For Users with Custom ID, how is the main app_user_id determined?

  • 14 November 2022
  • 1 reply

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If a user is first identified with an anon ID, then logs in to my app and is signed in to revenuecat with a custom ID, does that custom ID always override as the app_user_id?

The documentation explains how aliases are merged, but doesn’t say which ID is set as the main app_user_id (e.g. for webhook data).


I’m using the Firebase RevenueCat extension, and I want to be sure that the app_user_id will always be my custom ID if one is set, because the extension syncs data to firestore via that id. If it uses the anon id, then the data will not be correctly synced.


During testing it seems like this is the case, but I want to be sure. Will the custom ID always become the app_user_id?

1 reply

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Actually I’m noticing that for transfer events, the app_user_id used is consistently the anonymous $RC ID (for both sender and recipient). So the firebase extension is syncing data to phantom uids in my database. Is there a reason that these events would be different? And Is there any way to prevent it without forking my own version of the firebase extension?