Threema is an alternative to WhatsApp & friends, with a focus on privacy. It’s made in Switzerland, and it is on sale until December 31 for half the price.
Threema is a messenger alternative for smartphones and tablets, with a web version also available that connects through your installed app. All offerings are accessible to screen reader users. It is not a free app, and it is only partially open-source. But its privacy focus has won it several recognitions since it was started in 2012.
Threema offers text, voice messaging, voice calls, photo, video sharing, sharing of various other document types, you can send locations. It offers one-on-one as well as group chats. In group chats, it also offers polls so you can easily find common times or other agreement with friends without having to use any external services.
Unlike many other messengers, you don’t need to provide a phone number or e-mail address to use the service. You generate a completely anonymous ID on your device. You can share your phone number and/or e-mail address so others can find you, but you don’t have to. Likewise, you can share your contact info, and Threema will see if any of your other contacts are on Threema and have opted in to share their details.
Threema has three trust levels: Unverified, verified via e-mail or phone, and verified via personal contact and mutual scanning of QR codes. This verification also serves as a mechanism to guard against possible man-in-the-middle attacks. Threema have great documentation about all of this in their frequently asked questions.
I use Threema frequently as one of my main messengers now with friends, some colleagues, and in some grup chats. And if you like, you can drop me a line there as well.