Here’s what’s going on. Your phone is almost always searching for Wi-Fi networks, even when you’re not actively using Wi-Fi. Every time it does that, it sends out a little digital ping called a probe request. That ping includes your device’s MAC address — a unique ID number that belongs specifically to your phone, kind of like a fingerprint.
Retailers, schools, and other venues can set up small wireless sensors that silently listen for those pings. According to the Electronic Frontier Foundation, companies use these sensors to track the movement of specific devices over time — meaning they can see where inside a building your phone went, how long you stayed in each spot, and when you came back. The Federal Trade Commission has also noted that MAC addresses can be used to link your physical, real-world movements to your online behavior.
This tracking happens without you connecting to anything, agreeing to anything, or even knowing it’s happening. Your phone is doing it automatically in the background because it’s always looking for familiar networks.
There are some things you can do to reduce this. The simplest option: turn Wi-Fi off entirely when you’re not actively using it. You can also go into your Wi-Fi settings and ‘forget’ saved networks so your phone stops broadcasting those network names. Neither fix is perfect, but both reduce how much your phone announces itself.
Worth knowing: many newer phones — including iPhones running iOS 14 or later and most Android 10 or later devices — have a feature called MAC address randomization turned on by default. This rotates the ID your phone broadcasts so it’s harder to track consistently. It’s worth checking your phone’s Wi-Fi settings to confirm it’s enabled on yours.
The single most important thing to take away: your phone is talking to the room even when you’re not on Wi-Fi. Turning off Wi-Fi when you’re not using it is the simplest way to quiet it down.