Mandatory for many drivers: What does the blue sticker on the rear window mean?. Since August 1, 2021, the sticker is only mandatory for commercial driving service providers.
In practice, this affects companies such as Uber, FreeNow and Bolt. The clearly visible sticker makes it easier to identify the vehicles. The sticker also signals that the vehicle has undergone a TÜV test. The driver also has to pass tests to get the sticker, namely a health check and a background check. The absence of such a blue sticker should serve as a warning signal to all passengers.