Apple has clarified the scope of a contentious change to its Safari browser that severs communication between the browser and companies that turn email addresses into cross‑site advertising identifiers. The explanation, published by Safari engineers on 19 October, confirms the cut affects desktops and headsets as well as mobile devices and targets a class of firms the company says have replaced cookies with more persistent identifiers.
Which companies are affected
The update, which began rolling out in September, has already prevented a number of well‑known identity providers from receiving data via Safari. Names identified among those disrupted include LiveRamp, ID5, The Trade Desk’s UID 2.0, Permutive and Audigent.
| Company | Role in ecosystem |
|---|---|
| LiveRamp | Identity resolution and onboarding |
| ID5 | Identity graph provider |
| UID 2.0 (The Trade Desk) | Open identifier initiative |
| Permutive | Data and audience platform |
| Audigent | Identity and data solutions for advertisers |
Apple’s rationale
According to Apple’s engineers, the industry shifted from cookies to identifiers derived from email addresses and other login data. The company argues that when a user types their email into a site — to register, log in or subscribe — that information can be captured by a third party and converted into a persistent ID. Because many people reuse the same address across devices and services, Apple says these IDs provide a more durable way to track individuals than the cookies it banned in Safari years ago.
"Nobody signing up for a newsletter expects their details to be handed to a third party for something else,"
The blog post states the engineering change is intended to stop that practice by preventing Safari from communicating with those third parties once a user updates their software. Apple says the block applies across iPhones, iPads, Macs and its Vision Pro headset, meaning the protection is device‑agnostic within its ecosystem.
Consequences for advertisers and publishers
The decision tightens the constraints on an ad industry already adjusting to the end of third‑party cookies. Firms that have built identity graphs from login and email data rely on the ability to see and match identifiers across multiple sites and devices. With Safari severing that channel, the ability of advertisers and publishers to target and measure audiences on Apple platforms could be materially weakened.
- Advertisers may see reduced reach and accuracy when bidding for Safari users.
- Publishers could find it harder to monetise audiences on Apple devices if identity stitching is compromised.
- Identity providers will face immediate technical and commercial disruption on Apple’s browser.
Companies behind the affected services — several of which were among the first blocked when the update went live — will need to retool how they operate in the absence of Safari’s signalling. The change also raises questions for cross‑platform campaigns that rely on a single identifier to unify mobile, desktop and emerging headset inventory.
Wider industry debate
Apple’s move re‑ignites a long‑running debate between privacy advocates and parts of the ad industry. Proponents of identity solutions argue they are necessary to sustain ad revenue for free content online and to provide advertisers with measurement. Apple counters that users do not expect the email addresses they supply to a site to be harvested and repurposed into tracking identifiers kept by third parties.
How the ad market adapts will depend on whether alternative, privacy‑preserving approaches — such as cohort‑based targeting or server‑side solutions — can deliver enough scale and measurement to satisfy advertisers and publishers without breaching user expectations about data use. For now, Apple’s announcement represents a clear prioritisation of user control over the convenience of cross‑site identity matching.
The change is not limited to phones and tablets; by encompassing macOS and Vision Pro, Apple has signalled it intends the restriction to apply across its ecosystem. That makes the update one of the more significant privacy‑led interventions in digital advertising since the move to curtail cookies in mainstream browsers.
