html - Fallback background-image if default doesn't exist

Question

I want to set an image as a background, however the image name might be either bg.png or bg.jpg.

Is there any non-javascript way to create a fallback to an alternative image if the default background doesn't exist?

body{
    background: url(bg.png);
    background-size: 100% 100%;
    width: 100vw;
    height: 100vh;
    margin: 0;
}

Answer 1

You can use multiple backgrounds if there is no transparency involved and they occupy all available space or have the same size:

div{   
     background-image: url('http://placehold.it/1000x1000'), url('http://placehold.it/500x500');
     background-repeat:no-repeat;
     background-size: 100%;
     height:200px;
     width:200px;
}

<div></div>