Definition
First-party cookie
A first-party cookie is set by the site being visited, not by a third-party domain. It is what lets affiliate tracking survive Safari and ad blockers.
A third-party cookie is set by a domain other than the one in the address bar — typically the affiliate platform's. Safari has blocked them by default since 2020, Firefox partitions them, and any ad blocker removes them. Tracking that relies on them loses a significant share of sales, with no error anywhere to flag it.
A first-party cookie is set by the merchant's own domain. The browser treats it like any session cookie: not blocked, not shortened, not partitioned. In practice the tracking script reads the URL parameter, records the click server-side, then sets the cookie on the merchant's domain — the platform never appears in the visitor's browser.
This is not only about robustness. An anonymous visitor identifier, used solely to connect a click to a purchase on one site and feeding no advertising profile, is also far easier to defend under GDPR than a cross-site tracker.
At earnwithaffiliate
The cookie is set on the merchant's domain and holds only a referral code and an anonymous click id — no email, no profile, no third-party sharing.
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Related terms
Cookie duration
Cookie duration is how long a sale stays attributed to the affiliate who brought the visitor. Past that window, the purchase earns no commission.
Affiliate link
An affiliate link is a URL that identifies the affiliate who shared it, usually through a parameter such as ?via= or ?ref=.
Attribution
Attribution is the rule that decides which affiliate a sale belongs to. Without it, a purchase preceded by three clicks belongs to no one — or to everyone.