All cookies set via Javascript code are 1st party, and belong to the site that was in the address bar when the code ran (unless they are in a frame). GA primar

All cookies set via Javascript code are 1st party, and belong to the site that was in the address bar when the code ran (unless they are in a frame). GA primarily utilises 1st party JS cookies. If you have GA on example.com then the cookie will be stored against example.com. One of these cookies stores a unique ID for you as a user. GA will then send 'beacons' (GET requests to Google endpoint, with data passed in URL parameters) for pageviews and other events. Your unique ID is included in these URL parameters, which allows the various events from you to be joined up into a 'session'. That has not changed. Apple's ITP affects both 3rd party HTTP cookies and 1st party JS cookies. The main impact of ITP on GA is to limit the age of these cookies to auto delete after 7 days (usually), meaning that if you leave a site for more than 7 days your new session won't be able to be joined up with your previous session. There is an edge case where ITP 3rd party cookie limits will directly block GA JS cookies, which is when it is running inside an iFrame (hat tip to Simo [1] for alerting me to this), in which case the JS code may not be able to set a cookie and will not fire a beacon. [1] https://twitter.com/SimoAhava https://twitter.com/SimoAhava