Threema is an instant messaging app that generates a unique random ID for each user so that communication does not require a phone number or email address. It supports text, emoticons, voice messages, video calls, file sharing, and group chats across more than 175 regions and countries. All chats and calls are protected by end-to-end encryption that relies on the open-source NaCl cryptography library, with keys created and stored only on user devices. The service stays ad-free and states that it does not collect private data or chat logs. Users can verify contacts by scanning QR codes to reduce man-in-the-middle risks and can switch between light and dark themes or download additional themes from the settings menu.
How does Threema handle privacy when linking or unlinking phone numbers and email addresses?
Because a Threema ID is created independently of any phone number or email, users can add or remove these links at any time through the profile section without affecting the ID itself. Deleting an old number or address simply removes the association, and the same ID remains reachable by contacts who already know it. When a user obtains a new phone number, the old entry can be deleted and the new one added in the profile tab, leaving existing chats untouched. If access to a linked address or number is lost, an online removal option is available provided the user can still confirm ownership of that contact detail.
What backup and recovery options does the app provide for the Threema ID?
Every user is advised to create an ID export or enable Threema Safe immediately after generating a new ID so that the public and private keys can be restored on another device. Threema Safe encrypts the backup with a user-chosen password, applies the scrypt algorithm to derive the key, and then uses XSalsa20 and Poly1305 from the NaCl library for the actual encryption. The resulting file name is also derived from the password, preventing the server from matching a backup to a specific ID. Backups may be stored on Threema servers or on a user-chosen server, and the feature remains optional. Regular profile reviews by the service help maintain account security, yet the responsibility for keeping a usable backup rests with the user.
How do encrypted calls, conference calls, and polls work within the app?
Voice and video calls are encrypted by default once end-to-end encryption is enabled in settings. Conference calls support up to 16 participants on a single encrypted session. Polls can be created inside any group so that members vote on choices such as movie selections, meeting locations, or bill-splitting arrangements. The same encryption that protects one-to-one chats also covers these group features, ensuring that only intended recipients can read the content. Storage management settings allow automatic deletion of older messages by age, and emoji reactions have been added to individual messages.
What group chat and theme features are available, and how are they controlled?
Group chats accommodate hundreds of participants and permit the exchange of text, videos, stickers, and polls. Users can join or leave groups without exposing a phone number or email if they prefer to keep their ID fully anonymous. Theme selection occurs in the settings screen, where a dozen downloadable themes plus built-in light and dark modes can be applied. These visual options do not affect the encryption or data-handling behavior of the app.
Who is most likely to find Threema useful based on its design choices?
People who want messaging that does not tie identity to a phone number or email, who value the ability to verify contacts via QR code, and who need group tools such as polls and conference calls up to 16 people may consider the app. Those who already maintain separate backups or are comfortable managing an ID export will find the recovery process straightforward. Users who prefer an ad-free experience and servers located in Switzerland, along with the option to delete an account and start over with a new anonymous ID, will see these elements reflected in the service description. The presence of a web client and the ability to transfer an account between phones further support users who move between devices while keeping the same ID.