The command save-some-buffers , which is bound to C-x s by default is helpful when you need to save lots of buffers efficiently. We may then leverage this function to add a new association between a key, a function, and a brief explanatory statement. ( add-to-list 'save-some-buffers-action-alist ( list "d" ( lambda ( buffer ) ( diff-buffer-with-file ( buffer-file-name buffer ))) "show diff between the buffer and its file" ))