Web Privacy Census

Most people may believe that online activities are tracked more pervasively now than they were in the past. In 2011, we started surveying the online mechanisms used to track people online (e.g., HTTP cookies, Flash cookies and HTML5 storage). We called this our Web Privacy Census. We repeated the study in 2012. In this paper, we update the study to 2015. Results summary: Our approach uses web crawler software to simulate online browsing behavior, and we record the occurrences of tracking mechanisms for the top 100, 1,000, and 25,000 most popular websites. We found that users who merely visit the homepages of the top 100 most popular sites would collect over 6,000 HTTP cookies in the process (see Top 100 Websites -- Shallow Crawl). Eighty-three percent of cookies are third-party cookies. The homepages of popular sites placed cookies for 275 third-party hosts. In just visiting the homepage of popular sites, we found 32 websites placed 100 or more cookies, 7 websites placed 200 or more cookies, and 6 websites placed 300 or more cookies. We found that Google tracking infrastructure is on 92 of the top 100 most popular websites and on 923 of the top 1,000 websites. This means that Google's ability to track users on popular websites is unparalleled, and it approaches the level of surveillance that only an Internet Service Provider can achieve. -- We repeated a 2012 survey of tracking mechanisms such as HTTP cookies, Flash cookies, and HTML5 storage, used by top 25,000 most popular websites. -- We found that users who merely visit the homepages of the top 100 most popular sites would collect over 6,000 HTTP cookies with 83% being third-party cookies. -- We found that Google tracking infrastructure is on 92 of the top 100 most popular websites and on 923 of the top 1,000 websites, providing Google with a significant surveillance infrastructure online