Open source team chat tools

Workplace chat, encrypted messaging and community platforms

The tools in this category share channels and direct messages, but they are built for different groups of people.

• Workplace chat servers follow the Slack model: teams, public and private channels, threads, integrations with developer and business tools, and admin controls such as SSO and retention. Mattermost and Rocket.Chat are the established options. Zulip adds a twist by filing every message under a topic, which keeps busy channels readable. Campfire strips the idea down to rooms, DMs and search in a single container.
• Encrypted and federated messaging puts end-to-end encryption and communication between independent servers first. Element is the main client for the Matrix standard, and Wire encrypts everything with the MLS protocol. Nextcloud Talk brings chat and calls to a Nextcloud server and federates with other Nextcloud servers.
• Community platforms follow the Discord model: servers with text and voice channels, roles, moderation and bots. Stoat and Fluxer each run a public service and can be self-hosted, Spacebar reimplements the Discord API so existing clients and bots work, and Tailchat builds its groups around plugins.

Encryption: what it protects and what it costs

Every tool here encrypts traffic between clients and the server with TLS, and self-hosting means messages sit on hardware you control. End-to-end encryption goes further: only the participants’ devices hold the keys, so the server operator cannot read content. Element turns it on by default using Matrix’s Olm and Megolm protocols, Wire uses Messaging Layer Security, the IETF standard published as RFC 9420 in July 2023 for group key agreement, and Rocket.Chat offers it as an option for private rooms and direct messages.

The trade-off is real. Rocket.Chat’s documentation warns that encrypted messages do not show up in search, cannot be audited and may be unreadable to bots. Organizations with legal retention or eDiscovery duties need to check how a tool handles compliance before turning encryption on everywhere.

Open core and free edition limits

Licenses range widely. Zulip (Apache-2.0), Campfire (MIT), Element Web, Wire, Stoat, Fluxer and Spacebar (AGPL) publish the whole application openly. Mattermost and Rocket.Chat are open core: SSO, guest accounts, compliance exports, high availability and, for Rocket.Chat, federation are in paid editions, and their free editions have caps. Mattermost Entry shows only the latest 10,000 messages, Mattermost Team Edition is meant for small teams without SSO, and Rocket.Chat Community allows 100 concurrent users. Element’s free server distribution is aimed at non-commercial use, while ESS Pro and Synapse Pro are proprietary.

Watch mobile push notifications too. Native apps from app stores usually deliver notifications through the vendor’s push service, which may be metered: Zulip’s free self-hosted plan covers notifications for up to 10 users at workplaces.

Self-hosting effort

Effort varies more than in most categories. Campfire is one Docker container and one volume. Mattermost is a Go binary plus PostgreSQL. Zulip’s installer configures PostgreSQL, Redis, RabbitMQ and nginx on a dedicated machine with 2 to 4 GB of RAM. Stoat, Fluxer and Tailchat use Docker Compose stacks with several services; Fluxer recommends 8 GB of RAM. A complete Matrix stack runs on Kubernetes, and a production Wire deployment calls for separate database clusters and two Kubernetes clusters. Voice and video add TURN servers and open UDP ports.

Federation and open standards

Matrix is an open standard with a public specification for communication across a federation of servers, so users on different Matrix servers can share rooms. Rocket.Chat includes a native Matrix implementation, and Nextcloud Talk can link Matrix accounts. Wire federates between Wire backends, Nextcloud Talk between Nextcloud servers, and Fluxer has federation on its roadmap, with a stable release targeted for 2027. Most other servers are standalone.

What to check before you choose

1. Chat model. Channels and threads, topics, or Discord-style servers and voice rooms.
2. Encryption needs and how they square with search, bots and compliance.
3. License and edition limits, including user caps, history caps and which features are paid.
4. Migration. Mattermost, Rocket.Chat and Zulip import Slack exports; Zulip also imports Microsoft Teams, Mattermost and Rocket.Chat data.
5. Calls. Built in (Mattermost, Nextcloud Talk, Element Call, Stoat, Fluxer) or through an external provider such as Jitsi (Zulip).
6. Operations. Databases, upgrades, backups and push notification services.

Projects not listed

We did not find a notable team chat server released only under a source-available license such as BSL or SSPL; the proprietary parts in this field sit inside open-core projects, as described above. Matrix homeservers such as Conduit and Continuwuity are hosted on GitLab and Forgejo rather than GitHub, so they are outside our current scope. Let’s Chat is archived, and Raven, a team chat for the Frappe framework, is still small.