Apple protects a Safari user's identity online in iOS 27 and macOS 27 by preventing advertising firms from easily knowing who is accessing a webpage, and blocking some web traffic. Here's how it works.
Maintaining user privacy has been a core tenet of Apple's design philosophy for a very long time. While web surfing is one of the more challenging things to keep users anonymized while doing, Apple has worked on ways to try and keep the user's identity out of data broker's hands.
In an October 19 post to WebKit's blog, Apple explains the effort it goes through to minimize how much data is collected and how users are tracked.
Post-cookie era problem
Cross-site cookies have been blocked for six years already, preventing advertisers from using one cookie across multiple websites to view a person's browsing habits. Preventing cookies from being used as a persistent user identifier was a major step forward.
Techniques such as App Tracking Transparency have also helped at the app level to great success.
However, tracking industry firms are still building profiles about users to personalize online advertisements. All despite losing the ability to follow the same cookie's usage all over the Internet.
A new system is used, referred to as "identity resolution." Rather than using cookies of website owners, the technique instead collects email addresses from sites via third-party firms.
This happens when you use an email to log into a website, or if you sign up for a newsletter. That address is stored, an opaque tracking ID assigned to it, and that ID is sent to the webpage.
Blocking tracking services means an advertising profile about a user cannot be easily compiled - Image Credit: WebKit
That tracking ID is then used as a token to identify the user whenever they log in to that site in the future. A user's advertising profile can have multiple tracking IDs associated with it, so a user can still be tracked across multiple websites, just like cross-site cookies.
As usual, the third-party firms can collect personal data about the user to fill out the profile, known as an identity graph,
To Apple, email addresses are almost always a form of Personally Identifiable Information (PII), just like a phone number. While it is easy for users to use them to sign into websites, they are a form of identification for data brokers that can last years.
The problem in Apple's view is that users are supplying information for one intended purpose. They aren't doing so for further unstated purposes like building online profiles and tracking their online movements.
To be clear, Apple says that first-party personalization is not tracking, as in the website you hand your information to is not the problem. Apple's technology doesn't aim to stop that from happening.
The real problem is a third party that can use connected information across multiple sites to build a cross-device, cross-site, and cross-party identity graph. Something the first-party site cannot do alone.
Blocking identity resolution
To try and stop this cross-site tracking from happening, Apple explains that Safari and WebKit in iOS 27, iPadOS 27, macOS 27, and visionOS 27 block some network access. Specifically, the connections to identity resolution infrastructure, the firms that create the cross-site identity graph.
Apple says this is targeting third-party infrastructure firms that handle identity resolution. They aren't the first-party websites being accessed nor receive emails to handle standard user authentication, but firms that include invisible elements on webpages just for tracking purposes.
The technique blocks the email addresses from being sent to the identity resolution infrastructure in the first place. If the emails can't get through, a profile cannot be made or checked.
This block is done at the "domain" level. This means that, regardless of how the query or request is structured, Apple's blocks cannot be worked around.
For iCloud+ subscribers, there's also Hide My Email that does the same thing, but in a more literal sense. The emails it uses are unique to each new website, which means they cannot be tracked at all due to not having a common comparable element.
So far, Apple's techniques are working well, and in some cases, too well. In early October, it was revealed that an ad agency was blocked in its entirety by Apple, being classified as a blockable data broker.
It has complained to Apple, but it won't see a resolution until iOS 27.2 ships.
