Jitsi (formerly SIP Communicator) is a free and open source multiplatform voice (VoIP), videoconferencing and instant messaging application. Developed by University of Strasbourg (France), plus many others.
License: Open Source
Facebook Messenger is ideal for casual conversations and social interactions due to its integration with the Facebook platform, while Jitsi excels in privacy and security, making it perfect for professional and confidential meetings. The choice between the two depends on whether users prioritize social engagement or secure communication.