Open Source

Pidgin is a free and open-source chat client which supports AIM, Google Talk, ICQ, XMPP protocols.

Open Source

Jitsi (formerly SIP Communicator) is a free and open source multiplatform voice (VoIP), videoconferencing and instant messaging application.

Facebook Messenger

Free

Facebook Messenger is the official Facebook app that lets you have text conversations with all of your friends on the popular social network.

Miranda NG

Open Source

Miranda NG is a successor of Miranda IM, a popular multi-protocol instant messaging client for Windows.

Bitmessage

Open Source

Bitmessage is a decentralized, encrypted, peer-to-peer, trustless communications protocol that can be used by one person to send encrypted messages to another…

qutIM

Open Source

qutIM is free and open-source multiprotocol (ICQ, Jabber, Mail.Ru, IRC, VKontakte) instant messenger.

Tencent QQ

Free

Tencent QQ (QQ) is an instant messaging software service.

Coccinella

Open Source

Coccinella is a free and open-source cross-platform client for the XMPP/Jabber-instant messaging-protocol.

Free

Telegram is a free cloud-based instant messaging platform.

Miranda IM

Open Source

Miranda IM is an open source multiprotocol instant messaging application, designed for Microsoft Windows.

Gajim

Open Source

Gajim is an instant messaging client for the XMPP protocol which uses the GTK+ toolkit.

Instantbird

Open Source

Instantbird is a cross-platform instant messaging client based on Mozillas XULRunner and the open source library libpurple used in Pidgin.

Spark

Open Source

Apache Spark is an open-source cluster-computing framework.

Psi+

Open Source

Psi is a cross-platform powerful XMPP/Jabber client (Qt, C++) designed for the Jabber power users. Psi+ is a development branch of Psi IM XMPP/Jabber client.

Kadu

Open Source

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 …