What do you call the painful, sometimes fatal condition that typically begins with subtle, hard-to-notice symptoms?

  1. A heart attack
  2. Apple’s iOS 27 blocking a list of programmatic platforms from collecting data or serving ads on the Safari browser
  3. All of the above

If you answered 3, you’re correct.

Last month, The Trade Desk found itself unable to deliver ads to Apple device owners with the latest version of iOS. The culprit was WebKit’s block list of data brokers and ad tech vendors that conduct cross-site user tracking. On the block list: The Trade Desk and its Unified ID 2.0 initiative, ID5, LiveRamp, Audigent and Permutive.

Fast forward to this week, and Apple has removed The Trade Desk’s ad serving problem from a new beta version of iOS 27, saving the demand-side platform from a nightmare scenario. But there is still a colossal wrench in the gears of programmatic analytics on Apple devices. And WebKit has another list that spans multiple categories of ad tech and martech – meaning there’s a potential expansion of WebKit’s blocking from a handful of scaled vendors to the entire ecosystem.

And that list is pretty obscure. A company would have to download, decompile and pick apart WebKit code to figure out whether or not they’re on the hit list. Apple doesn’t “think very highly” of the ad tech industry’s ability to self-regulate, which is why it’s keeping its cards close to its chest, says Senior Editor James Hercher on this week’s episode of The Big Story. It’s an observation that’s separate from the fact that Apple also has its own advertising ambitions.

Some industry pundits might feel déjà vu thinking of Apple’s AppTrackingTransparency framework, which paralyzed the mobile ad industry until solutions and workarounds emerged. (Conversion APIs, anyone?)

But the iOS 27 block list hits different than ATT, according to Editor-in-Chief Allison Schiff. Whereas ATT stopped ad tech players from using identifiers without consent, Apple’s domain block list effectively blocks some companies from conducting parts of their business entirely.

Not that the industry has “really earned much benefit of the doubt on data practices,” she says.

Keep watching this space. (We sure will.)

Also in this episode: Our takeaways from Advertising Week New York, why creators are becoming more savvy in the elusive science of TV advertising, and ad tech platforms that sound like Pokémon.