First-party vs third-party cookies
A first-party cookie is set by the site you are on and read only by it; a third-party cookie is set by another domain, usually an ad tech company, and read across every site that loads that domain. First-party cookies run logins, preferences, and site analytics. Third-party cookies ran retargeting, frequency capping, and audience targeting across the open web until Safari and Firefox blocked them; Chrome kept them in 2025 after abandoning its removal plan.
| First-party | third-party cookies | |
|---|---|---|
| Set by | The site visited | A different domain (ad tech) |
| Readable across sites | No | Yes |
| Browser status | Allowed, lifespan limited in Safari | Blocked in Safari and Firefox; kept in Chrome with controls |
| Used for | Analytics, logins, first-party measurement | Retargeting, frequency, third-party audiences |
| Replacement | Server-side tagging, hashed emails | UID2, Privacy Sandbox APIs, contextual |
Terms in this comparison
Cite this page:
Agency Echelon. "First-party vs third-party cookies." Agency Echelon Reference, reviewed September 2026. https://agencyechelon.com/reference/compare/first-party-vs-third-party-cookies/