Unless there's techniques I'm unaware of, I assume you're talking about MAC address-based tracking? Apple has been working to eliminate that; they've been using

Unless there's techniques I'm unaware of, I assume you're talking about MAC address-based tracking? Apple has been working to eliminate that; they've been using randomized addresses during scanning since iOS 8. The other possibility here is tracking via geolocation or iBeacon, which require an app with location services/bluetooth enabled. And in those cases the tracking is most likely based on Apple IDFA/Google Advertising Id, so you at least have the option to opt out: https://dev.twitter.com/mopub/ui/opting-out-interest-based-advertising https://dev.twitter.com/mopub/ui/opting-out-interest-based-a... (assuming the app properly respects the setting).