Amazon has blocked Google's FLoC technology from its services, preventing the system from collecting user data across WholeFoods, Zappos, ShopBop and GoodReads.
FLoC (Federated Learning of Cohorts) is Google's proposed replacement for third-party cookies in Chrome. Rather than tracking individual users, the system groups people into anonymous cohorts based on browsing behavior, then serves ads to the cohort instead of the profile. Google frames this as privacy-forward targeting. The implementation requires only an HTTP header: Permissions-Policy: interest-cohort=().
Amazon's block reflects a straightforward business calculation. As one of the world's largest ad platforms, Amazon guards its first-party purchase data—its primary competitive asset. Allowing Google to build cohorts from Zappos or WholeFoods traffic would hand a rival signals Amazon carefully accumulates within its own ecosystem.
Amazon is not alone. WordPress, which powers a significant share of the web, has also blocked FLoC. Brave, Firefox and Safari declined to implement it. UK regulators opened a probe into whether FLoC breaches competition law. Each player protects its own interests: user data, ad revenue, or market position.
While FLoC remains in origin trial, practical impact on campaigns is limited. But the fragmentation signals how the shift away from cookies will unfold: no single standard, only proprietary solutions built on first-party data. For arbitrageurs, this means contextual targeting regains ground, direct partnerships with authenticated audiences outperform third-party networks, and diversifying traffic sources reduces reliance on any single browser mechanism.
