Using CSS Purge With Laravel Mix. Tutorial on how to use the following can be found https://paulund.co.uk/reduce-css-file-size-with-css-purge reduced a production ready CSS file from 179kb to 7.9kb.

css-purge-webpack-config.js

mix.webpackConfig({
    plugins: [
      new purgeCss({
        paths: glob.sync([
          path.join(__dirname, 'resources/views/**/*.blade.php'),
          path.join(__dirname, 'resources/assets/js/**/*.vue')
        ]),
        extractors: [
          {
            extractor: class {
              static extract(content) {
                return content.match(/[A-z0-9-:\/]+/g)
              }
            },
            extensions: ['html', 'js', 'php', 'vue']
          }
        ]
      })
    ]
  })

include-css-purge-in-webpack.mix.js

let purgeCss = require('purgecss-webpack-plugin')
let glob = require('glob-all')

install-css-purge.js

npm install purgecss-webpack-plugin --save-dev
npm install glob-all --save-dev

webpack.mix.js

let mix = require('laravel-mix');
let purgeCss = require('purgecss-webpack-plugin')
let glob = require('glob-all')
var tailwindcss = require('tailwindcss');

/*
 |--------------------------------------------------------------------------
 | Mix Asset Management
 |--------------------------------------------------------------------------
 |
 | Mix provides a clean, fluent API for defining some Webpack build steps
 | for your Laravel application. By default, we are compiling the Sass
 | file for the application as well as bundling up all the JS files.
 |
 */

mix.js('resources/assets/js/app.js', 'public/js');
mix.sass('resources/assets/sass/app.scss', 'public/css')
  .options({
    processCssUrls: false,
    postCss: [ require('postcss-import'), tailwindcss('tailwind.js') ],
  }).version();

if (mix.inProduction()) {
  mix.webpackConfig({
    plugins: [
      new purgeCss({
        paths: glob.sync([
          path.join(__dirname, 'resources/views/**/*.blade.php'),
          path.join(__dirname, 'resources/assets/js/**/*.vue')
        ]),
        extractors: [
          {
            extractor: class {
              static extract(content) {
                return content.match(/[A-z0-9-:\/]+/g)
              }
            },
            extensions: ['html', 'js', 'php', 'vue']
          }
        ]
      })
    ]
  })
}

Very useful Gist, thanks!

Great! I was going nuts trying to get this to work. Very helpful.