What does the SSID after a callsign mean?

A number 0–15 distinguishing multiple stations under one callsign. Conventionally -9 is a car, -7 a handheld, -1 a wide digipeater — a convention, not a rule.

What is WIDE1-1,WIDE2-1?

A digipeater path requesting one local repeat and then up to two wider ones. It is the standard path for mobile stations; longer paths flood the network and are discouraged.

Do I need a licence to transmit APRS?

Yes — APRS runs on amateur radio allocations, so transmitting requires an amateur licence. Receiving and decoding is unrestricted.

APRS Radio Decoder

Decode APRS position, weather and message packets from raw frames.

on the roadmapHardware, Radio & Telecomfree · no sign-up

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The aprs-decoder decoder is on the roadmap. The heavier binary and cryptographic parsers ship after the core text and token decoders — all of which are already live and working.

Browse the live decoders

Input is processed on your device. Nothing you paste is sent anywhere.

What is the APRS Radio Decoder?

APRS (Automatic Packet Reporting System) carries real-time position, weather and message data over amateur radio in AX.25 frames, and an APRS decoder parses those frames into callsign, coordinates, symbol and comment.

APRS packets ride inside AX.25 frames: a source callsign with an SSID, a destination that doubles as a software identifier, a digipeater path such as WIDE1-1,WIDE2-1, and an information field whose first character declares the packet type — ! or = for a position, / or @ for position with timestamp, : for a message, ; for an object, _ for weather.

Positions use a compact fixed-width format, ddmm.hhN/dddmm.hhW, with a symbol table and code selecting the icon that appears on a map. Between the coordinates and the symbol sits a course, speed or altitude field, and the rest of the line is free-text comment — often a station's power, antenna and gain in a compressed PHG code.

Nearly all of the world's APRS traffic is gatewayed into APRS-IS, which is why a packet heard on 144.800 MHz in Europe or 144.390 MHz in North America shows up on aprs.fi within seconds.

APRS Radio Decoder at a glance

Frame: AX.25 UI frame, callsign-SSID addressing
Frequencies: 144.390 MHz (NA) · 144.800 MHz (EU)
Type character: First byte of the information field
Position format: ddmm.hhN/dddmm.hhW plus symbol code

How to use the APRS Radio Decoder

1Paste the raw APRS frame, including the source, path and information field.
2Read the decoded callsign, packet type, coordinates and comment.
3Check the digipeater path to see how the packet reached you.

When you would reach for it

Debugging a tracker that reports the wrong position or symbol.
Learning the APRS packet format while building a decoder.
Analysing captured amateur radio traffic offline.

APRS Radio Decoder — frequently asked questions

Last reviewed 25 July 2026 · questions or corrections: contact@decoder.tools