react.dev/content/docs/installation.md

---
id: installation
title: Installation
permalink: docs/installation.html
redirect_from:
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  - "downloads.html"
  - "docs/tooling-integration.html"
  - "docs/package-management.html"
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next: hello-world.html
---

React is flexible and can be used in a variety of projects. You can create new apps with it, but you can also gradually introduce it into an existing codebase without doing a rewrite.

Here are a couple of ways to get started:

* [Try React](#trying-out-react)
* [Create a New App](#creating-a-new-application)
* [Add React to an Existing App](#adding-react-to-an-existing-application)

## Trying Out React

If you're just interested in playing around with React, you can use CodePen. Try starting from [this Hello World example code](http://codepen.io/gaearon/pen/rrpgNB?editors=0010). You don't need to install anything; you can just modify the code and see if it works.

If you prefer to use your own text editor, you can also <a href="https://raw.githubusercontent.com/reactjs/reactjs.org/master/static/html/single-file-example.html" download="hello.html">download this HTML file</a>, edit it, and open it from the local filesystem in your browser. It does a slow runtime code transformation, so don't use it in production.

If you want to use it for a full application, there are two popular ways to get started with React: using Create React App, or adding it to an existing application.

## Creating a New Application

[Create React App](http://github.com/facebookincubator/create-react-app) is the best way to start building a new React single page application. It sets up your development environment so that you can use the latest JavaScript features, provides a nice developer experience, and optimizes your app for production. You’ll need to have Node >= 6 on your machine.

```bash
npm install -g create-react-app
create-react-app my-app

cd my-app
npm start
```

Create React App doesn't handle backend logic or databases; it just creates a frontend build pipeline, so you can use it with any backend you want. It uses build tools like [Babel](http://babeljs.io/) and [webpack](https://webpack.js.org/) under the hood, but works with zero configuration.

When you're ready to deploy to production, running `npm run build` will create an optimized build of your app in the `build` folder. You can learn more about Create React App [from its README](https://github.com/facebookincubator/create-react-app#create-react-app-) and the [User Guide](https://github.com/facebookincubator/create-react-app/blob/master/packages/react-scripts/template/README.md#table-of-contents).

## Adding React to an Existing Application

You don't need to rewrite your app to start using React.

We recommend adding React to a small part of your application, such as an individual widget, so you can see if it works well for your use case.

While React [can be used](/docs/react-without-es6.html) without a build pipeline, we recommend setting it up so you can be more productive. A modern build pipeline typically consists of:

* A **package manager**, such as [Yarn](https://yarnpkg.com/) or [npm](https://www.npmjs.com/). It lets you take advantage of a vast ecosystem of third-party packages, and easily install or update them.
* A **bundler**, such as [webpack](https://webpack.js.org/) or [Browserify](http://browserify.org/). It lets you write modular code and bundle it together into small packages to optimize load time.
* A **compiler** such as [Babel](http://babeljs.io/). It lets you write modern JavaScript code that still works in older browsers.

### Installing React

>**Note:**
>
>Once installed, we strongly recommend setting up a [production build process](/docs/optimizing-performance.html#use-the-production-build) to ensure you're using the fast version of React in production.

We recommend using [Yarn](https://yarnpkg.com/) or [npm](https://www.npmjs.com/) for managing front-end dependencies. If you're new to package managers, the [Yarn documentation](https://yarnpkg.com/en/docs/getting-started) is a good place to get started.

To install React with Yarn, run:

```bash
yarn init
yarn add react react-dom
```

To install React with npm, run:

```bash
npm init
npm install --save react react-dom
```

Both Yarn and npm download packages from the [npm registry](http://npmjs.com/).

### Enabling ES6 and JSX

We recommend using React with [Babel](http://babeljs.io/) to let you use ES6 and JSX in your JavaScript code. ES6 is a set of modern JavaScript features that make development easier, and JSX is an extension to the JavaScript language that works nicely with React.

The [Babel setup instructions](https://babeljs.io/docs/setup/) explain how to configure Babel in many different build environments. Make sure you install [`babel-preset-react`](http://babeljs.io/docs/plugins/preset-react/#basic-setup-with-the-cli-) and [`babel-preset-env`](http://babeljs.io/docs/plugins/preset-env/) and enable them in your [`.babelrc` configuration](http://babeljs.io/docs/usage/babelrc/), and you're good to go.

### Hello World with ES6 and JSX

We recommend using a bundler like [webpack](https://webpack.js.org/) or [Browserify](http://browserify.org/), so you can write modular code and bundle it together into small packages to optimize load time.

The smallest React example looks like this:

```js
import React from 'react';
import ReactDOM from 'react-dom';

ReactDOM.render(
  <h1>Hello, world!</h1>,
  document.getElementById('root')
);
```

This code renders into a DOM element with the id of `root`, so you need `<div id="root"></div>` somewhere in your HTML file.

Similarly, you can render a React component inside a DOM element somewhere inside your existing app written with any other JavaScript UI library.

[Learn more about integrating React with existing code.](/docs/integrating-with-other-libraries.html#integrating-with-other-view-libraries)

### Development and Production Versions

By default, React includes many helpful warnings. These warnings are very useful in development.

**However, they make the development version of React larger and slower so you should use the production version when you deploy the app.**

Learn [how to tell if your website is serving the right version of React](/docs/optimizing-performance.html#use-the-production-build), and how to configure the production build process most efficiently:

* [Creating a Production Build with Create React App](/docs/optimizing-performance.html#create-react-app)
* [Creating a Production Build with Single-File Builds](/docs/optimizing-performance.html#single-file-builds)
* [Creating a Production Build with Brunch](/docs/optimizing-performance.html#brunch)
* [Creating a Production Build with Browserify](/docs/optimizing-performance.html#browserify)
* [Creating a Production Build with Rollup](/docs/optimizing-performance.html#rollup)
* [Creating a Production Build with webpack](/docs/optimizing-performance.html#webpack)

### Using a CDN

If you don't want to use npm to manage client packages, the `react` and `react-dom` npm packages also provide single-file distributions in `umd` folders, which are hosted on a CDN:

```html
<script crossorigin src="https://unpkg.com/react@16/umd/react.development.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.development.js"></script>
```

The versions above are only meant for development, and are not suitable for production. Minified and optimized production versions of React are available at:

```html
<script crossorigin src="https://unpkg.com/react@16/umd/react.production.min.js"></script>
<script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.production.min.js"></script>
```

To load a specific version of `react` and `react-dom`, replace `16` with the version number.

If you use Bower, React is available via the `react` package.

#### Why the `crossorigin` Attribute?

If you serve React from a CDN, we recommend to keep the [`crossorigin`](https://developer.mozilla.org/en-US/docs/Web/HTML/CORS_settings_attributes) attribute set:

```html
<script crossorigin src="..."></script>
```

We also recommend to verify that the CDN you are using sets the `Access-Control-Allow-Origin: *` HTTP header:

![Access-Control-Allow-Origin: *](../images/docs/cdn-cors-header.png)

This enables a better [error handling experience](/blog/2017/07/26/error-handling-in-react-16.html) in React 16 and later.