background image stretch to fill

background: url('../images/teaser.jpg') no-repeat center #eee;
background-size: cover;

.cover {
  object-fit: cover;
}

html { 
  background: url(image.jpg) no-repeat center center fixed; 
  -webkit-background-size: cover;
     -moz-background-size: cover;
       -o-background-size: cover;
          background-size: cover;
}