There are several open-source options available for instant messaging, which provide an alternative to proprietary services such as WhatsApp, Facebook Messenger, and Slack. One example is Signal, which is an open-source and end-to-end encrypted messaging app that can be used on both iOS and Android devices. Another example is Matrix, which is an open standard for decentralized real-time communication that places a strong emphasis on end-to-end encryption and distributed networks. Element is a Matrix client that offers support for text, voice, and video chat as well as file sharing.

Jitsi is another open-source video conferencing platform that can be run on your own server, with secure and fully-featured capabilities. Rocket. Chat is an open-source, self-hosted, and customizable team chat platform, providing a flexible option for team communication. Lastly, Tox is an open-source, peer-to-peer instant messaging and video calling platform that encrypts all communication, ensuring secure messaging and calls.

All of these options provide a great alternative to proprietary instant messaging services while also providing an extra layer of security and privacy.

Another open-source alternative is XMPP (Extensible Messaging and Presence Protocol) is an open-source protocol for instant messaging and presence information. XMPP is based on XML and is designed to be extensible, meaning it can be used for a wide variety of applications beyond instant messaging, such as Internet of Things (IoT) devices, social networks, and gaming platforms.

Additionally, there's also the which is an open-source and end-to-end encrypted instant messaging platform that is built on the Matrix protocol. offers a web-based client, as well as mobile apps for iOS and Android, and it also supports voice and video calls, as well as screen sharing.

Open-source instant messaging applications offer many benefits over proprietary apps, such as greater transparency and control over the software, as well as the ability to customize the app to suit specific needs. They also provide an added layer of security and privacy, as the code is open for review, which allows for independent security audits.