How does Threema Web work?
Threema Web establishes an encrypted direct connection between web browser and mobile device. This allows to synchronize messages directly between browser and mobile device, without having to temporarily store the messages on a server. In contrast to common, server-based approaches, the digital footprint is reduced to the bare minimum.
Once the session has ended, all synchronized messages are deleted in the browser. Threema Web acts merely as extension of the mobile app and hence meets Threema’s high security standard.
The technical details of Threema Web’s architecture are documented here.