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Create React Server

Config-free server side rendering for React applications based on React Router. Compatible with Redux apps and Webpack Dev Middleware for simple and painless development and production usage. Comes as CLI script, standalone server, and middleware.

This package is formerly known as react-router-redux-middleware (which is now deprecated).


npm install create-react-server babel-preset-react-app babel-preset-es2015 --save-dev

You don't have to install babel-preset-react-app if you use Create React App, it will be pre-installed already.


In order to use examples you should clone the repository and do npm install inside the repo and then separate npm install in example dir.

git clone
cd create-react-server
npm install
cd examples/[any-example]
npm install
npm run redeploy # launch in production mode

Async Routes

!!!ATTENTION!!! Due to changes in React Router 4 async routes are no longer supported by this package!

Official RR4 documentation says the following:

  1. You need synchronous module resolution on the server so you can get those bundles in the initial render.
  2. You need to load all the bundles in the client that were involved in the server render before rendering so that the client render is the same as the server render. (The trickiest part, I think its possible but this is where I gave up.)
  3. You need asynchronous resolution for the rest of the client app’s life.

Code Splitting & Server Rendering

So not at this moment at least, stay tuned, we will try to add this in future releases! Especially if React Fiber (16) will take care of some async component lifecycle.


Add .babelrc file or babel section of package.json

    "presets": [

Page (e.g. leaf router node)

Server rendering procedure takes getInitialProps static property and performs everything defined in it both on server and later on client (if needed). Anything that was returned from getInitialProps becomes the initial set of props when component will be rendered on server.

On client these props will be available with some delay, so you may use custom property initialLoading which will be true while getInitialProps function is resolving.

If an error occurs inside getInitialProps it will be available via initialError property. This property is populated from the server as well (as a string, no trace, you may capture this also in template function).

Component also receives a wrapped version of getInitialProps in its props, so that it can be called when needed, for example when componentWillReceiveProps on React Router route change to load new data, but be careful and don't cause infinite loops or race conditions.

If you use withWrapper you must wrap each leaf page, otherwise if you open unwrapped page in browser and then navigate to wrapped no getInitialProps will be called because wrapped will assume that it's first run.

// src/Page.js

import React, {Component} from "react";
import {connect} from "react-redux"; // this is optional
import {withWrapper} from "create-react-server/wrapper";

export class App extends Component {

    static async getInitialProps({location: {pathname, query}, params, store}) {
        await store.dispatch(barAction()); // this is optional
        return {custom: 'custom'};

    render() {
        const {foo, bar, custom, initialError} = this.props;
        if (initialError) return <pre>Initial Error: {initialError.stack}</pre>;
        return (
            <div>Foo {foo}, Bar {bar}, Custom {custom}</div>


App = connect(state => state)(App); // this is optional
export default withWrapper(App); // here we connect to WrapperProvider

Component which will be used as 404 stub should have notFound static property:

// src/NotFound.js

import React, {Component} from "react";

export default class NotFound extends Component {
    static notFound = true;
    render() {
        return (
            <div>404 Not Found</div>


Main App

You have to make a createApp function that should return an app with React Router routes.

// src/app.js

import React from "react";
import {Route, IndexRoute} from "react-router";
import NotFound from './NotFound';
import Page from './Page';
import IndexPage from './IndexPage';

export default ({state, props, req, res}) => {

    if (!state && !!req) { // this means function is called on server
        state = {
            'foo': req.url + ':' +

    return (
        <Provider store={createStore(state)}>
            <WrapperProvider initialProps={props}>
                    <Route exact path="/" component={IndexPage}/>
                    <Route path="/page" component={Page}/>
                    <Route component={NotFound}/>


If you don't use Redux then Provider is not needed.

Parameters that function receives are (all parameters may be null depending on where the function is launched, you may have custom logic specifically for server or client based on what paratements are available):

  • state — initial Redux state received from server (if any)
  • props — initial props received from server (if any)
  • req — NodeJS Request (if any)
  • res — NodeJS Response (if any)

Redux (optional)

If your app is using Redux, then you will have to make a createStore function, that should take initial state as an argument and return a new Store:

// src/store.js

import {createStore} from "redux";

function reducer(state, action) { return state; }

export default function (initialState, {req, res}) {
    if (req) { // it means it's launched from server in CLI mode
        initialState = {foo: res.url}; // so we can pre-populate something
    return createStore(

Main App Entry Point

You have to create a root app component, which normally consists only of BrowserRouter or HashRouter and a call to createApp.

// src/index.js

import React from "react";
import {render} from "react-dom";
import {BrowserRouter} from "react-router-dom";
import createApp from "./app";

const Root = () => (
            state: window.__INITIAL_STATE__, // you can skip this if you don't use Redux
            props: window.__INITIAL__PROPS__

render((<Root/>), document.getElementById('root'));

CLI Mode

First of all prepare your application according to steps in preconditions.

It is convenient to put console command into scripts section of package.json:

    "build": "react-scripts build",
    "server": "create-react-server --app path-to/src/app.js [options]"

All specified JS files must export functions as default export or as module.exports. It assumes that --app path-to-app.js as path to file which exports a createApp and so on.

Available options:

  • --app or -r path to JS file with createApp function
  • --template or -t path to JS file with template function
  • --outputPath or -o as path to your build (e.g. your static files)
  • --templatePath or -i path to your index.html
  • --debug or -d if you want to get more information of requests handling & stack traces of errors
  • --port or -p to bind to something other than 3000, port will also be automatically taken from process.env.PORT

You may also run with NODE_ENV=development to get more info:

NODE_ENV=development create-react-server [your options]

Then run from console:

npm run build
npm run server

Now if you open http://localhost:3000 you will see a page rendered on the server.


Middleware accepts following options:

  • options.outputPath required path with static files, usually equals to Webpack's output.path
  •{props, state, req, res}) required function must return an app that uses React Router
  • options.template optional, main template function, performs injection of rendered HTML to the template, default = replaces <div id="root"></div> with <div id="root">%HTML%</div> completely failed to render
  • options.templatePath optional path to index.html, default = %outputPath%/index.html
  • options.debug optional emits to console some extra information about request handling, default = false
  • options.initialStateKey optional key in window object that will be used to pass initial props, default = __INITIAL_PROPS__
  • options.initialPropsKey optional key in window object that will be used to pass initial state, default = __INITIAL_STATE__

Server accepts following options in addition to the ones accepted by middleware:

  • options.skipExtensions optional array of strings that represent most commonly imported non-JS extensions that has to be skipped during server build, default = ['css', 'jpg', 'gif', ...]
  • options.port optional port to listen, default = 3000
  • options.listen optional Express's listen function

Template Function

Template function performs injection of rendered HTML to the template. This function will also be called if React App failed to render (e.g. in case of server error).

Function accepts config as parameter with the following always available properties:

  • config.error error object if function is called as error handler, equals null otherwise
  • config.req instance of NodeJS Request
  • config.res instance of NodeJS Response
  • config.template contents of index.html or any other file defined in templatePath option

If function is called in a normal way, e.g. NOT as error handler, the following properties will also be provided, some of them still may be available in error handler mode, depending on which stage the error has happened:

  • config.component matched component (your leaf page)
  • config.html result of React rendering
  • config.initialProps result of getInitialProps (resolved result of Promise if it was returned)
  • instance of Redux Store

Most common cases when this function is called as error handler are:

  • You forgot to configure React Router's fallback route, e.g. <Route path="*" component={...}/>
  • React Router has returned an error

If you don't output any error information then the client will be rendered as if nothing happened.

By default this function replaces <div id="root"></div> (exactly as written). If there is an error — it's HTML is injected right before div#root.

If anything will be thrown from this function, then default error handler will take over. You should avoid this by placing try {} catch {} around your code, in this case default handler wiil not be called.

Custom server

First of all prepare your application according to steps in preconditions.

In these example we will use express server and babel-cli:

npm install express babel-cli --save-dev

Modify scripts section of package.json:

    "build": "react-scripts build && npm run build-server",
    "build-server": "NODE_ENV=production babel --source-maps --out-dir build-lib src",
    "server": "node ./build-lib/server.js"

It makes client side build using Create React App (React Scripts) and server side build using Babel, which takes everything from src and puts the outcome to build-lib. You may add this directory to .gitignore.

// src/server.js

import path from "path";
import {createExpressServer} from "create-react-server";
import app from "./app";

    port: process.env.PORT || 3000,
    app: app,
    template: ({template, html, req}) => (
            `<div id="root"></div>`,
            `<div id="root">${html}</div>`)),
    outputPath: path.join(process.cwd(), 'build')

Check out the ready-to-use example in examples/create-react-app folder.

In this mode your createStore function will on server will receive second config argument: {req, res} with request and response respectively. In other modes you can control what is passed where.


There are two middleware modes: for Webpack Dev Server and for Express server.

If you have access to webpack.config.js then you may run the Webpack Dev Server along with server side rendering, this example covers both.

In order to do that we need to install webpack-dev-server (in addition to packages from preconditions step), you may skip this if you have already installed it. In these example we will use express server and babel-cli to make server side builds:

npm install express babel-cli babel-preset-react-app webpack-dev-server html-webpack-plugin --save-dev

*Note: you don't have to install babel-preset-react-app if you use Create React App or you already have preset.

Modify scripts section of package.json

In this example we run server by Babel Node, in this case server will be transformed in runtime (which is not recommended for production). You also can build the server like in custom server section.

    "server-dev": "NODE_ENV=development babel-node ./src/server.js",
    "server-runtime": "NODE_ENV=production babel-node ./src/server.js"

Webpack Config

Main entry file index.html should be a part of webpack build, e.g. emitted to you output path. It could be a real file or generated by HtmlWebpackPlugin, but it has to be known by Webpack.

Make sure your webpack.config.js has all the following:

// webpack.config.js

var HtmlWebpackPlugin = require('html-webpack-plugin');
module.exports = {
    "output": {
        path: process.cwd() + '/build', // mandatory
        publicPath: '/',
    "plugins": [new HtmlWebpackPlugin({
        filename: 'index.html',
        favicon: './src/favicon.ico', // this is optional
        template: './src/index.html'
    devServer: {
        port: process.env.PORT || 3000,
        contentBase: './src',


// src/server.js

import path from "path";
import Express from "express";
import webpack from "webpack";
import Server from "webpack-dev-server";
import app from "./app"; // same file as in client side
import config from "../webpack.config";
import {createExpressMiddleware, createWebpackMiddleware, skipRequireExtensions} from "create-react-server";

skipRequireExtensions(); // this may be omitted but then you need to manually teach Node to ignore non-js files

const port = process.env.PORT || 3000;

const options = {
    app: app,
    template: ({template, html}) => (template.replace(
        // !!!!! MUST MATCH THE INDEX.HTML
        `<div id="root"></div>`,
        `<div id="root">${html}</div>`
    templatePath: path.join(config.output.path, 'index.html'),
    outputPath: config.output.path

if (process.env.NODE_ENV !== 'production') {

    const compiler = webpack(config);

    config.devServer.setup = function(app) {
        app.use(createWebpackMiddleware(compiler, config)(options));

    new Server(compiler, config.devServer).listen(port, '', listen);

} else {

    const app = Express();


    app.listen(port, listen);


function listen(err) {
    if (err) throw err;
    console.log('Listening %s', port);

Check out the ready-to-use example in examples/webpack-blocks folder.

Use with React Helmet

Take a look at React Helmet's readme note about server side rendering. In a few words you have to add renderStatic() call to your implementation of template option:

import Helmet from "react-helmet";

const template = ({template, html, req}) => {

    const head = Helmet.renderStatic();

    return template
            `<div id="root"></div>`,
            `<div id="root">${html}</div>`
            '<html ' + head.htmlAttributes.toString() + '>'


Asynchronous Require

If you use require.ensure in your app, you will have to install babel-plugin-transform-ensure-ignore.

npm install babel-plugin-transform-ensure-ignore --save-dev

And add it to .babelrc file or babel section of package.json:

    "presets": [
    "plugins": [

If you use dynamic import() function, then you will need more plugins babel-plugin-dynamic-import-webpack, it should be used together with babel-plugin-transform-ensure-ignore. Make sure it is used only on server, and Webpack (client build) will not pick it up. On client plugin babel-plugin-syntax-dynamic-import should be used.

Handling props updates

Your component may receive props from React Router without unmounting/mounting, for example query or param has changed.

In this case you can create a componentWillReceiveProps lifecycle hook and call this.props.getInitialProps() from it to force static getInitialProps method to be called again:

export class Page extends React.Component {

    static async getInitialProps({params}) {
        var res = await fetch(`/pages?slug=${params.slug}`);
        return await res.json();

    componentWillReceiveProps(newProps) {
        if (this.props.params.slug !== newProps.params.slug) this.props.getInitialProps();

    render() {
        // your stuff here


export default withWrapper(Page);

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