How to track user's action on another site?

Question

I am doing coupon gifting platform.I am working on rails platform.

My problem is I want to track whether user performed checkout using the coupon given by my site or not.

Means suppose I am running xyz.com to provide gift coupons of abc.com. Then if any user checkouts using the coupon code from my site how I will come to know about that?

Answer 1

This is not possible until the other site give you some sort of access to his purchases using coupons data.