Open-source alternatives to Slack, Microsoft Teams and Facebook Groups
The right open-source alternative depends on what you are replacing. Chat tools replace Slack and the chat of Teams; community platforms replace Facebook Groups and the social layer of Teams. This roundup says which is which, honestly, including when a chat tool is a better fit than HumHub.
Chat or community: what are you replacing?
| Chat tool (Slack, Teams chat) | Community platform (Facebook Groups, Workplace, Viva Engage) | |
|---|---|---|
| Rhythm | Real time, all day | Asynchronous, a few visits a week |
| Content | Messages that scroll away | Posts, documents, events and pages that stay |
| Who | Colleagues working together | Everyone in the organization, members, volunteers, partners |
| Measure of success | Fast answers | Information found, people reached |
The open-source options
| Tool | License | Replaces | Fits when | Free self-hosted edition |
|---|---|---|---|---|
| Mattermost | MIT (Team Edition); commercial editions on quote | Slack, Teams chat | Technical teams that chat all day and want to self-host | Team Edition, for fewer than 250 users without single sign-on |
| Rocket.Chat | MIT (Community); commercial plans on quote | Slack, Teams chat, customer chat | Chat with customers and teams, self-hosted | Community edition and a free Starter plan up to 50 users |
| Element (Matrix) | AGPL (Community); Enterprise per seat | Slack, Teams chat | Encrypted, federated messaging, public sector | Community edition for non-professional use and evaluation |
| Zulip | Apache 2.0 | Slack | Threaded chat for distributed teams and open-source projects | Yes |
| Nextcloud Talk | AGPL | Teams calls and chat, next to files | Organizations already on Nextcloud | Yes |
| Discourse | GPL | Facebook Groups, forums | Public discussion forums and support communities | Yes; hosted from a free plan |
| Open Social | GPL (open core) | Facebook Groups, Workplace | Institutional communities on Drupal | Yes (Drupal distribution) |
| HumHub | AGPL | Facebook Groups, Workplace, Viva Engage, the community side of Slack and Teams | Organizations and member communities: spaces, announcements, wiki, files, events, mobile app | Yes; hosted by HumHub GmbH or by partners such as CUZY |
When a chat tool fits better than HumHub
- Your team works in conversation all day and expects instant replies.
- Integrations (monitoring, code, sales tools) post into channels constantly.
- Everyone involved is an active colleague, and the group is small.
In that case, choose a chat tool, and keep HumHub, or another community platform, for announcements, documents and the people outside the core team. Both can run side by side, with members signing in to each through the same identity provider.
When HumHub fits better
- Announcements must reach everyone, including people who open the platform once a week.
- Knowledge must stay findable: procedures, minutes, the calendar, files.
- Members are not all employees: volunteers, parents, alumni, customers.
- You want one price whatever the number of members: see Slack, Microsoft Teams and Viva Engage and leaving Facebook and WhatsApp groups.
Questions
What is the best open-source alternative to Slack?
For real-time team chat, Mattermost, Rocket.Chat, Zulip and Element (Matrix) are the closest replacements. HumHub is not a chat tool: it replaces Slack when the real need is announcements, spaces with documents and a searchable archive rather than instant messaging.
What is an open-source alternative to Facebook Groups?
HumHub, Discourse and Open Social. HumHub adds spaces with events, files and a wiki plus a mobile app; Discourse is a forum; Open Social is a Drupal-based community platform.