Apple iOS 27 Safari blocklist targets major ad tech tracking firms

This technical shift by Apple immediately degrades the value of third-party identifiers for publishers, as Safari users represent a high-value demographic that is now harder to target and measure. Within the streaming and digital ecosystem, this move accelerates the transition toward server-side tracking and first-party data strategies to bypass browser-level restrictions. The inclusion of the WebKit engine means these blocks extend to Chrome and Firefox on iOS, centralizing control over the mobile advertising stack. Industry observers should watch for the official release of the dynamic update code, which will signal whether Apple intends to expand this list to hundreds of additional ad tech domains.

Apple's iOS 27 blocklist has expanded well beyond the initial handful of named firms. According to two sources with direct knowledge of the WebKit updates, Apple's original list of blocked ad tech and data vendors has been replaced by a longer list of hundreds of CDPs, ad tech and mar tech companies, data sellers and ID graph operators that can be dynamically updated without requiring a full software release. The initial targets, including The Trade Desk, LiveRamp, ID5, Permutive, and Audigent, remain blocked for Apple devices running iOS 27, but the scope of future additions is now substantially larger than the industry first understood.

The Trade Desk's situation illustrates the severity of Apple's approach. Unlike the other blocked vendors, which are primarily identity data sellers and ID graph operators, Apple added adsrvr.org, The Trade Desk's core ad request and delivery domain, to the blocklist. Apple has done more than just block the mechanisms The Trade Desk uses to match post-cookie identities, effectively shutting down the DSP's access to Safari inventory entirely, according to AdExchanger's reporting. The Trade Desk's senior director of engineering, Ian Meyers, filed an urgent request on WebKit Bugzilla arguing that adsrvr.org is not an identity domain but the company's core ad-serving infrastructure. Apple subsequently told The Trade Desk it had made changes in a new iOS beta release that appear to have untangled The Trade Desk's ad-serving domain from being blocked alongside its advertising identifier, Unified ID 2.0.

The broader impact extends to advertisers' ability to identify and reach people across the open web. By blocking the identifiers that many ad tech companies use to recognize users across websites, Apple effectively shrinks the pool of people advertisers can target. Rowena Lam, senior director of privacy and data at IAB Tech Lab, noted that the dynamic update code will allow Apple to make the block list expandable at will. ID vendors such as ID5 have been testing workarounds, including moving their pixels server-side and relying less on cookie-based technology, though these approaches face their own limitations given that WebKit powers every browser on iOS devices.