# What is Third-Party Cookies?

What is Third-Party Cookies? Cookies created by a domain different from the one being viewed (like Facebook, Google, or advertisers).

## How it works in practice

Third-party cookies are fading away. Safari blocked them in 2017. Firefox in 2019. Chrome announced deprecation (repeatedly delayed to 2025+). Any retargeting, remarketing, or cross-site tracking based on them will work less well. Those preparing now with a first-party strategy gain a competitive edge.

## Related metrics

- First-Party Cookies — the replacement for third-party
- Server-Side Tracking — a solution for the third-party loss
- iOS 14 — a similar disruption that already happened
- Privacy Sandbox — Google's solution to cookie deprecation

## Common misconception

'Third-party cookies disappearing means the end of advertising.' No. Meta Conversions API, Google Enhanced Conversions, and server-side tracking replace third-party cookies with platform-level matching. Advertising continues — just differently and less transparently.

## How to fix it

Preparing for third-party cookie deprecation? (1) Move to server-side tracking (Conversions API), (2) build first-party data — email lists, CRM, account creation, (3) contextual targeting — advertise based on page content rather than user profile, (4) clean rooms (advanced) — Meta / Google Clean Room.

## Real-world example

D2C store: 60% of retargeting relied on third-party cookies. Safari users: already invisible. Preparation: (1) Meta Conversions API, (2) email-based retargeting (Customer Match), (3) first-party segments. 18 months later: Meta ROAS fell 8% (from 4.1 to 3.8) — far less than expected.

## Where to start

Third-party deprecation is already well underway in Safari/Firefox. Start preparing now: (1) Conversions API, (2) email collection, (3) a first-party data strategy. A store that waits will be caught off guard.

---

Category: Technology · From the [Jimmy OS KPI Glossary](https://jimmy-os.com/glossary/kpi.md) · Source page: https://jimmy-os.com/glossary/kpi/third-party-cookies