Apple reverses course: The Trade Desk returns to Safari in iOS 27

This means the blockades could potentially expand: the entire ecosystem, not just individual large vendors, could be at risk.

Why don't companies know their own status?

The WebKit lists are opaque. To find out whether a company has been blocked, you have to download the WebKit code, decompile it and take it apart piece by piece. Apple deliberately does not publish its criteria.

Senior editor James Hercher explained the company's position on an episode of The Big Story podcast: Apple has "a rather low opinion" of the advertising industry's capacity for self-regulation — which is exactly why it isn't showing its cards. This observation stands apart from the fact that Apple also has its own ambitions in the advertising business.

How is this different from ATT?

The industry has already lived through a similar shock: the AppTrackingTransparency (ATT) framework paralyzed mobile advertising until workarounds emerged — primarily Conversion API. Many analysts see the new blockade as déjà vu.

But editor-in-chief Allison Schiff thinks otherwise: the iOS 27 blocklist "works differently" than ATT. While ATT prohibited advertising companies from using identifiers without user consent, Apple's domain blocklist effectively shuts down some companies' ability to run entire parts of their business at all.

At the same time, Schiff adds, the industry "hasn't exactly earned trust in matters of handling data."

What's next?

The situation remains fluid. Key risks for the market:

• potential expansion of the WebKit blocklists to the entire ad tech and martech stack;
• companies lacking any tool to check their status without reverse-engineering the code;
• conflict of interest: Apple tightens the rules for competitors while building up its own advertising business.

So far, only the major vendors from the first wave of the list have escaped the blockade. Apple's further decisions as the final version of iOS 27 rolls out will determine whether the market faces another large-scale restriction — or whether the story ends with targeted measures.