A simultaneous smartphone shock is coming for Brits

By Trevor Mogg Published July 8, 2025

Imagine the cacophony of some 85 million smartphones all going off at once. Well, that’s precisely what’s going to happen in the U.K. in September.  

It’s part of a test of the U.K.’s emergency alert system, and will involve the phones vibrating and making a siren sound for 10 seconds. The handsets will also show a message, though the precise wording has yet to be revealed.

The alert will go out across the country at 3 p.m. on September 7, with trains, buses, parks, beaches, and other communal spots set to erupt in a deafening chorus of tens of millions of phones all blaring at once. Orderly librarians will just have to suck it up. 

The alerts are used by the authorities to deliver urgent information directly to mobile devices during emergencies such as severe weather events and terrorist attacks, with instructions given on how to best protect lives and/or property.

While the test will be conducted nationwide, the system can be used to target particular areas, depending on the precise nature of the emergency. In December 2024, for example, people in several parts of the U.K. received alerts about extremely strong winds that were incoming. Another local alert was sent last year following the discovery of a World War II bomb in a busy part of Plymouth, about 190 miles west of London. 

Many other nations operate similar emergency systems and run regular tests, including the U.S. and Japan. Some countries, such as Finland, test their systems monthly, while others, like Germany, carry out the procedure annually. 

Lawmaker and senior government member Pat McFadden said: “Emergency alerts have the potential to save lives, allowing us to share essential information rapidly in emergency situations including extreme storms. Just like the fire alarm in your house, it’s important we test the system so that we know it will work if we need it.”

 U.K. officials will be hoping that September’s test goes more smoothly than the first one that it conducted two years ago. In that one, some people received the alert earlier than expected, while some failed to get it at all. 

While the government recommends that Brits keep the emergency alerts function enabled, it is possible to opt out of receiving them.