Off-the-Record Messaging!

Riot (formerly Vector) is an opensource interoperable app running on Web, iOS and Android. It is built around chat rooms, both public and private and provides messaging, filesharing, voice and video conferencing (beta on Android and web), integrations to tools like GitHub, Jira, Jenkins and much more soon. Vector is built on the Matrix.org open standard which provides bridges to other systems such as Slack, IRC and a lot more soon. One can use the hosted service or run their own. »

ChatSecure is a free and open source messaging app that features OTR encryption over XMPP. You can connect to your existing accounts on Facebook or Google, create new accounts on public XMPP servers(including via Tor), or even connect to your own server for extra security.

Bitmessage is a P2P communications protocol used to send encrypted messages to another person or to many subscribers. It is decentralized and trustless, meaning that you need-not inherently trust any entities like root certificate authorities. It uses strong authentication which means that the sender of a message cannot be spoofed, and it aims to hide "non-content" data, like the sender and receiver of messages, from passive eavesdroppers like those running warrantless wiretapping programs. If Bitmessage is completely new to you, you may wish to start by reading the whitepaper. »

Protect your communication in transit and on your phone. SMSSecure is a full replacement for the default text messaging application: all messages are encrypted locally and messages to other SMSSecure users are encrypted over the air.

Wickr is a free end-to-end encrypted text, video, picture and voice messenger with full sender control.

Open source anonymous, registration free P2P chat. You communicate directly and no logs are saved on the server. Otr.to is browser based, which means that you don't need to install or ask somebody to install software.

Technitium Bit Chat is a secure, peer-to-peer (p2p), open source instant messenger designed to provide end-to-end encryption. Primary aim of developing this instant messenger is to provide privacy which is achieved using strong cryptography. It can be used over Internet and private LAN networks for instant messaging and file transfer.

Cyanide is Tox client for Sailfish OS .

Encryption plugin for Pidgin, providing up to 4096 bit RSA encryption using the NSS crypto library from Mozilla. Keys are automatically transmitted and stored, making it very easy to use, but also resistant to man-in-the-middle attacks.

GoldBug is a secure Instant Messenger. You can be sure with using GoldBug (GB), that no third party can look into your chat communication. Private user-to-user communication remains private. GoldBug therefore uses strong multi-encryption with different layers of modern encryption technologies of well known and revised crypto libraries (like libgcrypt (GnuPG) and OpenSSL). The app offers as well decentral and encrypted Email and decentral public E*IRC-Chat.