§ 01
Definition
Every network card has a MAC address that used to be broadcast unchanged everywhere. Shops, venues and Wi-Fi analytics firms used it to recognise returning devices. Apple calls the feature 'Private Wi-Fi Address' (iOS 14 and later), and Android uses a randomised MAC by default since Android 10.
§ 02
How it works
The device generates a random address per network, and some systems rotate it over time. Only the local network sees the MAC; it never travels over the internet, so websites cannot see it either way.
§ 03
Why it matters
It is a separate layer from a VPN: a VPN hides your traffic and IP from the Wi-Fi operator, while MAC randomization stops the operator recognising your device. Leaving both on is a sensible default for public Wi-Fi.