Here's an example of what I mean:
-- brand new ios install --
- User downloads facebook
- User signs into facebook
- User downloads instagram
- Instagram allows user to sign in with the facebook account they just signed in with
Normally this could be accomplished using vendor id/app groups, however Instagram and the Facebook app are released on the app store under different vendors (Instagram, Inc. and Facebook Inc., respectively).
Is there a way to identify a user with a high degree of confidence across two apps (that you control) under different app store developer accounts?