Open Source Slack Alternatives

The best open source alternative to Slack is Mattermost. If that doesn't suit you, our users have ranked more than 100 alternatives to Slack and loads of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to Slack are Element, Zulip, Rocket.Chat and Matrix.org.

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Slack alternatives are mainly Instant Messengers but may also be Group Chat Apps or Video Calling Apps. Other popular filters includes Self-Hosted + Open Source. Filter by these or use the filter bar below if you want a narrower list of alternatives or looking for a specific functionality of Slack.

Slack

851

Group Chat App
Freemium • Proprietary

Facilitates teams' real-time collaboration with versatile chat interface and advanced search in configurable channels across multiple platforms.

More about Slack

Slack alternatives page was last updated Sep 18, 2024

OMEMO Instant Messenger
OMEMO Instant Messenger is a clean rebuild of the popular Android Jabber client Conversations. It includes minor graphical and user friendly feature improvements consisting of:
48 OMEMO Instant Messenger alternatives
+1
License model
- Free • Open Source
Application types
- Instant Messenger
- Group Chat App
Platforms
- Android
OMEMO Instant Messenger Features
1. OpenPGP
2. Privacy focused
3. End-to-End Encryption
4. No Tracking
5. Xmpp
Show all NaN OMEMO Instant Messenger features ▾
Discontinued
The last update is from November 2018.

OMEMO Instant Messenger VS Slack
Is this a good alternative to Slack?

Pensil
Pensil is a community building platform that brings together members, engaging discussion & live events for brands and creators.
28 Pensil alternatives
License model
- Freemium • Open Source
Application types
- Group Chat App
- Video Calling App
Platforms
- Online
- Android
- iPhone
- Android Tablet
- iPad
- Self-Hosted
- Google Chrome
- Software as a Service (SaaS)
+2
Top Pensil Features
1. Cloud Sync
2. Privacy focused
3. No registration required
4. End-to-End Encryption
5. Real time collaboration
6. Dark Mode
7. Sync with Google Calendar
8. Support for MarkDown
9. Multiple Account support
10. Lightweight
11. Online community platform
12. Live calls
Show all NaN Pensil features ▾
Pensil VS Slack
Is Pensil a good alternative to Slack?

Glitch Gaming
Content creators and influencers have the ability to monetize their platforms by promoting a range of games, from indie to AAA. They can preview new games, creating engaging content across a variety of social platforms such as TikTok, Twitch, Reddit, Twitter, and YouTube.
8 Glitch Gaming alternatives
License model
- Free • Open Source
Application type
- Group Chat App
Platforms
- Online
Glitch Gaming Features
1. Real time collaboration
2. Dark Mode
3. Support for @mentions
4. VoiP Calls
5. Screen Sharing
6. Cloud Sync
7. AI-Powered
Show all NaN Glitch Gaming features ▾
Glitch Gaming VS Slack
Is Glitch Gaming a good alternative to Slack?

Adapt Chat
Grow a community, connect with your friends, or whatever you're capable of with Adapt, a lightweight and customizable messaging platform which favors your privacy.
51 Adapt Chat alternatives
License model
- Free • Open Source
Application type
- Group Chat App
Platforms
- Online
- Self-Hosted
Top Adapt Chat Features
1. Dark Mode
2. Lightweight
3. End-to-End Encryption
4. Real time collaboration
5. VoiP Calls
6. Privacy focused
7. Support for @mentions
8. Multiple Account support
9. Screen Sharing
10. No Tracking
11. Support for MarkDown
12. Ad-free
Show all NaN Adapt Chat features ▾
Adapt Chat VS Slack
Is Adapt Chat a good alternative to Slack?

Linen
Linen is a Google-searchable community chat tool. Linen was built as an alternative to closed tools like Slack and Discord.
4 Linen alternatives
License model
- Free • Open Source
Platforms
- Online
Linen VS Slack
Is Linen a good alternative to Slack?