An affiliate tracking ID is a unique identification code or username that is used to track an affiliate's performance as part of an affiliate marketing program. It is usually included in a special URL that the affiliate uses to promote the brand's products or services. When a customer clicks on this URL and makes a purchase or takes another desired action, the tracking ID helps the brand track the affiliate's performance and the traffic that the affiliate has brought to the brand's site. Read the full review to learn more about affiliate tracking and the best tools to use in your affiliate marketing program.