Download Threema. The Secure Messenger for PC

Threema is a Swiss messenger that identifies you by a randomly generated Threema ID instead of a phone number or an email address. Text chats, voice messages, calls, group conversations and file transfers are end-to-end encrypted, and the app carries no ads or trackers. Threema GmbH also publishes its own computer builds for Windows, macOS and Linux, alongside a browser client called Threema Web. The sensible way to use Threema on a PC is to install the official desktop app and link it, by QR code, to the phone that already holds your Threema ID.

Reasons to keep Threema open on a computer

Threema's desktop builds are aimed at people who already type all day. Keyboard shortcuts speed up writing, files can be dragged straight from a folder into a conversation, and new-message alerts are handed to the operating system's own notification system instead of a phone screen. That matters for the kind of traffic Threema tends to carry: work documents, scanned paperwork, longer written replies.

The newer desktop generation adds two things a phone cannot give you. Threema's new desktop app can start and join encrypted group calls, including video, so a work meeting no longer means picking up a handset. And because the app can be linked as an independent device, it keeps working when the phone is switched off or has no connection. Threema also allows two computers to be linked to one mobile device, which covers an office machine and a home machine on the same Threema ID.

Desktop app, Threema Web, or the Android package

Threema GmbH supports more than one way to chat from a computer, and they are not equivalent.

• Threema 2.0 for desktop (beta) is the multi-device version for Windows, macOS and Linux. It links to one phone plus up to two computers and, once linked, runs even when the mobile device is off. There is no browser version of it, features are still limited, and Threema does not offer full customer support for it yet.
• The current desktop app (1.0) is the older, stable client for the same three platforms. It needs the mobile device switched on and online for the whole session, and it mirrors the phone rather than working on its own.
• Threema Web installs nothing. It runs in most browsers and, like the 1.0 app, depends on the phone staying connected. In feature terms Threema describes the 1.0 desktop app and the web client as identical, since they share one architecture.

The Android package is the odd one out. Because native Windows, macOS and Linux builds exist, running the mobile package inside an Android emulator on a PC buys nothing: an emulated install is a separate Threema installation needing its own Threema ID, and Threema's own setup instructions cover only the desktop app and the web client. Install the Android version on a phone or tablet, and link the computer to it.

What a linked computer can and cannot do

With the 1.0 app or Threema Web you get full access to chats, contacts and media files, and everything between phone and computer stays end-to-end encrypted. Nothing is left behind afterwards: when the session is closed, the synchronised messages are deleted immediately on the computer. Private chats are the exception in both cases, as Threema only displays them on mobile devices.

The multi-device beta trades some features for independence. Messages exchanged before you linked the computer are not shown there, sending and receiving locations is not yet supported, contacts can be added and edited but not deleted, the Do Not Disturb setting is ignored, and Perfect Forward Secrecy is not applied while the beta is linked. On Linux, voice messages recorded in the desktop app go out as ordinary audio files. Interface language is English or German only. One-to-one calls also cannot be started from the new desktop app yet; Threema suggests creating a group with just you and that contact and placing a group call.

There is no separate desktop account. The computer borrows the identity of the linked phone, Threema must stay installed on that phone, and messages sent or received show up on both devices. Threema recommends opening the app on each device at least once a week while online so that nothing is left undownloaded.

What Threema's desktop builds need

Threema states that the desktop app runs on current 64-bit versions of Windows (10, 21H2 or newer), macOS and Linux. Mac downloads are split between Apple-chip and Intel builds. On Linux, the 1.0 app is offered as DEB and RPM packages, while the multi-device beta is distributed through Flatpak, so Flatpak has to be set up for your distribution first. Threema publishes no RAM or disk-space figures for the desktop clients.

The phone side has its own floor: the multi-device beta requires Threema 6.0 or later on Android, or 6.4 or later on iOS. If group calls are part of the plan, outgoing UDP ports 22500 to 22532 need to be open on the network.

Where linking and syncing go wrong

The computer will not reconnect to an existing session. Threema attributes this to push notifications failing or to the app's background activity being restricted on the phone. On Android, exclude Threema from battery optimisation and lock it in the task manager so the system stops closing it.

Old conversations are missing on the desktop. In the multi-device beta, only messages exchanged after linking appear. The history stays on the phone; use the 1.0 desktop app or Threema Web in parallel if you need to see and send things the beta does not handle, such as locations.

The phone keeps announcing messages you already read on the computer. This is a known beta limitation. Opening the affected chats on the mobile app marks them as read.

The Windows installer download fails or stalls. Threema advises fetching the Windows build with a browser other than Microsoft Edge, for example Firefox.

Nothing connects on a company network. Enterprise proxies that do network-based content filtering are generally not supported by the beta.

The desktop app broke after a phone change. Moving Threema to a new handset unlinks the desktop app and can leave the mobile app misbehaving. Remove the linked device on the old phone before the move, then add the computer again from the new phone.

FAQ

Does Threema on a PC still need my phone?

Yes, in every case. Threema Web and the current desktop app require the mobile device to be switched on and connected during the session. The multi-device desktop app works while the phone is off, but Threema must remain installed on that phone and the two stay linked.

Can I place a Threema call from the desktop app?

Group calls, including video, can be started and joined in Threema's new desktop app. One-to-one calls use different technology and are still in development for desktop; the workaround Threema suggests is a group containing only you and the person you want to reach.

How many computers can use one Threema ID?

The multi-device desktop app supports one mobile device plus up to two computers. Threema says support for more linked devices, including tablets, is planned.

Why don't my private chats appear on the computer?

By design. Private chats are shown only on mobile devices, not in the desktop app or the web client.

Is the Android package in an emulator a reasonable substitute?

No. Threema publishes native builds for Windows, macOS and Linux, and an emulated Android copy would be a separate installation with its own Threema ID rather than a linked view of your existing account.