Tracking permission 1 sets device.ifa. An ID SDK 2 resolves login email into user.eids 3; both travel together. App dev owns integration, not ad ops; EIDs clear on cold start; new ID = app store release. Unlike web 4 and PBS 10, no sync pixels; IFA and EIDs never merge.
FIELD NOTES
- SharedId defaults OFF on mobile; flip it for free probabilistic signal
- Login apps bypass IFA: hashed email as EID keeps full addressability
- ATT opt-out ~75% on iOS — IFA null for most; EID path is critical