Isomorphic CSS style loader for Webpack
Latest commit 3722b99 Oct 30, 2016 @frenzzy frenzzy 1.1.0 (#70)

Isomorphic CSS style loader for Webpack

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An alternative CSS style loader, which works similarly to style-loader, but is optimized for isomorphic apps. In addition to what style-loader provides, it allow to render critical path CSS during server-side rendering (SSR), by adding two helper methods on to the styles object - ._insertCss() (injects CSS into the DOM) and ._getCss() (returns CSS string).

See getting started  |  changelog  |  Join #react-starter-kit chat room on Gitter to stay up to date

How to Install

$ npm install isomorphic-style-loader --save-dev

Getting Started

Webpack configuration:
  module: {
    loaders: [
        test: /\.scss$/,
        loaders: [

Note: Configuration is the same for both client-side and server-side bundles.

React component example
// MyComponent.scss
.root { padding: 10px; }
.title { color: red; }
// MyComponent.js
import React, { PropTypes } from 'react';
import withStyles from 'isomorphic-style-loader/lib/withStyles';
import s from './MyComponent.scss';

function MyComponent(props, context) {
  return (
    <div className={s.root}>
      <h1 className={s.title}>Hello, world!</h1>

export default withStyles(s)(MyComponent);        // <--

P.S.: It works great with CSS Modules! Just decorate your React component with the withStyles higher-order component, and pass a function to your React app via insertCss context variable (see React's context API) that either calls styles._insertCss() on a client, or styles._getCss() on the server. See server-side rendering example below:

import express from 'express';
import ReactDOM from 'react-dom';
import router from './router.js'; // <-- isomorphic router, see react-starter-kit for example

const server = express();
const port = process.env.PORT || 3000;

// Server-side rendering of the React app
server.get('*', (req, res, next) =>
  const css = new Set(); // CSS for all rendered React components
  const context = { insertCss: (...styles) => styles.forEach(style => css.add(style._getCss())); };
  router.dispatch({ ...req, context }).then((component, state) => {
    const body = ReactDOM.renderToString(component);
    const html = `<!doctype html>
          <script async src="/client.js"></script>
          <style type="text/css">${[...css].join('')}</style>
          <div id="root">${body}</div>

server.listen(port, () => {
  console.log(`Node.js app is running at http://localhost:${port}/`);

It should generate an HTML output similar to this one:

    <title>My Application</title>
    <script async src="/client.js"></script>
    <style type="text/css">
      .MyComponent_root_Hi8 { padding: 10px; }
      .MyComponent_title_e9Q { color: red; }
    <div id="root">
      <div class="MyComponent_root_Hi8" data-reactid=".cttboum80" data-react-checksum="564584530">
        <h1 class="MyComponent_title_e9Q" data-reactid=".cttboum80.0">Hello, World!</h1>

Regardless of how many styles components there are in the app.js bundle, only critical CSS is going to be rendered on the server inside the <head> section of HTML document. Critical CSS is what actually used on the requested web page, effectively dealing with FOUC issue and improving client-side performance. CSS of the unmounted components will be removed from the DOM.

Hot Reload

You can activate hot module reload for style by setting the debug option to true in your webpack configuration. If you are using webpack 2, you need to supply it though the LoaderOptionsPlugin because the debug option has been removed.


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Made with ♥ by Konstantin Tarkus (@koistya) and contributors