When you visit a web page, there's a better-than-even chance Google knows about it (GOOGL)

Google and Facebook dominate digital advertising, so it's no surprise they're also the leading companies in tracking what you do online.Ghostery, a company that makes a web browser add-on that allows users to see who is keeping tabs as they go from site to site, recently confirmed it.

Ghostery conducted a study to see which companies do the most tracking, looking at online activity from numerous countries around the world. As we can see in this chart from Statista, Google easily took the prize for tracking activity, with Facebook a distant second.

Tracking allows such companies to serve up personalized ads; they're why you might see a shoe ad days or months after shopping for shoes online. But they also allow those companies to create detailed profiles of us — often times without us realizing it or wanting them to do so.

Mike Nudelman/Business Insider

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