Overview
- Apple published a WebKit blog post on Monday, October 19 that explains iOS 27, iPadOS 27, macOS 27 and visionOS will block network calls to identity‑resolution infrastructure at the domain level.
- Identity resolution is when companies collect emails or other identifiers from a site, convert them into persistent IDs, and use those IDs to match the same person across many websites to build an identity graph for ad targeting.
- Early rollouts cut off domains for vendors including LiveRamp, ID5, Permutive and Audigent and briefly blocked The Trade Desk’s ad‑serving domain, which Apple restored after the company said it was caught up by accident.
- Apple can update the block list dynamically without an OS release and gives no public criteria for inclusion or removal, leaving publishers and ad tech firms uncertain and testing server‑side workarounds and measurement fixes.
- The change continues a years‑long shift away from cookie tracking that started with Safari’s ITP and iOS App Tracking Transparency and could shrink addressable audiences on the open web, push ad dollars to logged‑in platforms, and strain publisher revenue and fraud controls.