For nearly two years now, Google has been gradually rolling out a feature to all Chrome users that analyzes their browsing history within the browser itself. This feature aims to replace third-party cookies and individual tracking by categorizing you into an interest category and sharing that category with advertisers. It’s like having a function in your credit card account that evaluates your activities to pass on your spending habits to the advertising industry, so they can send you tailored ads. Ironically, it’s called “Privacy Sandbox”. To check if this is enabled in your Chrome or Chromium browser, simply enter chrome://settings/adPrivacy into the address bar (yes, the configuration page is called “Ad Privacy”). However, I wouldn’t even want to have this built into my browser, no matter if activated or not. If you’re not a fan of this, you might want to consider switching to Firefox.
Back in the old days, that used to be how it worked… but soon ad networks learned that showing ads “relevant to the user” had better click-through rates than showing ads “relevant to the content”, with the content becoming only a data point to classify the user for the best ads that might sway them.
Soon after, advertisers caught on the trend, started blindly paying for ads targeted at user profiles, then ad networks stopped showing stats about whether content-targeted or user-targeted ads were getting better conversion rates, and everyone has been coasting on blind faith in “the algorithm” ever since.