Tox is a free, secure, open source, and decentralised instant messaging and file sharing application. It allows you to communicate with friends over encrypted chat, voice call, and video calls, and securely share any type of file, large or small. With Tox, users can connect with friends and family from anywhere in the world, and stay connected even if the internet connection is unstable or unavailable. Tox is designed to keep all user data safe and secure, ensuring that your conversations and files are accessible only by you and your contacts. It also features end-to-end encryption, meaning that all messages and files are encrypted before they ever leave your device. With Tox, you can be sure that your private conversations and files are safe and secure.
It is not open source and lately they have made some questionable decisions, such as banning anything vaguely defined as "adult content" from appearing in searches.