SKAdNetwork
SKAdNetwork is Apple's privacy-preserving attribution framework for iOS ads: instead of identifying the user, iOS sends the ad network a signed, delayed postback saying a campaign produced an install, with a limited conversion value.
Postbacks are aggregated at campaign level, arrive hours to days after the install, and carry less detail for low-volume campaigns because of Apple's crowd-anonymity thresholds. No attribution provider can enrich them or make them real-time.
SKAdNetwork 5 added re-engagement attribution and coarse conversion values across its three postback windows. It runs alongside click-based attribution rather than replacing it — it can't route a user or report owned channels like email and QR. SKAdNetwork 5: what changed covers the details.