Alternatives to Slack for all platforms with Open Source License

Mattermost

Mattermost is an open source, self-hosted Slack alternative. As an alternative to proprietary SaaS messaging, Mattermost brings...
- Open source with control over your data. jaydeland • Apr 2020
- 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 shelehovchanin • Apr 2019 • 6 agrees and 0 disagrees
- It is very much a Slack clone with added features + it's open source! Guest • May 2017 • 3 agrees and 2 disagrees
- 1. Open source; 2. most of the same functionality; 3. secure and private server possibilities (the data is, therefore, yours until the end of time); 4. extra features when it comes to customization, a big difference actually. Only negative is that Slack look a lot better design wise, so you can't customize it optimally. Guest • May 2017 • 1 agrees and 1 disagrees
- Allmost the same interface and features kostya • Feb 2020 • 1 agrees and 0 disagrees
- it is similar in features, and has some more, for example XMPP compatibility (-> many more client choice) and ability to self host it! Guest • Jul 2018 • 3 agrees and 1 disagrees
- Mattermost is quite versatile and has been used within several of my past employers. Guest • May 2018 • 4 agrees and 1 disagrees
- Great interface, you control your data. liger1978 • 12 days ago
- It's faster for one thing. It's far superior in terms of data ownership, and it's extremely scalable. Guest • Apr 2020
- Has more flexibility due to its extensive plugin system compared to other alternatives. svelle • Apr 2020
- It covers just about every use-case with the ability to host it yourself, and the team edition should cover about all needs for smaller (~150) companies Guest • Apr 2020
- same features and ease of use. more control and costs less Guest • Apr 2020
- Lots of options for integrations! Guest • Apr 2020
- Looks and works very much the same as Slack and complete control over your data housed separately from anyone else. Mudie • Apr 2020
- Has all the features provided by Slack plus even more and can be self hosted. wget • Apr 2020
- Mattermost is on-prem, secure and available on desktop, browser and mobile lindy65 • Apr 2020
- 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 ! Guest • May 2017 • 5 agrees and 1 disagrees
Freemium $ $ $ Open Source Mac Windows Linux Android iPhone ... Android Tablet iPad Self-Hosted JavaScript Go (Programming Language) Cloudron
Group chat Team Collaboration On-premises software Chat Bot ... Data API Integrated File Sharing MarkDown support Multi Channel Plugin API Plugins Self-hosted in intranet or private cloud File Sending Slack integration Supports XMPP Webhook support Add a feature

188 Like
Zulip

Zulip is a group chat app in which messages are threaded by topic, helping you have long-running, organized conversations. Zulip's threading makes it easy for people...
- 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. Guest • Mar 2019 • 5 agrees and 1 disagrees
- 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 paulocoghi • Feb 2020 • 2 agrees and 0 disagrees
- Three reasons: 1. Open source. 2. Stream 3. Topics abijith • Dec 2017 • 8 agrees and 0 disagrees
- Open Source without limitations when on premises. Much better information categorisation with Streams & Topics. Vibrant community. superbiche • Dec 2018 • 3 agrees and 1 disagrees
- It's open source, and has really good threaded conversations. aviendha1591 • Nov 2017 • 6 agrees and 0 disagrees
- It's open source and you can self host. It has great threading to group conversations so things are easier to find and more organized . Guest • Jul 2018 • 1 agrees and 0 disagrees
- Zulip is very user friendly and is also open source! linacodes • Jan 2018 • 1 agrees and 0 disagrees
- It is open source and has a lot of topics. Guest • Jan 2018 • 1 agrees and 0 disagrees
- Open-source, streams, topics, quick responses from devs hrishikeshpatil • Jan 2018 • 1 agrees and 0 disagrees
- The concept of topics to each message is a super useful feature :) Guest • May 2019 • 2 agrees and 1 disagrees
- Zulip offers a great unbeatable chatting experience. It shines in many places where Slack tends to slack. Sethu • Dec 2017 • 6 agrees and 0 disagrees
- One can easily switch in between conversation between different threads! Extremely helpful for any organisation. shantnukumar • Aug 2018 • 1 agrees and 0 disagrees
- Great community Easy Access Many organization sirepherox • Jan 2018 • 1 agrees and 0 disagrees
- Good community with great support. gamefreakerxD • Dec 2017 • 1 agrees and 0 disagrees
Free Personal $ $ $ Open Source Mac Windows Linux Web Android ... iPhone Android Tablet BSD iPad Self-Hosted
Threaded Conversations Group collaboration Chat Bot Chat organizer ... Community based GitHub integration Group chat Integrated File Sharing Live topics MarkDown support Secure Chat Team Collaboration Todos Add a feature

157 Like
Riot.im

A free instant messaging and collaboration software based on the Matrix protocol.
- Federated, decentralized, encrypted, open-source. Guest • Jul 2019 • 3 agrees and 1 disagrees
- 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! brinerustle • Mar 2018 • 4 agrees and 0 disagrees
- Federated, free standard and free software Guest • Feb 2018 • 4 agrees and 1 disagrees
- decentralised, federated, end-to-end encrypted communication. User6044478 • Oct 2017 • 7 agrees and 0 disagrees
- It's built atop Matrix, which provides distributed, federated instant messaging, voice and video calling with the ability to bridge into other networks (IRC, etc.) lampholder • Jul 2017 • 4 agrees and 0 disagrees
- Free and opensource with better performance and features for team communication. Guest • Aug 2017 • 4 agrees and 1 disagrees
Free Open Source Mac Windows Linux Web Android ... iPhone Android Tablet iPad Self-Hosted
End-to-End Encryption Decentralized Group chat Team Collaboration ... Privacy-friendly Security & Privacy Video chat Federated Video calling Voice Call Add-ons Clean design Custom widgets Direct Messaging Encrypted chat Group collaboration Matrix.org protocol Message redaction Mobile friendly Moderation tools Per-room avatars Privacy focused Read receipts Text chat Typing notifications User Management User mentions Video/Audio Calling Voice chat Web Integaration Chat Bot Community based DRM Free GitHub integration Integrated File Sharing Live Chat MarkDown support Real time collaboration File Sending Server Moderation Server side history Slack integration Social network Video calling Voice chat Web-Based Add a feature

311 Like
Rocket.Chat

Rocket.Chat is a Web Chat Server, developed in JavaScript, using the Meteor fullstack framework.
- open source, locally hosted so you own your data. Guest • Nov 2018 • 2 agrees and 1 disagrees
- 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. JohnFastman • Dec 2016 • 7 agrees and 1 disagrees
- Rocket.Chat comes very close to slack regarding it's core features and handling. Guest • Jun 2018 • 3 agrees and 0 disagrees
Free Open Source Mac Windows Linux Self-Hosted Cloudron
Group chat Ad-free Channels Live Chat ... Video Conferencing Bots Chat Bot Extensible by Plugins/Extensions Integrated File Sharing Location Mapping Share your screen Self-Serve Capability Slack integration Video chat Voice messages Add a feature

110 Like
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...
- Open source, fecentralized, federation, chat-voice-video function. User6044478 • Oct 2017
- 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). Guest • Jul 2017
- Free open source instant messaging service with federation. Guest • Aug 2017 • 0 agrees and 1 disagrees
- Matrix is a protocol, not a client. somegirlfromit • Sep 2019 • 6 agrees and 0 disagrees
- Respects your Freedom. Increasingly popular Guest • Nov 2017
- Capable of everything Slack can do, but can be self-hosted - keeping a team's data in-house. nrg200 • Jul 2017
Free Open Source Mac Windows Linux Web Android ... iPhone Android Tablet iPad Self-Hosted WebRTC Python JavaScript Go (Programming Language) Java Perl
End-to-End Encryption Chat Decentralized Random video chat ... Voice chat Chat Bot Distributed Encrypted chat Group chat Messaging Real time collaboration Server side history Team Collaboration Voice Call WebRTC Add a feature

157 Like
Wire

Wire is the most secure collaboration platform featuring messenger, voice, video, conference calls, file-sharing, and external collaboration –all protected by the most...

Freemium Open Source Mac Windows Linux Web Android ... iPhone Android Tablet iPad Self-Hosted Software as a Service (SaaS)
End-to-End Encryption Security focused Encrypted chat Video calling ... Voice Call Encrypted calls Encryption Group chat Share your screen Security & Privacy Anonymity Integrated File Sharing Multiple Account support Photo Sharing Privacy focused Privacy Protected Private Chat Secure Chat Secure File Sharing File Sending Video calling Video chat Voice chat Voice messages WebRTC Add a feature

242 Like
Jitsi

Jitsi (previously SIP Communicator) is an audio/video and chat communicator with full encryption that supports protocols such as SIP, XMPP/Jabber, ICQ/AIM, Windows Live...

Free Open Source Mac Windows Linux Web Android ... iPhone Android Tablet BSD iPad
SIP Video Conferencing Privacy-friendly Security & Privacy ... Browser based Chat Cross-platform Desktop Sharing File sharing Group chat iPhone/iPod sync Live Meeting Support for Multiple protocols Multiple Account support No download No installation required No Login Required OTR Plugins Privacy focused Share your screen SIP Softphone Unlimited users Video calling Video chat Video Conferencing Voice chat WebRTC Xmpp Add a feature

364 Like
Conversations

Conversations is a privacy focused, open source XMPP Texting [Jabber] client for Android 4.0+ smart phones with wife-approved easy encryption [OTR, OMEMO, or GPG]. ...

Free Open Source Android Android Tablet
Decentralized End-to-End Encryption Encrypted chat Picture sharing ... Encrypted Connection Chat Bot Gpg encryption Group chat Group Messaging Intuitive Interface OTR Self destructing messages Audio Chat Chat Federated File sharing Messaging OMEMO Public groups chat Secure Chat Xmpp Add a feature

76 Like
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Gitter

Gitter is a chat and collaboration tool for developers and users. It's a place for developers to talk. KEY FEATURES - Unlimited public chat rooms for free -...

Free Open Source Mac Windows Linux Web Android ... iPhone
Cross-platform Public communities discovery Chat Real time collaboration ... Social network Add a feature

30 Like
Let's Chat

Self-hosted chat for small teams. Features and Stuff BYOS (bring your own server) Persistent messages Multiple rooms New message alerts /...
- Discontinued
  As stated at https://github.com/sdelements/lets-chat/issues/781 , the project is no longer developed since August 2017. Last version, 0.4.0, released in June 2015, can be still downloaded from GitHub together with the source code.
Free Open Source Self-Hosted
Chat Team Collaboration Add a feature

37 Like