With the advent of digitalization, the use of online services for everyday tasks has greatly increased. In this study, we examine privacy of the 500 most popular websites in the world to determine to what extent these websites leak their visitors’ personal data to third parties. We analyze the network traffic of the websites to see whether they leak the URLs visited by the user and search terms. Our findings show that 58.0% of the studied websites leak such personal data to outside actors. These results demonstrate that the user’s privacy is in danger on a large portion of the studied websites. The sheer number of found third-party services on many websites also introduces several challenges concerning sustainability and fair data processing practices.