Rsyslog is an open-source software utility used on UNIX and Unix-like computer systems for forwarding log messages in an IP network.

It implements the basic syslog protocol, extends it with content-based filtering, rich filtering capabilities, queued operations to handle offline outputs,[2] support for different module outputs,[3] flexible configuration options and adds features such as using TCP for transport.

The official RSYSLOG website defines the utility as "the rocket-fast system for log processing".

As the text of RFC 3164 is an informational description and not a standard, various incompatible extensions of it emerged.

"[5] Rainer Gerhards worked on rsyslog inside his own company, Adiscon GmbH.