Hello @Frank,

Great question!
At this time, Klaviyo forms do not have the functionality to create an alert if someone is already an existing subscribed to your Lists. 

Some plausible work around to this would be enabling the signup form targeting setting of Don’t show to existing Klaviyo profiles. By enabling this setting in your signup form, it would prevent the form from appearing for customers who are recognized as already being existing members of your Klaviyo account. Alternatively, you can also use the Target visitors by list or segment setting and exclude customers who are already existing subscribers of your particular list. You can learn more about all the available signup form settings and targeting behaviors from the Overview of the Signup Form Builder article. 

Another solution would be to build your own custom signup form while leveraging Klaviyo’s track and identify APi to evaluate the subscriber’s list membership to trigger that alert message or not. Since this would be a custom solution, I would recommend working with a developer you are familiar with or finding a Klaviyo partner who can assist you in this endeavor. Resources Klaviyo have on this custom solution can be found below:

• Legacy Signup Forms vs. Built-In Signup Forms
• How to Add and Customize a Legacy Embedded Signup Form
• How to Add and Customize a Legacy Popup
• How to Add and Customize a Legacy Flyout
• Track and Identify API Reference
• Getting Started with Klaviyo APIs

Thanks for being a member of the Klaviyo Community!

David

Hey David,

thank you for your reply.

I played with targeting settings and they seem to work as long as there are the cookies. Looks like some of the customers delete those cookies regularly and trigger the popup every time. (My Guess)

So need to check that custom signup path ...

Thank you David