tracking
First-Party Cookie
A cookie set by the merchant domain — survives browser restrictions that kill third-party tracking.
What is First-Party Cookie?
A first-party cookie is set by the same domain the user is visiting — as opposed to a third-party cookie set by an external domain — making it significantly less likely to be blocked by browser privacy restrictions, because browsers treat first-party cookies as essential to the visited site.
First-Party Cookie In Practice
First-party cookies matter to affiliates because the browser privacy changes blocking third-party tracking cookies do not affect first-party cookies. Safari's Intelligent Tracking Prevention and Firefox's Enhanced Tracking Protection both restrict third-party cookies while allowing first-party cookies to function normally. When a merchant implements first-party affiliate tracking — storing the click ID in a cookie on their own domain rather than through a third-party network script — attribution survives browser environments that kill pixel-based tracking. This requires merchant-side implementation: the merchant receives the affiliate click ID, stores it in a first-party cookie, and transmits it back to the network at conversion. S2S postback tracking is the most reliable alternative when first-party cookies are unavailable.
Example of First-Party Cookie
An affiliate promotes Moosend through PartnerStack. A reader clicks the affiliate link on Safari — PartnerStack's third-party cookie may be blocked by ITP. If PartnerStack also writes a first-party click ID on Moosend's own domain at the landing page load, that cookie persists through the evaluation period and credits the commission at conversion — surviving the restrictions that blocked the third-party cookie at the same point.