JavaScript and Node.js errorReferenceError: “require is not defined”

Why require is missing, and the fix

1. 01

   The file is an ES module

   “In most cases, the ES module import can be used to load CommonJS modules. If needed, a require function can be constructed within an ES module using module.createRequire().” Node.js, Modules: ECMAScript modules

   "type": "module" in package.json, or a .mjs extension, makes Node.js load the file as an ES module, where require, module.exports and __dirname do not exist. Switch to import and export, which can also load most CommonJS packages.

   // before
   const express = require('express');
   
   // after
   import express from 'express';

2. 02

   You need require for one thing

   Some packages, JSON files or native addons are easier to load with require. Create a require function inside the ES module instead of converting the whole project.

   import { createRequire } from 'node:module';
   const require = createRequire(import.meta.url);
   const config = require('./config.json');

3. 03

   __dirname or __filename is missing too

   “These CommonJS variables are not available in ES modules.” Node.js, Modules: ECMAScript modules

   Node.js does not define them in ES modules. Use import.meta.dirname and import.meta.filename on Node.js 20.11 and later, or build them from import.meta.url on older versions.

   const dir = import.meta.dirname;
   
   // older Node.js
   import { fileURLToPath } from 'node:url';
   import path from 'node:path';
   const dir2 = path.dirname(fileURLToPath(import.meta.url));

4. 04

   The code runs in the browser

   Code copied from a Node.js example and loaded with a script tag, or a package meant for Node.js imported into front-end code, fails because browsers have no require. Use import with a bundler (Vite, webpack, Next.js), and pick packages that support the browser.

   <script type="module">
     import { format } from 'https://cdn.jsdelivr.net/npm/date-fns@3.6.0/+esm';
   </script>

Checked against the vendor’s docs on November 7, 2026: Node.js: Modules: ECMAScript modules (differences from CommonJS); Node.js: Modules: Packages ("type" field).

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Related: “Cannot use import statement outside a module” · Node.js ERR_REQUIRE_ESM · Next.js “window is not defined”