via smashingmagazine.com => original post link
When it comes to form validation, we can explore it from two perspectives: usability and accessibility. “What’s the difference between usability and accessibility?” you may ask. Let’s start from there.
Usability
Usability is about improving a given action until it’s as easy and delightful as possible. For example, making the process of fixing an invalid field easier or writing better descriptions so the user can fill the field without facing an error message.