Fix __dirname is not defined in ES module scope in Node.js

Error signature:

ReferenceError: __dirname is not defined in ES module scope

node · javascript · esm · modules · windows · documented · FREE SAMPLE

Cause

An ES module does not receive the CommonJS __dirname binding. This fixture uses a .mjs file, so Node loads it as ESM. Derive the directory from that module's file URL instead of substituting the process working directory.

Fix

In a file-backed ES module, use dirname(fileURLToPath(import.meta.url)). This preserves native Windows paths and decodes URL characters. On the tested Node 22.23.2 runtime, import.meta.dirname is also available.

import { fileURLToPath } from 'node:url';
import { dirname } from 'node:path';

const __filename = fileURLToPath(import.meta.url);
const __dirname = dirname(__filename);
console.log(__dirname);

// Alternative on the tested Node 22.23.2 runtime:
// console.log(import.meta.dirname);

Verification

Local fixture verification, not a production incident: Windows, Node 22.23.2, 2026-09-05 UTC. Two fresh fixture directories and independent Node processes each reproduced the ReferenceError before the change, then exited 0 after the change. Both the URL conversion and import.meta.dirname matched a directory containing spaces and #. A .cjs control confirmed that CommonJS still supplies __dirname.

Gotcha

process.cwd() is the launch directory, which need not be the module directory. Do not use new URL(import.meta.url).pathname as a native Windows filename. Scope: file-backed Node ESM; browsers, custom loaders and other runtimes were not tested. Keep a CommonJS file as CommonJS when that is the intended module format.

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