XMPP or Extensible Messaging and Presence Protocol is an open communication protocol.
It has been actively developed since it was introduced in 1999.
Over time, a large part of its user base migrated to centralized cloud platforms.

IRC is a simple, reliable, text-based protocol.
Matrix is a robust but more complex protocol with higher resource requirements.
XMPP sits between them, closer to IRC in simplicity while offering more modern features.

In this article you will learn to install a private, non-federated XMPP server.