WebKit said on October 19, 2026, that Safari blocks network access to third-party identity-resolution infrastructure at the domain level. Identity resolution links an email address entered on one site to an identifier that can be used to match a person across sites and devices. WebKit says the protection is included in iOS, iPadOS, macOS, and visionOS 27 releases.
That matters because the same email-linked ID can help a third party connect information about someone across different services.
What identity resolution does
When someone enters an email address to log in or sign up for a newsletter, a third-party identity resolver can link that address to an opaque tracking ID and return the ID to the webpage. The resolver can then use information from different sites and devices to match identities and support targeting, WebKit says.
How Safari blocks it
WebKit describes the protection as a network block applied at the domain level. Changing the structure of a network request does not get around the block, according to WebKit.
Logging out of a site or unsubscribing from its newsletter does not, by itself, remove the email address or tracking ID already stored by a third party, WebKit says.
Which releases WebKit names
WebKit’s October 19 explanation names the iOS, iPadOS, macOS, and visionOS 27 releases. It describes the protection as aimed at third-party identity resolution. A site’s personalization for its own users is outside the stated target.
Early cases reported by Digiday
In its October 20, 2026 report, Digiday named LiveRamp, ID5, The Trade Desk’s UID 2.0, Permutive, and Audigent among companies affected early. Digiday also reported that The Trade Desk’s ad server was mistakenly blocked and later restored, citing an unnamed person familiar with the matter.
Digiday said most of the ad-tech web addresses it checked in its own test were still loading at the time of testing.
