Disable password confirmation during registration

Some users wants to make the registration process shorter and easier. One of fields that can be removed is the Password confirmation.

Easiest solution is: you can simply remove the password_confirmation field from the registration form located at devise/registrations/new.html.erb (new.html.haml if you are using HAML), which disables the need to confirm the password entirely!

The reason for this lies in lib/devise/models/validatable.rb in the Devise source:

Note that the validation is only triggered if password_required? returns true, and password_required? will return false if the password_confirmation field is nil.

Because where the password_confirmation field is present in the form, it will always be included in the parameters hash , as an empty string if it is left blank, the validation is triggered. However, if you remove the input from the form, the password_confirmation in the params will be nil, and therefore the validation will not be triggered.

Inspired by @mistertim in stackoverflow