At its annual conference for developers, Apple has revealed several ad-restriction related upcoming updates for Safari desktop browser.
The most interesting one is the Intelligent Tracking Prevention. The purpose of this technology is to protect users from "third party" data collection. There often are elements on websites, integrated from other websites (images, videos, scripts, analytic services). If site B has elements from site A, the owners of the latter receive information about visitors of site B, even if they never visit site A. This is called cross-site tracking. As a result, a user does not know who has their data and cannot control it. In addition, aggregating and analyzing information from different websites gives vast opportunities of behaviour prediction and control.
Apple's approach is based on giving information about users only to the sites they interact with and are interested in. So, if site A receives information about a user only as a "third party", through other sites, and the user hasn’t visited site A itself within 30 days, then the cookie files from site A get erased from user’s device and prevented from uploading again. »