First-party versus third-party
First-party cookies are set by the site you are on and handle things like logins, carts and site analytics. Third-party cookies come from outside services embedded on the page and are mainly used for cross-site tracking, retargeting and ad measurement.
Where browsers stand
Safari and Firefox block third-party cookies by default. Google planned to phase them out of Chrome for years, but in April 2025 it said it would keep its current approach, leaving the choice in Chrome's privacy settings. Incognito mode still blocks them by default.
What it means for marketers
A large share of browsing already happens without third-party cookies, and privacy rules keep tightening. Marketers rely more on first-party data, server-side tracking, consent tools and modeled measurement.
Why Third-Party Cookies matters
Tracking that depends on third-party cookies misses many visitors. Building on first-party data and solid conversion tracking gives more reliable measurement no matter how browser policies change.
Seeing the conversions Safari hid
An online store saw far fewer conversions from iPhone users in its ad reports than in its own order data. Adding server-side tracking based on first-party data closed much of that gap and gave its ad platforms better signals.
Common mistakes
Assuming Chrome removed them
Chrome still allows third-party cookies by default for most users. Plans changed in 2025.
Relying only on browser pixels
Browser-only tracking misses blocked and privacy-protected users. Add first-party and server-side signals.
Ignoring consent rules
Cookies used for advertising often need consent, depending on where users are. Set up a proper consent tool.
Where we work on this