Safari 27's identity blocklist hit an ad server, and the fix is in beta
A WebKit bug shows Safari 27 blocked The Trade Desk's ad domain; Apple marked it resolved after an iOS 27.2 beta.
Apple · Macfolio · 10 October 2026
Safari 27, released September 14, includes a built-in list of domains that WebKit blocks unconditionally. According to a public WebKit bug, that list included adsrvr.org, the domain The Trade Desk uses to request and deliver ads. Apple's WebKit privacy lead marked the bug resolved on October 9 (Pacific time).
What the WebKit bug shows
The Trade Desk engineer Ian Meyers filed the report on September 21. He listed the domains bundled with the change, including uidapi.com, id5-sync.com, rlcdn.com, pippio.com, permutive.com, and ad.gt. He argued that the intent was to block post-cookie identity services, but that adsrvr.org is "core ad request and delivery," not identity.
- February 13: WebKit lands the change to unconditionally block certain domains
- September 14: Safari 27 ships with iOS 27, macOS 27, and other updates
- September 21: The Trade Desk files the bug against iOS 27
- October 5: Apple's John Wilander asks for testing with the new iOS 27.2 beta, build 24B5099f
- October 9: Wilander writes "Confirmed resolved"
AdExchanger reported that identity vendors including LiveRamp, ID5, Audigent, and Permutive were also added. Apple has made no public statement, and the bug does not say exactly what changed.
This does not mean Safari now allows cross-site tracking, or that the other identity domains were removed from the list.
Who should check their numbers
Publishers and marketers who saw Safari ad revenue drop after mid-September may have part of the explanation. The bug was filed against iPhone and iPad. Safari 27 also runs on macOS 27, macOS 26, and macOS Sequoia, but the report does not say whether Mac traffic behaved the same way.
Our take: treat this as a reminder that Apple can change what loads in Safari with little notice. If your business depends on third-party ad tech, test in current Safari releases and betas, and watch WebKit's bug tracker rather than waiting for release notes. Safari 27's release notes do not mention the blocklist at all.
The fix was confirmed against a beta. Until iOS 27.2 ships, most users may still see the original behavior.