The core principle of affiliate marketing is that the referring affiliate earns a commission if a referred prospect makes a purchase. Any affiliate program that aims to succeed in its recruitment efforts must uphold this principle, regardless of whether the prospect buys immediately, or delays her purchase until some time in the future.

To fairly and accurately distribute affiliate commissions requires a database that maintains a list of the relationships between prospects and the affiliates that referred them. Ideally, this database would be centralized, hosted as part of the software application that manages the affiliatte program. But this approach would only be feasible if web visitors could be automatically distinguished from each other, using a unique and permanent identity code.

Unfortunately (for affiliate program operators) web users prefer to surf anonymously. Web browser software is designed to allow a surfer to visit any website without leaving a personal identity trail. So, affiliate programs need a less intrusive method of tracking the associations between their members and the surfing public. The solution adopted by most programs, including ClickBank, is to distribute the database throughout the internet, storing a tiny fragment of information on each prospect`s computer. They implement this using cookies.

ClickBank uses a mechanism known as the hoplink system tto record cookies on a prospect`s computer, storing multiple affiliate referral relationships in a single cookie. Every time a prospect is referred to a new merchant, her existing referral cookie is updated to reflect the association between the new merchant and the affiliate that referred her.