csso-webpack-plugin

CSSO Webpack Plugin

Why is not csso-loader or postcss-csso?

• Full restructuring in bundles:

• No problems with custom syntax like css-modules – :global(.c .d) .a { color: #fff; }

• Possible to generate both pure and minimized versions at the same time.

Install

npm i -D csso-webpack-plugin

For node < 8.0.0 use 1.x version with csso@^3:

npm i -D csso-webpack-plugin@1

Usage

Plugin good to use in pair with ExtractTextPlugin or MiniCssExtractPlugin.

const CssoWebpackPlugin = require('csso-webpack-plugin').default;

module.exports = {
  module: { /* ... */ },
  plugins: [
    new MiniCssExtractPlugin({
      filename: "[name].css",
      chunkFilename: "[id].css"
    }),
    new CssoWebpackPlugin(),
  ]
}

Options

new CssoWebpackPlugin([options: CssoOptions], [filter: function | RegExp])

Arguments:

• options — csso options.
• options.pluginOutputPostfix — function(file) or string postfix, if passed, plugin will create two assets vanilla and compressed. Example:

  {
      plugins: [
          new ExtractTextPlugin('test.css'),
          new CssoWebpackPlugin({ pluginOutputPostfix: 'min' })
          /* Generated:
              test.css — uncompressed file
              test.min.css — minimized with csso file
          */
      ]
  }
  

• filter — Detect should be file processed. Defaults: to ends with .css.

Flow support

I don't now why, but plugin ships with flow typings (typedef too). To use them in your project, add this to the [libs] section of your .flowconfig:

[libs]
node_modules/csso-webpack-plugin/lib/index.js.flow

Acknowledgements

Changelog

3.0.0 (August 20, 2025)

Release 3.0.0:

• Update CSSO to a new major version 5.x (closes #31)
• Drop support for Node.js < 10