TrueToolAIS NMEA Vessel Viewer
Inspect AIS !AIVDM and !AIVDO logs by vessel MMSI. Decode position, speed, course and available vessel details; select a ship, replay its reports and inspect the original NMEA messages. The file stays in your browser.
Click to upload or drag & drop an AIS log
.nmea, .log, .txt; AIVDM and AIVDO, including multipart messages. No upload.
What an AIS NMEA message contains
AIS receivers record vessels as NMEA sentences such as !AIVDM (received traffic) and !AIVDO (your own vessel). A position report includes an MMSI and may include SOG, COG and heading; static reports can contain a vessel name or call sign. Multiple reports from the same MMSI form a track. Multipart messages are reassembled before decoding, and incomplete messages remain visible instead of being silently dropped.
AIS NMEA viewer questions
Does this support AIS data in NMEA 2000 PGNs?
This viewer reads AIS AIVDM/AIVDO text. NMEA 2000 capture lines are handled by the NMEA Viewer & Analyzer, which retains AIS-related PGN numbers and raw bytes. Do not assume a raw N2K AIS PGN has been fully decoded here.
Can I open a file without uploading it?
Yes. Reading, decoding and playback happen locally in your browser. Basemap tiles may be requested over the network, but your log is not sent to the tile server.
Why is a vessel missing from the map?
Some AIS messages contain only static information, not coordinates; a checksum can also be invalid. Such messages remain in the vessel table, while only valid position reports draw on the map.