Cookies for cross-site reference will not be blocked by default. This, in turn, is expected to enhance privacy for Safari browser users. With this in place, Apple has effectively eliminated the scope for “a little bit of cross-site tracking.”
It might seem like a bigger change than it is. But we’ve added so many restrictions to ITP since its initial release in 2017 that we are now at a place where most third-party cookies are already blocked in Safari. To keep supporting cross-site integration, we shipped the Storage Access API two years ago to provide the means for authenticated embeds to get cookie access with mandatory user control. It is going through the standards process in the W3C Privacy Community Group right now.
Full-third-party cookie blocking will ensure that there is no ITP state that can be tracked via cookie blocking behavior. In simpler terms, the new feature will make sure that the advertiser will not be able to classify certain blocking behavior and use the same for targeting ads. This is also referred to as removing statefulness from cookie blocking.
Safari browser leads the way
Apple claims Safari is the “first mainstream browser to fully block third-party cookies by default.” It is worth noting that the Tor browser already features third-party cookie blocking, however, it is not considered a mainstream browser. Meanwhile, the Brave browser is close to implementing third-party cookies since it currently has some exceptions.[via Webkit.org]