I looked up many questions and answers here regarding labeling mandatory input fields. The de facto standard is an asterisk * to mark input as required. Also the common approach is to mark the required input as such.
My questions are:
- If all input in a form is required (or only 1-2 fields are optional) - does it still make sense sense to mark all of them as required?
- Is a caption like '* = mandatory input' still needed then or do people know what the asterisk means (balance b/w helpful information and added visual noise by the caption)?
 Just highlight the optional ones as such?