What is a SKAN Postback Window?

A SKAN Postback Window is a fixed time frame in Apple’s SKAdNetwork where user behavior is measured and encoded into a conversion value — before Apple sends the postback that attributes the install to an ad.

Instead of sending real-time event data, SKAN waits for one of these windows to end, adds a delay, and then sends a privacy-safe postback to the ad network or MMP.

Each window gives you a limited chance to capture user behavior and assign value.

How does it work?

SKAN 4.0 introduced three postback windows:

1. 0–2 days
   
   

2. 3–7 days
   
   

3. 8–35 days
   
   

You can choose to lock a window early (via lockWindow = true) to trigger a postback sooner. Otherwise, SKAN will wait until the window naturally closes and apply a random delay to protect user privacy.

Each postback contains:

• A conversion value (coarse or fine)
  
  

• A source identifier (ad campaign metadata)
  
  

• A postback number (1, 2, or 3 — depending on the window)
  
  

• A delayed timestamp range, not exact timing

Only one postback is sent per window — and no updates can happen once it’s triggered.

Why it matters

Understanding postback windows is essential for:

• Mapping key user actions (like trial start or purchase) to the right time frame
  
  

• Designing onboarding and paywall flows that fit within attribution windows
  
  

• Maximizing signal in a system with limited data
  
  

• Managing optimization cycles (since postbacks are delayed)
  
  

The SKAN postback window defines how and when your campaigns get credit — and how much visibility you have into user value over time.

Optimizing for it is the key to making SKAN work for performance.