What data is stored in the tech preview of Threema 2.0 for desktop, and how is it protected?

Version 2.0 of Threema’s desktop app is a major update that will not only introduce a completely redesigned user interface, but it will also be based on a totally new architecture. Thanks to multi-device functionality, this version of the desktop app no longer requires an active connection to the mobile device.

The tech preview of Threema 2.0 for desktop allows iOS users to test the upcoming multi-device functionality ahead of time. iOS users can connect the beta version of Threema for iOS with the tech preview of Threema 2.0 installed on one computer and use them independently from each other.

How to Get the Tech Preview of Threema 2.0 for Desktop

1. Join the beta program of Threema for iOS.
2. Install and open the tech preview of Threema 2.0 for desktop. (There is no browser version available for the preview.)
3. Follow the instructions on the screen to link your computer to your mobile device.

At the moment, the tech preview of Threema 2.0 is only available for iOS, not for Android. In the future, support for multiple linked devices, including tablets and Android devices, is planned.

The tech preview of Threema 2.0 for desktop is alpha software that has been released for preview purposes and is still being developed. You might encounter stability issues, and data loss might occur.

These are the current limitations of the tech preview of Threema 2.0 for desktop (subject to change):

• The tech preview only works with one iOS device and one computer (Windows/Mac/Linux).
• It’s available for the regular Threema version for iOS only (Threema Work and Threema for Android are not supported).
• The tech preview for desktop is only available in English.
• It’s required to keep Threema installed on your iOS device. Even though Threema works independently on linked devices, we recommend to open the app on each device at least once a week while connected to the Internet. This ensures new messages are downloaded to both devices.
• New text and file messages sent or received will appear on both devices. Any messages exchanged before linking will not be displayed in the tech preview.
• At the moment, only text and file messages are fully supported. Sending images, videos, voice messages, polls, and locations will be supported in a future release. You can simultaneously use the current desktop app or the web client to circumvent this limitation.
• Contacts and groups are synchronized across devices, but groups can only be created and modified on the mobile device.
• It is not yet possible to insert mentions.
• New message notifications will appear on your iOS device even if you have already read the messages in the desktop app. Open the iOS app to hide them.
• The “Read Receipts,” “Typing Indicator,” “Do Not Disturb,” and “Block Contact” settings are not yet available in the desktop app.
• Updates will not be performed automatically. You will be notified when updates are available.
• The chat history stored in the tech preview of Threema 2.0 for desktop will not be retained when switching to a future beta or release version of the product. Please keep important messages on your mobile device.
• If you have a new iPhone/iPad and move Threema to the new device, Threema 2.0 for desktop will be unlinked and may cause the Threema app to malfunction. To avoid this situation, please deactivate “Multi-Device Preview” on your old device before switching to the new one (the message history will be deleted in the desktop app). You can then activate “Multi-Device Preview” again on the new device.

We are aware of the following technical issues and plan to resolve them with a future update:

• The message timestamps shown on iOS sometimes differ from those shown on desktop.
• A chat containing thousands of messages on desktop can result in a slow UI. (As a workaround, you can delete the messages in the menu at the top right.)
• If a message is read on iOS while the desktop app is offline (or just recently came online), the message can appear as unread on the desktop app.
• If you block contacts that are members in certain groups on the mobile device, unexpected inconsistencies can appear in those groups between the mobile and the desktop app.
• When deleting a contact on the mobile device, any associated messages and conversations will be deleted on desktop too.
• Perfect Forward Secrecy (PFS) is not supported when “Multi-Device Preview” is activated.
• The connection between iOS/desktop and the multi-device “mediator” server is authenticated in one way only.
• Used cryptographic nonces are not yet persisted on desktop, which is why re-sending of old messages might not be detected.