Hi @SeanMcC ,
Thank you for this great question about Sign-Up forms!
It sounds like what you are looking for is a Hidden Field that would be captured as a user submits the form in order to collect URL. This field is not shown to users on the frontend, but is captured at a Profile level in Klaviyo as a Property, which you can then use to segment the user, or to add a conditional split to your Welcome Series flow in order to send them the most relevant content.
By default, all new signups have a Source property as a hidden field. This identifies where the profile came. To set up an additional Hidden Field, please follow these steps while in the Form Editor:
- Navigate into your button editor
- Select +Add a property under SUBMIT HIDDEN FIELDS
- Choose an existing profile property or create a new one
- Input the value for the property (URL)
- Save the button

Note: If you add hidden fields that correspond to properties that already exist on someone's profile, they will be overwritten by the new value when someone submits the form.
If you are unfamiliar with Properties in Klaviyo, feel free to check out this guide in the Help Center: Profile properties reference.
You can also reference these other helpful thread on the Community that discuss the use of Hidden Fields and Custom Properties:
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Hope this helps!
-- Ashley Ismailovski