This article is a short list with the very best OTR clients.
We all use messaging services, like SMS, WhatsApp, iMessage, Google Hangouts and Facebook messenger at work or for private conversations. Unfortunately, popular services are highly compromised when it comes to privacy. There are much better options. In this post, we will review the best OTR clients for every platform. If you would like to know what OTR is, you can read our article “Ultimate Chat Privacy with OTR Messaging”.
In our “OTR Messaging Guide with Pidgin”, we have introduced Pidgin, which we find to be the best desktop OTR client. If you do not like the interface of Pidgin for some reason, there are other chat clients you could use. They are of course open-source too. When privacy and security are of utmost importance, we cannot accept anything else.
The ones we are going to introduce support OTR messaging natively. You do not need to install any plug-ins. For maximum security, you should stick with Pidgin. It has been thoroughly tested and is the best choice.
A good OTR client should additionally support many different protocols. It is not necessary that it is able to use account data from any chat service, e.g. Google Talk, Facebook Chat, ICQ and Groupwise. It should, however, support both of the major protocols, XMPP and IRC.
The desktop is the ideal environment for OTR, since the protocol needs a reliable internet connection. You do not have to deal with the issues that plague OTR on mobile, e.g. empty battery, loss of network connection and limited processing power. Messages get delivered reliably on desktop.
Adium is one of the best clients for macOS only. It is open-source and supports Windows Live Messenger, Yahoo! Messenger, Google Talk, AIM, ICQ, IRC, XMPP and more. It is a simple client and has a very well designed interface. The keys you need to use OTR in Adium are called “fingerprints”. That should not confuse you, they are exactly the same as private and public keys in other clients.
Blink is similar to Adium and open-source. It offers OTR for macOS, Windows and Linux and has a modern and user-friendly interface, because of the PyQt toolkit it is built upon. On Wikipedia, you will read that it does not use OTR on Windows, but that was added recently. If you would like to install it, go for the free Light version, the Pro version is not completely open source and contains some proprietary modules. A great thing about Blink is that it also offers encrypted file transfer, which is achieved using the cryptographic protocol ZRTP (technical description).
Jitsi is open-source and available for all desktop OSs, Android and on the web. A great thing about Jitsi is that the complete server software is open-source too. The server program can also be downloaded from the website, so you can set up your own chat server and make it as secure as you want. That is especially interesting for companies. We also recommend it as one of the only safe clients for video chat, but we will write a different, dedicated article about video chat.
We only listed the GUI clients above, but there are also good clients with a command-line interface. The most important ones are Centericq, climm, WeeChat and MCabber.
For Linux, you can get Kopete. It is a sleek chat app from KDE, OTR support can be installed with a plug-in. The same applies to Miranda IM for Windows.
There are many other desktop clients. Lists can be found on Wikipedia, OTR.im and on the CypherPunks website.
OTR is designed for synchronous transports. That works well on desktop when both participants are online. On mobile, it will happen that one of the two people that are communicating goes offline (no internet/empty battery/etc.). OTR Messaging needs to perform a key exchange to send and receive messages, but that would fail in such cases. Apps that use OTR will notify you that a new message is available. You then have to open the app and the key exchange will happen. If your contact has gone offline in the mean time, that will fail. This can lead to messages being lost.
All in all, mobile OTR clients are not the best idea. The performance is worse than on desktop and mobile OSs (Android, iOS) are in general less secure, so there are higher risks of eavesdropping.
Signal is a better option for mobile devices, in our opinion. There are still some OTR clients that do the job pretty well:
This is an open-source chat client for iOS. ChatSecure uses the XMPP protocol. It supports OTR as well as OMEMO. OMEMO is another protocol, similar to OTR and is used for XMPP (Jabber). It offers some additional features, such as secure file transfer and better group chat options. We prefer the advanced privacy features of OTR, however, so that we do not necessarily recommend using OMEMO. OMEMO is convenient, but the verification and forward secrecy functions are missing.
This is an open-source chat client for Android. Conversations uses the XMPP protocol and OMEMO. It does not support OTR anymore, since 2018. Therefore, we recommend this app no longer.
As stated above, Conversations switched from OTR to OMEMO. OMEMO is not a bad protocol and enables you to send files, but you can still get OTR chat on Android with the Conversations Legacy app. It is the latest release before OTR was removed in version 2.0.0. It comes from the original developer Daniel Gultsch, since he knew that some people would prefer OTR and Conversations Legacy is still maintained well with security updates.
We do not recommend a web client if privacy and anonymity are crucial. Nonetheless, we would like to mention some well-known OTR Messaging web clients. Maybe you just want to try OTR, before installing any software. For that purpose, web clients are ideal.
A full list of chat clients with OTR support can be found on Wikipedia.