I have made a responsive website which is deployed on heroku. When I use chrome device toolbar to emulate phone viewport, the background image is scalable. But on an actual phone it's not; I just get a static zoomed-out image that occupies only part of the screen. Other than the image, everything else is working responsively.
Here's the CSS for my background image:
body {
  background-image: url('assets/backgroundimage2.jpg');
  background-position: center center;
  background-repeat: no-repeat;
  background-attachment: fixed;
  background-size: cover;
}