How do I fix 'Cannot use import statement outside a module' and 'require is not defined' in Node.js?

Node supports two module systems and decides per file.

ESM (import/export)

Used when the file ends in .mjs, or .js and the nearest package.json has "type": "module".

CommonJS (require/module.exports)

Used for .cjs, or .js when "type" is missing or "commonjs".

Fixing "Cannot use import statement outside a module"

You wrote ESM syntax in a CommonJS file. Either:

{ "type": "module" }

in package.json, or rename to .mjs, or switch to require.

Fixing "require is not defined in ES module scope"

You are in ESM. Replace:

import fs from 'node:fs';
import { createRequire } from 'node:module';
const require = createRequire(import.meta.url); // only if you really need require

Also, __dirname and __filename do not exist in ESM:

import { fileURLToPath } from 'node:url';
import path from 'node:path';
const __dirname = path.dirname(fileURLToPath(import.meta.url));

Recent Node versions also provide import.meta.dirname and import.meta.filename.

ESM rules

• Relative imports need the file extension: import x from './x.js'.
• JSON needs an import attribute: import data from './data.json' with { type: 'json' }.
• Top-level await works in ESM.
• ESM can import CommonJS; importing ESM from CommonJS is possible via await import(), and recent Node versions also allow require() of synchronous ESM (check your version's docs).

TypeScript

Set "module": "nodenext" (or esnext with a bundler) and keep "type": "module" consistent. Tools like tsx run both.

Pitfall: mixing "type": "module" with an old Jest/ts-node setup is a frequent source of this error; configure the tool for ESM or use Vitest.