Using Loaders

The power of webpack comes from its ability to load anything as a module. This is done through loaders.

If you try to require() a CSS file by default webpack will make no assumptions and consider it a JavaScript module. The CSS file needs to be first translated into a JavaScript module and then can be loaded.

Using npm, install the CSS loader with: npm install css-loader --save-dev

Then as you require the file, prefix the loader to perform the transformation separated by a '!' character:

var css = require('css!./css/style.css');

This will transform the CSS into a string and return that string. The useful part of this is the css-loader will treat @import and url() calls within the CSS just like require() statements. Thus making your CSS as modular as the rest of your application.

Note: By convention if a loader name ends with -loader that suffix can be dropped when being used. require('css-loader!./css/style.css') will work just the same as require('css!./css/style.css').

Chaining Loaders

Having your CSS as a raw string most of time isn't that useful. We likely would prefer to apply that CSS to the page and there is a loader for that: npm install style-loader --save-dev.

Now you just need to chain the loaders in the order you would like the transformation to occur:


Which will first transform the file into resolved CSS and then apply that CSS to the page as if you included it in a <link> tag.

Passing Options to Loaders

Some loaders have options that can be passed to them. Such as with the exports-loader, a loader for exporting a specific variable from within the module. For example if we have a module that does not use module.exports but rather just defines a global variable:

var Animal = (function() {
  return function(type) {
    console.log('I am a ' + type);

You can resolve this module by specifying which variable should be exported by passing an option to the exports loader using the '?' separator:

var Animal = require('exports?Animal!animals/dist/animals.js');

Which will effectively add module.exports = Animal; to the module's source when bundling.

Configure Loaders by File Type

Prefixing all your modules with a loader might be taxing where in a lot of instances you want a specific loader chain to always be applied depending on the file extension. This can be done with the module.loaders config array:

In your webpack.config.js:

module.exports = {
  module: {
    loaders: [
      { test: /\.css$/, loader: 'style!css' }

Now any module that ends with .css that is resolved will automatically have the CSS and style loader applied. Which shortens our previous call to apply CSS to our page to:


Common Useful Loaders

Here is a list of loaders you will likely encounter often and some explanation on their usage:


Loads the module either by base64 encoding as a string or via a separate network request. Configurable by setting the limit option.









// TODO: Using plugins section?