How does it work? Every image you add to a page or post will be automatically run through Smush.it behind the scenes. You don’t have to do anything different. N. B. In some cases GIFs should be replaced with PNG files. You can control this behaviour on the Options page. It is off by default. You can also run your existing images through Smush.it via the WordPress Media Library. Click on the Smush.it now! link for any image you'd like to smush.