PostCSS Preprocessing

• Basic Usage
• Add PostCSS Plugins
  • Apply Plugins Globally
  • Use a PostCSS Config File

Basic Usage

Imagine that you have the following CSS file that needs to be compiled and piped through a series of PostCSS plugins. In the example below, we'll need to pull in the postcss-custom-properties or postcss-preset-env PostCSS plugin.

:root {
    --some-color: red;
}

.example {
    color: var(--some-color);
}

{tip} You can view a list of all available PostCSS plugins here.

No problem. First, install the PostCSS plugin through npm.

npm install postcss-custom-properties --save-dev

Next, add PostCSS compilation to your webpack.mix.js file, like so:

// webpack.mix.js

let mix = require('laravel-mix');

mix.postCss('src/app.css', 'dist');

{tip} mix.postCss() and mix.css() are aliases. Both commands work for all examples in this section.

Add PostCSS Plugins

At this point, we're using PostCSS, but we haven't yet instructed Mix to pull in the postcss-custom-properties plugin. We can add an array of plugins as the third argument to mix.postCss(), like so:

// webpack.mix.js

let mix = require('laravel-mix');

mix.postCss('src/app.css', 'dist', [
    require('postcss-custom-properties')
]);

Apply Plugins Globally

The above example will exclusively pipe src/app.css through the postcss-custom-properties plugin. However, if you're compiling multiple CSS entrypoints, it can be cumbersome to duplicate your PostCSS plugins array for each call.

// webpack.mix.js

let mix = require('laravel-mix');

mix.postCss('src/one.css', 'dist', [
    require('postcss-custom-properties')
]);

mix.postCss('src/two.css', 'dist', [
    require('postcss-custom-properties')
]);

mix.postCss('src/three.css', 'dist', [
    require('postcss-custom-properties')
]);

Instead, you can apply your desired PostCSS plugins globally by either using mix.options()...

mix.postCss('src/one.css', 'dist')
   .postCss('src/two.css', 'dist')
   .postCss('src/three.css', 'dist');

mix.options({
    postCss: [
        require('postcss-custom-properties')
    ]
});

...or by creating a postcss.config.js file.

Use a PostCSS Config File

If you create a postcss.config.js file within the root of your project, Mix will automatically detect and import it.

// postcss.config.js

module.exports = {
    plugins: [
        require('postcss-preset-env')
    ]
}

With this adjustment, your webpack.mix.js file can return to:

// webpack.mix.js

let mix = require('laravel-mix');

mix.postCss('src/app.css', 'dist');

When you're ready, compile your code as usual (npx mix), and you'll find a /dist/app.css file that contains:

.example {
    color: red;
}

Perfect!