Looking at referral success stories at Gmail and Uber, Bindle founders decided to incentivize users to invite their friends. If a user signs up via a referral link – both the user and the referrer user get 7 days for free.
The mechanism for tracking such signups is exactly the same as for the UTM parameters. We can think about a referral link as a normal link to the website which has the referrer user ID parameter. Sometimes it could be a UTM parameter (which is probably not that intuitive since it’s not a marketing campaign). Sometimes it could...