This is super handy for password fields with requirements for certain characters/limits, and with email fields to make sure the email address looks real.
jQuery’s Formvalidation plugin is my go-to pick since it’s lightweight and super easy to customize. It works on all the major frameworks including Foundation and Bootstrap.
Plus the online docs are pretty straightforward so even non-coders should be able to figure them out.
But feel free to search through Google and see what else you can find. This is not the only form validation plugin and it’s not always the best choice for every website.