Using a value rule to restrict the data you collect
What is a value rule?
Validation rules are used to restrict data input by specifying a criterion that all valid field values must meet. These validations work while the visitor is filling in the form, before it is submitted. There are common field validations we all know, such as an “email validation”. In this validation the email field is checked and an error message is given if the format of the email address is not correct. In addition, there are custom field validations a form owner can decide to apply specifically on his form in order to collect a certain kind of data.