Safari on iOS 27 blocks The Trade Desk's ad domain, and AdExchanger says hundreds more ad data firms are on Apple's listSafari on iOS 27 blocks The Trade Desk's ad domain, and AdExchanger says hundreds more ad data firms are on Apple's list

Safari on iPhone and iPad running iOS 27 blocks adsrvr.org, the domain The Trade Desk uses to request and deliver ads, so the advertising company cannot serve ads in Apple's browser on updated devices.

The trade publication AdExchanger reported the block on 29 September, two weeks after iOS 27 was released on 14 September. Ian Meyers, The Trade Desk's senior director of engineering, said that "Adsrvr.org is The Trade Desk's core ad request and delivery domain, not identity." John Wilander, who leads privacy work on WebKit, said he would look into it but gave no timeline, and AdExchanger reported no fix. Google's ad domain, ad.doubleclick.net, still serves. Apple did not comment to AdExchanger.

How the block works

PPC Land traced the change to a WebKit commit merged on 13 February 2026, eleven lines that add a check named IS_REQUEST_UNCONDITIONALLY_BLOCKABLE. In the open-source code the check always returns false. The list of domains it actually blocks sits in a file only Apple's internal builds include. From the bug report, PPC Land lists nine entries, among them adsrvr.org and domains belonging to Unified ID 2.0, ID5, LiveRamp, Permutive and Audigent. These are identity companies that match people across websites so that ads can follow them.

The block applies to ordinary browsing, not only to Private Browsing, according to Meyers' screenshots. Neither source says whether Safari on macOS 27 behaves the same way.

What AdExchanger says comes next

On 2 October AdExchanger reported, citing two people with direct knowledge of the WebKit work and a look at a private repository, that the list is growing from a handful of companies to hundreds of data sellers, ad platforms and ID graph operators. According to the report, the list is now delivered remotely as a WebKit content rule list, so Apple can add a company without an iOS update, and it reaches other browsers on iOS as well as Safari, since they all use WebKit. This part is Reported grade: the sources are anonymous, and Apple has confirmed none of it. AppleInsider, writing on 7 October, describes The Trade Desk as collateral damage of a policy aimed at data brokers.

What does the block change for people using Safari?

Most people will see no difference, other than fewer ads from some networks. Tracking that depended on identity services stops working in Safari without any prompt or setting, which is different from the permission requests apps show. Publishers that sell ad space through The Trade Desk lose that income from Safari readers on iOS 27.

Our take

This is a bigger shift than the App Tracking Transparency prompt Apple is reworking for the EU. App Tracking Transparency asks the user. This list asks nobody, and nobody outside Apple can read it. A browser blocking known trackers is not new, and most privacy-minded readers will welcome it. What is new is a private list, updated remotely, that can switch off a company's business on every updated iPhone, with a bug report as the only way to appeal.

The Trade Desk case shows the risk. By Meyers' account, the domain blocked is the one that delivers ads, not the one that tracks, and if he is right, the list caught something it was not aimed at. Meanwhile Google's main ad domain keeps working. Regulators who already look at Apple's App Store as a gatekeeper will notice that Apple's browser engine now decides which ad companies can operate on iPhone.

We at APPDOOK think the policy can be good for readers and still need rules. Apple publishes its App Store guidelines; it should publish this list, or at least the test a company must fail to be added to it.