Session vs Threema

Session is a decentralized, end-to-end encrypted messaging app for Android, iOS, Linux, macOS, and Windows. Account creation does not require a phone number or email address. Its onion-request routing is designed so no single server knows both the origin and destination of a message. The app supports disappearing messages and encrypted group chats for up to 100 people. Attachments can be up to 10MB; they are encrypted on the device and stored through the Session File Server. Communities are self-hosted public channels, but are not fully end-to-end encrypted. Voice and video calling are beta features for one-to-one calls only, using peer-to-peer networking; calls can expose a user’s IP address to the call partner and an STF-operated STUN/TURN server. The code is open source, and the desktop, Android, and iOS clients have been audited by Quarkslab. The free plan includes encrypted messaging and attachments up to 10MB. Pro costs $2.99 a month and adds messages up to 10,000 characters, unlimited pinned conversations, animated display pictures, and badges.

Threema is a paid messaging service for private and business communication, supporting text and voice messages, voice and video calls, group calls, media sharing and file transfers. It can be used without a phone number or email address, and contact synchronization is optional. End-to-end encryption covers messages, media, calls, profile pictures, group names and group-member lists. The apps are open source, with repositories for Android, iOS, macOS, Windows, Linux and Threema Web. The regular desktop app and web client require a mobile device with Threema installed and activated. Threema operates its own servers in Zurich data centers of an ISO 27001-certified colocation partner. It says its apps receive regular audits by recognized security experts, including Cure53 audits in 2020 and 2024. Business tools include Gateway integrations, Work APIs and Broadcast features such as feeds, distribution lists, bots and managed group chats. Private use costs $6, paid once, with price varying by app store and country; Core starts at $3 a month billed annually. A 30-day trial is listed.