How does Google identify user-interests for showing interest based Ads?

I wonder how does Google tracks and identifies user interests for displaying its users, interest based ads?

For ex: If I visit Amazon and browse for few minutes and then visit to another completely different website then Google shows me Amazon ads, how will it come to know that I had visited

As per my knowledge Amazon nor uses Google any intergrations such Google Analytics, Sign-in using Google, nor Adsense by Google.

And even cross-site cookie fetching is not possible.

The how do they do it?

Thank you :blush:

Any time you search google, you tell it your interests. Any time you browse a site which uses analytics, fonts or tag manager google knows you are on the site and what you are looking at.

And even cross-site cookie fetching is not possible.

The trick is that it’s not cross-site. When you visit a page that runs google analytics it downloads the google analytics javascript from

I did an experiment to prove this and documented my findings here:


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