Your Mac uses Bluetooth to broadcast its location information after you turn on Find My when it’s offline or in sleep mode. This is part of the Find My network, which is an encrypted, anonymous network of hundreds of millions of Apple devices that can help you locate your device, even when it’s offline1. When your Mac is offline or in sleep mode, it sends out a secure Bluetooth signal that can be detected by other Apple devices nearby. These devices relay the location of your Mac to iCloud so you can view it in the Find My app2. The other options, Ultra Wideband (UWB), Emergency SOS, and Wi-Fi, are not used by your Mac to broadcast its location information in this scenario. References: 1 About the Find My network - Apple Support 2 Locate a device in Find My on Mac - Apple Support