What happens when a required form field is left blank?

When a required form field is left blank, it generates an error message. This mechanism is designed to ensure that users provide all necessary information before submitting the form. The error message typically alerts users that they must fill in the required fields, thereby preventing them from proceeding with the submission until they comply. This ensures the integrity and completeness of the data being collected, as incomplete forms would lead to insufficient information gathering for marketing or sales efforts.

In contrast, automatic default values could lead to misleading data, allowing forms to be submitted without true user input. Saving forms with incomplete data would defeat the purpose of having required fields, and preventing the form from opening altogether would disrupt user experience, as users would not even have the opportunity to participate if they cannot access the form.