The story. Advertisers whose programmatic budget runs through The Trade Desk may be buying less Safari reach on iOS 27 than their plan assumes. Apple’s iOS 27, released 14 September, blocks adsrvr.org, the DSP’s core ad request and delivery domain, and Apple had not resolved the issue when AdExchanger reported it on 29 September. (AdExchanger, Apple’s Latest Operating System Blocks The Trade Desk From Serving Ads On Safari, 29 September 2026)
01What happened
- A serving domain, not only identity. TTD engineer Ian Meyer wrote on GitHub that adsrvr.org is the “core ad request and delivery domain, not identity.” Apple’s iOS 27 also extends its block on data broker domains, newly listing UIDAPI.com (Unified ID 2.0), ID5, Audigent, LiveRamp and Permutive.
- The evidence is a bid-level example. TTD’s bug report shows a yahoo.com ad call where its bids were blocked while Google’s, on ad.doubleclick.net, went through cleanly.
- Apple has not committed to a fix. WebKit’s John Wilander said he would investigate and would tell TTD if changes are ready to test.
- The block can now move without an OS release. AdExchanger reported on 2 October that WebKit applies the list through “a remote list that Apple devices regularly call upon,” held in a private repository, so entries can be added or removed without a new iOS version. (AdExchanger, Apple Has Far-Reaching Plans To Block Hundreds Of Programmatic Data Companies From iOS, 2 October 2026)
- Neither company had commented. Neither Apple nor The Trade Desk responded to AdExchanger before the first report was published.
02Why marketers should care
| A blocked DSP does not return an error to you | A call that never leaves the browser means no bid and no impression. The campaign still spends elsewhere, so a Safari-on-iOS 27 shortfall can read as under-delivery or a pacing quirk instead of a blocked domain. |
|---|---|
| The block is reported to favour one competitor on the affected traffic | In TTD's own bug report, Google's bids cleared on the same ad call where TTD's were blocked. If you are comparing channels on blended results, one of them may be reaching an audience the other cannot. |
| Identity-based targeting can fail separately | If your targeting relies on UID2, ID5, LiveRamp or similar IDs, the same iOS 27 change lists those domains. Safari reach and Safari targeting are two different checks. |
The question for a buyer is not whether Apple was right, but whether your plan still delivers the Safari audience it was priced on.
03What marketers should do
04The bottom line
The question for a buyer is not whether Apple was right, but whether your plan still delivers the Safari audience it was priced on. The remote list means the answer can change mid-flight, so the control to put in place is a standing report by OS version.