In the absence of third-party cookies, which approach can help measure and optimize campaigns without sharing user-level data across sites?

• A. Cross-site data leakage
• B. Cohort-based targeting
• C. Simple one-size-fits-all banners
• D. Manual A/B testing only

Answer: (B)

When third-party cookies aren’t available, measuring and optimizing campaigns across sites relies on grouping users into cohorts rather than tracking individuals. Cohort-based targeting defines groups by shared characteristics or behaviors and analyzes performance at the group level. This lets you attribute outcomes, compare results across sites, and refine bids, messaging, or targeting by cohort, all without moving or linking single-user data between sites. Because data stays aggregated, it preserves privacy and complies with restrictions on cross-site data sharing.

Other approaches either risk exposing or distributing user-level data, offer little cross-site measurement or personalization, or depend on one-off experiments that don’t scale across multiple sites in a privacy-friendly way.