Understanding the Performance Costs and Benefits of Privacy-focused Browser Extensions

Advertisements and behavioral tracking have become an invasive nuisance on the Internet in recent years. Indeed, privacy advocates and expert users consider the invasion significant enough to warrant the use of ad blockers and anti-tracking browser extensions. At the same time, one of the largest advertisement companies in the world, Google, is developing the most popular browser, Google Chrome. This conflict of interest, that is developing a browser (a user agent) and being financially motivated to track users’ online behavior, possibly violating their privacy expectations, while claiming to be a ”user agent,” did not remain unnoticed. As a matter of fact, Google recently sparked an outrage when proposing changes to Chrome how extensions can inspect and modify requests to ”improve extension performance and privacy,” which would render existing privacy-focused extensions inoperable. In this paper, we analyze how eight popular privacy-focused browser extensions for Google Chrome and Mozilla Firefox, the two desktop browsers with the highest market share, affect browser performance. We measure browser performance through several metrics focused on user experience, such as page-load times, number of fetched resources, as well as response sizes. To address potential regional differences in advertisements or tracking, such as influenced by the European General Data Protection Regulation (GDPR), we perform our study from two vantage points, the United States of America and Germany. Moreover, we also analyze how these extensions affect system performance, in particular CPU time, which serves as a proxy indicator for battery runtime of mobile devices. Contrary to Google’s claims that extensions which inspect and block requests negatively affect browser performance, we find that a browser with privacy-focused request-modifying extensions performs similar or better on our metrics compared to a browser without extensions. In fact, even a combination of such extensions performs no worse than a browser without any extensions. Our results highlight that privacy-focused extensions not only improve users’ privacy, but can also increase users’ browsing experience.