#function-url-data-uris

Require or disallow data URIs for urls.

a { background-image: url('data:image/gif;base64,R0lGODlh='); }
/**                        ↑ 
 *                  This data URI */

This rule ignores variables inside url function ($sass, @less, --custom-property).

#Options

string: "always"|"never"

#"always"

There must always be data URIs in url.

The following patterns are considered warnings:

a { 
  background-image: url(image.gif) 
} 
@font-face { 
  font-family: 'foo'; 
  src: url(foo.ttf); 
}

The following patterns are not considered warnings:

a {
  background-image: url('data:image/gif;base64,R0lGODlhAQABAIAAAAUEBAAAACwAAAAAAQABAAACAkQBADs=')
}
@font-face { 
  font-family: 'foo'; 
  src: url(data:font/ttf;base64,R0lGODlhAQABAIAAAAUEBAAAACwAAAAAAQABAAACAkQBADs=); 
}

#"never"

There must never be data URIs in url.

The following patterns are considered warnings:

a {
  background-image: url('data:image/gif;base64,R0lGODlhAQABAIAAAAUEBAAAACwAAAAAAQABAAACAkQBADs=')
}
@font-face { 
  font-family: 'foo'; 
  src: url(data:font/ttf;base64,R0lGODlhAQABAIAAAAUEBAAAACwAAAAAAQABAAACAkQBADs=); 
}

The following patterns are not considered warnings:

a {
  background-image: url(image.gif) 
}
@font-face { 
  font-family: 'foo'; 
  src: url(foo.ttf); 
}