[riku_iki]

> I don’t think Google has a secret back door tracking mechanism their ad network is able to use.

they have 80% population using search, youtube, storing browsing history etc while logged into google account, so they have lots of data about most of the people.

[afavour]

Right but that’s not a secret back door tracking mechanism. It’s a pretty blatant one!

My point is that even this blatant logged in user tracking won’t be able to use user agent strings to track either.

[riku_iki]

yeah, no need some secret backdoor..

[asddubs]

you're the one who introduced the concept of it being secret, your quote just said they have access

[afavour]

> you're the one who introduced the concept of it being secret

There is no publicly known method by which Google’s ad network is able to siphon extra data from Chrome users for targeting etc. If there is one, as OP’s friend suggested, definitionally it must be secret.