An SID is a parameter you append to your product’s campaign URL. It allows you to pass us custom information. When a customer completes an advertiser’s offer, we will send the SID value back to you, along with the customer’s information.
Most merchants use the SID to pass us a unique value that identifies a customer.
For example, some merchants generate a user ID for every visitor to their Web site. If the visitor clicks a Get It Free link, the merchant passes the user ID to the SID value, which gets sent to us. Once the visitor completes an advertiser’s offer, we’ll send the merchant an HTTP request with the customer’s information and the SID. The merchant can then use the SID value to identify the customer and deliver the product. Note: the SID value cannot exceed 220 characters in length.