TLDR
Two sources told AdExchanger that Apple's Safari block list may grow from a handful of ad-tech domains to hundreds of companies, updated remotely without an iOS release. LiveRamp, ID5, UID2 and Audigent remain blocked; The Trade Desk's fix is weeks away.
KEY TAKEAWAYS
From eight domains to hundreds
When iOS 27 arrived in mid-September, Safari began unconditionally blocking requests to a short list of ad-tech domains, including The Trade Desk's adsrvr.org and endpoints used by UID2, ID5, LiveRamp, Permutive and Audigent. The WebKit change that makes such blocking possible, titled "Unconditionally block requests going to certain domains", was committed in February.[1] Prompt the Market reported the effect on The Trade Desk on 8 October.[2]
The list may be about to grow. Two sources told AdExchanger that Apple has replaced the original list with a much larger one covering hundreds of companies, including customer data platforms, ad-tech and martech vendors, data sellers and identity-graph operators. The list sits in a private repository, and because devices call it remotely, Apple can add or remove vendors without releasing a new version of iOS. Apple has not confirmed the report.[3]
Who is still cut off
The Trade Desk has a reprieve in sight. On 5 October, WebKit's John Wilander told The Trade Desk's Ian Meyers in the bug thread: "A new iOS 27.2 beta went out today. Please test with it."[4] AdExchanger reported that the beta removes adsrvr.org from the list, but that the fix is three to four weeks from reaching live installs.[5]
Others have no fix yet. LiveRamp, Audigent, UID2 and ID5 remain blocked, according to AdExchanger. Permutive rotated to a new domain as a temporary patch while it moves clients to its first-party product, and blocked vendors are rushing publisher and ecommerce clients onto first-party setups. Agency buyers are reconciling win logs for iOS 27 ads that never rendered.[5]
ID5 chief executive Mathieu Roche said the change was "released without warning or consultation in iOS27" and called it "an attack against the business model of the web and in favor of mobile applications". He added: "Maybe more regulators should look at their business practices."[6] Apple had not commented when Cult of Mac reported on the bug on 9 October.[7]
Why Australian buyers cannot route around it
Outside the European Union, Apple requires every iOS browser to use WebKit, so Chrome, Firefox and every other browser on an Australian iPhone inherits the same block. A buyer cannot move spend to a different iOS browser to get around it. For Australian publishers and agencies, the practical checks are which of their ad-tech and identity partners sit on the known list, how much iPhone web inventory runs through them, and whether invoices cover impressions that were bid on but never shown.
The industry's longer-term answer is IAB Tech Lab's Trusted Server, an open-source framework that moves bidding from the browser to a publisher-controlled server, out of WebKit's reach. Rowena Lam, the Tech Lab's senior director of product, expects production-level tests of campaigns by early 2027.[5]
SOURCES & CITATIONS
- WebKit bug 307853: Unconditionally block requests going to certain domains
- Prompt the Market: Apple shuts The Trade Desk out of iPhone browsers until iOS 27.2
- AdExchanger: Apple has far-reaching plans to block hundreds of programmatic data companies from iOS
- WebKit bug 324771: Inclusion of adsrvr.org in the unconditionally blockable list
- AdExchanger: How data and ad tech vendors are preparing for the iOS 27 fallout
- PPC Land: ID5 faces Apple's iOS 27 Safari block as CEO says regulators should look
- Cult of Mac: iOS 27 Safari update reportedly blocks ad vendors by mistake
FREQUENTLY ASKED QUESTIONS
Which ad-tech vendors are blocked in Safari on iOS 27?
Is Apple planning to block more companies?
When will The Trade Desk be unblocked?
Does this affect Chrome and other browsers on Australian iPhones?
Xaviery Malinao writes for Prompt the Market on how brands and agencies are adapting to answer engines, drawing on Bushnote's work with clients across search, AI search and content.
