Privacy
Intelligent Tracking Prevention
Also called ITP.
Intelligent Tracking Prevention is Safari's set of rules that cap or partition tracking storage and cross-site identifiers. It is usually shortened to ITP.
How it is measured
Script-written storage, including cookies and local storage, is deleted after seven days of Safari use without the person interacting with the site. Cookies from cross-site visits with link decoration can be cut to 24 hours. Cookies from known trackers are blocked.
Measure the effect by splitting reports by browser. Compare the returning-visitor rate and the age of the oldest ID in Safari against Chrome on the same pages.
Worked example
A news site sees 38 percent returning visitors in Chrome and 14 percent in Safari. Its ID cookie is written by JavaScript, so Safari wipes it after a week of no interaction.
Moving the cookie to a server header helps for first-party hosts, but a CNAME-hidden vendor domain is still treated as a tracker, so the gap only narrows to 14 versus 29 percent.
How it differs
ITP is one browser vendor's rule set. Tracking prevention is the whole category, including Firefox and Brave. ITP excludes other browsers' behavior; the category excludes nothing but is too vague to debug a Safari number.
Common errors
Assuming a first-party cookie always survives. Comparing browsers without adjusting. Trying to evade it with tricks that break at the next release. Forgetting the 24-hour link-decoration limit. Thinking it affects only ads.
In practice
Split your main report by browser and note the Safari gap. Expect lower returning rates there and do not chase them. If an ID matters for revenue, reconcile against orders.