What is the emergency alert in the UK?

Did you get a strange, loud alarm on your phone in September 2025?

The UK government conducted a test of its emergency alerts system on 7 September. Around that time, most smartphones across the country made a loud, siren-like sound for roughly 10 seconds.

When an event like this happens, misinformation and rumours can spread fast. Some posts claimed it was a sneaky way for the government to spy on your phone or that the alarm would still go off even if your phone was switched off. So what was the truth behind those claims?

Emergency alerts are official warnings sent directly to mobile phones by the UK government or emergency services. These alerts are designed to warn the public about life-threatening emergencies, such as severe flooding, fires, or extreme weather events.

When the alert sounds, your phone makes a loud, siren-style noise for about 10 seconds. A message also pops up on your screen explaining that it’s a test, and what you need to do if it was real.

Here’s what to expect:

• Your phone will emit a loud, siren-like sound.
• A message will pop up saying it’s a test.
• Your phone might buzz or vibrate too.

The alert is not a text or email people need to reply to, it pops up as a notification on screen. All people have needed to do so far is to acknowledge it, then swipe it away to carry on using their phone as normal.

In a real emergency, the alert would include clear instructions, like staying indoors or avoiding certain areas.

And despite some of the rumours you may have heard, alerts don't affect store opening times, Wi-Fi, or headphones. It’s a short, one-time test.

It’s true! Even if a phone is on silent, an alert still makes a noise (worth thinking about if one is ever scheduled when you are in the cinema).

But if your phone is switched off or in airplane mode, you don’t get the alert at all. It only comes through when a phone is on and connected to a mobile network (Wi-Fi doesn’t count).

Not all phones could get the September 2025 alert.

It only worked on 4G and 5G smartphones that support the technology. Anyone with older phones, or those that weren't smartphones, wouldn't have heard a thing.

It’s fake news! The government doesn’t know your phone number or your exact location. They’re not tracking you.

The alert works by using mobile phone towers in the area, which sends a message to all phones nearby. It doesn’t matter who you are, if your phone is connected for future alerts, you’ll get one.

BBC Bitesize Other Side of the Story contacted the Cabinet Office, which supports the Prime Minister and ensures the effective running of government, to confirm what happens when the alarm is sounded. Pat McFadden, Chancellor of the Duchy of Lancaster and a senior minister in the Cabinet Office, told us: "Emergency alerts do not need personal information, such as your telephone number, identity or location.

"When you tune into an AM/FM radio station, their output is broadcast without collecting any data about you. Similarly, emergency alerts are one way and do not provide any data to the Government or mobile network operators about you, your location or whether your phone has received an emergency alert."

If you’re on the phone to your mate when a future alert sounds, the alert won’t cut off any existing phone calls, so you can carry on as normal. If they follow the same procedure as the 2025 alert, other notifications will come through like texts or snaps, but to see them or answer a call, you would need to clear the alert first by tapping it away.

Speculation can spread quickly online . It’s important not to believe everything you see or hear on social media. Before you trust a post, make sure the info’s coming from an official source such as gov.uk, trusted news outlets, or verified accounts, and not just memes or random TikToks.

By staying informed, you’re helping to stop false information from spreading. So before you like, comment, or share, pause, double-check, and make sure it’s true before sharing.

This article was updated in September 2025