Apple names its targets: Safari block aims at identity IDs

Apple has confirmed that its Safari block targets identity resolution infrastructure, singling out the email-derived IDs that let advertisers recognize people across sites without cookies. The WebKit engineering team laid out the reasoning in a blog post on Monday, October 19, a month after the first cutoffs began.

The mechanics are straightforward. When someone types an email address into a website to log in or sign up for a newsletter, a company working with that site can receive the address and convert it into an identifier. That identifier allows advertisers to track the same person across different sites without cookies. Apple wants that practice stopped.

LiveRamp, ID5 and The Trade Desk's UID 2.0 all work this way, so there is little doubt about who the block was designed for. All three were among the first companies Safari cut off when Apple rolled out its latest software update in September, along with Permutive and Audigent.

What does the block change for marketers?

The Apple blog post confirms the block reaches beyond iPhones and iPads. It covers Macs and the Vision Pro headset as well. Once a user updates, Safari stops communicating with those companies altogether, and the tracking stops with it.

For practitioners, three consequences follow directly from the source:

• Email-based identity graphs lose their Safari signal across Apple's full device range, not just mobile.
• The update applies automatically, so audience recognition degrades as users install the software rather than through any opt-in decision.
• The named companies — LiveRamp, ID5, The Trade Desk's UID 2.0, Permutive and Audigent — represent the first wave, which signals Apple's intent to police the category itself rather than individual vendors.

The timing matters as much as the mechanism. Apple stayed silent for a full month while the cutoffs took effect, then published a technical explanation that names the method rather than issuing a policy announcement. That sequence suggests future enforcement will arrive the same way: quiet software changes first, documentation later.

For adtech and identity firms, the practical question is how much of their cross-site matching survives once Safari users are unreachable. Safari holds a substantial share of mobile and desktop traffic in key markets, and the block now applies uniformly across every device Apple ships.

The so-what for media planners: identity-based reach built on hashed email identifiers will read as inflated wherever Safari traffic is significant, and measurement stacks that depend on those IDs will need recalibration as the September update spreads through the installed base.