Comparison of VoIP software
This is a comparison of Voice over IP (VoIP) software used to conduct telephone-like voice conversations across Internet Protocol (IP) based networks. For residential markets, VoIP phone service is often cheaper than traditional public switched telephone network (PSTN) service and can remove geographic restrictions to telephone numbers, e.g. have a PSTN phone number in a New York area code ring in Tokyo.
For businesses, VoIP obviates separate voice and data pipelines, channelling both types of traffic through the IP network while giving the telephony user a range of advanced capabilities.
Softphones are client devices for making and receiving voice and video calls over the IP network with the standard functionality of most "original" telephones and usually allow integration with IP phones and USB phones instead of utilizing a computer's microphone and speakers (or headset). Most softphone clients run on the open Session Initiation Protocol (SIP) supporting various codecs. Skype runs on a closed proprietary network, though the network (but not the official Skype client software) also supports SIP clients. Online "Chat" programs now also incorporate voice and video communications.
Other VoIP software applications include conferencing servers, intercom systems, virtual FXOs and adapted telephony software which concurrently support VoIP and PSTN like IVR systems, dial in dictation, on hold and call recording servers.
Some entries below are Web-based VoIP; most are standalone applications.
General softphone clients 
|Program||Operating systems||License||Open Source||Protocols||Codecs||Encryption||Max conference peers||Other capabilities||Latest release|
|AOL Instant Messenger||Mac OS, Windows||Freeware / Closed Proprietary||No||SIP (Windows ver. only), RTP||Unknown||Unknown||Unknown||Video, file transfer, PC to phone, phone to PC||126.96.36.199 (May 31, 2012[±])|
|Avaya Application Server 5300 Soft Client||Windows||Proprietary||No||SIP, RTP,||Unknown||TLS, SRTP||Unknown||2.0 (2010)|
|Blink||Linux, Mac OS, Windows||GPL / Free software||Yes||ICE, SIP, MSRP, RFB (VNC)||Unknown||TLS, SRTP||Unlimited||IM, File Transfer, Desktop Sharing(only Mac OS), Multi-party conference, Wideband||1.8.1 (April 20, 2012)|
|Bria by CounterPath Corporation||Windows, Mac OS, Linux (Voice calling only)||Proprietary||No||SIP / SIMPLE, XMPP, STUN, ICE||Unknown||TLS, SRTP||6 party audio; 3 party video||Voice and HD (1280 x 720p) Video calling; Multiple Account Integration; Address Book Support (Mac and Windows); Company Chat Rooms; USB Support; Troubleshooting Assistant; Workgroups; Call Recording and Conferencing||3.4.3 (October 2012)|
|Cisco IP Communicator||Windows||Closed Proprietary||No||SCCP (Skinny), SIP, TFTP||G.722 wideband, G.711a, G.711u, iLBC, G.729a, G.729ab||SRTP||Unknown||Call Recording, Silent Monitoring, Multiple lines and directory numbers, Configurable speed dial, Calling name and number display, Call Waiting, Call Forward, Call Transfer, Three-Way Calling (conference), Call Park, Call Pickup, Redial, Hold, Barge, Callback, Extension Mobility, Message waiting indicator, iDivert, Meet Me conferencing, Group Pickup, Do Not Disturb||7.0.6 (Jan 2011)|
|Ekiga||Linux, Windows, OpenSolaris||GPL / Free software||Yes||SIP, H.323, STUN, Zeroconf, XMPP, RTP||H.263, H.264/MPEG-4 AVC, Theora, iLBC, Speex, SILK, GSM, ...||No||Unknown||Video, IM, LDAP, Call Forwarding, Call Transfer, Auto-answering, PC to phone, phone to PC, Multiple accounts, USP support, Message waiting indicator, SIMPLE-based presence etc.||4.0.1 (February 21, 2013[±])|
|Empathy||Linux||GPL / Free software||Yes||SIP, XMPP (Jingle), ICE (STUN/TURN), Zeroconf||Unknown||No||Unknown||IM, multi-user A/V, collaborative applications||3.8.2 (May 16, 2013[±])|
|Eyeball Chat||Windows||Freeware / Closed Proprietary||No||SIP, STUN, ICE, XMPP||Unknown||Yes||5||IM, Conferencing, Voice, Video and SIMPLE based presence||Windows 3.2 (2009)|
|eyeBeam by CounterPath Corporation||Windows||Proprietary||No||SIP / SIMPLE||Unknown||TLS, SRTP||6 party audio; 3 party video||Voice and Video calling; IM; Import Microsoft Outlook Contacts; USB Support; Call Recording and Conferencing||188.8.131.52 (March 2010)|
|Gizmo5||Linux, Mac OS X, Windows, Windows Mobile Phone, Blackberry, Nokia, PDA Java||Freeware / Closed Proprietary||No||SIP, XMPP||Unknown||SRTP||Unknown||Record Calls, Forward Calls, MSN IM, Windows Live Talk, Google Talk, Talk with Yahoo, Messenger, XMPP||Windows: 184.108.40.2065 (23 Sep 2009), Mac OS: 220.127.116.119 (23 Sep 2009)|
|Google Talk||Linux, Windows, Mac OS X||Closed Proprietary (using libjingle)||No||XMPP||Unknown||ZRTP||Unknown||Video, chat, file transfer, voicemail, mail via "GMail Integration"||Plugin Windows:
18.104.22.16888 (May 14, 2013[±])
|IBM Sametime||Linux, Mac OS X, Windows, mobile||Closed Proprietary||No||SIP, SIMPLE, T.120||H.323||TLS||Unknown||IM, File transfer, Voice, Presence, Server stored contact list, HTTP tunneling, plugins, embedable in Lotus Notes||8.5.2 (08. May 2011)|
|iCall||Linux, Mac OS X, Windows, iOS, Android||Freeware / Closed Proprietary||No||SIP AIM ICQ XMPP||Speex, CELT, WebM||TLS ZRTP||Unlimited||Video, file transfer, PC to phone, phone to PC, IM (MSN, AIM, ICQ, Yahoo!, XMPP, Google Talk), Voicemail||7.1.522|
|Messages||Mac OS X||Closed Proprietary||No||SIP AIM ICQ XMPP||H263, H264||Unknown||Unknown||Integrated, PBX independent||7.0 July 25, 2012|
|Jitsi||Linux, Mac OS, Windows XP/2000 (all java supported)||LGPL / Free software||Yes||SIP/SIMPLE, XMPP/Jingle STUN ICE, TURN||SILK, G.722, Speex, Opus, G.711 (PCMU/PCMA), iLBC, GSM, G.729, H.264, H.263||ZRTP, SRTP, TLS||Unknown||Text messaging, audio/video telephony, IPv6, call recording, 64-bit||2.2 (build.4603) (April 30, 2013[±])|
|KPhone||Linux (KDE)||GPL / Free software||Yes||SIP, STUN, NAPTR/SRV||Unknown||SRTP||Unknown||Video, voice, IM, external Sessions, IPv6 support for UDP||1.2 (November 2008)|
|Linphone||Linux, Windows, Mac OS, Android, iPhone, BlackBerry||GPL / Free software||Yes||SIP||Unknown||TLS, SRTP, ZRTP||Unknown||Video, IM, STUN, IPv6||3.5.2 (Feb 17th 2012)|
|MicroSIP||Windows||GPL / Free software||Yes||SIP, STUN, ICE, SIMPLE||Unknown||TLS, SRTP||Unknown||Video, voice, IM and Presence||3.2.4 (November 2012)|
|Mirial Softphone (Mirial s.u.r.l.)||Windows 2000/XP/2003/Vista/7 (including 64bit versions), Mac OS X (x86)||Closed Proprietary||No||SIP, RTSP||H.323||DTLS-SRTP||Unknown||H.264 Full-HD 1080p video rx/tx, Two independent lines supporting Call Control and 3-Party videoconference in Continuous Presence, G.722.1/C wideband audio, Call recording/export, DV/HDMI/Component capture, Presentation (H.239, RFC-4796), Encryption, Far End Camera Control, GPU accel (D3D and OpenGL)||7.0.24 (May 26, 2010)|
|Mumble||Linux, Mac OS X, iOS, Windows, Android||BSD||Yes||Unknown||CELT, Speex||TLS and OCB-AES128||No max (limited only by server bandwidth and memory)||Chat with (limited) embedded HTML, Automatic Gain Control, Access Control Lists for user management, Customizable In-Game Overlay, Directional Audio, Plugin Support, Nested Channels, Echo cancellation, Logitech G15 support||1.2.3 (February 19, 2011)|
|Nymgo||Windows, Android, iOS||Freeware, Proprietary, Closed||No||SIP, RTP and RTCP||Unknown||Yes||No||Address Book integration, Call recording/export, Mute, On Hold, Caller ID definition||4.2.9 (March, 2013)|
|oovoo||Mac OS X, iOS, Windows, Android||Freeware, Proprietary, Closed||No||Unknown||Unknown||No||12||Mobile or landline Phone Calls, Video chat, Video embed a video chat in website, Full Screen Mode, Video Call Recording, Send a video greeting to multiple people at once, Screen Sharing, Video Call Add up to six phones, Instant Messaging Message up to 12 friends,Send Files up to 25 MB, Call Me Button, Privacy Controls, Social Networking||22.214.171.124 (2012)|
|Phoner||Windows||Freeware / Closed Proprietary||No||SIP, TAPI, CAPI||Unknown||TLS, SRTP, ZRTP||8||Conferencing, call redirection, call recording||2.81 (16 April 2013[±])|
|PhonerLite||Windows||Freeware / Closed Proprietary||No||SIP||Unknown||TLS, SRTP, ZRTP||8||Conferencing, call redirection, call recording||2.08 (16 April 2013[±])|
|QuteCom||Linux, Mac OS X, Windows XP/2000||GPL / Free software||Yes||SIP||Unknown||SRTP, but key exchange via Everbee key Exchange which is not a Standard)||Unknown||Video, IM (MSN, AIM, ICQ, Yahoo!, XMPP, Google Talk), voicemail, wengo to phone, conferencing.||2.2.1 (June 22, 2011) [±]|
|Revation Communicator||Windows 2000/XP/Vista/7||Closed Proprietary||No||Proprietary||Unknown||TLS and SRTP||No max (limited by server mixing services)||Secure Multi-Party Chat/Instant Messaging, Presence, VoIP, Video, File Transfer, Desktop Sharing||5.3 (August 2011)|
|SFLphone||Linux||GPL3 / Free software||Yes||SIP, RTP, IAX2, STUN per account, SRV||Unknown||Voice encryption (SRTP), Signaling encryption (TLS), Multiple realms authentication mechanism||Unknown||Gnome/KDE client, address book, multiple accounts, unlimited number of calls, call transfer, call hold/unhold, call recording, Multi-way conferencing||1.2.0 (July, 2012)|
|SightSpeed||Mac OS X, Windows||Freeware / Closed Proprietary||No||SIP, RTP, Proprietary P2P protocol||Unknown||Unknown||Unknown||Video, voicemail, phone in, phone out, multiparty calling, conference recording, text messaging, NAT traversal, video mail||6.0 (2007)|
|Skype||Linux, Mac OS X, Windows 2000/XP/Vista/7/Mobile (no longer supported), BREW, Android, iPhone, PSP||Freeware / Closed Proprietary||No||Proprietary P2P protocol (a)||SILK||Yes||25 starting with version 126.96.36.199. 10 with 2.x||Conferencing, video, file transfer, voicemail, Skype to phone, phone to Skype, additional P2P extensions (games, whiteboard, etc...); depending on platform.||
|Spikko||Windows 2000/XP/Vista/7/Mobile, iPhone,||Freeware / Closed Proprietary||No||SIP||Unknown||Yes||8||Conferencing, voicemail, PC to phone, phone to PC, Free international phone numbers, address book integration;||Dec 2010|
|TeamViewer||Linux, Windows, Mac OS X, iOS, Android||Freeware (personal use only) Closed / Proprietary||No||Unknown||Unknown||AES256||Unknown||Unknown||Android
8.0.1055 (April 25, 2013[±])
|TeamSpeak||Linux, Windows, Mac OS X, FreeBSD, Android, iOS||Freeware Closed / Proprietary||No||Unknown||CELT, Speex||Yes||32 unlicensed / 1000 with Non-Profit License||Simultaneous Server Conferencing with Tabs, 3D Sound Effects, Scalable Permissions System, Firewall Friendly File Transfers, In-Game Overlay for DirectX & OpenGL Games, Global Public Server List, Plugin System||3.0.6|
|Telephone||Mac OS X 10.5||BSD / Free Software||Yes||SIP, STUN, ICE||Unknown||No||Unknown||Address Book integration||1.0.2 (April 30, 2011)|
|Tokbox||Mac OS X, Windows XP/2000/Vista||Freeware / Closed Proprietary||No||Unknown||Unknown||Unknown||Unknown||Video calling, video conferencing, chat, IM (MSN, AIM, Yahoo!, Google Talk)||Unknown|
|Toktumi Unlimited / Line2 Pro||Windows XP/Vista/7, Mac OS X, iOS, Android||Freeware / Closed Proprietary||No||Proprietary with SIP core||Unknown||Unknown||20||Conferencing, voicemail, caller ID, call-waiting, address book integration; auto-attendant, call-forwarding||Windows: August 2010 / OS X: October 2010|
|Tru App||Windows 2000/XP/Vista/7, Mac OS X, Linux
iOS, Android, Symbian, BlackBerry OS,
|Freeware / Closed Proprietary||No||SIP, XMPP||Unknown||Unknown||Unknown||Chat, file transfer, voicemail, inbound numbers, integration with GTalk, Microsoft Live, Skype|
|Twinkle||Linux||GPL / Free software||Yes||SIP||Unknown||SRTP, ZRTP||Unknown||Conferencing, chat, file transfer, Firefox integration, call redirection, voicemail, support of VoIP-to-Phone services||1.4.2 (February 25, 2009[±])|
|Vbuzzer||Windows 2000/XP/Vista||Freeware / Closed Proprietary||No||SIP||Unknown||TLS||Unknown||IM (MSN), voicemail, personalized voice greeting.||2.8.002|
|Ventrilo||Mac OS X, Windows||Freeware / Closed Proprietary||No||Unknown||Unknown||No||8||Conferencing, chat, text-to-speech||3.0.8|
|Voice Operator Panel||Windows 2000/XP/Vista||Closed Proprietary||No||SIP, RTP||Unknown||Unknown||Unknown||Call forwarding, Call transfer, Call recording, Presence, Outlook integration, Windows Messenger/MSN/Live integration, CRM, Built-in web browser & e-mailer, LDAP, APS.||1.3.2|
|X-Lite||Mac OS, Windows, (Linux)||Freeware / Closed Proprietary||No||SIP, STUN, ICE||Unknown||No||Unknown||IM, single login account, for Windows and Mac also Conferencing, Video and SIMPLE based presence||Windows and Mac OS: 5 (2012). Linux: Discontinued.|
|Yahoo! Messenger||Mac OS (8, 9, X), Windows, (Linux/FreeBSD version not VoIP capable)||Freeware / Closed Proprietary||No||SIP (using TLS) and RTP (media)||Unknown||Unknown||Unknown||Video, file transfer, PC to phone, phone to PC||Windows: 188.8.131.52 / May 31, 2012
Mac: 3.0.1 / July 20, 2011
Linux: 1.0.6 / September 2003
SunOS 5.7: 0.99.17-1 / September 2003
Solaris 8: 1.0.4 / September 2003
FreeBSD 4/5: 1.0.4 / September 2003 iOS: 2.2.6/ July 12, 2012
|Yate||Linux, Mac OS, Windows||GPL / Free software||Yes||SIP, IAX, XMPP||H.323||Unknown||Unknown|
|Zfone||Linux, Mac OS X, Windows||Freeware / Viewable source Proprietary (includes time bomb provision)||No||SIP, RTP||Unknown||SRTP, ZRTP||Unknown||Beta 2008-09-04 (Linux 0.9.224), (Mac OS 0.9.246), (Windows 0.9.206)|
Mobile phones 
For mobile VoIP clients:
|Program||Operating systems||License||Open Source||Protocols||Codecs||Encryption||Other capabilities||Latest release|
|Acrobits Groundwire||Android v2.2+, iOS v4.3+||Proprietary||No||SIP SIMPLE||G.711, G.722, iLBC, GSM, G.729||TLS, SRTP, ZRTP||Groundwire voip over wifi or 3G, supports audio codecs. Multi line, call conferencing, transfer and attended transfer, voicemail.
iOS only - Push Notifications, video, number rewriting, address book matching, sms for betamax providers and pennytel
|Groundwire (iOS) 2.4.5, Groundwire (Android) 3.21|
|Acrobits Softphone||Android v2.2+, iOS v4.3+||Proprietary||No||SIP||G.711, G.722, iLBC, GSM, G.729||TLS, SRTP, ZRTP||VOIP over wifi or 3G iOS only - Push Notifications, video, number rewriting, address book matching, sms for betamax providers and pennytel||Acrobits Softphone (iOS) 5.2, Acrobits Softphone (Android) 3.20|
|Bria by CounterPath Corporation||iOS 4.3+, Android v2.2+||Proprietary||No||SIP SIMPLE||G.711, G.722, iLBC, GSM, SILK, G.729, H.264||TLS, SRTP||VoIP over Wi-Fi or 3G/4G; Audio codecs ; Multiple languages; Option to purchase Video Calls add-on with H.264 codec and Messaging and Presence add-on which uses XMPP and SIP protocols.||2.1.3 (iOS), 2.0.3 (Android)|
|CSipSimple||Android v1.6+||GPL||Yes||SIP||G.711, Speex, GSM, iLBC, G.722, AMR, iSAC, SILK, G.726, G.722.1, Opus, Codec2, G.726||SRTP, ZRTP, TLS||VoIP over Wi-Fi or mobile data; Conference; Android integration with filtering/rewriting rules||0.04-04 (19 September 2012)|
|Gizmo5 Mobile||Windows Mobile (non-native, only through SJPhone), Motorola, Nokia, Blackberry, Java PDA's, Sony Ericsson, Samsung||Freeware||No||SIP, AIM, iChat, XMPP, MSN, Yahoo||Unknown||Yes||Online Phone over Edge, UMTS, 3G, Call Land and Cell phone, Voicemail, AOL, iChat, XMPP, Yahoo! Messenger, Windows Live. On April 3, 2011 Google shut down Gizmo5 and recommended users to use Google Talk as an alternative.||1.15 (as of May '08)|
|iCall Mobile||iOS v4.3+||Freeware / Proprietary||No||SIP AIM ICQ XMPP||Speex, CELT, WebM||TLS, ZRTP||VoIP over Wi-Fi or 3G, SMS, Voicemail, AOL, Facebook, XMPP, Yahoo! Messenger, Windows Live||2.0.1 (as of Apr '12)|
|Jajah Mobile Web||Symbian OS, Windows Mobile (version unknown)||web based service, Call back,no download||No||Unknown||Unknown|
|Line2||iOS, Android||Freeware / Proprietary||No||Proprietary with SIP core||Unknown||Unknown||Tri-mode calling (cellular, 3G/4G data, WiFi), SMS over IP, visual voicemail, 20-person conference calls, auto-attendant, call-forwarding||1.0.4 Android, 3.2.1 iOS|
|Sipdroid||Android||GPL||Yes||SIP||Unknown||Unknown||Uses wifi, 3G or EDGE||2.7|
|Truphone||Nokia-Symbian, iOS, Android, Blackberry||Freeware / Proprietary||No||SIP||Unknown||Unknown||WiFi VoIP out & in, SMS over IP, call-through & call-back, connection management, provisioning||Symbian 4.0, iOS 1.11.1|
|Vopium||Symbian, Java ME, Android, BlackBerry RIM, iOS, Windows Mobile 2003 SE and higher||Freeware / Proprietary||No||SIP, MSN, Skype, Yahoo, AOL, ICQ, Google Talk, Facebook & Twitter||GSM||Unknown||WiFi VoIP, GSM call-trough, SMS over IP, least cost routing, Synchronisation/back-up of mobile contacts and calendar||2.0|
|Windows Mobile 6||Windows Mobile 6 Professional/Standard||Proprietary||No||SIP to publicly and non-publicly routable servers||Unknown||Unknown||WiFi Mobile VoIP||6.1|
|X-PRO for Pocket PC||Windows Mobile 2003 (earlier versions support Windows PocketPC 2002)||Proprietary, discontinued in April 2007||No||SIP||Unknown||Unknown||Supported devices: AudioVox Maestro, Compaq/HP iPAQ: 365x, 37xx, 385x, 395x, hx4700, Dell Axim X51, X51v, Toshiba e550, e570. iPAQ 545x and Toshiba e7xx are not supported.||2.2|
Frameworks and libraries 
|Program||Operating systems||License||Protocols/based upon/compatible with||Encryption||Other capabilities||Key and target markets||Latest release|
|Tapioca||Linux||GPL||Telepathy (software)||Unknown||0.3.9 (June 12, 2006)|
|Telepathy/Farstream||Linux, Mac OS X, Windows||LGPL||SIP, XMPP (Jingle), ICE (STUN/TURN), UPnP||No||Multi-user A/V conferencing, IM, collaborative applications||Mobile devices (Maemo), Linux Desktop||spec 0.17.8 (24-Jul-2008)|
|OPAL||Windows, Linux (including embedded variants), Mac OS X||MPL||SIP, H.323, IAX2, CAPI, VXML||Unknown||Multi-user A/V conferencing, IM, IVR||Softphones, Softswitches, Telephony application servers||3.10.3 (14-Oct-2011)|
Server software 
|Program||Operating systems||License||Protocols/based upon/compatible with||Encryption||Other capabilities||Key and target markets||Latest release|
|3CX Phone System||Microsoft Windows||Proprietary||SIP||TLS, SRTP||Voice and Video IP telephony, Voice and Video conferencing, voice mail and instant messaging||25,000 - 50,000 users||11 (Jul 2012)|
|AS5300||Linux, Windows Server 2003||Proprietary||SIP, UNIStim, MLPP||SSL, TLS,
|Voice and Video IP telephony, Voice and Video conferencing, voice mail and instant messaging||1,000 - 25,000 users||1.0 (Jan 2008)|
|AskoziaPBX||no additional OS required (Linux based)||GPL / Open core||SIP, H.323, IAX, SCCP||No||ISDN, analog, Voicemail, Conferencing, MOH, ACD, IVR, Call forwarding, Call recording||SMEs up to 50 users||2.2.2 (Dec 2012)|
|Asterisk PBX||Linux/BSD, Mac OS X, Solaris||GPL||SIP, H.323, IAX||TLS, SRTP||VoIP Gateway, voicemail, basic accounting (can be expanded by interface with ODBC-compliant database), billing, conferencing, hot-desking, IVR trees with conditional logic, call queuing, automated call distribution||Enthusiasts, developers, enterprise users (capacity dependent on server design, scalable across multiple servers)||11.2.1 (22 January 2013[±]
184.108.40.206 (22 January 2013[±])
|CallMax Softswitch||Linux||Proprietary||SIP, H.323||SSL, TLS, HTTPS||Integrated billing, Residential/Hosted IP PBX, Multilevel IVR menu, Calling card platform, Callshop module, DID-numbers, SIP Trunking, Authorization by SIP, PIN, ANI, IP address and login/password||SIP Service Providers, VoIP service providers, IP PBX Users, Other Class 5 softswitch users||2.12 (January 2012)|
|Cisco Unified Communications Manager||Linux||Proprietary||SIP, SCCP, MGCP, H.323||SSL, TLS, SRTP||SIP Registrar/Proxy, Authentication||Enterprise users||9.0|
|ClearSea (Mirial s.u.r.l.)||Windows 2000/XP/2003/Vista/7 (including 64bit versions), Mac OS X (x86), iOS (iPhone 3S+, iPad 2), Android||Proprietary||SIP, H.323||No||H.239 presentation,H.224, H.281 (FECC), Acts as a Session Border Controller, H.323/SIP endpoint autodiscovery on local LAN, Support user authentication with external databases / LDAP,Centralized Contacts Directory, User Groups management, Video IVR for dialing endpoint extensions, Ajax-powered web-based administration console, ClearSea desktop client one-step installation via HTTP browser, Automatic provisioning, configuration and secure authentication of ClearSea client based on user credentials||Desktop video conferencing users, Enterprises, Educational and Healthcare organizations||1.0.3 (April 30, 2010)|
|CommuniGate Pro||Linux/BSD, Mac OS X, Windows, Solaris, HPUX, AIX||Proprietary||SIP, XIMSS Protocol, XMPP||SSL, TLS||SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, and many others...||Mobile Operators, ISP's, and SaaS providers||6.0.1 (December 2012)|
|Elastix||Linux||GPL||SIP, IAX, H323, XMPP||No||Unified communication server that also supports chat, mail and fax.||Capacity dependent on server design, scalable across multiple servers||2.4.0 (February 06, 2013)|
|FreeSWITCH||Linux/BSD, Mac OS X, Solaris, Windows||Mozilla Public License||SIP, NAT-PMP, STUN, SIMPLE, XMPP, Google Talk (Jingle), IAX, H.323, MRCP, RSS, Skype||TLS, SRTP, ZRTP||Recording, Voicemail, Conferencing, RADIUS, ENUM, IM Proxy, Streaming, Media gateway, Soft-PBX, IVR (modular)||Large soft-switch users, home PBX users, softphone users||1.2.7 (March 6, 2013[±])|
|GNU Gatekeeper||Linux/FreeBSD, Mac OS X, Windows XP/2000/Vista/Windows 7||GPL||H.323||H.235||H.460.18 firewall traversal, Routing, Accounting||video conferencing, VoIP carriers large and small||2.3.2, May 25, 2010|
|Integrics Enswitch||Linux||Proprietary||SIP, ISDN||SSL, TLS, HTTPS, SIPS, SRTP||Multi-tenant carrier services such as hosted PBX, ITSP, and calling cards. Integrated billing and invoicing.||Carriers with 500 to 1,000,000 users across many customers||3.9, January 15, 2013|
|MediaCore Softswitch||Linux||Proprietary||H.323, SIP||SSL, TLS, HTTPS||Dynamic routing mechanism, integrated billing, SIP-H.323 protocol converter, Transcoding - codec converter module, Guardian - revenue assurance module, SBC functionality, full and media proxy||Transit VoIP services providers, VoIP wholesale carriers||2.24 (December 2011)|
|Murmur||Linux/BSD, Mac OS X, Windows||BSD / GPL||CELT / Speex||TLS||Chat with (limited) embedded HTML, ACLs for user management, Customizable In-Game Overlay, Directional Audio, Plugin Support, Nested Channels||Individuals to Small and medium enterprise (25-5000 users)||1.2.3 (February 19, 2011)|
|Mysipswitch||Linux||BSD||SIP, Ajax||SSL||SIP proxy server which allows the use of multiple SIP accounts with a single SIP login||Individuals||August 2007|
|Objectworld UC Server||Windows XP/2003/2008||Proprietary||SIP||No||IP PBX, personal assistants, IVR, automated phone provisioning, fax server, unified messaging, Outlook, Exchange and Lotus Domino/Notes integration, conferencing, outbound dialing||Small and medium enterprise (25-2000 users)||4.4.2 (May 2009)|
|Kamailio/OpenSIPS (formerly known as OpenSER)||Linux/BSD, Solaris||GPL||SIP, XMPP||No||SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, least-cost-routing and many others.||SIP Service Providers||4.0.1 (25 April 2013[±])|
|snom ONE (formerly pbxnsip)||Linux/BSD, Mac OS X, Windows||Proprietary||SIP||SRTP||IP PBX, presence indication, IVR, automated phone provisioning, fax server, unified messaging, Outlook, Exchange integration, conferencing, outbound dialing||Small and medium enterprise (25-256 users)||220.127.116.1177 (April 2009)|
|Revation LinkLive||Windows server / Linux||Proprietary||Proprietary||TLS, SRTP||Secure Unified Communications, Presence, Instant Messaging/Chat, VoIP, Video, Desktop Sharing, File Sharing, IVR, PBX, Voicemail, ACD, Email Server||Unified Communications Service Providers||5.3 (August 2011)|
|SIP Express Router (SER)||Linux/BSD, Solaris||GPL||SIP||No||SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, and many others...||SIP Service Providers||2.0.0 Ottendorf|
|sipX ECS IP PBX||Linux||LGPL||Native SIP Call Control||TLS||Full redundancy (HA), plug & play management including phones and gateways, fully featured||Enterprises between 200 and 10,000 users, multi-site||4.4, April 2012|
|Unison||Linux||Proprietary||SIP, XMPP, IMAP, SMTP, CalDAV||SSL, TLS||Unified messaging, IP PBX, IVR, instant messaging, calendar server, LDAP server, E-mail server||Small and medium enterprise (25-256 users)||3.0, February 2010|
|vzRoom||Windows||Proprietary||SIP||SSL, TLS, AES||Instant Messaging/Chat, VoIP, Video, Desktop Sharing, Video Sharing, whiteboard, File Sharing, scheduler, recording||Individual to small and medium enterprise (2-1,000 users)||0.8.8.735, November 2010|
|Yate||Linux, Mac OS, Windows||GPL||SIP, IAX, H.323, XMPP||No||4.3, January 2013|
See also 
- "Skype Connect". Skype.com. Retrieved 2011-07-27.
- Peters, Frederic (2013-05-16), "GNOME 3.8.2 Release", gnome-announce mailing list, retrieved 2013-05-17
- Eyeball Chat 3.2 Features. EyeballlChat.com.
- "Telephony with Lotus Sametime software". IBM.com. Retrieved 2010-02-16
- Release history on PhonerLite download page
- Changelog on Phoner download page
- Announcement: QuteCom 2.2.1
- Liive, Raul (27 Febuary 2013). "Skype for Android now with calling to Messenger users". Skype Garage. Microsoft. Retrieved 12 March 2013.
- "Skype - free IM & video calls - Android Apps on Google Play". Retrieved 12 March 2013.
- Microsoft (13 November 2012). "Skype". App Store. Apple. Retrieved 4 May 2013.
- Microsoft (21 August 2012). "Skype for iPad". App Store. Apple. Retrieved 4 May 2013.
- Park, Beom Soo (7 March 2013). "Skype 4.6 for iPhone & iPad with a new calling experience". Skype Garage Blog. Microsoft. Retrieved 4 May 2013.
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