How to Fix "Module Not Found" Error in Node.js

"Module not found" error in Node.js occurs when the module resolution system cannot locate a required module. This error typically appears as Error: Cannot find module 'module-name' and indicates that Node.js searched for the module but couldn't find it in the expected locations.

Node.js uses a specific algorithm to resolve modules: it first checks if it's a core module, then looks in node_modules directories (starting from the current directory and moving up), and finally checks for local file paths. When none of these locations contain the requested module, Node.js throws a "Module not found" error.

Common causes include missing package installations, incorrect file paths, typos in module names, case sensitivity issues, missing dependencies in package.json, or corrupted node_modules directories. Understanding Node.js module resolution is key to fixing these errors.

Node.js module resolution works as follows:

"Module not found" errors occur in these situations:

Follow these methods to fix "Module not found" errors:

// Check package.json
{
  "dependencies": {
    "express": "^4.18.0",
    "lodash": "^4.17.21"
  }
}

# Using npm
npm install express
npm install --save-dev nodemon

# Using yarn
yarn add express
yarn add -D nodemon

# Install all dependencies from package.json
npm install
# or
yarn install

# Check if package exists
ls node_modules/express

# Or verify in code
const express = require('express');
console.log(express); // Should not throw error

// ❌ Incorrect - missing ./
const utils = require('utils'); // Looks in node_modules

// ✅ Correct - relative path
const utils = require('./utils');
const config = require('../config');

// ✅ Correct - with file extension (for ES modules)
import utils from './utils.js';
import config from '../config.js';

// File structure:
// project/
//   ├── index.js
//   ├── utils.js        (require('./utils'))
//   └── config/
//       └── config.js   (require('../config/config'))

// Check if file exists before requiring
const fs = require('fs');
const path = require('path');

const filePath = path.join(__dirname, 'utils.js');
if (fs.existsSync(filePath)) {
  const utils = require('./utils');
} else {
  console.error('File not found:', filePath);
}

// Or use try-catch
try {
  const utils = require('./utils');
} catch (error) {
  if (error.code === 'MODULE_NOT_FOUND') {
    console.error('Module not found. Check file path.');
  }
}

# Delete node_modules and lock files
rm -rf node_modules
rm package-lock.json  # or yarn.lock

# On Windows (PowerShell)
Remove-Item -Recurse -Force node_modules
Remove-Item package-lock.json

# Clear npm cache
npm cache clean --force

# Clear yarn cache
yarn cache clean

# Fresh install
npm install

# Or with yarn
yarn install

// ❌ Incorrect - wrong case
const express = require('Express'); // Error on case-sensitive systems

// ✅ Correct - exact case
const express = require('express');

// For local files, case also matters
// ❌ Incorrect
const utils = require('./Utils');

// ✅ Correct
const utils = require('./utils');

// package.json for ES modules
{
  "type": "module",
  "main": "index.js"
}

// Then use import
import express from 'express';
import { readFile } from 'fs/promises';

// package.json for CommonJS (default)
{
  "main": "index.js"
}

// Then use require
const express = require('express');
const fs = require('fs');

Fixing "Module not found" errors properly is important for several reasons:

Troubleshooting Checklist

Frequently Asked Questions