What is the difference between required and ng-required?

Question

What is the difference between required and ng-required (form validation)?

Answer 1

I would like to make a addon for tiago's answer:

Suppose you're hiding element using ng-show and adding a required attribute on the same:

will throw an error something like :

An invalid form control with name='' is not focusable

This is because you just cannot impose required validation on hidden elements. Using ng-required makes it easier to conditionally apply required validation which is just awesome!!