Some of the new input types simply change the appearance of the input field while others add validation. It is the ones that add validation that we are interested in here.
The most commonly used input field that has a new type is "email". A field of this type is allowed to contain one or more email addresses and in browsers that recognise the new type it performs at least basic validation to check that what the field contains at least look somewhat like email addresses. In fact there is nothing to stop future browsers from providing full validation of the email addresses for these fields without any changes to your code being required.
Other fields that also have built in validation based on the type include "url", "number" (which also allows you to specify min, max and step attributes to define the valid range for the numbers and the increment to use in browsers that display it as a spinner control), "range" (which also has min and max attributes but displays as a slider rather than an input field), "date" (which allows a minimum and maximum date to be specified and often displays a date picker to make entry easier), "month", "week", "time", "datetime", "datetime-local" and "color". With all of these field types the type already implies much of the required validation and the min and max attributes that some of these allow take care of much of the rest.
Between the new types and the extra attributes you can now specify most of the individual field validations that you need directly in the HTML. This just leaves the more complex individual field validations and cross field validations that can't be done by the HTML. In a lot of cases cross field validation isn't needed and the individual field validations are no more complex than can be handled by the new HTML and so relying on just the HTML validations is certainly possible for many forms.
This article written by Stephen Chapman, Felgall Pty Ltd.