Slack AlternativesOnly Open Source apps categorised as Group Chat Apps

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

Mattermost
Mattermost is a secure, open source platform for communication, collaboration, and workflow orchestration across tools and teams.
118 Mattermost alternatives
License model
- Freemium • Open Source
Application types
- Group Chat App
- Instant Messenger
Platforms
- Mac
- Windows
- Linux
- Android
- iPhone
- Android Tablet
- iPad
- Self-Hosted
- JavaScript
- Go (Programming Language)
- Cloudron
+1
Top Mattermost Features
1. Team Collaboration
2. Extensible by Plugins/Extensions
3. Chat Bot
4. On-premises software
5. Built-in viewer
6. Support for @mentions
7. Support for MarkDown
8. Real time collaboration
9. Lightweight
10. End-to-End Encryption
11. Full-Text Search
12. Dark Mode
Show all NaN Mattermost features ▾
Mattermost VS Slack
Is Mattermost a good alternative to Slack?
Comments about Mattermost as an Alternative to Slack

shelehovchanin
Same functionality. Same interface. At the same time, there are much fewer restrictions. IN my experience, the free version is great enough for a team of 100 people
Top positive comment •Apr 4, 2019
7
kostya
Allmost the same interface and features
Top positive comment •Feb 25, 2020
3
Alex Hoyau
Beware this is not free/libre software, not even fully open source, mattermost is open core (like freemium is not fully free/gratis)
Top negative comment •Sep 11, 2024
0
Indiana Lake
Same with more emphasis on privacy.
Positive comment •Feb 27, 2023
0
liger1978
Great interface, you control your data.
Positive comment •May 12, 2020
0
Show more comments
5 of 22 comments
- Almost everyone thinks Mattermost is a great Slack alternative.
- Mattermost is the most popular Windows, Android, Mac & iPhone alternative to Slack.
- Mattermost is the most popular Open Source & free alternative to Slack.
- Mattermost is Freemium and Open SourceSlack is Freemium and Proprietary
- Mattermost is LightweightSlack is not according to our users

Element
Element is a secure collaboration and messaging app based on the Matrix protocol. It’s decentralised to deliver digital sovereignty, and based on an open standard for easy connections and interoperability. It is end-to-end encrypted by default.
283 Element alternatives
License model
- Freemium • Open Source
Application types
- Instant Messenger
- Video Calling App
Platforms
- Mac
- Windows
- Linux
- Online
- Android
- iPhone
- Android Tablet
- iPad
- Self-Hosted
- Matrix.org
- Flathub
- F-Droid
- Cloudron
+1
Top Element Features
1. End-to-End Encryption
2. Decentralized
3. Federated
4. Team Collaboration
5. Privacy focused
6. Encrypted Chat
7. Video Calling
8. Instant Messaging
9. Matrix Protocol
10. Voice Chat
11. Federation
12. Direct Messaging
Show all NaN Element features ▾
Element VS Slack
Is Element a good alternative to Slack?
Comments about Element as an Alternative to Slack

brinerustle
because its open source, decentralised, and end-to-end secure. Plus the folks at matrix.org are working to get us out of our communication silos by creating standards for communication interoperability!
Top positive comment •Mar 3, 2018
6
Vladimir Studinsky
decentralised, federated, end-to-end encrypted communication.
Top positive comment •Oct 10, 2017
8
Dserver Hosting
this is a open source and free software that is very useful for me
Positive comment •Dec 20, 2022
1
kaspian
Encrypted, free, open-source, decentralized
Positive comment •Sep 28, 2022
0
Tommi
It is decentralized and it works with an open standard
Positive comment •Dec 5, 2021
2
Show more comments
5 of 12 comments
- Almost everyone thinks Element is a great Slack alternative.
- Element is the most popular Web-based alternative to Slack.
- Element is Freemium and Open SourceSlack is Freemium and Proprietary
- Element is Decentralized and Privacy focusedSlack is not according to our users

Zulip
Zulip is the only modern team chat app that is designed for both live and asynchronous conversations. Zulip topics create a separate space for each discussion, so different conversations will never get in each other's way.
225 Zulip alternatives
License model
- Free Personal • Open Source
Application types
- Instant Messenger
- Group Chat App
Platforms
- Mac
- Windows
- Linux
- Online
- Android
- iPhone
- Android Tablet
- BSD
- iPad
- Self-Hosted
+4
Top Zulip Features
1. Threaded Conversations
2. Team Collaboration
3. Support for Hotkeys
4. Community-based
5. Support for MarkDown
6. Syntax Highlighting
7. Integrated File Sharing
8. Chat Bot
9. GitHub Integration
10. Secure Chat
11. Third party integrations
12. Chat organizer
Show all NaN Zulip features ▾
Zulip VS Slack
Is Zulip a good alternative to Slack?
Comments about Zulip as an Alternative to Slack

Paulo Coghi
More than feature parity with Slack, it's better because of Streams and Topics. It offer the same free tier with 10.000 max messages and better paid plans to the hosted version, and also provide the open source self-hosted option to install it on your own server and also remove the max messages limits. 5 stars
Top positive comment •Feb 6, 2020
4
Guest
It's a little different, for sure, but what it does, it does better than slack. Not a open source copy of slack like mattermost. If you want slack and nothing else, but in open source, stick to mattermost, if you want something that exceeds that, choose zulip.
Top positive comment •Nov 25, 2020
3
Alex Hoyau
Beware this is not free/libre software, not even fully open source, zulip is open core (like freemium is not fully free/gratis)
Positive comment •Sep 11, 2024
0
Guest
the threading model is the best i've used for keeping up with active communities, and the open-source community is excellent.
Positive comment •Nov 25, 2020
2
Guest
The concept of topics to each message is a super useful feature :)
Positive comment •May 19, 2019
3
Show more comments
5 of 17 comments
- Almost everyone thinks Zulip is a great Slack alternative.
- Zulip is Free Personal and Open SourceSlack is Freemium and Proprietary

Rocket.Chat
Rocket.Chat is a Web Chat Server, developed in JavaScript, using the Meteor fullstack framework.
133 Rocket.Chat alternatives
License model
- Freemium • Open Source
Application types
- Group Chat App
- Instant Messenger
Platforms
- Mac
- Windows
- Linux
- Android
- iPhone
- iPad
- Self-Hosted
- Cloudron
+5
Top Rocket.Chat Features
1. Omnichannel messaging
2. Ad-free
3. Channels
4. Self-Serve Capability
5. Telegram integration
6. Whatsapp integration
7. End-to-End Encryption
8. Extensible by Plugins/Extensions
9. Screen Sharing
10. Bots
11. Integrated File Sharing
12. Video Conferencing
Show all NaN Rocket.Chat features ▾
Rocket.Chat VS Slack
Is Rocket.Chat a good alternative to Slack?
Comments about Rocket.Chat as an Alternative to Slack

John Fastman
Does everything Slack does AND it's open source. However, it's also self-hosted. This means you have to put in the effort to set it up, but you control your own data, which is a huge advantage to your privacy - your chats and files don't sit on someone else's servers, ready for them or hackers to look at.
Positive comment •Dec 26, 2016
10
Guest
Rocket.Chat comes very close to slack regarding it's core features and handling.
Positive comment •Jun 17, 2018
7
Guest
open source, locally hosted so you own your data.
Positive comment •Nov 29, 2018
2
- Almost everyone thinks Rocket.Chat is a great Slack alternative.
- Rocket.Chat is Freemium and Open SourceSlack is Freemium and Proprietary

Matrix.org
Matrix defines a set of open APIs for decentralised communication, suitable for securely publishing, persisting and subscribing to data over a global open federation of servers with no single point of control.
153 Matrix.org alternatives
License model
- Free • Open Source
Application types
- Instant Messenger
- Group Chat App
Platforms
- Mac
- Windows
- Linux
- Online
- Android
- iPhone
- Android Tablet
- iPad
- Self-Hosted
- WebRTC
- Python
- JavaScript
- Go (Programming Language)
- Cloudron
- Java
- Perl
Top Matrix.org Features
1. Decentralized
2. End-to-End Encryption
3. Federation
4. Team Collaboration
5. Random Video Chat
6. Privacy focused
7. Distributed
8. Ad-free
9. VoiP Calls
10. No Tracking
11. Multiple Account support
12. Real time collaboration
Show all NaN Matrix.org features ▾
Matrix.org VS Slack
Is Matrix.org a good alternative to Slack?
Comments about Matrix.org as an Alternative to Slack

Guest
Respects your Freedom. Increasingly popular
Top positive comment •Nov 3, 2017
3
nrg200
Capable of everything Slack can do, but can be self-hosted - keeping a team's data in-house.
Top positive comment •Jul 13, 2017
1
somegirlfromit
Matrix is a protocol, not a client.
Top negative comment •Sep 15, 2019
18
Vladimir Studinsky
Open source, fecentralized, federation, chat-voice-video function.
Positive comment •Oct 28, 2017
1
Guest
Free open source instant messaging service with federation.
Positive comment •Aug 21, 2017
0
Show more comments
5 of 7 comments
- Almost everyone thinks Matrix.org is a great Slack alternative.
- Matrix.org is Free and Open SourceSlack is Freemium and Proprietary
- Matrix.org is Decentralized and Privacy focusedSlack is not according to our users

Wire
Wire is the most secure collaboration platform featuring messenger, voice, video, conference calls, file-sharing, and external collaboration –all protected by the most secure end-to-end-encryption.
275 Wire alternatives
+2
License model
- Free Personal • Open Source
Application types
- Video Calling App
- Instant Messenger
Platforms
- Mac
- Windows
- Linux
- Online
- Android
- iPhone
- Android Tablet
- iPad
- Self-Hosted
- F-Droid
- Software as a Service (SaaS)
Top Wire Features
1. End-to-End Encryption
2. Security focused
3. Video Calling
4. Encrypted Chat
5. VoiP Calls
6. Encrypted calls
7. Screen Sharing
8. Privacy focused
9. Multiple Account support
10. WebRTC
11. File Sending
12. Voice Chat
Show all NaN Wire features ▾
Wire VS Slack
Is Wire a good alternative to Slack?
- Most users think Wire is a great Slack alternative.
- Wire is the most popular SaaS alternative to Slack.
- Wire is Free Personal and Open SourceSlack is Freemium and Proprietary
- Wire is Security focused and Privacy focusedSlack is not according to our users

Revolt
Revolt is a user-first, privacy focused chat platform.
34 Revolt alternatives
License model
- Free • Open Source
Application types
- Instant Messenger
- Group Chat App
Platforms
- Mac
- Windows
- Linux
- Online
- Android
- Rust
- Flathub
- F-Droid
- GitHub
+5
Top Revolt Features
1. Privacy focused
2. Ad-free
3. Text chat
4. No Tracking
5. VoiP Calls
6. Bots
7. Multiple Servers
8. Instant Messaging
9. Support for Themes
10. Cloud Sync
11. Dark Mode
12. Two-factor Authentication
Show all NaN Revolt features ▾
Revolt VS Slack
Is Revolt a good alternative to Slack?