier stored on the SIM that is never shared publicly. The two are linked in the operator's Home Location Register (HLR) / Home Subscriber Server (HSS).
What is ICCID and how does it differ from IMSI? +
The ICCID (Integrated Circuit Card Identifier) is a 19–20 digit number that identifies the SIM card itself (the physical chip). The IMSI identifies the subscription profile stored on that SIM. A SIM card can theoretically store multiple IMSI profiles (e.g. dual-SIM-on-one-chip solutions), though this is rarely used in practice.