The best open source Video Calling alternative to Slack is Element. It's not free, so if you're looking for a free alternative, you could try Element or Zulip. If that doesn't suit you, our users have ranked more than 100 alternatives to Slack and many of them are open source Video Calling Apps so hopefully you can find a suitable replacement. Other interesting open source Video Calling App alternatives to Slack are Threema, Element X, Mirotalk and Nextcloud Talk.
Provides secure collaboration with end-to-end encryption, supporting chat, voice, and video calls. Available on all major platforms, it enables digital sovereignty with a decentralized design and interoperability through bridges to systems like Slack and Teams. Includes enterprise-grade SaaS.
Threaded group conversations combine live and asynchronous messaging, separating topics for organized collaboration, supporting open-source, cloud, and self-hosted deployments, secure communication with encryption, and multi-platform access for diverse teams.
Secure communication platform featuring encrypted chats and calls, file and media sharing, self-deleting messages, device verification, group collaboration, and customizable settings. Supports use across multiple devices with no phone number required for access.
Threema is a new mobile messaging app that puts security first. With true end-to-end encryption, you can rest assured that only you and the intended recipient can read your messages.
It is the brand new, and fastest ever, Matrix client. It is for personal and community use, and will support enterprise functionality later this year.
Powered by WebRTC, Real-time video call, chat room and screen sharing entirely browser based.
Self-hosted communication platform with secure audio, video, chat, web conferencing, screensharing, advanced encryption, and metadata privacy, running on user-controlled servers, supporting web and mobile apps, and eliminating third-party data exposure.
Decentralized social and blog platform based on XMPP, enabling self-hosting, cross-network chat, video calls, and group collaboration. Users control and migrate their data, communicate across various networks, and access services from any node while preserving privacy and open-source principles.
Open-source platform unifying project, document, issue, and task management with real-time team collaboration, instant messaging, video conferencing, and GitHub bidirectional sync, all in one customizable workspace for developers and product teams.
The best Discord alternative. Mezon is a Live, Work, and Play platform. It’s perfect for gaming and chilling with friends, or even building a global community. Customize your own space to talk, play, and hang out.
Open source chat platform offering end-to-end encrypted messaging, uncensored communication, markdown support, file sharing, self-hosting, multi-device sync, server management, voice or video calls, no data tracking, transparent codebase, and community-driven development.
Open-source chat platform providing community-focused group messaging, video calls, profile customization with animated avatars, custom emojis, tags, post creation, discovery of communities, and full source code access on GitHub. Entirely donation-funded.
![Profile Interface [PC - 2025]](https://img.alternativeto.net/s/618x394/avif/nerimity_993222_full.png)
![Messages View [PC - 2025]](https://img.alternativeto.net/s/618x394/avif/nerimity_281418_full.png)
![Server Discovery [PC - 2025]](https://img.alternativeto.net/s/618x394/avif/nerimity_282508_full.png)
![Server Settings [PC - 2025]](https://img.alternativeto.net/s/618x394/avif/nerimity_628028_full.png)
United Kingdom
United States
Switzerland
Italy
EU
Germany
France
Vietnam
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!