Why Tracking Broke
ITP, consent, cookie loss.
The Old Tracking Model
For a decade, marketing measurement relied on a simple trick: drop a third-party cookie from an ad platform's domain, then read it across millions of sites. This let advertisers stitch a user's behavior into a single cross-site profile.
Client-side JavaScript fired pixels directly from the browser to Google, Meta, and others. It was easy to deploy and powerful, but it leaked everything to third parties with little user control.
Safari ITP Lands First
In 2017 Apple shipped Intelligent Tracking Prevention (ITP) in Safari. It used on-device machine learning to classify domains as trackers and then blocked or partitioned their cookies.
Later ITP versions capped client-side (document.cookie / JavaScript-set) cookies to a 7-day lifetime, and just 24 hours when the user arrived via a known tracker's link. Long-lived attribution windows quietly collapsed.
ITP cookie lifetime caps (Safari)
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Server-set (HTTP) cookie ........ honored
JS-set cookie (document.cookie) . 7 days
JS cookie + tracker referrer .... 24 hours
Third-party cookie .............. blocked
Impact: 30-day attribution window
-> truncated to 7 days for many usersAll lessons in this course
- Why Tracking Broke
- Server-Side Tagging
- Consent Mode and CMPs
- First-Party Data Strategy