# Postback URL

> A server-to-server URL that an affiliate network or external platform calls to notify AnyTrack of a conversion, matched back to the original click via the Click ID.

A postback URL (industry term; also **callback URL** or **server-to-server URL**) is how an affiliate network or external platform notifies AnyTrack that a conversion happened. The network stores the [Click ID](/glossary/click-id) — placed in its tracking/SubID parameter by [AutoTag](/glossary/autotag) — and, on conversion, calls the postback URL with that Click ID so AnyTrack can attribute the sale to the original ad click and forward it via the [Conversion API](/glossary/conversion-api).

## What a Postback URL means for each marketer

- **Affiliate marketer:** The core mechanism — the network credits the sale by calling this URL.
- **Lead-gen marketer:** Returns offline or CRM conversions from non-catalog platforms, server-side.
- **Business owner:** Reports conversions from their offers without a browser.
- **eCommerce marketer:** Rare — stores use platform webhooks instead.

## How a Postback URL differs from webhooks

- [Incoming Webhook](/glossary/incoming-webhook) — a Postback URL is the network-specific, Click-ID-keyed *subtype*; not the generic JSON-payload webhook.
- [Outgoing Webhook](/glossary/outgoing-webhook) — opposite direction.

## How AnyTrack uses the Postback URL

A postback requires a **paid** subscription and the Tracking Tag installed (for Click ID generation). AnyTrack classifies the conversion by the `amount` parameter: `amount = 0` is a **Lead**; `amount > 0` is a **Purchase**.

**Never trim a postback URL.** Removing parameters (especially the Click ID) breaks the Click ID handoff — a missing Click ID yields "No match found" and the conversion is lost. Avoid link shorteners on tagged affiliate links; they strip the tracking parameter.