google recently provided a chrome extention Ads Transparency Spotlight in an early version that visualize what cookies are used by whom
we’re providing this extension to help increase transparency in digital advertising. In the future, we also plan to add controls for users.
further interessting is the firefox plug Lightbeam that visualise the dependence of tracked cookies in the past
quite more interessting is to display what content is loaded from a reqested website, Requestmap visualise gathered data from visited sites and the third parties
scary hmpf … prevent of tracking with tracking free browser like Brave, Ghostery or DuckDuckGo