postcss.config.js

const purgecss = require('@fullhuman/postcss-purgecss')
const cssnano = require('cssnano')

module.exports = {
  plugins: [
    require('tailwindcss'),
    require('postcss-nested'),
    require('autoprefixer'),
    cssnano({
      preset: 'default'
    }),
    purgecss({
      content: [
        './src/*.html',
        './node_modules/tailwindcss-dark-mode/prefers-dark.js'
      ],
      defaultExtractor: content => content.match(/[\w-/:]*[\w-/:]/g) || []
    })
  ]
}