Hi,

I published a new writing about how Apple’s AirTag works.

It started with a simple question: if AirTag is not a GPS device, how does it know where it is?

In the post, I walk through how AirTag uses Bluetooth, nearby Apple devices, the Find My network, Ultra Wideband, encryption, and safety alerts to make the whole system work.

There is also a rough notes PDF at the end, with my handwritten sketches behind the explanation. I’ll add the separate math PDF later.

You can read it here:

How AirTag Works?