Safari does more than other browsers to prevent cross domain tracking. 3rd party cookies disabled by default, cookies in iframes considered 3rd party (so, blocked), and TIL it maintains a separate local cache for each domain to prevent fingerprinting a user across domains. I have a hunch you could probably drop 3rd party cookies using a <video> element (maybe for DRM stuff? Just a hunch I have because video-ad CPMs are consistent or better on iOS over android/desktop indicating perhaps advertisers know the user somehow). Awesome article, great reference links, super interesting!