End-to-end encrypted video calls: Signal and Threema compared

An end-to-end encrypted video call lets the participants decrypt the audio and video, not the provider. Signal and Threema both document end-to-end encrypted one-to-one calls.

In short:

• Group sizes differ. Signal group-chat calls support 75 participants versus Threema group calls at 16 for Private or 32 for Work and OnPrem.
• Links need Signal. Signal call links let other Signal users request entry with optional approval.
• Participants can disclose content. Someone you've admitted can share or record what they see and hear.

Choose the call mode you need

Choose by the call mode, group size and joining rules, using these documented options.

Signal's limit of 75 applies to its group-chat calling documentation. Its call-link page doesn't give a capacity specifically for link-based calls, so don't transfer that limit to links. Threema uses a Threema ID as your unique identifier instead of a phone number.

Keep an existing Signal setup when its group size or link-based joining fits your calls. Keep Threema when its ID-based calling and your edition's group capacity fit. Neither needs replacing just because both offer end-to-end encryption.

Who can decrypt your call

End-to-end encryption (E2EE) encrypts call content for the participants' devices, also called endpoints. That's different from encryption only between your device and a provider's server, where the provider could decrypt the content.

Signal's privacy policy explicitly says it cannot decrypt or otherwise access call content. It also says its servers store technical information, including keys and tokens needed to establish calls and transmit messages. Its provider-access statement isn't a claim that its servers store no keys of any kind.

Threema documents E2EE for both one-to-one and group calls. A direct connection doesn't itself prove E2EE, and routing through a relay server doesn't itself mean the provider decrypts the content. The route and the content's encryption are separate questions.

Direct connections and address exposure

Threema uses a direct device-to-device connection for one-to-one calls when possible. Calls involving verification-level-1 IDs use its server route to obscure the Internet Protocol (IP) address. You can also choose server routing for all one-to-one calls.

Threema group calls use a server route that obscures participants' IP addresses from one another. The one-to-one routing option doesn't change that group-call route. This peer-address protection is separate from what an admitted participant can see and hear.

Check who can join and what they see

Admission rules decide who gets access to the encrypted call's content.

For a sensitive Signal link call, require approval before admitting people. Waiting users don't receive anyone else's audio or video, and participants don't receive theirs. Previously approved users can be automatically approved when they request entry to a later call on the same link. Don't treat a reused link as a fresh identity check each time.

Signal's documentation includes removal as an exception to automatic approval, but don't rely on a particular removal-and-rejoining sequence as your privacy control. Check who is actually on the call before sharing sensitive content.

In Signal link calls, everyone receives your profile name and photo, including people who join after you. They also learn your phone number if “Who can see my phone number” is set to “Everyone”. Threema's group-call page doesn't establish matching profile-disclosure or approval rules, so don't infer either their presence or absence from Signal's documentation.

What a recording can still expose

E2EE doesn't stop an admitted participant from recording or sharing the call. They receive usable audio and video and could use another device to record the screen or room. This applies to both options, regardless of whether either app has a built-in recording tool.

A participant-made recording is a separate copy that needs its own protection during storage and sharing. Agree on recording before you share sensitive content, and check the participant list. Encryption protects the call content from the provider, not from someone you've allowed to receive it.

These calling documents don't establish either vendor's built-in recording support, recording notifications, operating-system capture restrictions or transcription features. They also don't establish encryption for saved recordings. Don't assume either app blocks recording or protects a copy after someone saves it.

Where doxx.net fits. doxx.net offers end-to-end encrypted chat as an optional channel for communication around your calls, not a verified video-conferencing replacement. Its privacy scope distinguishes network activity logs, which it does not keep, from account records. If that fits your needs, you can create a doxx.net account, download the app and connect a device to its private network.