Open Source Slack Alternatives

Its the same but you keep your server where you want so no one is playing with your data, and you can have an unlimited history depending on what you need for free so really way better !

Mattermost is quite versatile and has been used within several of my past employers.

Great interface, you control your data.

It's faster for one thing. It's far superior in terms of data ownership, and it's extremely scalable.

Has more flexibility due to its extensive plugin system compared to other alternatives.

Looks and works very much the same as Slack and complete control over your data housed separately from anyone else.

Open source with control over your data.

It is decentralized and it works with an open standard

decentralised, federated, end-to-end encrypted communication.

Privacy by design and based on matrix protocol!

Federated, decentralized, encrypted, open-source.

Open Source / Free Software,

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!

Federated, free standard and free software

the threading model is the best i've used for keeping up with active communities, and the open-source community is excellent.

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.

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

The concept of topics to each message is a super useful feature :)

Zulip is open source and the methods of communications used is vastly different. It is specially useful in professional environments where different teams might want to participate in different conversations at the same time. Zulip solves this problem by including topics, where in each channel/stream, multiple topics can exist at once, at the same time.

Open Source without limitations when on premises. Much better information categorisation with Streams & Topics. Vibrant community.

One can easily switch in between conversation between different threads! Extremely helpful for any organisation.

Rocket.Chat comes very close to slack regarding it's core features and handling.

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.

open source, locally hosted so you own your data.

It can be easily bridged to many other chat systems, including Slack, which makes transitioning much easier. It's also open source and decentralized (self-hostable + communication with other servers).

Respects your Freedom. Increasingly popular

Matrix is a protocol, not a client.

Open source, fecentralized, federation, chat-voice-video function.

Free open source instant messaging service with federation.

free, end-to-end encryption

Capable of everything Slack can do, but can be self-hosted - keeping a team's data in-house.