Definition

Postback (server-to-server) tracking

Postback tracking, or server-to-server (S2S), reports conversions from the merchant's server directly to the network's server using a click ID — no browser cookies involved. It is the cookieless backbone of modern affiliate attribution.

For publishers, S2S mostly means resilience: attribution survives cookie blocking and Safari's storage limits, as long as the click ID made it through the redirect. The link-health implication is unchanged — the click must register at the network hop — but the browser-side fragility shrinks.