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Tracker & Tracking Fundamentals
Lesson 4 of 5

CNAME cloaking

When trackers hide behind first-party domains.

5 min read

Trackers can be served from a subdomain of the site you're visiting, which makes their requests look first-party to the browser. Under the hood, DNS forwards the subdomain to a third-party tracker.

Good blockers resolve the DNS chain (or use maintained lists of cloaked domains) and block them anyway. This is one of the most important features that separates serious blockers from naïve ones.

Key takeaways

  • CNAME cloaking bypasses third-party cookie defences.
  • Resolution-aware blocking catches these requests.
  • Community lists track new cloaked domains daily.