Tox
Open Source
Tox is a peer-to-peer instant-messaging and video-calling protocol that offers end-to-end encryption.
Glip
Freemium
Glip is fully searchable, real-time group chat; video chat, task management, file sharing app.
ICQ
Free
ICQ is an open source instant messaging software.
KakaoTalk
Freemium
KakaoTalk (Korean: 카카오톡), or sometimes KaTalk, is a free mobile instant messaging application for smartphones with free text and free call features.
Zulip
Open Source
Zulip is a chat and collaborative software.
Signal
Open Source
Signal is the most scalable encryption tool.
IM+
Freemium
IM+ supports simultaneously major IM services, including Google Talk, Twitter DMs, Yahoo!, AIM/iChat, ICQ, Jabber (and Slack through Jabber), etc.
iMessage
Free
iMessage is an instant messaging service.
Tencent QQ
Free
Tencent QQ (QQ) is an instant messaging software service.
Dasher Messenger
Free
Dasher Messenger provids a way to message friends.
Compare Trillian with alternatives
Compare Tencent QQ and Trillian and decide which is most suitable for you.
Compare Dasher Messenger and Trillian and decide which is most suitable for you.