Apple's iOS 27 Block List Spares The Trade Desk — For Now

Apple has removed The Trade Desk from a new beta version of iOS 27, weeks after the platform's WebKit block list stopped the demand-side platform from serving ads to Safari users on the latest iOS release. The reprieve is partial. WebKit maintains a second, broader list spanning multiple ad tech and martech categories, and it could expand blocking from a handful of scaled vendors to the entire programmatic ecosystem.

The original block list targeted WebKit's inventory of data brokers and ad tech vendors that conduct cross-site user tracking. Named companies include The Trade Desk and its Unified ID 2.0 initiative, ID5, LiveRamp, Audigent and Permutive.

Apple publishes no simple registry for this second list. A company would have to download, decompile and pick apart WebKit code to determine whether it appears on it.

Why is Apple keeping the list quiet?

Senior Editor James Hercher, speaking on this week's episode of The Big Story, said Apple does not "think very highly" of the ad tech industry's ability to self-regulate, which is why it keeps its cards close to its chest. That assessment sits apart from the fact that Apple runs its own advertising business.

Editor-in-Chief Allison Schiff drew a sharp line between this move and Apple's AppTrackingTransparency framework, which paralyzed mobile advertising until workarounds such as Conversion APIs emerged. The iOS 27 block list "hits different," she said.

The distinction matters. ATT stopped ad tech players from using identifiers without consent. The domain block list effectively blocks some companies from conducting parts of their business entirely.

Schiff added that the industry has not "really earned much benefit of the doubt on data practices."

What does this change for ad tech practitioners?

For platforms named on the list, the immediate stakes are existential: parts of their business on Apple devices stop functioning at the browser level, not at the consent level. For the wider ecosystem, the open question is scope. A second list spanning multiple categories suggests Apple is weighing expansion beyond the handful of vendors currently affected.

Agencies and advertisers buying through affected demand-side platforms should verify delivery on Safari traffic running iOS 27, because blocked ad serving produces no standard error message for buyers.

Identity vendors face the sharpest risk. Unified ID 2.0, ID5 and LiveRamp alternatives all appear on the current list, which compresses the options for addressable reach on Apple inventory.

The episode also covered takeaways from Advertising Week New York, growing creator sophistication in TV advertising, and ad tech platforms that sound like Pokémon.

Watch this space. The beta reprieve for The Trade Desk signals Apple is willing to adjust under pressure, but the obscured second list remains in place, and its expansion would reset programmatic economics on Safari once again.