/config /nodejs/package-json-type-module

package.json "type": "module": ES modules in Node.js

updated 2026-10-20

tool: Node.js
file: package.json
key: type
type: "module" | "commonjs"
default: "commonjs"

The "type" field in package.json decides how Node.js loads .js files in that package: "module" makes them ES modules, "commonjs" (the default when the field is missing) makes them CommonJS. .mjs files are always ES modules and .cjs files are always CommonJS, whatever type says.

Example

bash

npm init -y >/dev/null
npm pkg set type=module
echo 'export const greet = (n) => `hello, ${n}`;' > lib.js
echo 'import { greet } from "./lib.js"; console.log(greet("esm")); console.log(typeof require);' > main.js
node main.js

Output

hello, esm
undefined

require is not defined in ES modules. Use import, or createRequire from node:module when you need to load a CommonJS-only file.

What changes with "type": "module"

	"type": "commonjs" (default)	"type": "module"
.js files	CommonJS	ES modules
import / export	only in .mjs	yes
require(), module.exports	yes	only in .cjs
__dirname, __filename	yes	use import.meta.dirname / import.meta.filename
Relative imports	extension optional	extension required: ./lib.js
Top-level await	no	yes

Pitfalls

Relative ESM imports need the file extension: import "./lib" fails with ERR_MODULE_NOT_FOUND.
Config files of some tools (for example older .eslintrc.js) are loaded with require; rename them to .cjs after switching.
The field applies to the folder of that package.json and its subfolders, up to the next package.json.

Sources

errors · nodejsError: Cannot find module '…' in Node.jsNode.js throws Cannot find module when require() or import cannot resolve a path or package. Install the package, fix the relative path or add the extension.codes · nodejsNode.js exit codes: 1, 9, 13, 124 and 128+ explainedNode.js exit codes: 1 uncaught exception, 5 fatal V8 error, 9 invalid argument, 13 unsettled top-level await, 124 process timeout, 128+n killed by a signal.cheat sheets · npmnpm cheat sheet: install, run, update, publishnpm cheat sheet: init, install and uninstall, version specifiers, scripts, outdated and update, npm ci for CI, ls and explain, config and cache commands.

Example

What changes with "type": "module"

Pitfalls

Sources

Related pages