Jitsi
Open source video-conferencing stack. Launched 2003. Owned by 8x8 since 2018. Jitsi Meet (client) + Jitsi Videobridge (SFU) + Jicofo (signaling). Free hosted at meet.jit.si — no account required.
Selective Forwarding Unit architecture: server forwards streams without transcoding, saving CPU. Competitors: BigBlueButton (education focus), Nextcloud Talk (its own solution), Zoom/Teams (proprietary). E2EE support via insertable streams since 2020. Self-hosting became popular during COVID — many municipalities and universities ran their own Jitsi instances. Mobile apps have been weaker than the desktop experience.