Inlining files in CSS with Webpack URL Loader

A simple technique to improve the performance of web applications is to reduce the number of HTTP requests inlining small files as base64 encoded URLs in the generated CSS files.

Webpack Encore provides this feature via Webpack's URL Loader plugin, but it's disabled by default. First, add the URL loader to your project:

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# if you use the Yarn package manager
$ yarn add url-loader --dev

# if you use the npm package manager
$ npm install url-loader --save-dev

Then enable it in your webpack.config.js:

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// webpack.config.js
// ...

Encore
    // ...
    .configureUrlLoader({
        fonts: { limit: 4096 },
        images: { limit: 4096 }
    })
;

The limit option defines the maximum size in bytes of the inlined files. In the previous example, font and image files having a size below or equal to 4 KB will be inlined and the rest of the files will be processed as usual.

You can also use all the other options supported by the URL Loader. If you want to disable this loader for either images or fonts, remove the corresponding key from the object that is passed to the configureUrlLoader() method:

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// webpack.config.js
// ...

Encore
    // ...
    .configureUrlLoader({
        // 'fonts' is not defined, so only images will be inlined
        images: { limit: 4096 }
    })
;