An MSISDN is the telephone number of a mobile subscription in its full international form: the country code, the national destination code and the subscriber number, written as one string of digits. It is the number people dial to reach a mobile phone. 3GPP defines it in TS 23.003 as the Mobile Station International ISDN Number. The industry often expands it as Mobile Station International Subscriber Directory Number.
What does an MSISDN look like?
An MSISDN follows the ITU-T E.164 numbering plan, so it has at most 15 digits and three parts:
- Country code (CC): 1 to 3 digits, such as 44 for the United Kingdom or 1 for the North American Numbering Plan.
- National destination code (NDC): identifies a network or a number range inside the country, such as 7700 in the UK example below.
- Subscriber number (SN): the rest of the digits.
The UK number +44 7700 900001 has the MSISDN 447700900001. It is the same number as the E.164 form, just without the plus sign. Telecom systems and many SMS APIs write it this way. Web forms and most modern APIs, including ours, use the E.164 form with the plus.
How is an MSISDN different from an IMSI?
They identify different things:
| MSISDN | IMSI | |
|---|---|---|
| Identifies | The phone number (the service people call) | The subscription on the SIM |
| Public? | Yes, it is shared with contacts | No, it stays inside the network |
| Standard | ITU-T E.164 | ITU-T E.212 |
| Changes when | The subscriber takes a new number | The subscriber gets a new SIM or eSIM profile |
The home network's subscriber register links the two. That link is why a number can survive a SIM replacement, and why a SIM swap is dangerous: the number stays the same while the SIM behind it changes. See IMSI for why that identifier should never leave the network.
Does the MSISDN tell you the network?
Only partly. The national destination code shows which network the number range was allocated to. After mobile number portability, the number may be served by a different network. The current network is identified by its MCC/MNC code, which has to be looked up.
Where do you meet the term?
- SMS and A2P APIs, where the destination field is often called
msisdnand expects digits only. - HLR lookups, which query the home register by MSISDN. See HLR lookup.
- Billing and CRM systems of mobile operators, where the MSISDN is the customer's line identifier.
- Number recycling. Operators reassign disconnected MSISDNs to new customers after a quarantine period, so a number in your database may now belong to someone else.
How does MobileValidate handle MSISDNs?
MobileValidate accepts numbers in common formats, converts them to E.164 for free and returns the e164 form in every result. A carrier lookup adds the line type and the current carrier. The upcoming HLR lookup will query the home network by MSISDN and report whether the number is reachable. It will never return the IMSI or other network identifiers behind the number.
Frequently asked questions
Is an MSISDN the same as a phone number?
In practice, yes. The MSISDN is the mobile subscriber's phone number written in full international form, without the plus sign or any national prefix. +44 7700 900001 has the MSISDN 447700900001.
Is the MSISDN stored on the SIM card?
Not necessarily. The SIM holds the IMSI, which identifies the subscription to the network. The home network maps the IMSI to one or more MSISDNs, so a number can move to a new SIM without changing.
How long can an MSISDN be?
At most 15 digits, because an MSISDN follows the ITU-T E.164 numbering plan, which sets that limit including the country code.