I don’t think I quite understand @Richard Fahey , how would you be able to link unknown users to anything, if you don’t know them.
Can you provide a little more context?
In my setup, we fire an Identify call at login (and several other places) inside of our SaaS tool. This allows us to know who the users are. We have a unique model, where inside our product, you might relate to several businesses, and so by switching to a specific business, we fire a group call, which includes the User ID, to attribute the user to that business.
I’d love to get a better sense of your use case to be able to help out.
Curious to hear more details as well - for the meantime, just remember that Profiles:Groups is a many:many relationship, which can add extra caveats to any probabilistic matching like you’re describing.