# BSD-syslog or legacy-syslog messages

New to AxoSyslog? AxoSyslog is a binary compatible `syslog-ng` replacement, from the original creator, developed by the same team.

Same architecture, same config files, same paths. Cloud-native images, fast releases, modern observability (OTel, K8s), and powerful data processing: read more about the [differences between AxoSyslog and `syslog-ng`](<https://axoflow.com/axosyslog-vs-syslog-ng?utm_source=docs&utm_medium=banner>).

Also, it’s super easy to [install](../../../docs/axosyslog-core/install/index.md), and you can [upgrade from `syslog-ng` in minutes](../../../docs/axosyslog-core/install/upgrade-syslog-ng/index.md).

This section describes the format of a syslog message, according to the [legacy-syslog or BSD-syslog protocol](<https://datatracker.ietf.org/doc/rfc3164/>). A syslog message consists of the following parts:

  * [`PRI`](../../../docs/axosyslog-core/chapter-concepts/concepts-message-structure/concepts-message-bsdsyslog/concepts-message-bsdsyslog-pri/index.md)
  * [`HEADER`](../../../docs/axosyslog-core/chapter-concepts/concepts-message-structure/concepts-message-bsdsyslog/concepts-message-bsdsyslog-header/index.md)
  * [`MSG`](../../../docs/axosyslog-core/chapter-concepts/concepts-message-structure/concepts-message-bsdsyslog/concepts-message-bsdsyslog-msg/index.md)



The total message cannot be longer than 1024 bytes.

The following is a sample syslog message
```
 
    <133>Feb 25 14:09:07 webserver syslogd: restart
    
```

The message corresponds to the following format:
```
 
    <priority>timestamp hostname application: message
    
```

The different parts of the message are explained in the following sections.

Note The AxoSyslog application supports longer messages as well. For details, see the `log-msg-size()` option in [Global options reference](../../../docs/axosyslog-core/chapter-global-options/reference-options/index.md). However, it is not recommended to enable messages larger than the packet size when using UDP destinations. 

* * *

[The PRI message part](../../../docs/axosyslog-core/chapter-concepts/concepts-message-structure/concepts-message-bsdsyslog/concepts-message-bsdsyslog-pri/index.md)

[The HEADER message part](../../../docs/axosyslog-core/chapter-concepts/concepts-message-structure/concepts-message-bsdsyslog/concepts-message-bsdsyslog-header/index.md)

[The MSG message part](../../../docs/axosyslog-core/chapter-concepts/concepts-message-structure/concepts-message-bsdsyslog/concepts-message-bsdsyslog-msg/index.md)

Last modified July 7, 2025: [Adds banner to high-traffic pages (8f28f4e1)](<https://github.com/axoflow/axosyslog-core-docs/commit/8f28f4e12f0a8d65bc57eba8ddc5d4cccf1cab81>)