tracking
Cookie
The small file a browser stores that connects a visitor's click to your affiliate commission.
What is Cookie?
A cookie is a small text file stored in a visitor's browser that records their affiliate link click — containing your affiliate ID, a timestamp, and an expiry date — which the merchant reads when the visitor returns to purchase, allowing the commission to be credited to your account.
Importance of Cookie
The cookie is the foundational mechanism that makes traditional affiliate attribution work. Without a cookie being successfully set and read, there is no commission — even if a visitor you sent makes a purchase. Understanding exactly what can prevent a cookie from working (browser blocks, user deletion, cross-device journeys, short expiry) explains why affiliates lose commissions they legitimately drove, and why choosing programs with robust tracking infrastructure is as important as choosing programs with high commission rates.
Cookie In Practice
When a visitor clicks your affiliate link, the merchant's tracking system redirects them through a tracking server before delivering them to the product page. During this redirect, a cookie containing your affiliate ID is stored in the visitor's browser. When the visitor returns and completes a purchase — whether in the same session or days later — the merchant's system reads the cookie, identifies you as the referring affiliate, and credits the commission. Three things can break this chain: the cookie expiring before the purchase (cookie duration), the visitor clearing their browser cookies or using private browsing, or the visitor's browser blocking the cookie. In 2026, Safari and Firefox block third-party cookies by default, which affects programs that set tracking cookies from a domain other than the merchant's own. Programs using first-party cookies (set from the merchant's own domain) or server-side postback tracking are unaffected by these browser restrictions and maintain reliable attribution across all browsers.
Cookie Best Practices
- →Verify whether a program uses first-party or third-party cookies — first-party cookies set by the merchant's own domain survive Safari and Firefox restrictions; third-party cookies from a tracking domain may not.
- →Never rely solely on the stated cookie duration to estimate your attribution window — the actual window depends on the tracking method, browser restrictions, and whether the visitor clears their cookies.
- →For high-value programs, ask the affiliate manager whether they use server-side postback tracking — this method does not depend on browser cookies at all and provides the most reliable attribution.
- →Understand that private browsing and incognito mode may prevent cookies from persisting after the session ends — visitors who switch to private mode after clicking your link may not be tracked.
- →When a purchase you expected to be attributed to you does not appear in your dashboard, cross-device journeys and cookie deletion are the most common causes — contact the affiliate manager with your link click data as evidence.
Example of Cookie
A reader clicks your Moosend affiliate link from a blog post on desktop Chrome. The tracking system sets a cookie in their browser recording your affiliate ID and a 90-day expiry. Three days later, the reader returns to Moosend on the same browser and upgrades to a paid plan. Chrome reads the cookie, confirms it has not expired, and the commission is credited to your account. If the same reader had clicked on Safari — which restricts many tracking cookies by default — the cookie may have been blocked or shortened, and the commission might not have been credited unless Moosend's tracking uses a first-party or server-side method. Same click, same purchase, different outcome depending entirely on browser and tracking infrastructure.
Related Terms
Related Tools & Services
- Moosend Affiliate Program — Example program used to illustrate cookie attribution mechanics across browsers
Frequently Asked Questions
What is a cookie in affiliate marketing?
A cookie is a small text file stored in a visitor's browser when they click your affiliate link. It records your affiliate ID and an expiry date. When the visitor returns to the merchant's site and makes a purchase within the expiry window, the merchant reads the cookie and credits the commission to your account. If the cookie is blocked, deleted, or expired before the purchase, the commission is not credited to you even if the visitor came from your link.
Can I still earn commissions if cookies are blocked?
Yes, if the program uses an alternative tracking method. Server-side postback tracking (S2S) does not rely on browser cookies — it records the click on the merchant's server using a click ID, and when a conversion occurs, the merchant's server sends a postback to the affiliate network confirming the attribution. Programs using this method maintain accurate attribution even when browsers block cookies. First-party cookies set by the merchant's own domain also survive most browser restrictions that affect third-party cookies.
What is the difference between a first-party and a third-party cookie?
A first-party cookie is set by the merchant's own domain — the domain the visitor is actually browsing. A third-party cookie is set by a different domain, typically the affiliate network's tracking domain, during the redirect. Safari and Firefox block third-party tracking cookies by default, which can cause attribution loss for programs using third-party cookie methods. First-party cookies are not blocked by these restrictions and survive the full stated cookie duration.