I'm trying to set up cross device tracking in Google Analytics and was wondering what the best user ID to use to track the most users?
Here's what I have:
Email subscribers IDs Customer IDs
I don't see any ID for just those who purchase without starting an account.
It seems the one thing that most would have in common would be the email address but one isn't supposed to use personally identifiable information in Google analytics. So might one convert the email into a number that could be used?