Any good way to save an unsubmitted form?

Any good way to save an unsubmitted form?

I know it's a difficult task, but is there any good way to save form input
when the user navigates to a different page without submitting, so when
they come back they won't have to re-enter the info?
I'm using Rails 4, Simple Form, and jQuery, but I'm open to any solution
that isn't an ugly hack.