Node.js errorNode.js: “Error [ERR_MODULE_NOT_FOUND]: Cannot find module ... imported from ...”

What the import points at, and the fix

1. 01

   A relative import without the file extension

   “A file extension must be provided when using the import keyword to resolve relative or absolute specifiers.” Node.js, ECMAScript modules: mandatory file extensions

   import './utils' works with bundlers and require(), but not with Node.js ES modules. Add the extension. A directory import such as './lib' fails with a different error, ERR_UNSUPPORTED_DIR_IMPORT, and needs './lib/index.js'.

   // wrong
   import { slugify } from './utils';
   
   // right
   import { slugify } from './utils.js';
   import { db } from './lib/index.js';

2. 02

   TypeScript output without extensions

   TypeScript does not add extensions when it compiles. With "module": "NodeNext", write imports with .js in your .ts files (TypeScript resolves them to the .ts source), so the compiled output is valid for Node.js. TypeScript 5.7 and newer can instead rewrite .ts imports with rewriteRelativeImportExtensions.

   // src/index.ts
   import { slugify } from './utils.js';  // points at src/utils.ts

3. 03

   A deep import into a package

   “Directory indexes (e.g. './startup/index.js') must also be fully specified.” Node.js, ECMAScript modules: mandatory file extensions

   import 'lodash/get' gives Cannot find module '.../node_modules/lodash/get' when the package has no exports map for that path. Add the extension (lodash/get.js), or import from the package entry point.

4. 04

   Cannot find package: not installed where it runs

   The package is missing from node_modules in the folder that runs the code: a production install that skips devDependencies, a Docker image that copied the code but not node_modules, or a monorepo package that does not list the dependency itself. Add it to that package’s dependencies and reinstall.

   npm ls express
   npm install express

5. 05

   Letter case on Linux

   macOS and Windows usually ignore the difference between Utils.js and utils.js; Linux servers and CI do not. Match the import to the file name exactly.

Checked against the vendor’s docs on November 8, 2026: Node.js: ECMAScript modules (mandatory file extensions).

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Related: Node.js “Cannot find module” · Node.js “Cannot use import statement outside a module” · Vercel “Module not found: Can’t resolve” · Node.js ERR_INVALID_ARG_TYPE