Asterisk

Asterisk is free software that transforms a computer into a communication server. Asterisk lets you build applications like PBX, VoIP gateway, IVR and ACD.

Free Open Source Mac OS X Windows Linux

FreeSWITCH

FreeSWITCH is a scalable open source cross-platform telephony platform designed to route and interconnect popular communication protocols using audio, video, text or any other form of media.

Free Open Source Mac OS X Windows Linux BSD

3CX Phone System

3CXPhone is a free VoIP phone available for Windows, iPhone or any Android based smart phone such as Google Nexus, Sony Xperia, Motorola Droid or Samsung Galaxy.

Freemium Windows Android iPhone

freepbx

FreePBX is a web-based open source GUI (graphical user interface) that controls and manages Asterisk (PBX), an open source communication server.

Free Open Source Linux

FusionPBX

FusionPBX is an open source FreeSWITCH GUI. FusionPBX can be used as a high available single or domain based multi-tenant PBX, carrier grade switch, call center server...

Free Open Source Linux BSD

Kamailio

Kamailio® (successor of former OpenSER and SER) is an open source SIP server released under GPL, able to handle thousands of call setups per second. Among features:...

Free Open Source Linux

VoipSwitch

VoipSwitch is a SoftSwitch System with routing and billing, with SIP protocol support (in older versions also H323). Basic package includes softswitch app, IVR app...

Commercial Windows

Starfish PBX

Starfish PBX aims to be an open source alternative to Digium’s Switchvox. The goal is to have a software equivalent to which we can add additional functionality like: ...

Free Open Source Linux

Thirdlane Multi Tenant PBX

Thirdlane® Multi Tenant PBX Platform is a reliable, cost-effective Multi Tenant IP PBX and Unified Communications software platform with support for voice...

Commercial Linux

Ozeki Phone Systems

Ozeki Phone System XE is a Software PBX telephony platform for Windows. Ozeki enables your applications to connect PBX and access IVR, Webphone, SMS sending, 3D video...

Commercial Windows

Mizutech VoIP Server

A robust SIP/H.323/WebRTC softswitch for Windows with a long list of features including PBX and billing.

Free Windows

opensips

OpenSIPS (Open SIP Server) is a mature Open Source implementation of a SIP server. OpenSIPS is more than a SIP proxy/router as it includes application-level...

Free Open Source Linux