I can't seem to find if the header size for Sigfox. Looking at their website (https://build.sigfox.com/study) it says "The Sigfox uplink payload is limited to 12 bytes (excluding the payload headers). The downlink payload is limited to 8 bytes (excluding the payload headers)." It never mentions anything about the size of these payload headers and I can't seem to find information on it anywhere. Any help would be greatly appreciated.

1 Answer 1


It's all documented in the Sigfox device radio specifications. For an uplink:

  • 19 bits preamble
  • 13 bits frame type
  • 2 bits length indicator
  • 1 bit bidirectional frag
  • 1 bit repeated flag
  • 12 bits message counter
  • 32 bits identifier
  • variable length uplink authentication (between 2 and 5 bytes)
  • 16 bits CRC

Which gives a total of 112 to 136 bits, 14 to 17 bytes.

Note that I just glanced at the doc, so I may have missed things, there may be more stuff.

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