What is First-Party Cookies?

A cookie is a small piece of data a website stores in the browser and reads back on later requests. What makes a cookie 'first-party' is simply that its domain matches the site being visited. When a shopper on example-store.com receives a cookie scoped to example-store.com, that is a first-party cookie; a cookie set by an embedded advertising script for adnetwork.com would be third-party.

First-party cookies do the unglamorous work that makes the web usable: keeping a user logged in, remembering cart contents between pages, storing language and currency preferences, and recording the visitor's own consent choice. Many of these qualify as 'strictly necessary' and are exempt from consent requirements under the EU's ePrivacy rules.

But first-party is a technical description, not a legal safe harbor. A first-party analytics cookie still requires consent in the EU, because the exemption turns on whether the cookie is necessary for the service the user requested — not on who set it. Likewise, modern marketing stacks increasingly write third-party identifiers into first-party cookies (the Meta Pixel's _fbp cookie is set as first-party) precisely because browsers block third-party cookies; the data still flows to the third party, and the legal analysis follows the data flow.

As browsers restrict third-party cookies, 'first-party data strategy' has become the industry's response: collecting data through your own domain, with consent, and syncing it to partners server-side. That shifts the compliance question from cookie mechanics to data-sharing governance.