Page tree
Skip to end of metadata
Go to start of metadata


In this Introduction we provide a brief overview of FreeSWITCH in laymen's terms. We will then introduce all the key concepts in FreeSWITCH and guide you on how to navigate the documentation. By following this introduction, you should be able to setup a basic deployment of FreeSWITCH in no time. Should you decide to dig deeper and get familiar with more advanced features, we provide the links where you can find that too. At the end we will also provide a walkthrough of the default configuration, so that you can get a hands-on tutorial and most commonly used features.

 Click here to expand Table of Contents

What is FreeSWITCH?

FreeSWITCH is an open source communications platform that can handle voice, video and text communications from an IP Network (VoIP) and the PSTN(Public Switched Telephone Network - regular landlines). FreeSWITCH supports all popular VoIP protocols as well as interfacing with PRIs. For a full listing of supported protocols see the Endpoints page. Some common capacities that FreeSWITCH is used for include

  • PBX (Office phone system) 
  • Class 5 Softswitch (Telephone carrier)
  • Application server such as Voicemail, conferencing, IVR
  • Softphone

This list is by no means comprehensive, FreeSWITCH is extremely flexible and can be used in any way you can imagine.

The default configuration showcases a full-featured PBX with many applications.

Where can I run FreeSWITCH?

At it's core FreeSWITCH is a library which can embedded in your application on any device. However more commonly it is built to run as a daemon (service on Windows). When you run FreeSWITCH as a daemon you can use the CLI to interact with FreeSWITCH.

FreeSWITCH can run on many Platforms including Linux, Mac OS X, BSD, Solaris and even Windows.

 Although FreeSWITCH can run on many Linux distributions such Debian, Ubuntu, CentOS, Fedora and RHEL, our preferred distribution is Debian, this is because we have worked out all dependencies on Debian so you can have a smooth installation and startup. Debian is also what the FreeSWITCH developers use, therefore have the most experience with. If you run on other distributions you might have a hard time getting all dependencies right. For 1.6.x we support Debian Jessie. FreeSWITCH 1.8 is expected to support Debian Stretch.

Hardware requirements depend on how you will use FreeSWITCH. FreeSWITCH can run on hardware as small as a Raspberry Pi and can scale up to powerful data center servers with dozens of CPU cores. For more information about hardware requirements see the performance page. FreeSWITCH is capable of handling thousands of concurrent phone calls depending on what hardware you have and which applications you are using. 


When designing FreeSWITCH the goal was to have the following properties
  • Extensible - allowing new features to be added easily
  • Flexibility - users should be able to pick and choose which functionalities are enabled, also allow users to replace parts of the system with different implementations
  • Scalability - FreeSWITCH can be run on systems as small as an embedded softphone or as big as a cluster of full-blown carrier switches
  • Stability - Problems with one feature should not bring down the whole system

To accomplish these goals FreeSWITCH is built using a modular system. There is a small core that provides the base system used by all modules, however most of the functionalities are not implemented in the core itself, rather in standalone modules that are not dependent on each other. When you install FreeSWITCH with the default configuration, the modules that are required for most common scenarios are enabled. We will see later in the configuration section how to enable/disable modules.

The modules are grouped by the type of functionality they provide. We will now explore the types of modules and what functionality is provided by each.

Module Types


Endpoint modules support types of communications devices such as VoIP, PSTN (Public Switched Telephone Network - regular landline), Skype, Google Talk etc. Endpoint modules are one of the most important modules in FreeSWITCH

ApplicationThis is where all the action is happening! There are hundreds of application modules included in the default setup a few examples are playing a file, joining a conference, send a call to voicemail, play an IVR menu. Many of the common applications are provided by the dptools module.
DialplanA Dialplan module is responsible for routing calls, based on information such as Caller ID, Destination Number and more. The default dialplan module is the XML Dialplan. We will cover this in detail in the Dialplan section.
DirectoryProvides logins and configurations for users that can register with FreeSWITCH. The most common directory module is the XML Directory.


Codecs are used to encode and compress audio for streaming.
File FormatsPlay audio files, most of the common formats are supported by the sndfile module which is included by default. For a list of formats supported by sndfile as well as other modules see the playback page.
LoggersRecord log messages. Some of the included loggers are console and log file. xml_cdr is another commonly used logger to output call detail records.
LanguagesSupport scripting languages which can be run as part of the dialplan. The most popular language is Lua. Javascript and a few others are also supported.

There a few more types of modules, but these are the common ones. For a listing of common module see the Modules page. If you require some functionality that's not provided by one of the existing modules, you can write your own module. Modules can be written in many popular programming languages. See the developer documentation for more information.


Many modules also have API commands that can be issued from the command line, script or sent from a remote computer via the event socket. What the API commands can do are up to each individual module, but some common functionalities include returning status information (such as how many listeners are in a conference) or control the currently running application (such as pausing a file being played) There are hundreds of APIs available from the different modules. In the command line you can type show api to see all APIs based on the modules that are loaded.

There are also API commands provided by the core, these are in the Commands module.

Navigating the documentation

This table provides a roadmap you can use to go through the documentation in a structured fashion.

InstallationHow to download and install FreeSWITCH
ConfigurationOverview of the structure of freeswitch Configuration files.
Running FreeSWITCHHow to run Freeswitch in the conosle or as a daemon
Call LegsExplains an important concept required to better understand Endpoints and Dialplans
Endpoints Explains the endpoint concept in general, as well as a more detailed overview of the common endpoints
Introduction to DialplanDialplan is one of the most complex parts of FreeSWITCH, this page distills it
DirectoryHow to setup users and devices
Logging & CDRSetup Logging and Call Records
DatabasesHow to configure FreeSWITCH to store channel state in a database
Default ConfigurationWalkthrough of the default configuration
ScriptingHow to create custom functionality by writing scripts that run in the dialplan
Event SocketAllows an outside program to interact with FreeSWITCH over a network connection. The CLI uses the Event Socket to allow you to run commands and view the output of FreeSWITCH.



FreeSWITCH itself is licensed under the MPL 1.1 (Mozilla Public License), however some individual modules might be using other licenses.

Additional Resources

  • Join the weekly conference to keep up-to-date with the latest developments in the FreeSWITCH world.
  • The annual ClueCon takes place in Chicago, Register today!
  • FAQ
  • Buy our books