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Reference

AIS codes, decoded

AIS packs a lot into small numbers. A two-digit ship type, a four-bit status, nine digits of identity. Every code has its own page here: what the standard says, what it really tells you, and how many vessels our shore-based receivers can hear using it right now.

MMSI decoderIMO number checker

Ship and cargo type · 100 codes

Ship type codes 0–99

Rows are the tens digit — the family. Columns are the units digit — in most families, the hazardous-cargo declaration. Dashed cells are reserved.

x0x1x2x3x4x5x6x7x8x9
0xNot available / reserved0123456789
1xReserved for future use10111213141516171819
2xWing-in-ground (WIG) craft20212223242526272829
3xSpecial activities30313233343536373839
4xHigh-speed craft (HSC)40414243444546474849
5xSpecial craft50515253545556575859
6xPassenger ships60616263646566676869
7xCargo ships70717273747576777879
8xTankers80818283848586878889
9xOther type90919293949596979899

Navigational status · 16 codes

Navigational status

What the vessel says it is doing. Set by hand, so read it as testimony.

  1. 0Under way using engine
  2. 1At anchor
  3. 2Not under command
  4. 3Restricted manoeuvrability
  5. 4Constrained by her draught
  6. 5Moored
  7. 6Aground
  8. 7Engaged in fishing
  9. 8Under way sailing
  10. 9Reserved for future amendment (HSC)
  11. 10Reserved for future amendment (WIG)
  12. 11Power-driven vessel towing astern
  13. 12Power-driven vessel pushing ahead or towing alongside
  14. 13Reserved for future use
  15. 14AIS-SART, MOB-AIS or EPIRB-AIS active
  16. 15Undefined (default)

MMSI · 10 formats

MMSI identity formats

Who is transmitting: a ship, a coast station, a buoy, a life-raft.

  1. MIDxxxxxxShip station
  2. 00MIDxxxxCoast station
  3. 0MIDxxxxxGroup of ships
  4. 111MIDxxxSAR aircraft
  5. 99MIDxxxxAid to navigation
  6. 98MIDxxxxCraft associated with a parent ship
  7. 970xxyyyyAIS-SART (search and rescue transmitter)
  8. 972xxyyyyMan-overboard device
  9. 974xxyyyyEPIRB with AIS
  10. 8MIDxxxxxHandheld VHF with DSC and GNSS

Tool

MMSI decoder

Paste nine digits. Get the station type, where the country digits sit, the registry they point to, and whether the number makes sense at all.

Tool

IMO number checker

Check a seven-digit IMO ship number against its check digit, with the arithmetic shown. Catches typos and numbers that were never IMO numbers.

Background

Reference guides

How AIS works, why ships go dark, and what coverage from shore-based receivers can and cannot show.