What are Third-Party Cookies?
Third-party cookies are browser cookies set by domains other than the one you’re visiting, used for cross-site tracking and ads.
Understanding Third-Party Cookies
Browsers are deprecating third‑party cookies due to privacy changes, reducing cross‑site tracking. Targeting is shifting toward first‑party data, contextual signals, and modeled measurement that relies less on user‑level IDs. Server‑side events and clean consent flows help maintain reliable optimization. Walled gardens will keep strong signals; the open web will lean more on context and publisher data. Expect reporting to blend deterministic and modeled methods more often.
These changes affect planning and creative too. Catalog strategies that align product sets to intent and context become more important. Feed quality and on‑ad clarity raise conversion so you need fewer granular identifiers. Teams should map current use of third‑party cookies and migrate workflows to resilient alternatives. Test incrementality and MMM‑style triangulation to validate gains beyond last‑click.
Why Third-Party Cookies matter
Third-party cookies matter because their deprecation fundamentally changes how ads are targeted and measured across the web. Cross-site audiences shrink as browsers block tracking, and more attribution becomes modeled rather than deterministic, which can increase measurement uncertainty. This shift elevates the importance of first-party data, server-side events, and contextual targeting to keep optimization reliable.
- Targeting: Fewer cross-site audiences.
- Measurement: More modeled attribution.
- Strategy: Bigger role for first-party data and server-side events.
How third‑party cookies work
Third‑party cookies work by allowing domains other than the one a user visits to store identifiers in the browser. Ad tech uses these IDs to recognize users across sites and to track conversions. Browsers now restrict or block these cookies, limiting cross‑site recognition. Alternatives include first‑party cookies, server‑side events, and publisher IDs. Measurement leans more on modeled lift and aggregated reporting. Plan for a mixed environment with multiple signals rather than a single cross‑site ID.
