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Maps and YouTube are from the same developer which means they're allowed to setup shared storage on your device and in iCloud, and google surely uses that to store a unique identifier. So there's nothing you can do to stop them being linked.

For safari, they do that by setting a cookie and comparing it with your IP address. Once you use a google service in safari from a few different IP addresses, and also use maps or youtube in those locations, they correlate the data and uniquely identify you from then on. Safari will block this technique on iOS 15 if iCloud Private Relay is enabled.

Thank you sir, it’s always nice to have someone who understands better this, to explain it.

By the way, if I only use YouTube from Safari without logging in, and no Google Apps on my iPhone, can I still be accurately tracked? Oh and I use DuckDuckGo as a search engine by default, except for a couple of searches per month that I need to use Google.
 
Plot twist: the real-time location sharing is for sharing your location directly to advertisers.
 
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