At 3 pm today (Sunday, September 7), Brits up and down the UK will have seen their phones emit a loud siren-like sound, as the government tests out a nationwide test of an early warning system.
In what marks the second national test of its kind, almost everyone with a mobile phone or tablet received the alert, which is intended to warn Brits of potentially life-threatening disasters such as extreme weather events or terrorist attacks.
It's anticipated that nearly 100 million phones will have received today's alerts. But not everyone will have been alerted, causing some confusion. Here's why your phone may have remained silent, even as friends and family members' devices sounded out.
READ MORE: Emergency alert LIVE as warning sent to almost all mobile phones

Approximately 95 per cent of the population will have had the 4G or 5G access required for today's test, while those with older phones connected to just 2G or 3G, or WiFi only, won't have received a message. You also won't have been alerted if your device was switched off or in aeroplane mode at the time. Having had it on silent wouldn't have made a difference, as domestic abuse survivors with secret phones were previously warned.
It's understood that the emergency alert will only have worked on iPhonesrunning iOS 14.5 or later, as well as Android phones and tablets running Android 11 or later. If your phone or tablet isn't running the latest software updates, then you may not have alerted.
Today's test alert marked the second-ever for Brits, with the first one taking place a couple of years back, in April 2023. The first time around, phone users received the same advance warning; however, it was discovered that some devices failed to receive the warning, which could well mean the difference between life and death during dangerous real-world situations.
Although emergency alerts have been mostly popularised as tests, they have also been previously used during emergency situations. In 2024, the system was used on multiple occasions. In January of that year, Leicestershire residents were warned of adverse weather conditions, while in February, the alert helped to aid the evacuation of some 10,000 Plymouth residents after an unexploded World War II bomb was discovered. A few months later, in May 2024, Cumbrian residents were alerted to dangerous flooding.
Those who have received today's alert will have also been sent the following explanatory message: "This is a test of Emergency Alerts, a UK government service that will warn you if there's a life-threatening emergency nearby. You do not need to take any action. In a real emergency, follow the instructions in the alert to keep yourself and others safe."
For additional details on the UK's emergency alerts, visit GOV.UK.
Do you have a story to share? Email me at julia.banim@reachplc.com
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