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A softphone is a software program for making telephone calls over the Internet using a general purpose computer rather than dedicated hardware. The softphone can be installed on a piece of equipment such as a desktop, mobile device, or other computer and allows the user to place and receive calls without requiring an actual telephone set.[1] Often, a softphone is designed to behave like a traditional telephone, sometimes appearing as an image of a handset, with a display panel and buttons with which the user can interact. A softphone is usually used with a headset connected to the sound card of the PC or with a USB phone.[2]


See Comparison of VoIP software

Communication protocols[edit]

To communicate, both end-points must support the same voice-over-IP protocol, and at least one common audio codec.

Many service providers use the Session Initiation Protocol (SIP) standardized by the Internet Engineering Task Force (IETF). Skype, a popular service, uses proprietary protocols, and Google Talk leveraged the Extensible Messaging and Presence Protocol (XMPP). [3]

Some softphones also support the Inter-Asterisk eXchange protocol (IAX), a protocol supported by the open-source software application Asterisk.


A typical softphone has all standard telephony features (DND, Mute, DTMF, Flash, Hold, Transfer etc.) and often additional features typical for online messaging, such as user presence indication, video, wide-band audio. Softphones provide a variety of audio codecs, a typical minimum set is G.711 and G.729.


To make voice calls via the Internet, a user typically requires the following:

See also[edit]


  1. ^ "Citation from article entitled - Softphone initiation". Retrieved 14 October 2017.
  2. ^ "SoftPhone - Community Help Wiki". Retrieved 14 October 2017.
  3. ^ "Freetring - Free calls online". Retrieved 22 July 2021.