Free

Telegram is a free cloud-based instant messaging platform.

Signal

Open Source

Signal is the most scalable encryption tool.

Off-the-Record Messaging

Open Source

Off-the-Record Messaging (OTR) is a cryptographic protocol that provides encryption for instant messaging conversations.

Torchat

Open Source

TorChat is a decentralized anonymous instant messenger that uses Tor hidden services as its underlying network. It provides cryptographically secure text mess…

Finch

Open Source

Finch is a console-based IM program that lets you sign on to AIM, Jabber, MSN, Yahoo!, and other IM networks. It runs on Unixes. It uses GLib and ncurses.

Zulip

Open Source

Zulip is a chat and collaborative software.

Pidgin-Encryption

Open Source

Pidgin-Encryption transparently encrypts your instant messages with RSA encryption.

Tox

Open Source

Tox is a peer-to-peer instant-messaging and video-calling protocol that offers end-to-end encryption.

Ring

Open Source

Ring (SFLphone) is an open-source SIP-compatible softphone and instant messenger for Linux, Microsoft Windows, OS X and Android.

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…

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.