Many of these cookies, known as “third-party” cookies because they aren’t controlled by the site that loads them, can be blocked by browsers already. But advertisers also use “first-party” cookies, loaded by a site the user does visit but updated as they move around the net. Blocking those breaks many other aspects of the internet that users expect to work, such as the ability to log into sites using Facebook or Twitter passwords.

To tackle this, the new Safari feature uses a “machine learning model”, Apple says, to identify which first-party cookies are actually desired by users, and which are placed by advertisers. If the latter, the cookie gets blocked from third-party use after a day, and purged completely from the device after a month, drastically limiting the ability of advertisers to keep track of where on the web Safari users visit.