By now, we understand how important and critical forms are to all our applications. Since we will be working on data we receive from users, it's very important to make sure that the data we receive from our users is correct and valid.

For example, when we expect the user to enter an email address, we should not allow spaces or a few special characters in the email address. One more example, if we request the user to enter the phone number, it should not have more than 10 digits (excluding country code of course).

There can be many such custom valid checkpoints that we may want to have in our forms. 

In this section, we will continue to use both the login form and our registration form to learn how to add validations in both template-driven forms and model-driven forms.