Nuxt/examples/with-purgecss/nuxt.config.js

import path from 'path'
import PurgecssPlugin from 'purgecss-webpack-plugin'
import glob from 'glob-all'

class TailwindExtractor {
  static extract (content) {
    return content.match(/[A-Za-z0-9-:/]+/g) || []
  }
}

export default {
  build: {
    extractCSS: true,
    postcss: {
      postcssOptions: {
        plugins: {
          tailwindcss: path.resolve('./tailwind.js')
        },
        preset: { autoprefixer: { grid: true } }
      }
    },
    extend (config, { isDev }) {
      if (!isDev) {
        config.plugins.push(
          new PurgecssPlugin({
            // purgecss configuration
            // https://github.com/FullHuman/purgecss
            paths: glob.sync([
              path.join(__dirname, './pages/**/*.vue'),
              path.join(__dirname, './layouts/**/*.vue'),
              path.join(__dirname, './components/**/*.vue')
            ]),
            extractors: [
              {
                extractor: TailwindExtractor,
                extensions: ['vue']
              }
            ],
            whitelist: ['html', 'body', 'nuxt-progress']
          })
        )
      }
    }
  },
  css: ['~/assets/css/tailwind.css']
}