A form key is a unique id of the corresponding form. With this key, you are able to determine which form has already been opened and/or submitted. The following article will explain where you can find this form key.
In the left-hand panel, go to ‘Data collection’ > ‘Feedback forms’.
Click on the icon with three dots of the feedback item you would like the form key of. Select ‘Copy form key’. The form key, a number and letter combination, is now copied to your clipboard.
Open the form builder and go to DEPLOY
In the public landing page link, you will find the unique form key at the end of the URL.