How do I preview a form before publishing it?

Open the form in the form builder and click "Preview" (also available in the "Share form" dialog). A new browser tab opens showing a mock web page titled "Your website" with the note "This is a preview of how the widget will look and behave on your website", and your widget embedded exactly as it will appear. Any unsaved edits are saved before the preview opens so it always reflects the latest state.