ejabberd is an Extensible Messaging and Presence Protocol (XMPP) application server and an MQ Telemetry Transport (MQTT) broker, written mainly in the Erlang programming language.

[4] XMPP: The Definitive Guide (O'Reilly Media, 2009) praised ejabberd for its scalability and clustering feature, at the same time pointing out that being written in Erlang is a potential acceptance issue for users and contributors.

[6] ejabberd has a number of notable deployments, IETF Groupchat Service,[7][8] BBC Radio LiveText,[9] Nokia's Ovi,[10] KDE Talk[11] and one in development at Facebook.

It was also announced that further development will be split into an "ejabberd Community Server" and an "ejabberd Commercial Edition [which] targets carriers, websites, service providers, large corporations, universities, game companies, that need high level of commitment from ProcessOne, stability and performance and a unique set of features to run their business successfully.

"[15] Alexey Shchepin started ejabberd in November 2002[16] for three main reasons: success with Tkabber (his previous project, an XMPP client), a rather unstable first alpha release of jabberd2, and his wish to play with Erlang features.

[36][37] Mxit was a large server for mobile instant messaging client that started using ejabberd in 2005, but was replaced with a custom IM engine.

[42] In the FOSS world, there is a pair of notable generic deployments of ejabberd, namely the KDE Talk[11] and the Fellowship of the Free Software Foundation Europe.

[43][44] ejabberd chatroom feature provides the IETF Groupchat Service, used by the various working groups, areas, and BOF sessions during meetings and at other times.

[45][46] Other deployments include Chesspark (online chess playing site),[47] Collecta (real-time search),[48] and Notifixious (notifications of website subscriptions).

Facebook developers made a presentation on the topic at Commercial Users of Functional Programming (CUFP) 2009 conference,[12] and in November 2009 chat.facebook.com was detected as running a modified version of ejabberd.

Om Malik commented on the development as "disruptive" competition for "older IM networks such as AOL's AIM and Microsoft's MSN".

XMPP: The Definitive Guide (O'Reilly Media, 2009) refers to ejabberd in those terms: The server is well-known for its scalability, and it can be clustered across multiple instances.