Postback tracking, also called server-to-server (S2S) tracking, is how most affiliate networks record conversions today. Instead of relying on a cookie in the visitor’s browser, the advertiser’s server tells your tracking server directly that a conversion happened.
The problem with cookies and pixels
Browser pixels fire from the visitor’s device. Ad blockers stop them, browsers limit third-party cookies, and in mobile apps there is often no browser at all. Every lost pixel is a conversion nobody gets paid for, and the affiliate who sent the traffic stops trusting your numbers.
A postback doesn’t depend on the visitor. The only thing that has to survive is one value: the click ID.
How a postback works, step by step
- The click. A visitor clicks an affiliate’s tracking link. Your tracking server records the click and gives it a unique click ID.
- The redirect. The visitor is sent to the advertiser’s landing page with the click ID added to the URL, for example
?click_id=abc123. - The advertiser stores it. The advertiser’s site or app keeps the click ID with the visitor’s session or order.
- The conversion. When the visitor signs up, deposits or buys, the advertiser’s server calls your postback URL with that click ID, for example
https://trk.yournetwork.com/postback?click_id=abc123&amount=499. - The match. Your tracker finds the click, credits the right offer and affiliate, and records the revenue and the payout.
- The affiliate postback. If the affiliate has their own postback set up, your tracker passes the conversion on to them, with their sub IDs.
What goes in a postback URL
The advertiser fills in placeholders, often called macros, with real values. The usual ones are:
- Click ID: the only required value. It ties the conversion to the click.
- Amount: the sale value, for revenue share or CPS offers.
- Event: which goal was reached, such as install, signup or first deposit, when an offer pays for several.
- Transaction ID: the advertiser’s own order ID, so the same conversion isn’t counted twice.
- Currency and status, when the advertiser can send them.
When the advertiser limits the click ID
Some advertisers only accept numbers in the click ID field, or only a short value of 10 to 12 characters. If your tracker can’t send the click ID in their format, the postback can’t match. In Affilix you choose the click ID format per offer: standard, numbers only, or a short 12-character ID. The short ID still resolves to the full click, so reports and postbacks work the same.
How to test a postback before going live
- Open the offer’s tracking link yourself and copy the click ID from the landing page URL.
- Call the postback URL with that click ID, from the advertiser’s side or with a test tool.
- Check the conversion appears against the right affiliate, and look at the postback log for the response.
- Fire the affiliate’s postback and confirm they received it.
Affilix logs every incoming and outgoing postback with its response, so when a number doesn’t match you can see exactly which call failed and why.
Postback vs pixel: which should you use?
Use a postback whenever the advertiser can make a server call. Keep an image pixel for the cases where they can’t, such as a simple thank-you page on a hosted store. Many networks run both: postbacks for most offers, pixels for the few advertisers who can only paste a tag.
Read more about affiliate tracking in Affilix and postbacks, webhooks and the API.