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What Is a Postback URL? A Complete Guide for Affiliates

A postback URL is a server-to-server callback that tells your ad platform a conversion happened. Learn how postbacks work, what parameters they carry, and why they beat pixel tracking.

A postback URL is an HTTPS endpoint that an affiliate network or tracker calls when a conversion is confirmed. It's a server-to-server (S2S) notification — no cookie, no browser, no pixel — that pushes the click ID back to the platform that originated the click so the conversion can be attributed.

If you spend money on Meta, Google, TikTok, or any other ad platform and earn revenue through Impact, PartnerStack, ShareASale, or another affiliate network, postback URLs are how those two worlds stay in sync.

How a postback URL works

  1. A user clicks your ad. The ad platform appends a click ID (gclid, fbclid, ttclid) to the destination URL.
  2. Your landing page captures the click ID and passes it to the affiliate link as a SubID.
  3. The user converts on the merchant's site. The affiliate network records the conversion against your SubID.
  4. The network fires a postback URL with the SubID and conversion details to your tracker — or directly to the ad platform's conversion API.

What a typical postback URL looks like

https://affpixel.com/p/your-id?sub_id={SUBID1}&payout={PAYOUT}&order_id={OID}

The values in curly braces are macros. The affiliate network replaces them with real values at fire time — {SUBID1} becomes your stored click ID, {PAYOUT}becomes the commission, and so on.

Postback URL vs conversion pixel

  • Pixel: fires from the browser. Breaks under ad blockers, ITP, and iOS 14+ restrictions.
  • Postback: fires server-to-server. Independent of the user's device or cookies.

For affiliate marketing the postback wins almost every time. Mobile users, privacy browsers, and cross-device journeys all drop pixel data; the postback still arrives.

Why affiliates need postbacks in 2026

Ad platforms now require conversion data to optimize bids. Without a postback you either feed them noisy on-site events (lead form fills that aren't real revenue) or nothing at all. With a postback you send confirmed, payout-verifiedconversions back to Meta CAPI and Google's offline conversion endpoint, which dramatically improves auction bidding.

Next steps

Read our step-by-step postback setup guide to wire your first one, or jump straight to the Impact.com and PartnerStack integrations.