Bluetooth

Bluetooth is a wireless standard for connecting devices that are close to each other, typically within about ten meters. It is what links your phone to wireless headphones, a smartwatch, a car's audio system, a keyboard or a mouse, with no cables and no need for Wi-Fi or an internet connection. Devices from different brands work together because they follow the same specification, managed by an industry group called the Bluetooth SIG.

Before two devices can talk, they pair: you confirm on both that they may connect, they exchange keys, and from then on they recognize each other and reconnect automatically. Bluetooth shares radio frequencies with many Wi-Fi networks and hops quickly between many narrow channels to dodge interference. Over the years it has become faster and more efficient, and newer versions add better audio and longer range.

A low-power variant, Bluetooth Low Energy (BLE), is made for devices that send small amounts of data now and then and must run for months on a tiny battery: fitness trackers, item finders, medical sensors, smart locks. Phones also use it to discover devices nearby. One practical note: range and quality depend a lot on walls, other radio noise and even your own body, which is why audio can stutter when the phone is in a back pocket.