openSIPS Review, Pricing & Features

openSIPS review covering the open-source SIP server's features, history, free pricing, commercial support options, and alternatives like Kamailio and…

Category
Communication
Pricing
Open Source, from Free
Verified
Not yet
Last updated
July 19, 2026
Founded
2001
Headquarters
Bucharest, Romania
Open SourceSelf-Hosted

Overview

openSIPS is a mature, open-source SIP proxy and server used to build VoIP, unified communications, and telecom signaling infrastructure. Its history dates back to 2001 as SIP Express Router, later forked into OpenSER in 2005, and renamed openSIPS in 2008 after a trademark dispute split the project into Kamailio and openSIPS.

The project is maintained by OpenSIPS Solutions, a small telecommunications company based in Bucharest, Romania, and is used by carriers, ITSPs, and enterprises worldwide to run production-grade SIP signaling platforms.

Key Features

openSIPS supports building Class 4/5 residential telephony platforms, wholesale trunking, enterprise and virtual PBX systems, session border controllers, application servers, load balancers, IMS platforms, and call centers.

Its scripting language and modular architecture allow deep customization of call routing logic, making it a flexible foundation rather than an out-of-the-box product for non-technical users.

Pricing

The core openSIPS software is free and open source under the GPLv2 license, with no licensing fees for deployment at any scale.

OpenSIPS Solutions monetizes through paid commercial support, consulting, custom development, and training services rather than software licensing.

Key Features

Pros & Cons

Pros

  • Free and open source with no licensing costs
  • Mature, carrier-grade codebase with roots dating back over two decades
  • Highly flexible scripting for custom call routing logic
  • Recognized by Google with an Open Source Peer Bonus award
  • Active community and dedicated annual OpenSIPS Summit conference

Cons

  • Steep learning curve requiring SIP and telecom protocol expertise
  • No graphical management interface out of the box
  • Small maintaining company means limited commercial support capacity
  • Overlaps closely with Kamailio, creating some ecosystem fragmentation
  • Not suitable for non-technical users without telecom engineering skills

Pricing

Frequently Asked Questions

Is openSIPS free?

Yes, the core openSIPS software is free and open source under the GPLv2 license.

What is openSIPS used for?

It is used to build SIP-based VoIP infrastructure including residential and wholesale telephony platforms, virtual PBX systems, session border controllers, and call centers.

How is openSIPS different from Kamailio?

Both trace back to the same OpenSER codebase and split in 2008 due to internal disagreements; they remain similar in purpose but have diverged in features and community over time.

Who maintains openSIPS?

openSIPS is maintained by OpenSIPS Solutions, a small telecommunications company based in Bucharest, Romania.

Does openSIPS offer commercial support?

Yes, OpenSIPS Solutions offers paid support, consulting, training, and custom development services.

Is openSIPS suitable for enterprises or only carriers?

Both; it is used for carrier-grade Class 4/5 platforms as well as enterprise and virtual PBX systems.

What are the main alternatives to openSIPS?

Kamailio, FreeSWITCH, and Asterisk are the main open-source alternatives, alongside commercial session border controller products.

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