Overview
- The nationwide Warntag will take place on Thursday, Sept. 10, 2026, when sirens, warning apps and the Cell Broadcast system will send synchronized test messages at 11:00 to check reach and functioning across all federal states.
- Cell Broadcast sends a short text and loud tone from a mobile network cell to every device registered in that cell without needing personal data or an app, and it has been active across Germany since February 2023.
- A 2023 update to the DE‑Alert technical guideline (DE‑Alert 1.1) required operators to send highest‑priority German warnings on three‑digit Message‑ID 919 to widen reach to older devices, a change already trialed successfully in 2023.
- The BBK says broadly compatible devices include Apple iPhones running iOS 16.1 or later and Android devices on Android 11 or newer, and some older phones can receive alerts only after users enable three‑digit message IDs or enter channel 919 manually.
- If you miss a test alert the usual causes are an incompatible device or SIM, flight mode or a Wi‑Fi only device, and users who want extra redundancy should install internet‑based apps like NINA or KATWARN because Cell Broadcast messages are not retransmitted later.