What is a postback in search arbitrage?
A postback is a message sent from one server to another to report that something happened, such as a keyword click or an amount of revenue. It carries the click ID of the visit, so the receiving system can match the event to the original ad click. Because it is server-to-server, it does not depend on browser cookies.
The chain has two hops. The feed or its provider sends a postback to the tracker with the Click ID and the revenue. The tracker then forwards a conversion, with its value, to the traffic source through that platform's Conversions API.
Postbacks are more reliable than a tracking pixel, which runs in the browser and can be blocked or lost. They still have limits. Revenue for a visit may be reported hours later and revised afterwards, a problem known as revenue reporting delay. Many set-ups therefore fire an early event on the keyword click as a proxy, then send the actual value when it is known. Attribution is only as good as the data the feed releases.