AIS ship type codes explained

The AIS “ship and cargo type” field is a single number from 0 to 99, sent in the static report. It carries two pieces of information stacked into two digits, and once you can read it, the coloured dots on a vessel map stop being a legend you have to memorise.

The decade structure

The tens digit sets the family:

Range	Family
20–29	Wing-in-ground (WIG) craft
30–39	Special activities — one code per activity, no cargo qualifier
40–49	High-speed craft (HSC)
50–59	Special craft — one code per role, no cargo qualifier
60–69	Passenger ships
70–79	Cargo ships
80–89	Tankers
90–99	Other type

Two of those ranges, the 30s and the 50s, break the pattern deliberately. Instead of a family plus a qualifier, each code in those ranges is its own distinct meaning.

The 30s — what the ship is doing:

Code	Meaning
30	Fishing
31	Towing
32	Towing, tow exceeding 200 m in length or 25 m in breadth
33	Dredging or underwater operations
34	Diving operations
35	Military operations
36	Sailing
37	Pleasure craft
38, 39	Reserved

The 50s — what the ship is for:

Code	Meaning
50	Pilot vessel
51	Search and rescue vessel
52	Tug
53	Port tender
54	Vessel with anti-pollution equipment
55	Law enforcement
56, 57	Spare, for local assignment
58	Medical transport
59	Non-combatant ship, per Resolution No. 18 of the Radio Regulations

The cargo qualifier

For the ranges that do follow the pattern — 20s, 40s, 60s, 70s, 80s and 90s — the units digit says something about the cargo, using the IMO dangerous-goods categories:

Units digit	Meaning
0	All ships of this type
1	Carrying dangerous goods, category A
2	Carrying dangerous goods, category B
3	Carrying dangerous goods, category C
4	Carrying dangerous goods, category D
5–8	Reserved for future use
9	No additional information

So 70 is a cargo ship, plain. 71 is a cargo ship declaring category A dangerous goods. 80 is a tanker; 82 is a tanker declaring category B. 60 is a passenger ship, 69 a passenger ship with no additional information given.

The categories A through D come from the IMDG framework and relate to the hazard of the cargo carried in bulk, with A the most severe. In practice the qualifier is used sparsely — many operators set the family code and leave the units digit at 0 or 9 — so its absence tells you very little, while its presence is a genuine declaration.

What the code is not

It is not verified. The ship-and-cargo type is typed into the transponder at commissioning and updated by hand thereafter. There is no authority checking it against the ship’s certificates.

It is not the ship’s class or design. A code of 70 covers a 200,000-tonne bulk carrier and a 1,000-tonne coaster equally. AIS does not distinguish container ship from bulker from general cargo — that is a common misconception, and any site claiming to show you “all container ships” from AIS alone is inferring it from elsewhere.

Zero means unset. A ship-and-cargo type of 0 is “not available”, not a valid category. Our decoder returns “Unknown” for it and for anything outside 1–99, and vessel pages say so rather than guessing.

How we group them

The site collapses the 99 codes into a dozen readable categories for map colours, filters and ship-type pages. The mapping is deliberate and documented:

Our category	Codes
Cargo	70–79
Tanker	80–89
Passenger	60–69
Fishing	30
Tug & tow	31, 32, 52
Pleasure craft	37
Sailing	36
High-speed craft	20–29, 40–49
Service	33, 34, 50–58
Military	35, 55, 59
Other	90–99
Unknown	0, and anything undefined

A few codes appear in two of our groupings by intent — 55, law enforcement, reads as both service and military depending on what a reader is looking for, and we resolve it to military. Every ship-type page states which raw codes it contains, so you can always get back to the underlying number.

Reading a type code in the wild

Given 82 on a vessel page:

1. Tens digit 8 → tanker.
2. Units digit 2 → declaring category B dangerous goods.
3. Therefore: a tanker whose operator has declared a category B hazardous cargo.

Given 32:

1. In the 30s, so it is an activity code, not a family plus qualifier.
2. 32 → towing with a tow over 200 m long or 25 m wide.
3. Therefore: this vessel is warning you that its tow is very large. That is a navigational warning encoded in a ship type, and it is the sort of thing AIS does well.