Threema sells a messenger for a one-time fee. A random Threema ID replaces your phone number. Chats are end-to-end encrypted. The company is in Switzerland and has published outside audits. You can use it without handing over a number or an email.
The apps are open source. The server is not. You are trusting Threema GmbH to run the closed side the way the audits described. Almost nobody you know has it, so it stays a tool for a newsroom, a company, or a small circle. A purchased app can still be updated badly. Read the changelog when they ship one.
Use it if the people you need are willing to pay once. threema.ch
Threema’s one-time purchase is not a subscription, and it is also not a promise of a large network. Back up the ID the way they describe or a new phone is a new identity and your contacts see a stranger. The closed server means you cannot recompile the network. You can read the apps. For a newsroom that already standardized on it, that trade is understood. For a family, Signal will get installed and Threema will not.
