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Is @vitest/mocker ESM-only? Can you require() it?

Vitest module mocker implementation

Last verified Sep 9, 2026 against @vitest/mocker@5.0.0. Markdown · JSON

ESM-only ESM-only — it has never shipped a CommonJS build

@vitest/mocker has been ESM-only since its first stable release; there is no CommonJS version to pin.

On Node.js 20.19+, 22.12+ and newer, require("@vitest/mocker") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. On Node.js 18, which has no require(esm), require("@vitest/mocker") fails with ERR_REQUIRE_ESM.

What to do

  1. On Node.js 20.19+, 22.12+ and newer, require("@vitest/mocker") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26.
  2. From a CommonJS file, use a dynamic import inside an async function: const mocker = await import("@vitest/mocker"). That works on every Node.js version the package supports.
  3. There is no CommonJS release of @vitest/mocker to pin; without require(esm) the only option is a dynamic import().
  4. TypeScript: types are bundled; install nothing extra.
Latest
5.0.0 (Sep 3, 2026)
Module format
ESM-only
Last CommonJS version
none
ESM-only since
2.1.0 (Sep 12, 2024)
TypeScript types
Bundled
Node engines
not declared
Weekly downloads
75.6M
License
MIT

Does @vitest/mocker@5.0.0 actually load? Runtime test results

Installed and executed on Sep 9, 2026 with require("@vitest/mocker") from a CommonJS file and import "@vitest/mocker" from an ES module.

Runtimerequire("@vitest/mocker")import "@vitest/mocker"
Node.js 18✗ failsERR_REQUIRE_ESM✓ works
Node.js 20✓ works✓ works
Node.js 22✓ works✓ works
Node.js 24✓ works✓ works
Node.js 26✓ works✓ works
Bun 1.4.0✓ works✓ works

How to import @vitest/mocker

ES modules (import)

import * as mocker from "@vitest/mocker";

Namespace import shown because the ESM entry may have no default export; use named imports for what it exports.

CommonJS (require)

// Node.js 20.19+, 22.12+ and newer (verified):
const mocker = require("@vitest/mocker");

// Any Node.js version the package supports, from an async function:
async function main() {
  const mocker = await import("@vitest/mocker");
}

Module format by version

Derived from the type, main and exports fields of every stable release on npm, corrected where a runtime test of that version contradicted them (65 versions; the newest 60 shown).

VersionsFormatFirst published
2.1.5 – 5.0.0ESM-onlyNov 13, 2024

Frequently asked

Is @vitest/mocker ESM-only?

@vitest/mocker@5.0.0 is ESM-only. @vitest/mocker has been ESM-only since its first stable release; there is no CommonJS version to pin.

Which version of @vitest/mocker still supports CommonJS / require()?

None. @vitest/mocker has always been ESM-only. Use import, or a dynamic import("@vitest/mocker") from an async function in CommonJS.

How do I use @vitest/mocker from a CommonJS file?

From a CommonJS file, use a dynamic import inside an async function: const mocker = await import("@vitest/mocker"). That works on every Node.js version the package supports. On Node.js 20.19+, 22.12+ and newer, require("@vitest/mocker") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26.

Does @vitest/mocker work in Bun?

Yes. import "@vitest/mocker" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

Does @vitest/mocker ship TypeScript types?

Yes. @vitest/mocker bundles its own type declarations; no @types package is needed.

Links

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