Voice over IP clients for Linux

Skype () was a proprietary telecommunications application operated by Skype Technologies, a division of Microsoft, best known for IP-based videotelephony, videoconferencing and voice calls. It also had instant messaging, file transfer, debit-based calls to landline and mobile telephones (over traditional telephone networks), and other features. It was available on various desktop, mobile, and video game console platforms.

Discord is an instant messaging and VoIP social platform that allows communication through voice calls, video calls, text messaging, and media. Communication can be private or in virtual communities called "servers". A server is a collection of persistent chat rooms and voice channels accessed by invitation links. Discord runs on Windows, macOS, Android, iOS, iPadOS, Linux, and in web browsers.

Gizmo5 (formerly known as Gizmo Project and SIPphone) was a voice over IP communications network and a proprietary freeware soft phone for that network. On November 12, 2009, Google announced that it had acquired Gizmo5. On March 4, 2011, Google announced that the service would be discontinued as of April 3, 2011.

Guilded was a VoIP, instant messaging, and digital distribution platform designed by Guilded Inc. and was bought by Roblox Corporation on August 16, 2021 for $90 million. Since then, Guilded had been integrated with Roblox. The company was based in San Francisco. Users communicated with voice calls, video calls, text messaging, media and files in private chats or as part of communities called "servers". Guilded was founded by Eli Brown, a former Facebook and Xbox employee. Guilded was available on Windows, Linux, macOS, Android, and iOS. == Features == Guilded was a main competitor of Discord