Overview

• Compatible 4G and 5G phones and tablets across the UK will vibrate, sound a distinctive siren for about 10 seconds and display a test message that overrides silent mode.
• Older devices or those on 2G/3G, switched off or in airplane mode, and Wi‑Fi‑only tablets may not receive the alert.
• The government has published the exact test wording, including a link to gov.uk/prepare and a Welsh version, and stresses that alerts are broadcast from masts without collecting personal data.
• The April 2023 national test missed about 7% of compatible devices, with issues traced to specific networks such as Three; officials say those faults were fixed and performance will be reviewed after Sunday’s drill.
• Drivers are urged not to touch phones during the alert due to safety and £200 fine/6‑point penalties, and opt‑out guidance is available, including for people with concealed phones highlighted by domestic abuse charities.