The Default Cookie Policy implemented by Safari 1.0 blocks a site's access to its cookies in third-party context unless the site is first 'seeded' with first-party cookies. This means that for a third-party site to read or write cookies while a user is on a different site, the user must have first visited the third-party site directly and received first-party cookies from it.

Apple Safari started blocking all third-party cookies by default in 2020 with the release of a version of WebKit's tracking prevention. The only exception to this rule is the Storage Access API, which requires mandatory user control.

To enable third-party cookies for a site on Safari, a user must first visit the site in a first-party context, which allows the site to set first-party cookies. After this 'seeding' process, the site will then have access to its storage in a third-party context.