If you want to reject duplicate input values for a form field, you can easily do that by enabling the option Don’t allow duplicate values. You can find it in the Form Editor → Edit Field panel after you select a field.
The most relevant use case example is that of unique email addresses. There are situations in which you don’t want to accept duplicate email addresses. If
email@example.com has been used once, it can’t be used again.
When form users provide input that already exists in your form submissions, they get the following field validation error:
The following form fields have the option to reject duplicate values: Short Text, Name, Number, Email, Website, Masked data.