AIM was an instant messaging and presence computer program created by AOL, which used the proprietary OSCAR instant messaging protocol and the TOC protocol to allow registered users to communicate in real time.
ICQ New is a cross-platform instant messaging (IM) and VoIP client. The name ICQ derives from the English phrase "I Seek You". Originally developed by the Israeli company Mirabilis in 1996, the client was bought by AOL in 1998, and then by Mail.Ru Group in 2010.
Messenger was an instant messaging and presence system developed by Microsoft in 1999 for use with its MSN Messenger software. It was used by instant messaging clients including Windows 8, Windows Live Messenger, Microsoft Messenger for Mac, Outlook.com and Xbox Live. Third-party clients also connected to the service. It communicated using the Microsoft Notification Protocol, a proprietary instant messaging protocol. The service allowed anyone with a Microsoft account to sign in and communicate in real time with other people who were signed in as well.
Pidgin is a free and open-source multi-platform instant messaging client, based on a library named libpurple that has support for many instant messaging protocols, allowing the user to simultaneously log in to various services from a single application, with a single interface for both popular and obsolete protocols, thus avoiding the hassle of having to deal with a new software for each device and protocol.
Extensible Messaging and Presence Protocol is an open communication protocol designed for instant messaging (IM), presence information, and contact list maintenance. Based on XML, it enables the near-real-time exchange of structured data between two or more network entities. Designed to be extensible, the protocol offers a multitude of applications beyond traditional IM in the broader realm of message-oriented middleware, including signalling for VoIP, video, file transfer, gaming and other uses.
climm is a free CLI-based instant messaging client that runs on a wide variety of platforms, including AmigaOS, BeOS, Windows, OS X, NetBSD/OpenBSD/FreeBSD, Linux, Solaris, HP-UX, and AIX.
iChat is a discontinued instant messaging software application developed by Apple Inc. for use on its Mac OS X operating system. It supported instant text messaging over XMPP/Jingle or OSCAR (AIM) protocol, audio and video calling, and screen-sharing capabilities. It also allowed for local network discussion with users discovered through Bonjour protocols.
Centericq is a text mode menu- and window-driven instant messaging interface that supports the ICQ, Yahoo!, AIM, MSN, IRC, XMPP, LiveJournal, and Gadu-Gadu protocols.
Fire is a discontinued instant messaging client for macOS that can access IRC, XMPP, AIM, ICQ, Microsoft, Yahoo!, and Bonjour. All services are built on GPL’d libraries, including firetalk, libfaim, libmsn, XMPP, and libyahoo2. Fire supports OS X v10.1 and higher.
Psi is a free instant messaging client for the XMPP protocol which uses the Qt toolkit. It runs on Linux, Windows, macOS and OS/2.
Colloquy is an open-source IRC, SILC, ICB and XMPP client for Mac OS X. Colloquy uses its own core, known as Chat Core, although in the past it used Irssi as its IRC protocol engine. One of the primary goals behind Colloquy was to create an IRC, SILC and ICB client with Mac OS X visuals. Colloquy contains a user interface that follows Apple's Human interface guidelines in addition to containing support for traditional IRC command-line controls such as /nick and /join.
Google Talk was an instant messaging service that provided both text and voice communication. The instant messaging service was variously referred to colloquially as Gchat, Gtalk, or Gmessage among its users.
Gajim is an instant messaging client for the XMPP protocol which uses the GTK toolkit. The name Gajim is a recursive acronym for Gajim's a jabber instant messenger. Gajim runs on Linux, BSD, macOS, and Microsoft Windows. Released under the GPL-3.0-only license, Gajim is free software. A 2009 round-up of similar software on Tom's Hardware found version 0.12.1 "the lightest and fastest jabber IM client".
Skype for Business Server is real-time communications server software that provides the infrastructure for enterprise instant messaging, presence, VoIP, ad hoc and structured conferences and PSTN connectivity through a third-party gateway or SIP trunk. These features are available within an organization, between organizations and with external users on the public internet or standard phones.
Skype for Business is an enterprise software application for instant messaging and videotelephony developed by Microsoft as part of the Microsoft Office suite. It is designed for use with the on-premises Skype for Business Server software, and a software as a service version offered as part of Microsoft 365. It supports text, audio, and video chat, and integrates with Microsoft Office components such as Exchange and SharePoint.
Jingle is an extension to XMPP which adds peer-to-peer (P2P) session control (signaling) for multimedia interactions such as in Voice over IP (VoIP) or videoconferencing communications. It was designed by Google and the XMPP Standards Foundation. The multimedia streams are delivered using the Real-time Transport Protocol (RTP). If needed, NAT traversal is assisted using Interactive Connectivity Establishment (ICE).
MCabber is a free software client for the instant messaging protocol XMPP with a text user interface based on ncurses. It runs on a range of platforms, including Linux, BSD, and Mac OS X. As free software it is freely available – including the source code – under the terms of the GNU GPL-2.0-or-later. MCabber is the successor of Alejandro Jimenez Macias's earlier Cabber that has had releases from 2002 to 2004. In 2005 it has been forked off the last version of Cabber (0.5.0).
Kadu is a free and open source multi-platform instant messaging client that supports Gadu-Gadu, XMPP IM networks and other services based on XMPP like Google Talk. It is written in C++ using Qt Framework, and released under the GNU GPL-2.0-or-later.
Tkabber is a GPL instant messaging client for the XMPP protocol which uses the Tk toolkit for the GUI. It runs on anything to which Tcl/Tk is ported: almost any X-based system, Microsoft Windows, and Mac OS X.
Spark is an open-source instant messaging program that allows users to communicate in real time. It can be integrated with the Openfire server to provide additional features such as controlling the various Spark functionalities from a central management console, or integrating with a proprietary customer support service known as Fastpath which allows its users to interact with the platform using the Spark client. Being a cross-platform application, Spark can run on various systems. Installers for Windows, macOS and Linux are available on the official website.
