In this post I will show you how to get the background-size CSS property working in IE 6 - 8 without using JavaScript. Instead we will use the filter attribute recognised by older versions of Internet Explorer.

Background

As you can see on Can I Use, IE 6 - 8 are the only browsers not supporting background-size at all.

Microsoft does however offer a AlphaImageLoader filter with sizingMethod options that correlate to the CSS3 background-size options.

  • auto = image
  • cover = scale
  • contain = crop

(CSS3 on left, sizingMethod on right)

The Solution

We will write a mixin that applies the filter rule for us. In this example I will use SCSS syntax and implement a fix for background-size: cover, as this is the most common use case.

If you want to convert this to SASS, please check out SASS to SCSS.

The mixin looks as follows:

@mixin background-cover($image-path) {
  background-size: cover;
  background-image: url(#{$image-path});
  filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(src='#{$image-path}', sizingMethod='scale');
  -ms-filter: "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='#{$image-path}', sizingMethod='scale')";
}

This mixin accepts an argument that is the path to the image. So it could be used for example like so:

.foo {
  @include background-cover('images/bar.jpg');
  background-color: #fff;
  background-position: right bottom;
}

A great advantage of this approach is that if you are using Ruby on Rails and need to include the asset pipeline paths in your CSS, you can use the standard asset-path helper wrapped around the argument.

.foo {
  @include background-cover(asset-path('bar.jpg'));
  ...
}

Conclusion

You may want to note that Internet Explorer filters are not valid CSS, so if you are an advocate of purely valid CSS, you may want to use a JavaScript polyfill or isolate this code in a separate stylesheet.

In general though, I think this is a great solution when older IE support is required. No JavaScript or CSS plugins are necessary and the method can easily be dropped into a SASS/SCSS project.

The solution could also easily be adapted for preprocessors such as LESS.js, or even pure CSS with little effort.

Please let me know if you find any other short solutions to this problem, I'd love to hear about other options.