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Fix MAVLink 2 overhead byte counts #731

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Merged
hamishwillee merged 1 commit into from
Jul 15, 2026
Merged

Fix MAVLink 2 overhead byte counts #731

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2 changes: 1 addition & 1 deletion en/about/faq.md
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Expand Up @@ -4,7 +4,7 @@

<dl>
<dt>How efficient is MAVLink?</dt>
<dd>MAVLink is a very efficient protocol. MAVLink 1 has just 8 bytes overhead per packet, including start sign and packet drop detection. MAVLink 2 has just 14 bytes of overhead (27 if signing is used), but is now a much more extensible protocol.</dd>
<dd>MAVLink is a very efficient protocol. MAVLink 1 has just 8 bytes overhead per packet, including start sign and packet drop detection. MAVLink 2 has just 12 bytes of overhead (25 if signing is used), but is now a much more extensible protocol.</dd>

<dt>How many vehicles does MAVLink support?</dt>
<dd>255 vehicles, with system IDs ranging from 1 to 255 (0 is not a valid vehicle ID).
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2 changes: 1 addition & 1 deletion en/guide/serialization.md
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Expand Up @@ -32,7 +32,7 @@ Below is the over-the-wire format for a [MAVLink 2](../guide/mavlink_2.md) packe
| <a id="v2_msgid"></a>7 to 9 | `uint32_t msgid:24` | Message ID (low, middle, high bytes) | 0 - 16777215 | ID of _message type_ in payload. Used to decode data back into message object. |
| <a id="v2_payload"></a>For _n_-byte payload:<br>`n=0`: NA, `n=1`: 10, `n>=2`: 10 to (9+n) | `uint8_t payload[max 255]` | [Payload](#payload) | | Message data. Depends on message type (i.e. Message ID) and contents. |
| (n+10) to (n+11) | `uint16_t checksum` | [Checksum](#checksum) (low byte, high byte) | | CRC-16/MCRF4XX for message (excluding `magic` byte). Includes [CRC_EXTRA](#crc_extra) byte. |
| (n+12) to (n+25) | `uint8_t signature[13]` | [Signature](../guide/message_signing.md) | | (Optional) Signature to ensure the link is tamper-proof. |
| (n+12) to (n+24) | `uint8_t signature[13]` | [Signature](../guide/message_signing.md) | | (Optional) Signature to ensure the link is tamper-proof. |

- The minimum packet length is 12 bytes for acknowledgment packets without payload.
- The maximum packet length is 280 bytes for a signed message that uses the whole payload.
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2 changes: 1 addition & 1 deletion en/index.md
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Expand Up @@ -22,7 +22,7 @@ MAVLink was first released early 2009 by Lorenz Meier and has now a [significant

## Key Features

- Very efficient. MAVLink 1 has just 8 bytes overhead per packet, including start sign and packet drop detection. MAVLink 2 has just 14 bytes of overhead (but is a much more secure and extensible protocol).
- Very efficient. MAVLink 1 has just 8 bytes overhead per packet, including start sign and packet drop detection. MAVLink 2 has just 12 bytes of overhead (but is a much more secure and extensible protocol).
Because MAVLink doesn't require any additional framing it is very well suited for applications with very limited communication bandwidth.
- Very reliable. MAVLink has been used since 2009 to communicate between many different vehicles, ground stations (and other nodes) over varied and challenging communication channels (high latency/noise). It provides methods for detecting packet drops, corruption, and for packet authentication.
- [Many different programming languages](#supported_languages) can be used, running on numerous microcontrollers/operating systems (including ARM7, ATMega, dsPic, STM32 and Windows, Linux, MacOS, Android and iOS).
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