Hi @theokoles
Thank you for reaching out to Paid Memberships Pro.
I recommend setting up an analytics software such as Google Analytics with a custom goal and track your top referring sites or some similar service.
We do not track external referrers during signup.
Another option would be to create a custom field of “How did you hear about us” and let new members fill this out during their checkout. You may add custom fields to Paid Memberships Pro by using the Register Helper Add On – https://www.ads-software.com/plugins/pmpro-register-helper/
You then can export member data to a CSV and aggregate this data.