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Tracker & Tracking Fundamentals
Lesson 2 of 5

Third-party cookies

Why every browser is killing them.

5 min read

A first-party cookie is set by the site you're visiting. A third-party cookie is set by an embedded resource from a different domain, typically an ad network. Third-party cookies powered cross-site tracking for two decades.

Safari and Firefox block them by default. Chrome is phasing them out. The industry has responded with workarounds like CNAME cloaking and server-side tagging, which is why dedicated blockers still matter.

Key takeaways

  • Third-party cookies are blocked in Safari and Firefox by default.
  • Workarounds like CNAME cloaking move trackers onto first-party domains.
  • An ad blocker keeps blocking the request regardless of cookie policy.