A test alarm caused many mobile phones to ring at 11 a.m. on the nationwide warning day in Germany. The warning was triggered by the Federal Office for Civil Protection and Disaster Assistance (BBK).

For the first time, citizens also received a warning via the cell broadcast system. The test alarm was also distributed via radio and television stations. Anyone who installed warning apps such as Nina or Katwarn on their smartphone also received a notification of the test warning in this way.

With the nationwide warning day, the authority wants to find out how many people a warning of dangers would reach in an emergency. With the cell broadcast method, an automatic notification is sent to every mobile phone that is switched on at the time, has reception and is running the latest software. Because it's just a test, the people who receive the alert don't have to do anything. The all clear was to follow at 11:45 a.m.

A lot went wrong on the first nationwide warning day on September 10, 2020. Among other things, the message from the warning apps Nina and Katwarn only arrived on the smartphones a good half hour late. If it had actually been an emergency, many citizens would not have noticed. The Federal Ministry of the Interior had therefore described the test alarm as "failed".