MSISDN — Mobile Station International Subscriber Directory Number
What is MSISDN?
An MSISDN (Mobile Station International Subscriber Directory Number) is the actual dialable phone number assigned to a mobile subscription — the number a caller dials or a message is addressed to, written in full E.164 form with its country code. It differs from the IMSI, a separate identifier fixed to the SIM: a carrier network maps the MSISDN to whichever IMSI currently serves it, and updates that mapping whenever a subscriber ports to a new carrier or swaps SIMs, while the dialable MSISDN itself stays the same throughout.
More detail
A carrier's HLR/HSS maps each MSISDN to the IMSI currently authorized to use it, and refreshes that mapping on every port or SIM swap. Messaging and voice platforms always address traffic to the MSISDN, never the IMSI, since the MSISDN is the number the public telephone network actually routes calls and messages against.
MSISDN follows the E.164 numbering plan (country code plus national number), which is why it's also the shape expected in most messaging and voice APIs' phone-number fields — MSISDN is simply the formal telecom name for that same dialable number.
Frequently asked
- Is my MSISDN the same thing as my phone number?
- Yes — MSISDN is the formal telecom term for the actual dialable phone number assigned to a mobile subscription, the same number a caller dials or a text is addressed to. Outside carrier and network documentation it's simply called the phone number.
- What's the difference between an MSISDN and an IMSI?
- The MSISDN is the dialable phone number; the IMSI is a separate identifier fixed to the SIM that networks use internally for authentication and routing. A carrier's network maps the MSISDN to whichever IMSI currently serves it, and that mapping changes when a subscriber ports numbers or swaps SIMs — but the MSISDN itself stays the same dialable number throughout.
See also
Build it on Orbit
Voice, messaging, email, video, and AI agents on one platform and one pay-as-you-go bill. Start free — no credit card required.