When Sally Met Trackers: Web Tracking From the Users' Perspective

Web tracking has evolved to become a norm on the Internet. As a matter of fact, the web tracking market has grown to raise billions of dollars. Privacy cautious web practitioners and researchers extensively studied the phenomenon proving how widespread this practice is, and providing effective solutions to give users the option of feeling private while freely surfing the web. However, because all those studies looked at this trend only from the trackers' perspective, still there are a lot of unknowns regarding what the real impact of tracking is on real users. Our goal with this paper is to fill this gap in the web tracking topic. Thanks to logs of web browsing telemetry, we were able to look at this trend from the users' eyes. Precisely, we measure how fast a user encounters trackers and research on options to reduce her privacy risk. Moreover, we also estimate the fraction of browsing histories that are known by trackers and discuss two tracking strategies to increase the existing knowledge about users.