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… are made for workgroups (“groupware”) and can be seen as open source alternatives to “Slack” (“Slack is your digital office - revolutionize the way you work with one central place for everyone and everything you need for your daily work.”). What they all have in common is that interfaces are available so that other systems can be integrated into the internal workflow.

As a rule, these exist in both an open-source and a paid enterprise variant with professional support. The business packages offer additional features such as support for high availability.

Cross-reference: System comparison


„An open network for secure, decentralized communication“
„Matrix is an open standard for interoperable, decentralised, real-timecommunication over IP.“

Chat and work via distributed database (a lá Git). Split between (protocol development) and (distribution and hosting). Matrix compares itself (external) not with other team messengers, but with IRC, XMPP, Trillian and Pidgin.

Examples of educational use: Uni Bochum (external), TU Dortmund (external), Uni Hannover (external), Uni Insbruck (external)
More examples: BWI (Bundeswehr) (external), French government (Tchap) (external), German health care (TI-Messenger) (external), Handmade Seattle (external)


  • positive: open source system
  • positive: many other services can be integrated
  • positive: server with federation possibility
  • positive: interoperability possible (if activated) via bridge to international standard XMPP
  • positive: no trackers detectable in Android app element (40 permissions): Exodus (external)
  • negative: NO german webpage
  • negative: according to webbkoll (external) 81 Third party requests (third-party) on the website
  • negative: according to webbkoll (external) 9 third-party requests on the website of


More information about the matrix protocol: >> here <<
Interface: (external)
Project page: (extern; Englisch)


„Make your work flow”
„Finally, an open source platform for developer collaboration. Secure, flexible, and integrated with the tools you love.“
„From creating AAA games to coordinating rescue missions, over 800 organizations around the globe trust Mattermost to ship better software, faster.“

Examples for educational use are Uni Kaiserslautern (external) Uni Mainz (external), FH Münster (external), WWU Münster (external), The University Of British Columbia (external).
More examples (like Bosch, DuckDuckGo, NASA, Nasdaq, Samsung, …) can be found on the site of Mattermost (external).

  • positive: open source system
  • positive: very good as standalone solution
  • positiv: integration of BigBlueButton possible (example Uni Mainz (external))
  • negative: server without federation / no interoperability
  • negative: NO german webpage
  • negative: 1 tracker (Google Firebase Analytics) in the Android app (17 permissions): Exodus (external)
  • negative: according to webbkoll (external) 1 third-party cookie and 27 third-party requests (third-party) on the website

Prices: (external)
Nice manual: (external; PDF)
Interface: (external)
Project page: (external)


„The world’s largest open source communications platform. Own your data, customize anything, integrate everything.“
„Trusted by 12M+ users in over 150 countries.“
„Your privacy, our priority.“ / „The communications platform for companies where complete privacy is business critical.“
„The open source alternative to Slack, Zendesk for Service, Intercom and Sendbird. All-in-one.“

In the documentation of Rocket.Chat it is stated that a federation is possible, however (as of 05/2022) it is disadvised from productive use. Here is in the configuration settings for federation (screen shot) the warning:
“Federation support is a work in progress. Federation support is a work in progress. Use on production system is not recommended at this time.”
Source (English): (external)

Examples of use: Uni Bremen (external), Heinrich-Heine-Universität Düsseldorf (external), Hochschule Koblenz (external), Uni Köln (external), Uni Regensburg (external)
More examples (like DB, VW, Audi, …) can be found on the page of Rocket.Chat (external).

  • positive: open source system
  • positive: german website
  • positive: own servers are possible (these are then however closed systems)
  • positive: interoperability is concretely in planning (external) based on international standard XMPP
  • positive: federation with Matrix should be possible via Matrix-typescript library (external)
    Experimental support for Matrix federation announced and in alpha status (external) since May 2022
  • negative: server without recommended federation / no interoperability
  • negative: the desktop client is based on electron
  • negative: With version 4.0 the automatic LDAP synchronization was moved from the free to the enterprise version
  • negative: 3 trackers (Bugsnag, Google Firebase Analytics & CrashLytics) in the Android app (19 permissions): Exodus (external))
  • negative: according to webbkoll (external) 33 cookies; 17 from third parties; 96 third-party requests (third-party) to Facebook, Google, linkedin, Twitter, Zoom, … among others. on the website

Example usage: “Fairchat” (external; uses Rocket.Chat)
Price list: (external; English)
Project page: (external)


„Chat for distributed teams.“
„Zulip combines the immediacy of real-time chat with an email threading model. With Zulip, you can catch up on important conversations while ignoring irrelevant ones.“
„Over 120 native integrations.“

This Teammessenger is also made for working in distributed groups and “threads”. Zulip explicitly advertises that the paid variant funds the open-source version. Other services such as Dropbox, email, GitHub, GitLab, GoogleCalender, Matrix, Youtube and many more can be integrated and it is possible to run your own Zulip server. Examples of educational use include University of Munich (external) and University of San Diego (external).

Compared to the open source competitors Mattermost or Rocket.Chat, Zulip offers free hosting on Zulip servers in addition to the option of self-hosting.

  • positive: open source system
  • positive: own servers are possible
  • positive: many other services (> 120) can be integrated ( (external)
  • negative: server without federation / no [interoperability](/en(/begriffe/interoperabilitaet/gedanken)
  • negative: NO german webpage
  • negative: 1 tracker (Google Firebase Analytics) in Android app (26 permissions): Exodus (external)
  • negative: according to webbkoll (external) 30 third party requests (third-party) on the website

Comment on Zulip:
The most important difference, in my opinion, between Zulip and most of the other popular chat systems is their conversation model. With most systems, like Slack, Matrix or even XMPP, conversations are separated into channels, rooms or chat rooms respectively. For some of the newer chat systems, threads have been added to conversations as an after thought, but in Zulip, threading was an initial design feature so the system was built to support threading, in a similar way to email.
Source: (external)

More detailed description: (external)
Source code: (external)
Client (F-Droid): (extern)
Interface: (external)
Project page: (external; unfortunately only English)

External comparisons