This add-on sends your page URI to a third-party server, which in turn retrieves it in hopes of getting the same output as you do in your browser. Obviously, any page that requires any sort of authentication will be broken. That is not to mention that you probably won't want your pages sent anywhere for a job which can perfectly be done locally. Probably works for some static public websites if you disregard privacy, useless for anything else. Use a local adblocker to block ads and remove clutter.