You wake up and your smartwatch has already synced with your phone. On the way to work, your phone connects to your car. Later, you put in wireless earbuds. On a crowded bus, dozens of other Bluetooth-enabled devices may be just metres away from yours.

You may not think about Bluetooth at all – it has become an almost invisible part of everyday life.

So what is actually happening when we leave Bluetooth switched on all day? And should we follow official advice that it’s best to turn it off when you’re not using it?

How does Bluetooth work?

Bluetooth is a short-range wireless technology that allows nearby devices to communicate without cables. Your phone might use it to send audio to earbuds, exchange information with a smartwatch or connect to your car.

Before many devices communicate, they go through “pairing”. This means when Bluetooth is on, your phone constantly sends out tiny digital handshakes, basically asking “is there anything I know nearby?”

This establishes a relationship between devices.

Sometimes these relationships can be compromised, although modern Bluetooth security can include authentication, encryption and protection against unauthorised access to information shared between devices. This means having Bluetooth switched on does not normally mean a stranger nearby can simply........

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