eSIMratIMSI (international subscriber identity)
by RonyThe IMSI (International Mobile Subscriber Identity) is the international identifier of a mobile subscriber, stored in the SIM profile: 15 digits at most, made of the country code (MCC), the operator code (MNC) and the subscriber number. It is what the network checks at every connection to know who you are and who bills you. Invisible day to day, but central in roaming.
Why it matters when travelling
In roaming, your IMSI says where you “come from”: a local network reads the country and operator codes of your IMSI to know who to bill for your traffic. That is why some travel eSIMs use IMSIs issued in countries with favourable agreements: your eSIM “comes from” a different country than the provider, and that is perfectly normal.
It is also the key to multi-IMSI: some profiles carry several identities and switch to the most favourable one depending on where you are. The result for you: one eSIM, with local deals optimised behind the scenes.
The misconception
“The IMSI and the ICCID are the same thing.”
They are not: the ICCID is the serial number of the medium (the card or the profile), the IMSI is the subscriber identity it contains. An analogy: the ICCID is the passport number as an object, the IMSI is the identity of the person inside. A multi-IMSI profile has one ICCID and several IMSIs.
What it changes when you compare
You never handle an IMSI, but its country of issue explains visible behaviour: an exotic network name, a banking app that thinks you are in Estonia, speeds that vary with the agreements. The esimrat comparisons flag these quirks when they affect the real use of a plan.
Compare eSIM plans by destination
The rat's tip: If your banking app or a streaming site thinks you are in another country while on your travel eSIM, that is often the effect of the IMSI or of the provider's breakout. Nothing abnormal: switch to wifi or your home line for the sensitive operation, then come back to the eSIM.
See also
Frequently asked questions
Where can I see my SIM's IMSI?
It is not shown in the standard iOS or Android settings: it is internal network data, reachable through specialised apps or technical codes depending on the model. Day to day you do not need it: a provider's support works with the ICCID.
Is the IMSI sensitive data?
Moderately: captured at scale, it allows subscribers to be tracked (the “IMSI catchers” used in surveillance). Recent networks (4G/5G) encrypt its transport with temporary identities. At your level, there is nothing particular to do or to fear.
Why does my travel eSIM have a foreign IMSI?
Because its issuer registered its subscribers in a country where it holds good roaming agreements (often a small telecoms jurisdiction). That is standard on the travel eSIM market and has no consequence for you, beyond a sometimes surprising country of origin shown by certain services.