Apple Blocks The Trade Desk From Safari On iOS 27

Apple's iOS 27, released 14 September, has cut The Trade Desk off from serving ads on Safari for devices that updated. The block is not about identity this time: Apple added The Trade Desk's adsrvr.org domain, its core ad request and delivery domain for third-party cookies, to the block list, alongside UIDAPI.com (UID2.0), ID5, Audigent, LiveRamp and Permutive. "Adsrvr.org is The Trade Desk's core ad request and delivery domain, not identity," senior director of engineering Ian Meyer wrote in an urgent GitHub request to Apple's WebKit team. Apple's John Wilander, manager of WebKit privacy and ad tech, has acknowledged the flag but as of Monday only said "I will let you know if and when any changes are available for you to test." The Trade Desk's bug report included an ad call where its bids were blocked on Safari while Google's bids went through cleanly. The best-case read is an inadvertent over-block; the worst case is Apple reaffirming a decision to shut the open web's biggest independent DSP out of Safari.

The crux

Apple can flip a switch and sever a major demand source from roughly 20% of web traffic, and the two-week-plus timeline with no resolution shows how little recourse the open programmatic ecosystem has against platform decisions.

Sell-side read

If you are a publisher whose Safari inventory is monetised through The Trade Desk demand, this is revenue at risk right now. The response is the same as for every platform dependency: build first-party data and direct-sold paths so no single DSP or browser decision can zero out a channel.

Watch

Apple's resolution or reaffirmation on the WebKit ticket, and whether other DSPs move to protect their ad-serving domains against the same treatment.