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What is a postback, and how do I set one up for my campaign?

Reviewed by Visprisca Ad Tech Engineering Team•Last updated: October 2026
Direct Answer

A postback (or server-to-server callback) is an automated HTTP request sent from an attribution platform (MMP) or web server to a DSP when a user converts. It passes back the original auction click_id, timestamp, and event value, allowing the bidding engine to attribute success and train machine learning models.

Detailed Explanation

When a user clicks an ad served by a DSP, the DSP creates a unique identifier (often called click_id or transaction_id) and embeds it into the destination click URL. The mobile attribution platform (such as AppsFlyer, Adjust, or Singular) captures and stores this ID.

Later, when the user installs the application or completes a purchase, the MMP's SDK logs the event on its servers. The MMP looks up which ad click brought the user in, and fires an HTTP GET or POST request directly to the DSP's postback endpoint with that click_id.

Because this communication happens server-to-server, it does not rely on third-party browser cookies, making it the most resilient attribution mechanism in modern programmatic advertising.

Technical Definition: Server-to-Server (S2S)

Direct machine-to-machine communication over HTTP APIs, bypassing client-side web browsers or mobile operating system sandboxes.

Illustrative Worked Example*Clearly labeled illustrative per Accuracy Rule

Typical Postback Payload Anatomy

A user purchases a $49.00 product subscription after clicking a programmatic ad.

›1. Click Event: DSP serves click URL: https://app.appsflyer.com/app.id?clickid=vis_9a8f7c1e
›2. User Action: User completes in-app subscription 4 hours later.
›3. S2S Postback Triggered: https://engine.visprisca.com/postback?click_id=vis_9a8f7c1e&event=subscription&revenue=49.00&currency=USD
›4. DSP Resolution: DSP matches vis_9a8f7c1e to Campaign #402, Creative #12, Publisher Domain 'newsapp.com'.

The bidding engine instantly rewards that publisher placement and device cohort with higher valuation weights.

What to Do Next

  • 1Configure your MMP's partner integration dashboard with your DSP postback endpoint URL.
  • 2Verify macro tokens: ensure {click_id} and {revenue} match your DSP's parameter documentation.
  • 3Execute a test conversion with a test device before launching live spend.

Related Questions

What happens when conversion postbacks are delayed?Why is my CPA rising, and what should I check first?Which events should I send back as postbacks, and why?
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Postback Troubleshooting Guide

Test your postback URL formatting and inspect macro expansions.

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