Mixpanel can track events across domains and hosted subdomains
Tracking your users across multiple domains is possible with Mixpanel if you:
Ensure data from the sites are going to the same project: In other words, initialize the Mixpanel library using the same project token on all sites.
Keep the user’s identity consistent across sites: Mixpanel uses a unique identifier called distinct_id to differentiate one user from another. The distinct_id lives in the cookie, but since the user’s cookie changes as they move from one site to another, you’ll need to pass the distinct_id from the first site to the second.
Steps to pass distinct_id between sites
Grab the distinct_id of a user from the first domain by using mixpanel.get_distinct_id() in the loaded callback.
Pass the user’s distinct_id from the first site to the second via a URL parameter (Not sure how? Here’s more information on adding properties into the URL). You can also pass properties assigned to a user from the first site to the second via the URL parameter.
When the user lands on the second site, call mixpanel.identify(distinct_id) before making any other Mixpanel calls.