If your team's chat history, files and call metadata live on a vendor's servers, you depend on that vendor for access, retention, backups and where your data sits. Self-hosted, open-source team chat moves that data onto infrastructure you control. Three projects in the Web Apps category cover this well: Rocket.Chat, Mattermost and Synapse, a Matrix homeserver.

The problem with vendor-hosted chat

When conversations are stored only on a third-party service, several practical issues follow:

  • Retention rules are set by the vendor, not by your security or compliance team.
  • Exporting a full history can be slow or limited to what the service allows.
  • Access to archived messages depends on your subscription staying active.
  • Engineering teams that discuss internal systems have no way to confirm where those discussions are stored or processed.

For developer teams and technical founders, the question is simple: who holds the database, and who can restore it if something goes wrong?

How self-hosted open-source chat solves it

A self-hosted chat server runs on your own servers or cloud accounts. The database, file storage and logs belong to you, so you decide backup schedules, retention periods and who has administrative access. Because the code is open source, your team can read it, audit it and modify it when needed.

Rocket.Chat

Rocket.Chat is an open-source, self-hostable team communication platform. It covers secure chat and voice calls, and supports federation with other privacy-focused organizations. It fits teams that want a general-purpose workplace chat with the option to connect to partner organizations without moving data to a central vendor.

Mattermost

Mattermost is an open-source, self-hosted team collaboration platform aimed at software development teams. It combines chat with workflow automation and secure communication. It suits engineering groups that want chat closely tied to their development processes and internal tooling.

Synapse

Synapse is an open-source Matrix homeserver licensed under AGPL-3.0. Matrix is an interoperable protocol, so a Synapse server lets your team or community run its own real-time chat and communicate with other Matrix servers. It is a good choice when interoperability and running your own homeserver are the priorities. Note that the AGPL-3.0 license has obligations for those who modify and offer the software over a network, so check them before deploying a modified version.

Choosing between them

  • Pick Rocket.Chat for general team chat, voice calls and federation.
  • Pick Mattermost when developer workflows and automation are central.
  • Pick Synapse when you want a Matrix-based, interoperable homeserver.

All three are self-hosted, so the core data-control benefit is the same. The differences lie in the surrounding features and protocol choices.

How to start

  1. Define your requirements: number of users, retention rules, whether you need voice calls, and whether you need federation.
  2. Choose a server environment you can maintain, with backups and monitoring in place from day one.
  3. Deploy a test instance of your shortlisted tool and invite a small group of users to try it.
  4. Check the official documentation for the installation method that fits your infrastructure, and confirm the backup and restore process before you move real conversations.
  5. Plan user onboarding and admin access, including who can change retention settings and who can export data.
  6. Migrate your team gradually, and keep the previous service available for read access until the transition is complete.

For teams that browse open-source options, the Developer tools and Open-source publishers pages in the catalog list related projects. The Linux apps page is also useful if you plan to run these services on Linux servers.

Recommendation

If your priority is data ownership with a broad feature set, start with Rocket.Chat or Mattermost and run a short trial with your team. If interoperability with the Matrix ecosystem matters most, evaluate Synapse and review its AGPL-3.0 obligations early. In every case, the value comes from owning the database and the backup process, so set those up before anything else.