A Boston University study examines how removing third-party cookies affects online advertising and the broader internet economy. The researchers combined an analysis of 200 million ad impressions with data from ad manager Raptive and a Google-run experiment overseen by the United Kingdom’s Competition and Markets Authority. In that experiment about 60 million desktop and mobile Chrome users were randomly assigned to three groups: cookies-enabled, cookies-disabled, or cookies replaced by Google’s Privacy Sandbox.
Results show removing third-party cookies cut publisher ad revenue by about 35% overall and by about 66% in the European Union, where privacy rules are stricter. Privacy Sandbox — a six-year Google effort that is now defunct — recovered only about 4% of the lost revenue. The authors explain that cookies let advertisers identify users across many sites, which raises ad effectiveness.
Researchers and quoted authors warn that reduced cookie use will likely lower ad effectiveness and the revenue that supports much of the open web. Critics stress the privacy cost, with one researcher calling website cookies online surveillance tools. The BU team notes Google abandoned its plan to replace cookies and says the episode illustrates the difficulty of balancing privacy, performance and competition in digital markets. The research received financial support from the Center for Industry Self-Regulation and appears in PNAS.
- placing paywalls and selling subscriptions,
- requiring log-ins that work across multiple sites,
- developing privacy-enhancing technologies such as Privacy Sandbox
Difficult words
- third-party cookie — small data files that track users across sitesthird-party cookies
- ad impression — one view of an online advertisementad impressions
- ad revenue — money websites earn from selling space to marketerspublisher ad revenue
- defunct — no longer existing or working
- oversee — be responsible for supervising a project or processoverseen
- self-regulation — process where an industry controls its own behaviour
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- Which of the listed strategies (paywalls, cross-site log-ins, privacy-enhancing technologies) seems most realistic to replace lost ad revenue? Explain why.
- How might stricter privacy rules, like those in the European Union, affect small publishers and the open web?
- The article mentions balancing privacy, performance and competition. How should companies weight these priorities when designing online advertising?
