npm Cannot find module — how to fix

Quick Answer

# Install the missing module
npm install xyz

# If it's a dev dependency
npm install --save-dev xyz

# Rebuild node_modules from scratch
rm -rf node_modules package-lock.json
npm install

When this happens

Error: Cannot find module 'express'
Require stack:
- /home/user/project/src/index.js
    at Function.Module._resolveFilename (node:internal/modules/cjs/loader:1039:15)

Node.js cannot locate the module because it is not installed, the package name is misspelled, or node_modules is missing.

Other causes & fixes

Check if it is installed

# List installed packages
npm ls express

# Or check node_modules
ls node_modules/express

Relative path import errors

For local file imports, check the path is correct relative to the importing file.

// WRONG — missing ./ prefix
const utils = require('utils');     // looks in node_modules

// CORRECT — explicit relative path
const utils = require('./utils');
const utils = require('../lib/utils');

TypeScript — missing @types package

# Install type definitions
npm install --save-dev @types/express

# Or check if types are bundled
npm info express types

ESM vs CJS mismatch

# package.json "type": "module" uses ESM — use import instead of require
import express from 'express';

# Or rename file to .cjs to use CommonJS
// index.cjs
const express = require('express');