Definition
Pixel tracking puts an image or script on the thank-you page and relies on the visitor's browser to report the conversion. It fails when the browser blocks third-party requests, when the user converts on another device, or when the conversion happens later, as a deposit does. A postback moves the report to the server side: the ad network stamps a unique click ID on every click and passes it to the landing page; the advertiser's system stores it; when the conversion happens, the advertiser's server calls the network's postback URL with that ID. No browser is involved.
How a postback works, step by step
- The advertiser appends the network's click-ID macro to the campaign's destination URL, for example
?cid={tracking}; the network replaces it with a unique ID on each click. - The landing page or tracker stores the ID with the visitor's session, lead or order.
- When the conversion happens, the advertiser's server (or the affiliate network's) requests the postback URL with the stored ID, a conversion type and, optionally, the payout.
- The ad network matches the ID to the click, credits the conversion to the right campaign, GEO, source and creative, and shows it in statistics.
- Duplicate calls for the same click are rejected unless the conversion type allows repeats, as revshare rebills do.
Postback chains with trackers and affiliate networks
Most media buyers put a tracker (Voluum, Keitaro, Binom, RedTrack, BeMob and others) between the ad network and the offer. The chain then has two postbacks: the affiliate network calls the tracker's postback with the tracker's click ID, and the tracker calls the ad network's postback with the ad network's click ID, which it stored when the click passed through. Each platform documents which macro carries its click ID; mismatched macros are the most common reason conversions do not appear.
Why postbacks fail
| Symptom | Usual cause |
|---|---|
| No conversions recorded | Click ID not passed to the landing page, or the wrong macro used in the postback |
| Rejected as unknown click | The ID was altered, truncated or expired before the conversion |
| Rejected as duplicate | A second call for the same click on a type that does not allow repeats |
| Conversions without revenue | The payout parameter was left empty |
Related terms
| Term | Relation | Where defined |
|---|---|---|
| CPA | What postbacks measure | Term page |
| ROAS | Needs the payout parameter | Term page |
| Tracking macros | The tokens in the URLs | Glossary entry |
| Ad server | Receives the postback | Term page |
FAQ
What is the difference between a postback and a pixel?
A pixel fires from the visitor's browser on the thank-you page; a postback is a server call that does not depend on the browser, so it survives ad blockers, cookie restrictions and cross-device conversions.
What does a postback URL contain?
The ad network's endpoint, the click ID of the visit, usually a conversion type, and optionally the payout or order amount so revenue appears in reports.
Why do my conversions not show up?
Most often the click ID was not passed to the landing page or the postback uses the wrong macro for it. Test with one click and one conversion before scaling, and check the platform's rejected-postbacks list for the reason.