AISStream.io

The Automatic Identification System (AIS) is the set of radio messages that ships and shore stations exchange.^1,2 AISStream.io passes them on free and in real time over a WebSocket, a connection that stays open and pushes each message as it arrives.^1,4 The messages come from a network of AIS receiving stations it describes as global.¹ No company or person is named as the operator; the copyright line reads "AIS Stream".¹

A position report gives a vessel's identity number (MMSI), its position, its speed and course over ground and its heading.² The other 24 message types include ship and voyage data such as name and destination, safety messages, search-and-rescue aircraft positions, aids to navigation and binary messages between ships.^1,2 Each arrives as JSON with the ship's name and last known position attached.²

To use it you sign in with GitHub and create an API key.¹ Within three seconds of connecting, a client sends a subscription with the key and at least one bounding box, and may narrow it to up to 200 vessels by MMSI or to chosen message types.² An account may hold three subscribed connections and an IP address three open ones, and a subscription may change at most once a second.² Browsers may not connect directly, so a key stays on a server that passes on what its users need.² A client that reads too slowly loses messages, and from September 2026 uncompressed connections face per-user bandwidth limits.² There is no uptime guarantee, and missed events are not replayed.² Apart from a privacy policy, the site published no terms of use or data licence on 30 October 2026.^1,3

Someone modelling a harbour, strait or stretch of coast can subscribe to a box around it and keep their own record of the traffic, since the stream holds no history to go back to.² For vessel presence and fishing activity worked up from AIS over years, Global Fishing Watch publishes processed data through its APIs.⁵