In affiliate marketing context, cookie-based tracking is a way to track affiliates sales or leads. When an affiliate link is clicked through, the affiliate network (or the merchant) drops a cookie on the visitor’s browser.
If the visitor leaves the merchant site without ordering but orders later within the cookie lifespan, the commission is due to the affiliate who referred the customer.
In affiliate marketing, the standard cookie lifetime is often 30 day. It can be adjusted to typical length of consideration phase related to the industry.
Cookie lifespan is an important element of choice when affiliates consider affiliate programs.
Of course the cookie can always be overwritten by other affiliates (see cookie overwriting).
In affiliate marketing, the alternative of cookie-based tracking is session-based tracking.