When iOS 27 was released, a legit advertising company found it could no longer serve ads to the Safari browser. This block appears to be a mistake on Apple's side, but the ad industry is up in arms about the implications.

Apple introduced App Tracking Transparency back in 2021 in order that users had to choose to allow ad companies to track them using identifiers. After a heavy initial impact, though, the rates of users allowing tracking has risen again, and advertisers have found alternative ways to learn about users.

However, according to advertising trade journal AdExchanger, The Trade Desk ad agency was blocked in iOS 27 by Apple itself. It appears that Apple is intentionally blocking data brokers who sell on tracked data, but in doing so it prevented The Trade Desk serving ads.

The Trade Desk filed a bug report that surmised that the "intent seems to be to hard block domains that power 'post-cookie' identity." However, the affected addresses include the company's "ad request and delivery domain, not identity [tracking]."

This is the system where The Trade Desk, or any other vendor like Google, bids on ad space in real-time as a page loads for the user. If it wins that bid, the company then serves an ad to the web browser based on what the ad vendor thinks it knows about the viewer. This is not in itself about tracking individual users.

So far this sounds like a mistake on Apple's part, and that appears to have been backed up by how the block on The Trade Desk has effectively been removed. However, it is only removed in iOS 27.2, which so far is solely in beta testing.

That means The Trade Desk still cannot serve ads to Safari, and will remain blocked from doing so until iOS 27.2 ships.

Apple's dynamic blocking

Curiously, it also appears that Apple's new moves include the aim of having a dynamic block list. So in future, without having to wait for a new iOS update, Apple could elect to block or unblock specific advertisers.

It's not clear why that isn't happening right now with The Trade Desk.

What does appear to be clear is that iOS 27 blocked a number of firms in Safari. Since that really means they were blocked in WebKit, those firms are also shut out of Chrome or any other browser on iOS.

AdExchanger claims to have had sight of a list of ad tech firms that Apple either is or may target. Reportedly, it includes hundreds of firms, but allegedly that may not include Google.

While it's still supposition, the idea that Google is not blocked is backed up by The Trade Desk's bug report. The Trade Desk claims to have logs of its advertising bids being blocked while Google's went through as normal.

Cat and mouse

Apple has not made any announcements about its iOS 27 advertising identity blocking, nor is it expected to. But it does fit with how the company adds privacy protections that advertisers then continually work to circumvent.

Since the introduction of App Tracking Transparency in 2021, that has meant advertisers looking for ways to gain more information about users. One way involves this bidding process, which can mean advertisers being told details such as how many people are expected to see the ad.

The advertising industry wants as much information about users as it can get, and Apple wants to protect users' privacy as much as it can. Up to now, that may have made advertisers unhappy, but it was intended to help users.

It has instead drawn the ire of Meta, for one. And, many antitrust investigations have sprung up about it.

Today, though, Apple is expanding its own advertising business, with ads in Apple Maps, and soon perhaps in Visual Intelligence.

Consequently, advertisers are concerned about Apple having the facility to turn off ads from its rivals. That seems unlikely, though, as it would doubtlessly lead to antitrust lawsuits, and Apple is embroiled in enough of those already.