Difference between `form.validate_on_submit()` and `form.validate()`

Question

What is the difference between form.validate_on_submit() and form.validate()?

In the Flask WTF docs, the author uses form.validate_on

Answer 1

validate_on_submit() is a shortcut for is_submitted() and validate().

From the source code, line 89, is_submitted() returns True if the form submitted is an active request and the method is POST, PUT, PATCH, or DELETE.

Generally speaking, it is used when a route can accept both GET and POST methods and you want to validate only on a POST request.