ES modules vs CommonJS in Node.js: `require is not defined` error

Question

After adding `"type": "module"` to package.json I get `ReferenceError: require is not defined in ES module scope`. Without it, `import` statements fail. What's the right setup in 2026?

Accepted Answer

`"type": "module"` tells Node to treat `.js` files as **ES modules**, where `require`, `module.exports` and `__dirname` don't exist.

For new projects, go all-in on ESM:

```js
import fs from 'node:fs/promises';
import path from 'node:path';

const dir = import.meta.dirname; // Node 20.11+ replacement for __dirname
```

If you must load a CommonJS-only package, a default import usually works (`import pkg from 'old-lib'`). As a last resort:

```js
import { createRequire } from 'node:module';
const require = createRequire(import.meta.url);
```

Recent Node versions (22.12+) can also `require()` ES modules synchronously, which removes most of the old interop pain.

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