ERR_MODULE_NOT_FOUND

What is ERR_MODULE_NOT_FOUND?

The ERR_MODULE_NOT_FOUND error occurs when an ES Module (ESM) import statement fails to resolve. Unlike CommonJS require(), which resolves file extensions automatically, ES Modules inside Node.js mandate explicit file extensions (e.g. .js or .mjs) in relative paths.

Common Causes

• Omitted File Extensions: Attempting relative imports without adding .js or .mjs extensions (e.g. import './utils').
• Missing module field targets inside third-party packages.
• Forgetting to define 'type': 'module' inside package.json while executing ESM import syntax.

Common Mistakes

• Expecting Node.js ESM to resolve paths without extensions exactly like Webpack or TypeScript compilers do.
• Omitting 'type': 'module' inside package.json while executing ESM code.

How to Fix

Framework-Specific Examples

import express from 'express';
import { userRouter } from './routes/users.js'; // Note the mandatory .js extension

const app = express();
app.use('/users', userRouter);

Server Configuration Examples

# Compiles files to standard builds

Best Practices

• Configure ESLint rules to enforce explicit ESM import extensions.
• Use modern module bundlers (like Vite, esbuild, or TSUp) to compile outputs.

Frequently Asked Questions (FAQ)