What is it about?
Many websites rely on advertising that uses browser cookies to recognize users across websites and show more relevant ads. This study uses a large real-world experiment to test what happens to website ad revenue when those cookies are removed and privacy-friendly alternatives take their place. The results show how hard it is to protect privacy while preserving the ad revenue that supports online content.
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Why is it important?
Many websites rely on advertising to fund their content, but online ads often depend on tools like browser cookies that raise privacy concerns. As regulators seek to improve privacy by restricting these tools, tech companies like Google have explored privacy-enhanced alternatives. Our study shows that this transition is difficult: removing cookies sharply reduced website ad revenue, while Google’s alternative recovered only a small share of the loss.
Perspectives
Major digital platforms often control the data needed to evaluate them, which makes independent oversight difficult. For us, one of the coolest parts of this study is the open experiment that generated its evidence. The UK competition regulator and Google created a novel experiment that allowed outside firms and researchers to measure real-world outcomes. We see this as a promising model for platform accountability—especially when platform decisions can affect competition, privacy, and the websites people rely on.
Garrett Johnson
Boston University
Read the Original
This page is a summary of: Can privacy technologies replace cookies? Ad revenue in a field experiment, Proceedings of the National Academy of Sciences, May 2026, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2603752123.
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