PRIVACY
First-party and third-party cookies
Learn what first-party and third-party cookies mean, how cross-site tracking works, and what blocking cookies can and cannot do.
The short answer
First-party cookies belong to the site you are visiting. Third-party cookies are used in a cross-site context, such as an embedded service on another website. The distinction describes context—not a guarantee of safety.
Compare the two
| Example | Context | Possible purpose |
|---|---|---|
| A shop remembers your cart | First-party | Keep items together as you browse |
| A shop measures repeat visits | First-party | Analytics |
| An outside service appears on several sites | Third-party | Embedded features or cross-site tracking |
Imagine visiting two unrelated shops that load the same advertising service. If the browser allows that service to use the same cookie in both places, it can associate the visits with one identifier. It need not know your name to build a browsing profile. MDN describes third-party cookie contexts and tracking.
First-party does not mean private
A first-party cookie can support analytics or advertising as well as a useful feature. A third-party service can provide something you deliberately want, such as an embedded tool. Judge the purpose, the information collected, and the service’s explanation of data sharing.
Also separate two questions: who can use this cookie in this context? and how long does it last? First-party cookies can be persistent; third-party cookies can be session-based. Our cookie lifetime guide covers that second distinction.
What browser protection changes
Browsers can block third-party cookies or partition their storage so an embedded service gets separate cookie storage for each top-level site. Partitioning limits reuse of an identifier across those sites while allowing some embedded functionality.
Firefox’s Total Cookie Protection uses separate cookie jars for websites. Its tracking controls also offer more restrictive options, which can affect site behavior. Check Mozilla’s current explanation for the settings available in Firefox.
There is no single cookie setting shared by every browser. Device, browser version, privacy mode, and workplace policies can change what you see. Read your browser’s description rather than assuming “block cookies” means only advertising cookies.
A practical way to choose
- Start with tracking protection. Review the cross-site tracking controls in the browser you actually use.
- Keep useful functions in mind. Test sign-in, checkout, and the embedded services you need after changing a setting.
- Make exceptions deliberately. If a trusted site fails, try a site-specific exception before relaxing protection everywhere.
- Review the exception later. A temporary fix should not become a forgotten permanent allowance.
This sequence is a practical troubleshooting approach: change one control, test the result, and keep the narrowest exception that solves the problem.
What blocking cookies does not do
Cookie controls address cookie storage and access. They do not make you anonymous or prevent every form of tracking. Signed-in accounts, information you submit, and other identification methods can still connect activity. MDN’s third-party cookie guide discusses alternatives and privacy limitations.
Will blocking third-party cookies remove advertisements?
Do not treat it as an ad-blocking switch. A page can display an advertisement without a third-party cookie.
Should I delete cookies as well?
Deleting saved data and restricting future cookie use are separate choices. Use deletion for a specific purpose, such as resetting a broken site, and expect saved preferences to change.