Did not know this. I figured all those wifi connections I get near stoplights were slurping up mac addresses to track people. I wonder if it generates a mac address every single time or just upon first interaction with a wifi network it doesn't know about?
Apparently the initial implementation (iOS 8) randomized it every time the screen sleeps or wakes. I wasn't able to find any recent documentation detailing the current behavior - probably similar?
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iOS uses a randomized Media Access Control (MAC) address when conducting
Wi-Fi scans while it isn’t associated with a Wi-Fi network. These scans could
be performed in order to find and connect a preferred Wi-Fi network or to
assist Location Services for apps that use geofences, such as location-based
reminders or fixing a location in Apple Maps. Note that Wi-Fi scans that happen
while trying to connect to a preferred Wi-Fi network aren’t randomized.
