What is CNAME tracking, and how does the DNS "subdomain trick" disguise a third-party tracker as first-party?

A tracker is hidden behind a subdomain of the visited site (e.g. daten.meine-tierwelt.de) that CNAME-points in DNS to the external tracker, so the browser sees only the first-party domain and lets it through.

Why it's needed: browsers and ad-blockers now block obvious external trackers. A direct call to analytics-riese.com is blocked instantly, and Safari/ITP deletes third-party cookies within 24 hours.

The trick, step by step:

1. Create a subdomain on your own domain: daten.meine-tierwelt.de
2. Set a CNAME record in DNS: daten.meine-tierwelt.de → analytics-riese.com
3. Point the tracking script at daten.meine-tierwelt.de/log
4. The browser reads only meine-tierwelt.de — no blocker fires — while the DNS redirect to the real tracker stays invisible

Because the browser sees a same-site subdomain, the tracker's cookies are treated as first-party, sidestepping third-party-cookie protections entirely. The redirection happens silently at the DNS level.