Janus (launched 2014) was one of the earliest open-source WebRTC servers and remains widely deployed. Unlike mediasoup or LiveKit, which present themselves primarily as SFUs, Janus is a general-purpose WebRTC gateway with a plugin architecture: the SFU is one plugin (videoroom), but other plugins handle one-way streaming (streaming), recording (recordplay), SIP gateway (sip), TextRoom and others. This makes Janus the Swiss-army-knife choice for projects that need WebRTC integration with multiple non-WebRTC systems.
Janus is written in C for performance, with HTTP, WebSocket and Unix-socket APIs for control. It runs single-process with worker threads — more traditional than mediasoup's per-CPU-process model. The community is large and active; commercial support is available from Meetecho and several partners. Large-scale deployments include Slack Huddles, Linphone, and many telecom-adjacent video conferencing systems.
Janus's strengths are flexibility (plugins for everything) and broadcast/streaming integration. Its weaknesses are a steeper learning curve than LiveKit and a less JavaScript-friendly API than mediasoup. For pure WebRTC SFU use, mediasoup or LiveKit are often easier. For complex hybrid deployments — WebRTC plus SIP plus broadcast streaming plus recording — Janus's plugin ecosystem is hard to beat.
