PostCSS and autoprefixing (postcss-loader)

PostCSS is a CSS post-processing tool that can transform your CSS in a lot of cool ways, like autoprefixing, linting and more!

First, download postcss-loader and any plugins you want, like autoprefixer:

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$ yarn add postcss-loader autoprefixer --dev

Next, create a postcss.config.js file at the root of your project:

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module.exports = {
    plugins: {
        // include whatever plugins you want
        // but make sure you install these via yarn or npm!

        // add browserslist config to package.json (see below)
        autoprefixer: {}
    }
}

Then, enable the loader in Encore!

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// webpack.config.js

Encore
    // ...
+     .enablePostCssLoader()
;

Because you just modified webpack.config.js, stop and restart Encore.

That's it! The postcss-loader will now be used for all CSS, Sass, etc files. You can also pass options to the postcss-loader by passing a callback:

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// webpack.config.js

Encore
    // ...
+     .enablePostCssLoader((options) => {
+         options.config = {
+             // the directory where the postcss.config.js file is stored
+             path: 'path/to/config'
+         };
+     })
;

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{
+  "browserslist": [
+    "defaults"
+  ]
}

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{
+  "browserslist": [
+    "> 0.5%",
+    "last 2 versions",
+    "Firefox ESR",
+    "not dead"
+  ]
}