The URL Builder helps you construct URLs that can populate Marketo hidden form fields.
Learn how to create hidden fields in forms and edit their settings in Set a Form Field as Hidden.
Select a landing page, click on Landing Page Actions, hover over URL Tools, then click on URL Builder.
Select the field(s) you want to use, enter the value, and click Update URL.
Great work! You can now copy and paste the URL and use it on the web.