The XMPP Standards Foundation develops the XMPP/Jabber instant messaging and voice/video calling standards. You can follow them at:

➑️ @xmpp

The official site is xmpp.org

It's a free open standard, so anyone can use it in their software and hardware.

Senfcall.de is a privacy-friendly free open source video conferencing site which aims to provide an alternative to proprietary services. You can follow them at:

➑️ @senfcall (in German and English)

Their website is at senfcall.de/en

Calls are made via your web browser using the FOSS BigBlueButton system.

Matrix is a free open source federated communications platform with support for messaging and calling. You can follow their official account at:

➑️ @matrix

The platform has many different apps available including the popular Element (formerly known as Riot). The official Matrix site is at matrix.org

Jami is a free open source alternative to Skype, featuring video chat, audio and messaging. You can follow the project here:

➑️ @Jami

Jami is available for Android, iOS, Windows, Mac and Linux. You can get it from the official site at jami.net

It works peer-to-peer, so calls connect directly instead of passing through a server.

Mastodon

This is a brand new server run by the main developers of the project as a spin-off of mastodon.social 🐘 It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!