Using a Promo URL will allow you to offer discounts to your customers by sending out custom links, or having the links installed on certain web pages. Promo URLs can be handy if you're running a special or want to have local businesses or partners be able to offer discounted pricing for your event.
Promo URLs are available for every promo code you have on the system, both on venues and events. When you're in the screen managing your codes you'll see a "View Promo URL" button. Click that button to display the custom URL, and then copy the link on screen to use.
When a customer uses that link to go to the venue or event page the discount will be automatically applied to their order total when they add tickets to cart. So, it's easy on the customer - they don't need to enter the code. Then, in your reporting you'll easily be able to track how many tickets have been sold from that link by filtering for the promo code.