Overview

• BBK will issue a nationwide probe warning via MoWaS at 11:00 on September 11 with an all‑clear planned around 11:45.
• Multiple channels will be exercised, including Cell Broadcast, warning apps like NINA, KATWARN and BIWAPP, radio and TV, digital displays, Deutsche Bahn systems, sirens and loudspeaker vehicles.
• Cell Broadcast delivers the warning to compatible phones without an app, though it cannot send the all‑clear message in this round.
• Participation by municipalities is voluntary, creating uneven siren coverage, with some places adding first‑time tests and cities like Munich relying on digital channels due to lacking siren networks.
• For reliable reception, authorities highlight current OS requirements (generally Android 11 or iOS 16.1 and newer) and invite public feedback through an online survey at warntag-umfrage.de.