SoK: Advances and Open Problems in Web Tracking

TL;DR

This paper provides a comprehensive overview of the evolution, techniques, countermeasures, and regulatory landscape of web tracking, highlighting current challenges and future research directions in this complex field.

Contribution

It consolidates fragmented research on web tracking into a unified framework, analyzing technical mechanisms, countermeasures, and regulations, and identifying open challenges and future directions.

Findings

Web tracking techniques have become increasingly sophisticated.

Browser anti-tracking measures are impacting tracking practices.

Regulatory enforcement is shaping the future of web tracking.

Abstract

Web tracking is a pervasive and opaque practice that enables personalized advertising, retargeting, and conversion tracking. Over time, it has evolved into a sophisticated and invasive ecosystem, employing increasingly complex techniques to monitor and profile users across the web. The research community has a long track record of analyzing new web tracking techniques, designing and evaluating the effectiveness of countermeasures, and assessing compliance with privacy regulations. Despite a substantial body of work on web tracking, the literature remains fragmented across distinctly scoped studies, making it difficult to identify overarching trends, connect new but related techniques, and identify research gaps in the field. Today, web tracking is undergoing a once-in-a-generation transformation, driven by fundamental shifts in the advertising industry, the adoption of anti-tracking countermeasures by browsers, and the growing enforcement of emerging privacy regulations. This Systematization of Knowledge (SoK) aims to consolidate and synthesize this wide-ranging research, offering a comprehensive overview of the technical mechanisms, countermeasures, and regulations that shape the modern and rapidly evolving web tracking landscape. This SoK also highlights open challenges and outlines directions for future research, aiming to serve as a unified reference and introductory material for researchers, practitioners, and policymakers alike.