Third-Party Cookie Deprecation
Third-party cookie deprecation is the ongoing removal and restriction of cross-site tracking cookies by web browsers, which has forced ad tech to rebuild targeting, frequency, and measurement on new identity foundations.
Key takeaways
- Third-party cookies enabled cross-site tracking, targeting, and frequency capping.
- Safari and Firefox blocked them years ago; Chrome's path has been slower and shifting.
- Their loss breaks classic DMPs, retargeting, and cross-site measurement.
- Replacements include first-party data, UID2, contextual, and clean rooms.
What actually breaks
Third-party cookies let one company recognize a user across unrelated sites. Removing them undermines cross-site retargeting, frequency capping across the open web, third-party audience segments, and much of multi-touch attribution. First-party contexts and walled gardens are far less affected.
The state of play
Safari and Firefox blocked third-party cookies by default years ago. Chrome "” the majority of open-web traffic "” announced deprecation, delayed repeatedly, and shifted toward user-choice controls, leaving the market planning for a low-signal future regardless of the exact timeline.
What replaces cookies
No single successor. The industry is assembling a portfolio: first-party data and CDPs, deterministic IDs like UID2, probabilistic identity graphs, contextual targeting, and data clean rooms for privacy-safe matching.
| What breaks | Cross-site targeting, frequency, attribution |
|---|---|
| Already gone | Safari, Firefox (default block) |
| Chrome | Announced, delayed, shifted to user choice |
| Replacements | First-party data, UID2, contextual, clean rooms |
Frequently asked questions
Are third-party cookies gone?
In Safari and Firefox, yes "” they've been blocked by default for years. In Chrome the picture is more complicated, with repeated delays and a shift toward user-choice controls, but the industry is planning for a low-signal open web regardless.
What replaces the third-party cookie?
There is no single replacement. The market uses a mix of first-party data, deterministic IDs like UID2, probabilistic identity graphs, contextual targeting, and data clean rooms.
Does cookie loss affect walled gardens?
Far less. Large logged-in platforms rely on first-party identity, so they retain targeting and measurement power that the open web loses "” which is part of why cookie deprecation shifts leverage toward them.