Product Metrics

Search

Glossary

First-party cookie

A first-party cookie is a cookie set by the site the visitor is on, such as your shop, rather than by another domain.

By Berend Vrakking, founder of Product Metrics. Updated 7 October 2026.

Example

Three cookies on one visit to shop.example
CookieSet byType
cart_idshop.exampleFirst-party
languageshop.exampleFirst-party
ad_network_idadnetwork.exampleThird-party

The visitor is on shop.example. The first two cookies come from that same domain, and the third comes from another one. Illustrative data.

For one product, and for an account

Because your shop’s own domain stores it, a first-party cookie can carry a value such as a click ID from the landing page all the way to the purchase. A third-party cookie belongs to someone else’s domain, such as an ad network’s.

Being first-party does not make a cookie permanent. Browsers limit cookies, and how hard depends on how the cookie was created. WebKit says Safari’s Intelligent Tracking Prevention deletes all cookies created in JavaScript, and all other script-writeable storage, after 7 days of no user interaction with the website. For cookies set in an HTTP response, it states a 7-day cap only for requests it detects as third-party CNAME cloaking or IP address cloaking.

Full Signal Tracking’s first-party cookie lasts 30 days when it is served from your own origin. Full Signal Tracking sends purchases from a unique endpoint on your own domain and gets through every adblocker, and it reads the visitor’s consent choice before sending anything: first-party does not mean consent-free.

Common mistake

Assuming a first-party cookie is exempt from browser limits. WebKit’s 7-day rule applies to cookies created in JavaScript, whichever domain they belong to.

Questions

What is the difference between a first-party and a third-party cookie?

A first-party cookie comes from the same site as the page in the address bar. A third-party cookie comes from a different domain. The difference is who set the cookie, not what it holds.

Can you give an example of a first-party cookie?

A shop’s cart cookie is one. The shop’s own domain sets it so the basket stays the same between pages. A language choice saved by the same domain is another.

What is a third-party cookie?

A cookie set by a domain other than the one the visitor is on. A page only has to embed an image or a frame from another site for that site to set one.

Sources

Keep reading