SKAd post-backs play an important role in conversion attribution. When a user installs and launches an app after viewing an ad, the device notifies the ad network to validate the install.
Apple has said the post-back conversion may include a conversion value and the source app’s ID if Apple determines that providing the values meets their privacy threshold.
Apple’s privacy threshold helps prevent advertisers from identifying a unique user. When Apple believes there’s a risk of identifying a user, it will mark all daily post-backs from that publisher as null.
Avoiding null values
To avoid null values for SKAd post-backs, you need to ensure that you get a minimum number of installs above Apple’s privacy threshold. The Unity team recommends aiming for a minimum of 30 installs per day.
If you see a lot of null values, we recommend reducing the number of campaigns and/or creatives per campaign. While you have a limit of 50 live campaigns and/or creative packs per app, using all of these may cause you to be below the minimum of 30 installs per day for the privacy threshold.