AIS Technical Reference
A complete guide to all 27 AIS message types, their purposes, transmission frequencies, and the data they contain.
27
Message Types
8
Position Reports
2
Static Data
3
Safety Messages
AIS (Automatic Identification System) uses a standardized set of 27 message types to transmit different kinds of maritime information. Each message type serves a specific purpose and is transmitted at defined intervals.
Messages are organized into categories: position reports for real-time tracking, static and voyage data for vessel identification, safety messages for maritime safety communications, and other messages for system management and specialized applications.
These message types make up the majority of AIS traffic you'll encounter.
The most common AIS messages. Transmitted by Class A transponders on large commercial vessels every 2-10 seconds depending on speed.
Data Included:
Contains vessel identification and voyage information. Transmitted every 6 minutes or when requested.
Data Included:
Position report from Class B transponders on smaller vessels. Less frequent updates than Class A.
Data Included:
Position and status from navigation aids like buoys, lighthouses, and markers.
Data Included:
Full list of all 27 AIS message types with their specifications.
| Type | Name |
|---|---|
| 1 | Position Report (Class A) |
| 2 | Position Report (Class A) |
| 3 | Position Report (Class A) |
| 9 | SAR Aircraft Position Report |
| 18 | Position Report (Class B) |
| 19 | Extended Position Report (Class B) |
| 21 | Aid-to-Navigation Report |
| 27 | Position Report (Long Range) |
| Type | Name |
|---|---|
| 5 | Static and Voyage Data |
| 24 | Class B Static Data |
| Type | Name |
|---|---|
| 12 | Addressed Safety Message |
| 13 | Safety Acknowledge |
| 14 | Safety Broadcast Message |
| Type | Name |
|---|---|
| 4 | Base Station Report |
| 6 | Binary Addressed Message |
| 7 | Binary Acknowledge |
| 8 | Binary Broadcast Message |
| 10 | UTC/Date Inquiry |
| 11 | UTC/Date Response |
| 15 | Interrogation |
| 16 | Assignment Mode Command |
| 17 | DGNSS Broadcast Binary Message |
| 20 | Data Link Management |
| 22 | Channel Management |
| 23 | Group Assignment Command |
| 25 | Single Slot Binary Message |
| 26 | Multiple Slot Binary Message |
AIS equipment comes in two main classes, each with different capabilities.
Required on SOLAS vessels (300+ GT international, passenger ships). Higher power, more frequent transmission.
Voluntary for smaller vessels. Lower cost, reduced functionality, but still provides essential tracking.
Get real-time vessel positions, historical tracks, and static data from all AIS message types through our REST API.