Safari 27 has been blocking several ad tech domains on iPhone and iPad, including a core The Trade Desk delivery domain. Apple has asked The Trade Desk to test an iOS 27.2 beta, but advertisers should treat the change as unresolved and measure Safari delivery separately.
What changed in Safari 27?
A WebKit bug filed by The Trade Desk says Safari 27 unconditionally blocked requests to nine domains. The list includes adsrvr.org, which the filing identifies as The Trade Desk's core ad request and delivery domain. It also includes domains connected with ID5, LiveRamp, Permutive and Audigent.
The underlying WebKit change was merged as a request-blocking mechanism for selected domains. The public code does not expose the private domain list or explain how Apple chooses entries. That matters because a domain-level block can affect more than a narrow identity function. It can interrupt calls used for ad delivery or measurement.
The filing was opened on September 21. On October 5, an Apple engineer asked The Trade Desk to test a new iOS 27.2 beta. The Trade Desk engineer replied that changes were visible in build 24B5099f and that the company would test them. The bug remained open when we reviewed it. There is no public confirmation that every affected request now works, that all nine domains were changed, or that the beta behavior will reach a production release.
Why does this matter for advertisers?
The immediate risk is uneven campaign delivery. A campaign can appear healthy in aggregate while Safari impressions, match rates or measurable conversions decline. If reporting combines browsers and devices, the drop can hide inside the total. Buyers may then move budget for the wrong reason, change bids too quickly or blame creative and inventory that are not causing the problem.
The issue is also larger than one DSP. Domain-level blocking can affect identity, audience activation and measurement vendors across the supply chain. That can reduce the signals available when an impression is evaluated, even if the ad still serves. The practical result may be lower addressability, weaker attribution or different bid behavior on Safari traffic.
Publishers are looking again at server-side infrastructure. IAB Tech Lab says Trusted Server is ready for publisher testing and can move ad requests, exchange communication and server-side tagging into publisher-controlled infrastructure. Digiday reported on October 8 that publisher interest increased after the Safari blocks and that Paradium was testing a Trusted Server setup for Permutive.
That architecture may reduce reliance on browser-executed third-party calls, but it is not an instant buyer-side fix. Publishers still need to test performance, consent handling, auction behavior and measurement. Advertisers should expect supply paths to change at different speeds.
What should advertisers do now?
Split reporting by browser and operating system. Compare Safari on iPhone and iPad with other environments. Watch impressions, win rate, CPM, click-through rate, conversion rate and attributed revenue. Use the same date range before and after the change.
Check delivery with platform and publisher partners. Ask whether they see blocked requests, reduced match rates or missing measurement on Safari. Request evidence by domain, browser and device instead of a general assurance.
Protect the test budget. Do not make a large allocation change from blended results alone. Hold a controlled Safari segment where possible, define the success metrics, and document any platform or supply-path change during the test.
Review measurement dependencies. Map which pixels, identity partners and attribution calls rely on the affected domains. Strengthen privacy-safe first-party measurement where it is available. Our guide to contextual targeting also offers a useful option when user-level signals weaken.
Audit supply and cost together. A move to a different route can change both signal quality and price. Compare the results with current programmatic CPM benchmarks, then apply the controls in our programmatic buying checklist.
What do we not know yet?
Apple has not published the internal domain list, the criteria for inclusion or a formal appeal process. It has not said what changed in the iOS 27.2 beta. The WebKit thread also does not confirm whether the beta restores every affected function or whether the same behavior applies on Mac.
We also do not know the advertiser-level effect across markets, publishers and campaign types. Reports of publisher impact are important, but they do not replace a controlled test using your own delivery and conversion data.
FAQ: what are advertisers asking?
Is The Trade Desk blocked on Safari?
A WebKit bug shows adsrvr.org among nine blocked domains in Safari 27 and identifies it as a core The Trade Desk delivery domain. Apple asked the company to test an iOS 27.2 beta, so the production outcome is not confirmed.
Does iOS 27.2 fix the Safari ad tech blocklist?
Not yet as a confirmed public result. The Trade Desk saw changes in one beta build and said it would test them. The bug remains open and does not document the final scope.
Can Trusted Server solve this for advertisers?
Trusted Server may help publishers move some ad execution away from browser-side third-party calls. It still requires publisher implementation and testing, so advertisers should treat it as an infrastructure option, not a universal immediate fix.
Sources
Talk to AdGeeks about testing your programmatic strategy against browser and platform changes.
