How to use SASS/SCSS with Webpack in Phoenix 1.4

How to change the Webpack configuration in Phoenix 1.4 from CSS to using SASS/SCSS

Phoenix 1.4 is on it’s way and one of the big changes is that webpack is replacing brunch. If you are a SASS fan then this is how to update the default Webpack configuration to use SASS (SCSS flavour).

Install NPM packages

The first step is to install the node-sass and sass-loader packages from NPM.

Using Yarn

$ yarn add node-sass sass-loader --dev

Using NPM

$ npm install node-sass sass-loader --save-dev

Update webpack.config.js

Update the assets/webpack.config.js file with a change to chain the sass-loader plugin after the css-loader.

diff --git a/assets/webpack.config.js b/assets/webpack.config.js
index 5225785..4c14948 100644
--- a/assets/webpack.config.js
+++ b/assets/webpack.config.js
@@ -26,8 +26,18 @@ module.exports = (env, options) => ({
-      test: /\.css$/,
-      use: [MiniCssExtractPlugin.loader, 'css-loader']
+      test: /\.scss$/,
+      use: [
+        MiniCssExtractPlugin.loader,
+        {
+          loader: 'css-loader',
+          options: {}
+        },
+        {
+          loader: 'sass-loader',
+          options: {}
+        }
+      ]

Update app.css

Rename your assets/css/app.css to assets/css/app.scss.

$ mv assets/css/app.css assets/css/app.scss

Update app.js

Because the CSS files are loaded by Webpack through the javascript file, you need to update the css import path as well.

diff --git a/assets/js/app.js b/assets/js/app.js
index 8ee7177..0aa55a0 100644
--- a/assets/js/app.js
+++ b/assets/js/app.js
@@ -1,7 +1,7 @@
 // We need to import the CSS so that webpack will load it.
 // The MiniCssExtractPlugin is used to separate it out into
 // its own CSS file.
-import css from "../css/app.css"
+import css from "../css/app.scss"

 // webpack automatically bundles all modules in your
 // entry points. Those entry points can be configured

Build assets

Finally test your assets build.

$ node node_modules/webpack/bin/webpack.js --mode development
Jun 18, 2018 elixir, sass, scss, css, phoenix
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