# Comparison of VoIP software

This is a comparison of voice over IP (VoIP) software that examines applications and systems used for conducting voice and multimedia communications across Internet Protocol (IP) networks. VoIP technology has transformed telecommunications by offering alternatives to traditional telephony systems while providing enhanced features and cost savings.
For residential users, VoIP services typically provide significant cost advantages compared to traditional public switched telephone network (PSTN) services. These systems eliminate geographic restrictions on phone numbers, enabling users to maintain local numbers in any area code regardless of their physical location. For example, a user can operate a New York phone number while residing in Tokyo, facilitating global mobility and reducing international communication costs.
In enterprise environments, VoIP technology enables the consolidation of voice and data networks into a unified IP infrastructure. This consolidation eliminates the need for separate voice and data pipelines while providing advanced capabilities including:
* Unified communications integration
* Presence management systems
* Advanced call routing
* Mobile device integration
* Multimedia conferencing capabilities
Softphone applications serve as the primary client-side implementation of VoIP technology. These applications transform standard computing devices into full-featured communication endpoints, supporting voice and video calls over IP networks while providing standard telephony functions. Most softphone clients utilize the Session Initiation Protocol (SIP), an open standard that supports various audio and video codecs. Some systems, like Skype, operate on proprietary protocols but can integrate with SIP-based systems through specialized business telephone system (PBX) software.
The VoIP ecosystem encompasses various specialized applications beyond basic communication endpoints:

## Core components

* Conferencing servers for large-scale virtual meetings
* Intercom systems for internal communications
* Virtual foreign exchange services (FXOs)
* Hybrid systems supporting both VoIP and PSTN integration

## Specialized applications

* Interactive Voice Response (IVR) systems
* Automated dictation platforms
* Professional call recording solutions
* Custom hold music and messaging systems
VoIP implementations generally fall into two categories:
* Web-based solutions that operate through browsers, offering simplified deployment and platform independence
* Standalone desktop applications that provide enhanced features, superior reliability, and advanced feature sets

## Desktop applications

| Program | Operating systems | License | Costs | Protocols | Codecs | Encryption | Max conference peers | Other abilities | Latest release |
| Blink | Linux, macOS, Windows | Mixed: free software versions under GNU GPLv3 + shareware versions under gplv3 with exception of including proprietary code | macOS version proprietary on App Store, free version limited to sponsored SIP provider; Windows version proprietary; Linux version open source | ICE, SIP, MSRP, RFB (VNC), XCAP | Opus, speex, G.722, GSM, iLBC, PCMU, PCMA | TLS, SRTP and ZRTP on all versions, OTR/SMP on Linux and macOS only | No limit | IM, file transfer, desktop sharing, multi-party conference, wideband | Blink Qt |
| Battle.net | macOS, Android, iOS, Windows | Proprietary | Free | Un­known | Un­known | Un­known | Un­known | IM, multi-party conference | Un­known |
| Discord | macOS, Android, iOS, Windows, Linux | Proprietary | Free, Premium "Nitro" Subscription for Additional Features. | RTP, UDP, WS, HTTPS | Opus | TLS | 5000 soft limit for voice calls, 25 hard limit for video | IM, file sharing, in-game overlay | 10.0.19045; December 19, 2024; 51 days ago (2024-12-19) |
| Eyeball Chat | Windows | Proprietary | Free | SIP, STUN, ICE, XMPP | Un­known | Yes | 5 | IM, Conferencing, Voice, Video and SIMPLE based presence | Windows 3.2; 2009; 16 years ago (2009) |
| FaceTime | iOS, macOS | Proprietary | Free | SIP, IETF, Signaling protocol for VoIP, STUN, TURN and ICE| IETF, technologies for traversing firewalls and NAT | H.264 Video, AAC-ELD Audio, H.263 and VP8 | RTP, SRTP IETF|standards for delivering real-time and encrypted media streams for VoIP. | 20 | Video, voice, conferencing, with additional tools available as "Services". | |
| IBM Sametime | Linux, macOS, Windows, mobile | Proprietary | ? | 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; May 8, 2011; 13 years ago (2011-05-08) |
| Jami | Android, FreeBSD, iOS, iPhone, Linux, Microsoft Windows, OS X | GPL-3.0-or-later | Free | SIP, RTP, STUN per account, SRV, DHT, P2P | Audio: Opus, Speex, G.722, G.711, GSM, VP8, G.729, iLBC. Video: H.264, H.263, VP8, MPEG-4 | Voice encryption (SRTP with SDES or ZRTP) and signaling encryption (TLS), multiple realms authentication mechanism | No limit | Blockchain ID-management, Gnome-KDE client, address book, multiple accounts, unlimited call number, call transfer, call hold-unhold, call recording, multi-way conferencing | iOS3.28 / December 17, 2021; 3 years ago (2021-12-17)Android20211210-01 / December 21, 2021; 3 years ago (2021-12-21)Windows202112221025 / December 22, 2021; 3 years ago (2021-12-22)macOS2.10 / December 16, 2021; 3 years ago (2021-12-16) |
| Jitsi | Linux, macOS, Windows (all java supported). Experimental Android builds are also available. | Apache-2.0 | Free | SIP-SIMPLE, XMPP-Jingle STUN ICE, TURN | SILK, G.722, Speex, Opus, G.711 (PCMU/PCMA), iLBC, GSM, G.729, H.264, H.263, VP8 | ZRTP, SRTP, OTR, TLS | Un­known | Text messaging, audio-video telephony, IPv6 (often broken, P2P not supported), call recording, 64-bit | 2.10 (build.5550) (February 5, 2017; 8 years ago (2017-02-05)) |
| Linphone | Linux, Windows, macOS, Android, iPhone, BlackBerry | GPL-3.0-or-later | Free | SIP | Speex, Opus, G711, GSM, G.722, VP8 (WebM), H263, MPEG4, Theora and H264 (plugin) | TLS, SRTP, ZRTP | Un­known | Video, IM, STUN, IPv6 (disables IPv4 support when enabled), P2P, Secure Encryption, User own Encryption via Provided API https://gitlab.linphone.org/BC/public/linphone-desktop | 4.2.5; June 25, 2020; 4 years ago (2020-06-25), provides daily snapshots via http://www.linphone.org/snapshots |
| Messages | macOS | Proprietary | Free, only macOS and iOS | SIP AIM ICQ XMPP | H263, H264 | Un­known | Un­known | Integrated, PBX independent | 7.0; July 25, 2012; 12 years ago (2012-07-25) |
| MicroSIP | Windows | GPL-2.0-or-later | Free | SIP, STUN, ICE, SIMPLE | Speex, iLBC, GSM, G.711, G.722, G.729, SILK, Linear PCM | TLS, SRTP | Un­known | Video, voice, IM and Presence | 3.20.7 (25 August 2021; 3 years ago (2021-08-25)) |
| Movim | Any, Progressive web application | GPL-2.0-or-later | Free | XMPP, STUN, TURN | Depending the web-browser | TLS | 2 | IM, microblogging, social-network, OMEMO encryption, screen-sharing, file transfer | 2025-01-26 |
| Mumble | Linux, macOS, iOS, Windows, Android | New BSD license | Free | ICE | CELT, Speex, Opus | TLS and OCB-AES128 | No limit (limited only by server bandwidth and memory) | Chat with (limited) embedded HTML, Automatic Gain Control, very low latency, Access Control Lists for user management, Customizable In-Game Overlay for OpenGL and DirectX, Directional Audio, Plugin Support, Nested Channels, Echo cancellation for headset free use, Global Public Server List, Logitech G15 support, Push-To-Talk and Voice-Activation | 1.4.287; September 14, 2022; 2 years ago (2022-09-14) |
| Nymgo | Windows, Android, iOS | Proprietary | Free | SIP, RTP and RTCP | Un­known | Yes | No limit | Address Book integration, Call recording/export, Mute, On Hold, Caller ID definition | 4.2.9; March 2013; 11 years ago (2013-03) |
| Phoner | Windows | Proprietary | Free | SIP, TAPI, CAPI | G.711a, G.711u, G.722, G.726, G.729, GSM, iLBC, speex, Opus | TLS, SRTP, ZRTP | 8 | Conferencing, call redirection, call recording | 3.23 (5 March 2021; 3 years ago (2021-03-05)) |
| PhonerLite | Windows | Proprietary | Free | SIP | G.711a, G.711u, G.722, G.726, G.729, GSM, iLBC, speex, Opus | TLS, SRTP, ZRTP | 8 | Conferencing, call redirection, call recording | 3.28 (10 January 2025; 29 days ago (2025-01-10)) |
| Roger Wilco GameSpy | Windows | Proprietary | ? | Proprietary | ? | ? | Un­known | ? | 2001; 24 years ago (2001) |
| Signal | Linux, macOS, Windows, Android, iPhone | GPLv3 clients and AGPLv3 server | Free | RingRTC (WebRTC over Signal protocol) | Opus | TLS, Signal Protocol | 50 | Signal also allows users to send text messages, files, voice notes, pictures, GIFs, and video messages over a Wi-Fi or data connection to other Signal users on iOS, Android and a desktop app. The app also supports group messaging, read receipts and typing indicators, both of which can be disabled. | Android7.31.1 / 24 January 2025iOS7.40.5 / 27 December 2024Desktop7.36.1 / 18 December 2024 |
| Skype | Linux(with limited functionality), macOS, Windows 2000-XP-Vista-7-Mobile (unsupported), BREW, Windows Phone, Android, iPhone, PSP | Proprietary | Free | Proprietary P2P protocol | SILK | TLS | 25 starting with version 3.6.0.216. 10 with 2.x | Conferencing, video, file transfer, voicemail, Skype to phone, phone to Skype, additional P2P extensions (games, whiteboard, etc...); depending on platform. | Windows, UWP15.136.3203.0 / 5 February 2025; 3 days ago (2025-02-05)Windows, desktop8.136.0.203 / 5 February 2025; 3 days ago (2025-02-05)macOS8.136.0.203 / 5 February 2025; 3 days ago (2025-02-05)Linux8.136.0.203 / 5 February 2025; 3 days ago (2025-02-05)Android8.136.0.203 / 5 February 2025; 3 days ago (2025-02-05)iOS8.136.1.203 / 6 February 2025; 2 days ago (2025-02-06) |
| Steam Chat | Web, Phones, Desktop | Proprietary | | WebRTC | | | | | |
| TeamSpeak | Linux, Windows, macOS, FreeBSD, Android, iOS | Proprietary | Free | Un­known | CELT, Speex (both until server version 3.5.0), Opus | Yes | 32 unlicensed, 512 with Non-Profit License (available until September 2018), up to 1024 (Gamer License), 2000 | 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 | 3.5.5; November 4, 2020; 4 years ago (2020-11-04) |
| TeamTalk | Linux, Windows, macOS, Android, iOS, Raspbian | Proprietary | Free | Proprietary | Opus, Speex, VP8 | No | 1000 | Video, file sharing, desktop sharing, stream media files (MP3, AVI) | 5.3.3; November 2018; 6 years ago (2018-11) |
| TeamViewer | Linux, Windows, macOS, iOS, Android | Proprietary | Free (personal use only) | Un­known | Un­known | AES256 | Un­known | Un­known | Windows (desktop app)15.62.4 / 28 January 2025; 11 days ago (2025-01-28)macOS15.62.4 / 28 January 2025; 11 days ago (2025-01-28)Linux15.62.4 / 28 January 2025; 11 days ago (2025-01-28)Android/ChromeOS15.62.652 / 28 January 2025; 11 days ago (2025-01-28)iOS15.62.1 / 28 January 2025; 11 days ago (2025-01-28)Windows (UWP app)15.53.6 / 15 April 2024; 9 months ago (2024-04-15) |
| Telephone | macOS 10.10.2 | BSD | Free | SIP, STUN, ICE | Un­known | No | Un­known | Address Book integration | 1.1.4; March 6, 2012; 12 years ago (2012-03-06) |
| Tuenti | Android, iPhone, Windows Phone | Proprietary | Free | WebRTC, SIP, XMPP | iLBC, Opus | Yes | Un­known | Voice, video, Instant messaging, group chat, photo and video sharing, SMS and MMS, native and social network contacts integration, incoming call/IM push notifications. | |
| Twinkle | Linux | GPL-2.0-or-later | Free | SIP | G.711 A-law μ-law, G.726, GSM, iLBC, Speex narrow wide ultrawide | SRTP, ZRTP | 3 | Conferencing, chat, file transfer, Firefox integration, call redirection, voicemail, support of VoIP-to-Phone services | 1.10.3 (February 19, 2022; 2 years ago (2022-02-19)) |
| Ventrilo | macOS, Windows, iOS, Android | Proprietary | Free | Un­known | Un­known | No | 8 | Conferencing, chat, text-to-speech | 3.0.8 |
| Viber | Linux, macOS, Windows, Android, Bada, BlackBerry OS, iOS, Series 40, Symbian, Windows Phone | Proprietary | ? | Un­known | Un­known | Yes | Un­known | Varies by platform: Text, picture and video messaging on all, voice calling only on iPhone, Android and Microsoft's Windows Phone | Android20.4.3.0 / 2 July 2023; 19 months ago (2 July 2023)iOS20.4.0 / 4 July 2023; 19 months ago (4 July 2023)Windows20.2.0 / 12 June 2023; 19 months ago (12 June 2023)macOS20.2.0 / 12 June 2023; 19 months ago (12 June 2023)Linux20.3.0.1 / 14 June 2023; 19 months ago (14 June 2023) |
| Wire | Linux, Windows, macOS, iOS, Android, Web | GPLv3 | not free | ? | Audio: Opus Video: VP8 | DTLS, SRTP | 10 | End-to-end encryption by default for everything, instant messaging, video call, video group call, file sharing, GIF sharing, push to talk, edit message, delete message (on both side), timed messages, doodling, identity verification, screen sharing (desktop only) | ? |
| Yate Client | Linux, macOS, Windows | GPL | Free | SIP, IAX, XMPP, H.323 | G.711a, G.711u, GSM 06.10, iLBC, Speex, G.723, G.726, G.728, G.729 | SRTP, maybe ZRTP? | Un­known | | 6.0.0; September 2017; 7 years ago (2017-09) |
| Zfone | Linux, macOS, Windows | Proprietary (with viewable source) | Includes time bomb provision | SIP, RTP | Un­known | SRTP, ZRTP | Un­known | | Beta 2008-09-04 (Linux 0.9.224), (macOS 0.9.246), (Windows 0.9.206) |
* ↑ It is possible to connect by SIP to the Skype network via additional "Skype Connect" PBX software and alternative (SIP) client software/hardware. Neither the Skype software nor the Skype network supports SIP directly
* 1 2 3 Viber must be first installed on a mobile phone to function on a desktop operating system

## Mobile phones

For mobile VoIP clients:
| Program | Operating systems | License | Open source | Protocols | Codecs | Encryption | Other abilities | Latest release |
| Jami | iOS, Android | GPLv3 | Yes | SIP | Video: H264, VP8, MP4V, H263, Audio: Opus 48000 hz, G722 PCMA, PCMU | SRTP, SIP over TLS | ? | Version 202103261733 March 2021; 3 years ago (2021-03) |
| Line | Android, iOS | Proprietary | No | ? | ? | ? | ? | |
| Signal | iOS, Android | GPLv3 | Yes | WebRTC | Opus | TLS, Signal Protocol | End-to-end encryption by default for everything. CallKit and location privacy, one-to-one and group messaging, video calling, image/video sharing, timed messages, identity verification, screenshot blocking. Android only: SMS/MMS messaging, doodling, GIF sharing. | Android 5.2.3 / 15 September 2023 iOS 6.41.1 / 15 September 2023 Desktop 1.33.4 / 13 September 2023 |
| Sipdroid | Android | GPL | Yes | SIP | ? | ? | Uses Wi-Fi, 3G or EDGE | 2.7 |
| Tango | iOS, Android, Microsoft Windows, macOS, Windows Phone | Proprietary, freeware | ? | ? | ? | ? | VoIP, Wi-Fi out & in, SMS over IP, call-through & call-back, instant messaging, videoconferencing | ? |
| WhatsApp | Android, BlackBerry, iOS, Symbian, Windows Phone | Proprietary, freeware | No | ? | ? | ECDH, SRTP | VoIP and instant messaging over Wi-Fi or a data connection. | iOS24.25.79 / December 16, 2024; 54 days ago (December 16, 2024)Android2.25.1.76 / January 22, 2025; 17 days ago (January 22, 2025)Windows2.2502.3.0 / January 20, 2025; 19 days ago (January 20, 2025)macOS24.25.79 / December 16, 2024; 54 days ago (December 16, 2024) |

## Frameworks and libraries

| Program | Operating systems | License | Protocols, based on, compatible with | Encryption | Other abilities | Key and target markets | Latest release |
| Telepathy, Farstream | Linux, macOS, Windows | LGPL | SIP, XMPP (Jingle), ICE (STUN/TURN), UPnP | No | Multi-user A/V conferencing, IM, collaborative applications | Mobile devices (Maemo, Meego), Linux desktop or embedded | spec 0.27.2; September 24, 2013; 11 years ago (2013-09-24) |
| OPAL | Windows, Linux (including embedded variants), macOS | MPL | SIP, H.323, IAX2, CAPI, VXML | Un­known | Multi-user A/V conferencing, IM, IVR | Softphones, softswitches, telephony application servers | 3.14.3; October 10, 2014; 10 years ago (2014-10-10) |
| GNU oSIP | Linux, Windows, macOS, Android, iPhone, BlackBerry | LGPL | SIP, SDP | Un­known | Multi-user A/V conferencing, IM, IVR | Softphones, embedded and mobile devices, telephony application servers | 4.1.0; December 18, 2013; 11 years ago (2013-12-18) |

## Server software

| Name | Operating systems | License | Protocols | Encryption | Notable features | Target markets | Latest release |
| 3CX Phone System | Windows, Linux | Proprietary | SIP | TLS, SRTP | VoIP/VideoOverIP calls and conferencing, voicemail and instant messaging | < 50,000 users | 18.2; December 8, 2021; 3 years ago (2021-12-08) |
| AskoziaPBX | Standalone program (Linux-based) | Proprietary | SIP, H.323, IAX, SCCP | No | ISDN, voicemail, conferencing, MOH, ACD, IVR, call forwarding, call recording | SMEs up to 50 users | 5.4; September 2, 2017; 7 years ago (2017-09-02) |
| Asterisk PBX | Linux, BSD, macOS, Solaris | GPL-2.0+, optional: Proprietary | SIP, H.323, IAX, MGCP, VoFR, XMPP, Google Talk, TDM | TLS, SRTP | VoIP gateway, voicemail, basic accounting (expandable with ODBC-compliant database), billing, conferencing, hot desking, IVR trees with conditional logic, call waiting, automated call distribution | Enthusiasts, developers, enterprise users (capacity dependent on server design, scalable across multiple servers) | 21.3.1 (17 May 2024; 8 months ago (2024-05-17)) 20.5.0 LTS (18 October 2023; 15 months ago (2023-10-18)) 19.8.1 (7 July 2023; 19 months ago (2023-07-07)) 18.20.0 LTS (18 October 2023; 15 months ago (2023-10-18)) |
| Brekeke PBX | Linux, Windows Server 2016 and Server 2019 | Proprietary | SIP | TLS, SRTP | VoIP/VideoOverIP calls and conferencing, voicemail | Hosted service providers, Mid-large enterprise | 3.12.2.2; January 11, 2022; 3 years ago (2022-01-11) |
| CommuniGate Pro | Linux, BSD, macOS, Windows, Solaris, HP-UX, AIX | Proprietary | SIP, XIMSS, XMPP, WebRTC | SSL, TLS, SRTP | SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM | Mobile network operators, ISPs, SaaS providers | 6.2.14; August 16, 2019; 5 years ago (2019-08-16) |
| Dial Gate VoIP Softswitch | Linux, Windows | Proprietary | SIP | TLS, SRTP | Billing server, real-time account and line monitoring, web portal | Softswitch users, service providers | 4.3; June 1, 2014; 10 years ago (2014-06-01) |
| Dial-Office IP-PBX | Linux, Windows | Proprietary | SIP | TLS, SRTP | Unified communications, conference calls, remote worker support and voicemail | Small businesses, Mid-large enterprises | 4.1; December 2013; 11 years ago (2013-12) |
| Elastix | Linux | Proprietary | SIP, IAX, H.323, XMPP | TLS, SRTP | Unified communication server that also supports chat, mail and fax. | Capacity dependent on server design, scalable across multiple servers | 5.0.0; December 7, 2016; 8 years ago (2016-12-07) |
| FreeSWITCH | Linux, BSD, macOS, 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 | 1.10.11 (December 22, 2023; 13 months ago (2023-12-22)) |
| FreePBX | Linux, BSD, Solaris | GPL | SIP, IAX, H.323, XMPP | TLS, SRTP | Complete PABX Service, based on Asterisk and PHP 5.6; provides a full replacement for a legacy non-VoIP phone system; under current and active development | Scales from Raspberry PI (3 users) to multiple parallel clusters (10K+ simultaneous calls) | 14.0; August 2017; 7 years ago (2017-08) |
| Galene | Linux, Unix, Mac OS, Windows | MIT Licence | WebRTC, WHIP | TLS, SRTP | Lightweight, efficient, easy to install and to administer | Teaching, conferences, meetings | 0.96.2; January 2025; 1 month ago (2025-01) |
| GNU Gatekeeper | Linux, FreeBSD, macOS, Windows XP-2000-Vista-7 | GPL | H.323 | H.235 | H.460.18 firewall traversal, routing, accounting | video conferencing, VoIP carriers large and small | 3.7; August 15, 2014; 10 years ago (2014-08-15) |
| HERO Hosted PBX | Linux, Windows | Proprietary | SIP | TLS, SRTP | Unified Communications, billing server, cloud-based management and web interface | Mid-large enterprises, VoIP carriers and service providers, telecom operators | 4.3; December 2013; 11 years ago (2013-12) |
| Murmur | Linux, BSD, macOS, Windows | BSD, GPL | CELT, Speex, Opus | 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) | 1.2.17; September 24, 2016; 8 years ago (2016-09-24) |
| Kamailio, OpenSIPS (formerly named OpenSER) | Linux, BSD, Solaris | GPL | SIP, XMPP | TLS, SRTP | SIP registrar-proxy, authentication, Diameter, RADIUS, ENUM, least-cost-routing, many others | SIP Service Providers | 5.2.8; October 2020; 4 years ago (2020-10) |
| SIP Express Router (SER) | Linux, BSD, Solaris | GPL | SIP | No | SIP Registrar/Proxy, Authentication, Diameter, RADIUS, ENUM, many others | SIP Service Providers | 2.0.0 Ottendorf |
| sipXecs IP PBX | Linux | AGPL | Native SIP call control, XMPP | TLS, SRTP | Full redundancy (HA), instant messaging, voicemail, user portal, admin GUI, plug & play management including phones and gateways, fully featured | Enterprises between 10 and 10,000 users, multi-site | 14.04.2; July 2014; 10 years ago (2014-07) |
| vzRoom | Windows | Proprietary | SIP | SSL, TLS, AES | Instant messaging-chat, VoIP, video, sharing (desktop, video, file), whiteboard, scheduler, recording | Individual to small and medium enterprise (2-1,000 users) | 0.8.8.735; November 2010; 14 years ago (2010-11) |
| Yate | BSD, Linux, macOS, Windows | GPL | SIP, IAX, H.323, ISDN, XMPP (Jabber), Jingle (Google Talk), MGCP, SS7 over IP, Cisco SLT (Signalling Link Transport) (SS7 MTP2 backhaul over IP), SCTP, SCCP, TCAP, MAP CAMEL | SSL, TLS, SRTP | Voice, video, file transfer, data, H323 to SIP signalling proxy, instant messaging, IVR, PC2Phone and Phone2PC gateway, SCCP — GTT routing between networks, Secure Unified Communications, SIP registrar-proxy, SIP SBC (session border controller), USSD, voicemail, VoIP, VoIP to PSTN gateway, conference server (max 200 voice channels per conference), call centre server, prepaid and postpaid cards | Deployed on home servers and large networks with millions of users | 6.3; February 2021; 4 years ago (2021-02) |

## Secure VoIP software
### VoIP software with client-to-client encryption

The following table is an overview of those VoIP clients which (can) provide end-to-end encryption.
| Client name | Development status | Open source client | End-to-end authentication | Encryption protocols | Encryption protocols | Encryption protocols | Encryption protocols | Forward secrecy | Multiple encryption | Encrypted group calling | Proxy, Tor |
| Client name | Development status | Open source client | End-to-end authentication | ZRTP | ECDH | DTLS | SRTP | Forward secrecy | Multiple encryption | Encrypted group calling | Proxy, Tor |
| FaceTime | Active | No | Yes | ? | ? | ? | Yes | Yes | ? | Yes | No |
| Jami | Active | Yes | Yes | No | ? | Yes | Yes | Yes | ? | Yes | ? |
| Jitsi | Active | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes | ? |
| Line | Active | No | ? | ? | ? | ? | ? | ? | ? | No | No |
| Linphone | Active | Yes | Yes | Yes | ? | Yes | Yes | Yes | Yes | ? | No |
| Signal | Active | Yes | Yes | No | Yes | No | Yes | Yes | Yes | Yes | Depends |
| Skype (opt-in per conversation, one pair of devices per conversation) | Active | No | Yes | No | No | No | Yes | ? | ? | No | No |
| Telegram | Active | Yes | Yes | No | No | No | No | Yes | ? | No | No |
| Threema | Active | Partially | Yes | No | Yes | Yes | Yes | Partially | Yes | No | No |
| Viber | Active | No | ? | ? | ? | ? | ? | ? | ? | ? | No |
| WhatsApp | Active | Partially | Yes | No | Yes | No | Yes | Yes | Yes | Yes | No |
| Wire | Active | Yes | Yes | No | ? | Yes | Yes | Yes | Yes | Yes | No |
| Zfone | Abandonware | Viewable source | Yes | Yes | Optional | ? | Yes | Yes | Yes | ? | ? |