Safari on iOS 27 blocks The Trade Desk and identity trackers, and an iOS 27.2 beta loosens one block

Since iOS 27 arrived on September 14, Safari on iPhone and iPad has stopped talking to a short list of advertising and identity companies. Apple never announced the change. It surfaced through a WebKit bug report filed by an engineer at The Trade Desk, was first reported by AdExchanger on September 29, and has become the talk of Advertising Week New York this week, according to Digiday.

The newest development: Apple appears to have taken The Trade Desk's ad server off the list in an iOS 27.2 test build, while leaving the identity companies blocked.

What Safari is blocking

The list comes from Ian Meyers, The Trade Desk's senior director of engineering, who filed WebKit bug 324771 on September 21. He wrote that Safari 27 shipped with these domains marked as always blockable:

• The Trade Desk: adsrvr.org, its ad request and delivery domain, plus uidapi.com for the Unified ID 2.0 program it backs
• ID5: id5-sync.com and eu-1-id5-sync.com
• LiveRamp: rlcdn.com and pippio.com
• Permutive: permutive.com
• Audigent (Experian): ad.gt

The list also contains tainted.example, a reserved test domain. Apple hasn't confirmed the contents or explained how domains get added.

According to an analysis of the public WebKit code by PPC Land, the check was added in an 11-line change merged in February, and the actual list lives in a private Apple file that isn't in the open-source repository. It applies to an entire registrable domain, so every subdomain is caught, and it targets cross-site requests made from inside a page. Visiting one of these sites directly isn't affected. Because every iPhone browser has to use WebKit, Chrome, Firefox, and other browsers on iOS 27 are affected too.

Most of these companies sell ways to recognize the same person across different websites, a business that grew after Safari began blocking third-party cookies by default in 2020. That's why Meyers argued in the bug that adsrvr.org didn't belong on the list: it serves The Trade Desk's ads, not just identity matching. With it blocked, the company couldn't serve ads in Safari on updated iPhones at all. In a test on a Yahoo article attached to the bug, The Trade Desk's bids were blocked while Google's went through, AdExchanger reported.

The Trade Desk gets a reprieve, identity firms don't

On October 5, Apple's John Wilander replied in the bug thread that a new iOS 27.2 beta had gone out that day and asked Meyers to test it. Meyers answered that he could see "the changes in the 24B5099f build." Neither comment says what changed, and the bug is still open.

Digiday filled in the gap on October 7, reporting that The Trade Desk's ad server is now off the list in a test version of iOS. People on the current release won't get that fix until the end of the month at the earliest. The identity companies have no such reprieve. Digiday notes that Apple doesn't compete with them directly and can defend blocking them on privacy grounds, while keeping a rival's ad delivery blocked could have exposed Apple, which runs its own ad business, to accusations of abusing its position.

A bigger list may be coming

AdExchanger reported on October 2, citing two sources, that Apple is preparing a much longer list covering hundreds of data brokers, customer data platforms, and ID graph operators. New WebKit code (pull request 74381) replaces the built-in domain list with a rule list that Apple's WebPrivacy service supplies and can refresh, which would let Apple add or remove companies without a software update.

There's little sign of a wider block yet. Digiday said a test of more than 70 ad-tech domains found only the original handful blocked, with LiveIntent, Lotame, and Yahoo's ConnectID loading normally. According to Digiday, the dynamic-list code hasn't shipped.

What it means for you

There's nothing to turn on. The blocking happens automatically in Safari and other browsers on iOS 27 during regular browsing, as The Trade Desk's own test showed, and websites still load. You may see fewer ads built on cross-site profiles, and publishers may earn less from Safari readers as a result.

Apple is also keeping an eye on how other companies behave inside Safari in other ways. iOS 27.2 beta code lets Safari log Google's prompts to switch to Chrome. The update is on its third developer beta, alongside changes like per-type switches for Messages suggestions and a reworked Apple Books reading view.

Apple didn't respond to requests for comment from AdExchanger or Digiday.

Sources

• WebKit Bugzilla, bug 324771, "Inclusion of adsrvr.org in IS_REQUEST_UNCONDITIONALLY_BLOCKABLE domain list," filed September 21, 2026
• AdExchanger, James Hercher, "Apple's Latest Operating System Blocks The Trade Desk From Serving Ads On Safari," September 29, 2026
• AdExchanger, James Hercher, "Apple Has Far-Reaching Plans To Block Hundreds Of Programmatic Data Companies From iOS," October 2, 2026
• Digiday, Ronan Shields, Seb Joseph, and Krystal Scanlon, "Apple's secret blocklist is the talk of Advertising Week New York (mostly off the record)," October 7, 2026
• PPC Land, Luis Rijo, "Safari 27 blocks The Trade Desk's ads via 11 lines WebKit merged in February," 2026
• PPC Land, Luis Rijo, "Trade Desk to test iOS 27.2 beta as Safari ad-domain ticket stays open," October 6, 2026
• GitHub, WebKit pull request 74381, "Block requests with a WebPrivacy provided content rule list instead of a network process check"