Describe the bug

In Node v25.0.0 released one week ago the Web Storage API is enabled by default (nodejs/node@3312e4e946 , nodejs/node#57666), of which the behavior is however different with the browser. Now localStorage in Node is no longer undefined. Test units with Vitest with either jsdom or happy-dom environment will fail to provide methods like localStorage.getItem. I'm not completely sure it's a bug from Vitest, but I guess it's some downstream software detects its existence and gives up mocking it up. With limited exploration I find jsdom has consistent behavior in Node v25 and Node v24, so I first post it here.

A workaround for people encountering the same error: Set an environment variable to disable Web Storage API: export NODE_OPTIONS="--no-webstorage".

Reproduction

I created a minimal reproduction here:

{
  "name": "node25-vitest",
  "version": "1.0.0",
  "description": "",
  "scripts": {
    "test": "vitest"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "type": "commonjs",
  "devDependencies": {
    "jsdom": "^27.0.1",
    "vitest": "^3.2.4"
  }
}

import { defineConfig } from 'vitest/config';

export default defineConfig({
    test: {
        environment: 'jsdom',
    },
});

import { describe, expect, it } from 'vitest';

describe('localStorage demo', () => {
    it('foo', () => {
        expect(typeof localStorage.getItem).toEqual('function');
    });
});

services:
  test-25:
    image: node:25
    volumes:
      - ./:/app
    command: "sh -c 'node --version && cd /app && npm install && npm test'"
  test-24:
    image: node:24
    volumes:
      - ./:/app
    command: "sh -c 'node --version && cd /app && npm install && npm test'"

The demo.test.ts will fail with Node v25 and succeed with Node v24. The docker compose file might help if you already have such environment.

System Info

vitest/3.2.4. Any system with Nodejs v25.0.0

Used Package Manager

npm

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