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OpenSIPS vs Kamailio: catalog facts
OpenSIPS	Kamailio
Free Free and open source; paid training courses are offered separately.	Free Free and open source under the GPLv2 or later.
Linux, Self-hosted	Linux, Self-hosted
Handles high SIP traffic volumes Covers many roles from PBX to load balancer	Handles thousands of call setups per second WebSocket support for WebRTC plus TLS for secure signalling
Steep learning curve, aimed at telecom engineers Signaling server only, not an end-user calling app	Infrastructure for engineers, not an end-user calling app Configuration requires solid SIP and VoIP knowledge
Downloadable app, Self-hosted	Downloadable app, Self-hosted
Open source	Open source
License: GPL-2.0	License: GPL-2.0-or-later
No account needed	No account needed
Not stated if it works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.