Self-hosted alternatives to Slack
The free plan now hides messages older than 90 days — your team's history disappears unless you pay per seat.
Below are 10 open-source projects that cover the same ground, each scored 0–100 on how actively it is actually maintained — commit volume, release cadence and recent trend. 10 of the 10 are currently rated healthy or better. Ordering reflects that score, not sponsorship.
| Project | Health | Activity (11 mo) | Stars | Licence | Last release |
|---|---|---|---|---|---|
| Rocket.Chat Communications platform that puts data protection first (alternative to Gitter.im and Slack). | Thriving · 92 | 46k | MIT | 23 Sept 2026 | |
| Novu Notification infrastructure for developers. | Thriving · 92 | 40k | MIT | 7 Sept 2026 | |
| Chatwoot Customer communication platform (alternative to Intercom and Zendesk). | Thriving · 92 | 37k | ⊘ Proprietary | 18 Sept 2026 | |
| Mattermost Platform for secure collaboration across the entire software development lifecycle, can be integrated with Git | Thriving · 91 | 39k | ⊘ Proprietary | 25 Sept 2026 | |
| Element Fully-featured Matrix client for Web, iOS & Android. | Thriving · 91 | 14k | Apache-2.0 | 23 Sept 2026 | |
| One Time Secret Share sensitive information securely with self-destructing links that are only viewable once. | Thriving · 91 | 2.9k | MIT | 23 Sept 2026 | |
| Zulip Zulip is a powerful, open source group chat application. | Thriving · 86 | 26k | Apache-2.0 | 21 Sept 2026 | |
| Tuwunel High-performance and feature-rich chat server for Matrix, and the successor to conduwuit (fork of Conduit). | Thriving · 86 | 2.6k | Apache-2.0 | 25 Sept 2026 | |
| WorkAdventure Virtual office / virtual conference application presented as a 16-bit RPG video game. | Thriving · 84 | 5.8k | AGPL-3.0 | 18 Sept 2026 | |
| Fluxer Instant messaging and VoIP platform built for friends, groups, and communities (alternative to Discord). | Thriving · 83 | 10k | AGPL-3.0 | 28 Sept 2026 |
How these were picked
Every project listed here is open source and can run entirely on hardware you control. We start from the categories that match Slack's job — Communication - Custom Communication Systems — then rank by health score so that a popular-but-abandoned project never appears above a smaller one that is actively shipping. The scoring method is documented in full.
The scores are recomputed from repository data on every rebuild, so this page reflects the state of these projects as of 1 Oct 2026 — not the day it was written.
Rocket.Chat
Communications platform that puts data protection first (alternative to Gitter.im and Slack).
Best fit: It is a strong fit for organisations that require a custom communication system and need strict control over their data privacy. It suits teams migrating away from third-party Software-as-a-Service chat tools.
Worth knowing: Managing a Node.js application at scale requires careful resource monitoring and regular maintenance to handle updates safely. It also overlaps heavily with well-established proprietary messaging tools, which may offer easier initial onboarding.
Novu
Notification infrastructure for developers.
Best fit: Development teams building applications that require complex multi-channel alert routing and template management.
Worth knowing: Self-hosting involves running a Node.js-based stack with multiple dependent services, which can introduce significant operational and resource overhead.
Chatwoot
Customer communication platform (alternative to Intercom and Zendesk).
Best fit: Teams looking for an open-source or self-hosted alternative to mainstream customer support helpdesks to maintain data control.
Worth knowing: The software is distributed under a proprietary licence rather than a standard open-source licence, which may restrict how you can commercialise or modify it. It also carries a high operational burden typical of a monolithic Ruby application with multiple background workers.
Mattermost
Platform for secure collaboration across the entire software development lifecycle, can be integrated with Gitlab (alternative to Slack).
Best fit: Engineering teams looking for a self-hosted communication hub that integrates closely with their GitLab infrastructure and adheres to strict security requirements.
Worth knowing: The software uses a proprietary licence model for certain distributions, which may limit free access to advanced enterprise capabilities. It also requires careful resource management compared to simpler communication tools.
Element
Fully-featured Matrix client for Web, iOS & Android.
Best fit: It suits technical teams or individuals who want to maintain full control over their communication channels using the open Matrix protocol.
Worth knowing: You will need to manage user authentication, homeserver federation, and client updates independently, which adds ongoing administrative overhead.