Why does the import work on Windows but fail on Linux?

Linux filesystems are usually case-sensitive. Match the exact casing of every directory and filename in the import.

Do ES module imports need a file extension?

Relative ES module imports in Node.js normally need the exact filename including its extension unless a supported loader or build tool rewrites them.

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Node.jsBeginnerHigh severity

Error [ERR_MODULE_NOT_FOUND]: Cannot find package

Node.js could not resolve an imported package or file from the current project and module system.

5-15 min Popularity 97/100 Verified 2026-07-21

Debug with AI

What does this error mean?

The Node.js module loader followed an `import` statement and could not map its package name or file path to an installed, exported, and readable module.

Why does this happen?

The dependency is missing from node_modules or package.json.
The import contains the wrong package name, path, letter casing, or file extension.
Dependencies were installed in another workspace or directory.
The package exports map does not expose the imported subpath.
CommonJS and ES module configuration are being mixed incorrectly.

AI explanation

Plain-English analysis

Node resolves package imports from the current project boundary and local dependency tree. For a bare package name, verify installation and workspace location. For a relative import, verify the exact path, casing, extension, and module format. The URL shown in the error identifies the resolution point that failed.

Quick fix

Terminal

npm install
npm ls --depth=0
node -p "process.version"

Expected output: Dependencies install without errors, the required package appears in npm ls, and the application starts without ERR_MODULE_NOT_FOUND.

Step-by-step fix

1Install the missing package in the active projectRun the package manager from the directory containing the package.json used by the application.86%

Command

npm install <package>
npm ls <package>

2Correct the relative import pathMatch the real filename, letter casing, and required extension for the current Node.js module mode.69%

3Repair the workspace dependency installUse the repository's lockfile and package manager from the monorepo root.48%

Command

npm ci
npm run build

Alternative solutions

npm

npm install
npm ls <package>

Use npm when package-lock.json is the committed lockfile.

pnpm

pnpm install
pnpm why <package>

Run from the workspace root when pnpm-workspace.yaml is present.

Yarn

yarn install
yarn why <package>

Keep the Yarn version aligned with the repository configuration.

ES modules

node --input-type=module -e "import('./src/index.js')"

Relative ESM imports commonly require explicit file extensions.

Real example

Broken

javascript

import { createServer } from "./server";

createServer();

Corrected