Server-to-Server Tracking Basics for Affiliate Marketing Campaigns

In affiliate marketing (and virtually all performance marketing), there are two primary ways to track transaction flow from the moment of first click to the point where conversion takes place. Either you are tracking users via cookies on their browser, or doing a server call to store a unique identifier. You might have read my post a while ago about the difference between client-side tracking and server-side tracking. Based on a large number of inquiries to our customer support and a general misunderstanding of how server-based tracking works, I thought it would be helpful to cover the basics of server-to-server tracking, including various implementations and benefits.

The Basics of Server-to-Server Tracking

Generally speaking, server-to-server tracking on the web works by generating and storing a unique identifier of some kind when a user clicks a tracking link or generates an ad impression. When the same user later makes a conversion (or other trackable action), the unique ID is matched back to the user. This is done by posting that same unique identifier back to the tracking server.

How Server-Side Tracking Works with Affiliates

Affiliate tracking software like TUNE allows you to track which conversions come from which affiliates. If you choose to utilize server-to-server tracking (sometimes called server-side tracking, server response tracking, or postback tracking), a unique transaction identifier (ID) is generated when a user views or clicks an ad with an affiliate link.

The ID gets passed through the tracking URL to the server hosting the offer landing page, where it is stored by the advertiser. This ID is then passed through as a variable throughout the conversion funnel.

When the transaction is complete, the ID is passed back to the affiliate tracking server by calling a “postback URL” at the time of conversion.

How Does the Advertiser Store the Transaction ID?

There are several ways an advertiser can store the transaction ID. One method is for the advertiser to generate a cookie on the landing page that carries through the duration of the transaction. Another method is to log the transaction ID as a hidden variable. A third option is to continue carrying the transaction ID as a URL parameter until the conversion completes. This process will likely vary depending on the CRM solution used by the advertiser.

This diagram shows the progression of a transaction from the initial click to postback.

Types of Identifiers in Server-Side Tracking

The Transaction ID generated for server-side tracking can be a number of things. In some cases, it may be a randomly generated unique ID. A transaction ID can also be based on a combination of available variables, like a username, email address, or the IP address logged at the time the transaction starts. For some types of affiliate transactions, using the affiliate ID may also work as the identifier to track the transaction.

Third-Party Tracking Systems

For affiliates who are tracking campaigns independently, it’s important to note that they must implement their own postback URL. The round trip for third-party tracking systems starts with the affiliate appending a transaction ID to the offer URL. When that offer URL is clicked, the affiliate transaction ID is logged. The tracking server then passes a unique transaction ID to the advertiser’s server, where the transaction ID is logged by the advertiser. When a conversion occurs, the advertiser posts back to the tracking software, which in turn posts back to the third-party tracking system for the affiliate, completing the round trip.

Using an iframe or image pixel for third-party tracking will not work if the advertiser is only using server-side tracking, because the postback process will not cause the image pixel to fire on conversion.

Server-to-Server Tracking Benefits

The simplicity of placing an iframe or JavaScript pixel for cookie tracking is certainly attractive, but there are definitely benefits to getting server-side tracking in place.

One primary advantage of server-to-server tracking is accuracy. By generating a unique identifier at the time a click or impression occurs, you get a greater degree of accuracy in tracking a specific transaction back to a specific affiliate. In most cases, the transaction ID is tied to something constant, like an email address or username, which again results in a higher degree of accuracy.

Another added benefit of server-side tracking is the ability to add additional third-party tracking, so an affiliate can use the transaction ID to verify campaign results independently.

Pixel tracking will never come close to the accuracy that server-to-server tracking provides, especially as more browsers continue to block cookie-based tracking by default. For more on this trend, see our articles on the impact of full third-party cookie blocking by Apple ITP and the restrictions placed on third-party cookies in Google Chrome.

The Dual-Tracking Option

While server-to-server tracking is extremely accurate, it’s also possible to simultaneously track a transaction using both an image pixel and server postback tracking. When both options are used, server-side tracking is configured as described above, while a cookie is also placed on the user’s browser. If both tracking methods log the same transaction, the tracking software only counts the transaction once, since the transaction ID for the cookie and the transaction ID for the server response postback are the same value.

The primary reason most affiliate tracking continues to rely on cookie-based methods such as iframe and image pixels is because server-side tracking requires advertisers to do some additional work: storing the tracking identifier on their own servers and passing it back to the affiliate tracking platform. For this reason, the convenience of an iframe is often chosen over the required implementation for the advertiser. It is simply easier to place a pixel than store and pass transaction IDs.

Marketers who continue to use cookie-based tracking do so at their own risk. Like I said above, browsers are moving toward a cookieless future. If you don’t have a cookieless tracking solution to keep up, then your campaigns and your business will suffer.

Learn More About Conversion Tracking

To learn more about the various types of tracking methods used in affiliate marketing, read our white paper, “How to Become a Track Star: Your Guide to Tracking for Performance Marketing Campaigns.”

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