How can I restrict form so only known users can access or submit

We have a few forms we've been running for years with great success. On one of the forms we want to restrict it so only known users can either access it or submit it.

Can Jotform refer to a list or table of email addresses or something to prevent unknown users from submitting data?

Hello,

We do not have a feature to accomplish this, but we have a workaround such as using our spreadsheet to form widget to authenticate email addresses or any value you want.

Guide: https://www.jotform.com/help/442-How-to-Use-the-Spreadsheet-to-Form-Widget.

Here's a demo you can check: https://www.jotform.com/92244553290961. Enter email1@example.com for existing email, and email5@example.com for non-existing email.

The method to show fields is by conditional logic:

Guide: https://www.jotform.com/help/196-Hide-or-Show-Multiple-Fields-at-Once.