ChatSecure
ChatSecure is a free and open source messaging app that features OTR encryption over XMPP.
Riot (formerly Vector) is an opensource interoperable app running on Web, iOS and Android.
ChatSecure is a free and open source messaging app that features OTR encryption over XMPP.
Free Open Source iPhone iPad
Off-the-Record (OTR) Messaging allows you to have private conversations over any instant messaging (MSN,Gtalk, Facebook and so on) by providing encryption, authentication, deniability, perfect forward secrecy
Free Open Source Mac OS X Windows Linux Java Mobile
Conversations is a privacy focused, open source XMPP Texting [Jabber] client for Android 4.0+ smart phones with wife-approved easy encryption [OTR, OMEMO, or GPG].
Free Open Source Android Android Tablet
BlackBerry Messenger is a FREE messaging app available for Blackberry, iOS, Android and Windows Phone.
Freemium Android iPhone Android Tablet iPad Android Wear Blackberry Windows Phone Apple Watch
Group messaging platform owned by Microsoft. It's absolutely free, whether you're talking to a group of friends, or texting with one person. Best of all, it works on nearly every phone, via push or SMS.
Free Personal Android iPhone Web Android Wear Blackberry Windows Phone Windows Mobile
The massively-scalable XMPPJabber mobile messaging platform, for mobile and web, by Erlang Solutions.
Free Open Source Mac OS X Linux Amazon Web Services Microsoft Azure