Error: Cannot find module 'express'

What causes this

Node.js can’t find a package you’re trying to import. This is one of the most common Node errors and usually means the package isn’t installed, or Node is looking in the wrong place.

Common causes:

• The package isn’t installed (npm install was never run)
• node_modules is corrupted or incomplete
• You’re running the script from the wrong directory
• The package is installed globally but you’re importing it locally
• A typo in the module name
• The package’s main field in package.json points to a missing file

Fix 1: Install the missing package

# Check if it's in package.json
cat package.json | grep express

# If it's listed, install all dependencies
npm install

# If it's not listed, add it
npm install express

Fix 2: Delete node_modules and reinstall

Corrupted node_modules is surprisingly common:

rm -rf node_modules package-lock.json
npm install

If you’re using other package managers:

# yarn
rm -rf node_modules yarn.lock && yarn install

# pnpm
rm -rf node_modules pnpm-lock.yaml && pnpm install

Fix 3: Check you’re in the right directory

# Where am I?
pwd

# Is there a package.json here?
ls package.json

# Is the module in node_modules?
ls node_modules/express

If you’re in a monorepo, make sure you’re in the right workspace directory.

Fix 4: Fix the import path

// ❌ Typo in module name
const express = require('expresss');

// ❌ Wrong relative path
const utils = require('./util');  // file is actually ./utils.js

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

For local files, check the exact filename and path. Node.js is case-sensitive on Linux even if your Mac doesn’t care.

Fix 5: Check for global vs local confusion

# ❌ Installed globally but importing locally
npm install -g some-cli-tool
# Then in code: require('some-cli-tool') — won't work

# ✅ Install locally for code imports
npm install some-cli-tool

# Global installs are only for CLI commands, not code imports

Fix 6: Clear npm cache

npm cache clean --force
rm -rf node_modules package-lock.json
npm install

Related resources

• npm cheat sheet
• npm complete guide

How to prevent it

• Always run npm install after cloning a repo or pulling changes
• Use exact versions in package.json to avoid resolution issues
• Commit package-lock.json to ensure consistent installs across machines
• Use a .nvmrc file to pin the Node.js version for your project