Threema is an end-to-end encrypted instant messaging application for iOS, Android and Windows Phone.The software is based on the privacy by design principles and the service doesn’t require users to provide a phone number or any other personally identifiable information: The Threema app can be used anonymously.In addition to text messaging, users can make voice calls, send multimedia, locations, voice messages and files. Using the web app “Threema Web,” the service can be used on PCs.Threema is developed by the Swiss company Threema GmbH. The servers are located in Switzerland and the development is based in Pfäffikon SZ. As of April 2017, Threema had 4.5 million users. As of January 2019, the business version, Threema Work, was used by 3.000 companies and organizations.