FIDELIO is a utility app designed for experienced users and developers seeking to leverage advanced functions of the German identity card. This application integrates the traditional online features of the German ID with the FIDO U2F authentication protocol, ensuring that personal data such as name and address are not accessed during the authentication process. Instead, it utilizes a pseudonym to derive keys, enhancing user privacy. The app operates alongside the Google Authenticator and supports U2F-compatible websites using Chrome or Firefox with an additional plugin.

The FIDELIO app provides a significant advantage by enabling user verification through an eID-PIN, rather than relying solely on the physical presence of a token. Furthermore, it includes a central hotline for blocking the ID in case of theft or loss. Users must ensure their device supports NFC functionality and is free from interference from metallic objects to ensure optimal performance. The app is open-source under the EUPL1.1 license, with its source code available for review.