Should you mark required fields?
Summary: Using an asterisk to mark required fields is an easy way to improve the usability of your forms. Only marking optional fields makes it difficult for people to fill out the form.
What does fields marked with an asterisk are required mean?
Fields marked with * are mandatory
Using an asterisk (*) symbol content authors notify mandatory field. This is said to be one of the accessible modes of identifying a mandatory field, however this method also will be a problem with screen readers in certain times.