What is Postback?

A postback is a server-to-server signal sent by Apple to confirm that a campaign led to an install. In SKAdNetwork, it’s the only mechanism available for ad networks to know whether their ads resulted in successful conversions, without any access to user identifiers.

Think of it as a digital receipt: when someone installs and opens your app after clicking an ad, Apple sends a postback to the ad network that “won” the attribution. For example, if a user installs a language learning app after seeing an ad on TikTok, Apple will send a postback to TikTok with limited, anonymized information confirming the install.

How does it work?

After the app is opened, SKAdNetwork starts a measurement window to observe user behavior. You can assign conversion values during this window to summarize what the user did. Once the window ends — or if you lock it early — Apple sends a postback to the attributed ad network.

The postback includes:

• A campaign ID (set by the ad network)
  
  

• A conversion value (what the user did)
  
  

• A timestamp (delayed and sometimes coarse)
  
  

Only one ad network receives the postback, the one that Apple determined to be responsible for the install. In SKAN 4.0, multiple postbacks can be sent across different time windows to reflect longer-term behavior.

Why it matters

Postbacks are the core unit of measurement in SKAdNetwork. They replace traditional user-level attribution with aggregated feedback. They allow advertisers to:

• Know which campaigns are working
  
  

• Tie in-app performance to media spend
  
  

• Inform budget decisions without compromising user privacy
  
  

Because postbacks are delayed and anonymized, their value depends entirely on how well your conversion values are structured. If your team knows what to signal, postbacks become a reliable foundation for optimization, even in a privacy-first world.