---
title: "How to polyfill node core modules in webpack 5"
description: "Learn how to polyfill node core modules in webpack version 5 and above using the react-app-rewired package, installing the required dependencies, and overriding the default webpack configuration."
---

# How to polyfill node core modules in webpack 5

In this tutorial, you’ll learn how to polyfill node core modules in webpack version 5 and above using the **react-app-rewired package**, installing the required dependencies, and overriding the default webpack configuration.

### What causes the polyfill node core module error?

Until the latest update to webpack version \_\_\_, webpack \< 5 used to include NodeJS polyfills by default. Because the [current version of webpack](https://github.com/webpack/webpack) no longer includes NodeJS polyfills by default, it is causing issues for developers that use create-react-app with webpack \> 5 to build applications with the [web3.js](https://www.alchemy.com/dapps/web3-js) and [alchemyweb3.js library](https://www.alchemy.com/docs/alchemy-quickstart-guide).

Here’s what the polyfill node core module error looks like:

## 4 easy steps to fix polyfill node core modules in webpack 5

The main issue with create-react-app and the polyfill error is that create-react-app, by default, **hides the webpack config file inside the node-modules**, and by doing so, generates the file at build time leaving developers unable to modify it.

Luckily there is a package, [react-app-rewired](https://www.npmjs.com/package/react-app-rewired), that allows developers to easily edit the webpack config file and fix the polyfill node core module error.

### 1. Install react-app-rewired

First, install the reach-app-rewired package with your preferred package manager.

Install react-app-rewired package with yarn:

Install react-app-rewired package with npm:

### 2. Install missing dependencies

Next, install these missing dependencies:

- crypto-browserify
- stream-browserify
- assert
- stream-http
- https-browserify
- os-browserify
- url

Install missing dependencies with yarn:

yarn add process crypto-browserify stream-browserify assert stream-http https-browserify os-browserify url buffer

Install missing dependencies with npm:

### 3. Override the create-react-app webpack config file

In the root folder of your project, create a new file called config-overrides.js, and add the following code to it:

This config-overrides.js code snippet is telling webpack how to resolve the missing dependencies that are needed to support web3 libraries and wallet providers in the browser.

### 4. Override package.json to include the webpack configuration

Within the package.json file, replace **react-scripts** with **react-app-rewired** scripts for the three following scripts fields to update the webpack configuration:

- start
- build
- test

Here’s what the package.json file looks like **before** replacing the react-scripts:

Here’s the package.json file **after** replacing the react-scripts with react-app-rewired scripts:

That’s it!

Now, the polyfill node core module error should be fixed, missing NodeJS polyfills should be included in your app, and your app should work with the web3.js and [Alchemyweb3.js library](https://github.com/alchemyplatform/alchemy-web3).