What is Bluetooth and how does it work?

A short invisible cable

Bluetooth is a way for two nearby devices to talk by radio instead of a cable. Your phone uses it to send music to headphones, show messages on a smartwatch, make hands-free calls in a car and share files with a laptop.

Unlike Wi-Fi, which connects you to a whole network and the internet, Bluetooth usually links just two devices directly. Think of Wi-Fi as a road network and Bluetooth as a short garden path between two neighbours.

How pairing works

Before two devices can use Bluetooth, they must be paired. This is a one-time introduction:

1. Put the new device, such as earbuds, into pairing mode. Often you hold a button until a light flashes.
2. On your phone, open the Bluetooth settings and choose the device from the list.
3. Sometimes both screens show a number. Check they match and confirm.
4. From then on, the two devices recognise each other and reconnect automatically.

During pairing the devices agree a secret key, so later conversations between them are encrypted.

Range, power and dropouts

• Range: roughly 10 metres for most everyday devices, often less through walls or your own body. Keeping your phone in a back pocket can cause music to cut out.
• Power: Bluetooth uses little battery, especially the newer "Low Energy" version used by fitness trackers and smart tags.
• Interference: Bluetooth shares the same radio band as some Wi-Fi, so very crowded places can cause stutters.
• One at a time: some headphones only connect to one device at once. If they will not connect, check whether they are still linked to another phone or laptop.

Tip: If a device keeps misbehaving, "forget" it in your Bluetooth settings, turn both devices off and on, and pair again from scratch.

Staying safe with Bluetooth

Bluetooth problems are rare for most people, but a few habits help:

• Keep your phone and accessories updated; makers fix Bluetooth flaws through updates.
• Pair in private where possible, and never accept a pairing request you did not start.
• Remove old pairings, for example a hire car you used on holiday. Cars can also store your contacts and call history, so delete your phone from the car's system before you return it.
• Turn on your phone's setting that hides it from discovery when you are not pairing, if it has one.

Bluetooth in the smart home

Many smart plugs, lights and locks use Bluetooth for setup and then switch to Wi-Fi or a home hub. Item trackers use Bluetooth to report their position through nearby phones. If you ever get an alert that an unknown tracker is travelling with you, take it seriously and follow your phone's instructions to find it.

Want the technical version? Read our note on Wi-Fi and Bluetooth Low Energy.

Bluetooth versions in plain words

You will see version numbers such as 5.0, 5.3 or 6.0 on boxes. Newer versions generally connect faster, reach a little further and use less power, but both devices need to support a feature for you to benefit. Your phone and headphones will simply agree on the best version they both understand, so you do not need to match numbers exactly.