An MMSI, or Maritime Mobile Service Identity, is a nine-digit number that identifies a ship’s radio station in systems such as AIS and digital selective calling. The first three digits are a country code reflecting the vessel’s flag, so an MMSI changes when a ship reflags.
The MMSI is what an AIS receiver actually hears: every position report carries it. It is assigned by the flag state’s telecoms authority to the radio installation, not the hull, which is the key difference from the permanent IMO number.
Because reflagging changes the MMSI, long-term vessel histories keyed only by MMSI fragment. Serious tracking systems therefore map MMSI to IMO number continuously and treat MMSI as the live-broadcast key rather than the identity key.
When a container’s carrier events go quiet mid-ocean, live vessel data fills the gap: AIS positions keyed by MMSI show where the ship actually is between load and discharge. TrackingMCP joins that feed to your shipment, so the answer to where the box is right now is the vessel’s track, visible from tracking, and port arrival pages like Singapore show the destination side.
An MMSI, or Maritime Mobile Service Identity, is a nine-digit number that identifies a ship’s radio station in systems such as AIS and digital selective calling. The first three digits are a country code reflecting the vessel’s flag, so an MMSI changes when a ship reflags.
Yes. Reflagging assigns a new MMSI with the new flag’s country prefix. The IMO number is the identifier that survives such changes.
They are the maritime identification digits, a country code allocated by the International Telecommunication Union that indicates the flag administration of the station.
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