Blocking Identity Resolution Infrastructure

Identity resolution is a post-cookie tracking technique where third parties invisibly collect identifiers like email addresses when users log in or sign up, exchange them for opaque tracking IDs, and return those IDs to websites. Those IDs are stored and persist even after logout, enabling cross-site and cross-device profiling as the third party accumulates more data into an identity graph. Email addresses and phone numbers are treated as PII and often serve as long-lived global identifiers; when submitted for one purpose they are frequently repurposed without user expectation. Even when matching is used to enable first-party personalization, a central identity resolver acting as a third-party clearinghouse gives multiple sites a tracking capability they would not have independently.

Safari and WebKit now block network access to known identity-resolution infrastructure to prevent those third parties from receiving email addresses and constructing identity graphs. The protection ships in iOS, iPadOS, macOS, and visionOS 27 and is implemented at the domain level so simple request changes cannot evade it. Users with iCloud+ can further protect themselves using Hide My Email, which issues unique randomized addresses per site. This builds on earlier work to block cross-site cookies and partition storage, and reflects a continued commitment to prevent covert cross-site tracking while preserving legitimate first-party personalization.