The Safari iOS 27 block on The Trade Desk’s ad domain, adsrvr.org, has a short public primary record: a WebKit bug and an 11-line code switch. TTD’s Ian Meyers filed the bug on September 21 and says the block shipped in Safari 27. On October 5, John Wilander, a WebKit engineer whom PPC Land identifies as Apple’s, replied on the bug: “A new iOS 27.2 beta went out today. Please test with it.” The list behind the block is not public.
What Is IS_REQUEST_UNCONDITIONALLY_BLOCKABLE?
IS_WebPrivacyHelpers.mm, added by a pull request merged on February 13, 2026. In open-source WebKit builds it is defined as false, so it blocks nothing. The diff’s only route to a working definition is a file in Apple’s internal SDK, so the domain list itself is not in WebKit’s public source.
The code does show how the check behaves. It matches the registrable domain, so a hit covers every subdomain, including the match subdomain Meyers mentions. It also returns before the existing tracker-list lookup, which is where an entry marked as one Safari cannot block would normally be exempted. The code does not say whether the internal list is fixed or remotely updated, and the truncated function signature does not show whether any user setting gates it.
What Did Safari 27 Block?
Bug 324771 gives Meyers’ account of nine entries that shipped. Apple has neither published nor confirmed that list. The vendor mapping below follows PPC Land.
| Entry | Vendor |
|---|---|
adsrvr.org |
The Trade Desk |
uidapi.com |
Unified ID 2.0 |
id5-sync.com |
ID5 |
eu-1-id5-sync.com |
ID5 |
rlcdn.com |
LiveRamp |
pippio.com |
LiveRamp |
permutive.com |
Permutive |
ad.gt |
Audigent |
tainted. |
Appears to be a test fixture |
Meyers reads the intent as blocking domains that power post-cookie identity. His objection is that “adsrvr.org is The Trade Desk’s core ad request and delivery domain, not identity.” The bug names iPhone and iPad on iOS 27. His attached screenshot shows blocked requests on a yahoo.com article in non-private browsing. Mac Safari behavior is not established.
Where Does the Safari iOS 27 Block Stand on the WebKit Bug?
The bug is rated P1 and Major, and as of October 9 its status is still NEW with the assignee “Nobody”. Wilander replied on September 22 (“We’re investigating”) and on September 28 (“I will let you know if and when any changes are available for you to test”). After the October 5 beta comment, Meyers answered: “Acknowledged I see the changes in the 24B5099f build.”
The bug does not say what changed in that build. AppleInsider reports that the block on The Trade Desk “has effectively been removed” but only in iOS 27.2, which is in beta. Digiday also reports that a test version of iOS no longer blocks TTD’s ad server. Both are trade-press accounts, not an Apple statement. There is no 27.2 release date. Digiday estimates users will not see the fix “until the end of the month at the earliest.”
How Long Is the List?
AdExchanger’s October 2 report cites two unnamed sources who describe a library of hundreds of companies, called by devices remotely, so changes would not need an iOS release. Digiday saw results of a test of more than 70 ad tech domains. Only the first handful were blocked: The Trade Desk, LiveRamp, ID5, Permutive and Audigent. LiveIntent, Lotame and ConnectID got through. Digiday does not name the tester, date or iOS version, and Apple did not comment.
Other platform rules have left a record to work from: Germany’s Bundeskartellamt made Apple’s App Tracking Transparency commitments binding in a decision announced in August, and published telemetry showed that in Firefox an AliExpress WebAudio fingerprint collapses to three values. Here there is no published list and no Apple rationale.
What Should Analysts and Publishers Check?
- List every domain in the table that your tags, ID solutions or buying paths call. If you buy through TTD, include it.
- Annotate reports from September 14, the rollout date reported by PPC Land. Meyers’ screenshot is captioned as showing various requests blocked on a yahoo.com article in non-private browsing on iOS 27.
- Plan TTD-bought campaigns on the assumption that the block lasts until iOS 27.2 ships, as AppleInsider expects.
- Test your own vendor domains on a physical device, and repeat the test without waiting for an iOS update: AdExchanger’s sources say the list can change without a new release.
Until Apple publishes something, a device test is the most direct way to check whether a given vendor’s requests are blocked.