I have a pop-up where users can sign up to receive a promo code. What's the best way to handle this in Klaviyo?

Hi @stjoad - welcome to the community!  It’s a common and excellent question.  For your newsletter signup Flow (Welcome Series), my recommendation is either of the following options:

1. In your List Subscribed Triggered Flow (Newsletter) - you can put a Flow Filter where Placed Order is Zero Times Over All Time.  This means if someone makes a purchase, they exit the Flow completely (including any subsequent emails in your Flow) and won’t receive any emails from this Flow.  If you still want people to go through the Flow even if they’ve purchased, you can do the next method here.
2. Alternatively, you can put a Conditional Branch in your Flow for anyone who has purchased and send an alternative first Email without the discount code.  Then, link that Flow path back to the rest of the messages in your Flow to continue to through the rest of the Flow.

For your Footer Subscribe, if you are using an embedded Klaviyo Signup Form, you can apply a “Source” value like “Footer Subscribe” that specifies it came from the Footer.  Then, similar to the method #2 above, in your Flow, you can put a Conditional Branch in your Flow where the Source is ”Footer Subscribe” to get the alternate email without the discount code.

If your Footer Subscribe is a Shopify form or a custom Klaviyo legacy HTML form, you can either use a Shopify Tag or reference the Klaviyo Legacy HTML guide to define a “Source” value.  Make sure you set your Conditional Branch on the proper field and value. 

Some documentation for reference here:

• Getting Started with Flows - Set Up Your Trigger Filters and Flow Filters
• How to Add a Conditional Split to a Flow
• Customize the Signup Source Property of a Legacy Form

Hope this helps!