Alternatively, if they perform an action that in your backend identify them (but this data isn't stored in analytics), you can send the visitor ID to your backend and then perform visitor stitching in your business warehouse. To then get it back to Adobe Analytics, you could collect Visitor ID, create a classification on that variable and upload a unique identifier back. That would allow you to see performance for each unique customer across devices...
The Visitor ID is reliant on the cookie, so if you browse (not logged in) across different devices and browsers you'll have different Visitor ID's. The only way I know of to de-duplicate is via visitor stitching if that user logs on across these browsers or devices. If the user doesn't log on then i don't believe there is a simple answer.
Alternatively, if they perform an action that in your backend identify them (but this data isn't stored in analytics), you can send the visitor ID to your backend and then perform visitor stitching in your business warehouse. To then get it back to Adobe Analytics, you could collect Visitor ID, create a classification on that variable and upload a unique identifier back. That would allow you to see performance for each unique customer across devices...
