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Threema is a paid cross-platform encrypted instant messaging app developed by Threema GmbH in Switzerland and launched in 2012. Users can make voice and video calls, send photos, files, and voice notes, share locations, and join groups. The service offers end-to-end encryption. Unlike many other popular secure messaging apps, Threema does not require phone numbers or email addresses for registration, only a one-time purchase that can be paid via an app store or anonymously with Bitcoin or cash.