How to Find a Vessel's MMSI Number (and When You Don't Need It)

An MMSI number is the closest thing a ship has to a passport number for its radio. If you've been asked for one — or a tracking site is demanding it — here's what it is, where to find it, and why you often don't need it at all.

What is an MMSI?

MMSI stands for Maritime Mobile Service Identity. It's a unique nine-digit number assigned to a vessel's radio equipment, and it's the identifier the ship broadcasts over AIS. The first three digits (the MID) indicate the country the vessel is registered to.

Where to find a vessel's MMSI

• On the AIS or radio equipment on the bridge.
• In your carrier's booking or shipping documents.
• In public vessel registries and ship databases, searched by name or IMO number.

The catch

In practice you usually start with the name, not the number — which means an extra lookup step, and the risk of picking the wrong ship when names are similar.

When you don't need it at all

Ship Lens resolves the vessel name to the right ship for you, so you can skip the MMSI hunt entirely. See how to track a ship by name.