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

Lightweight Jest compatible spy implementation

Last verified Sep 9, 2026 against @vitest/spy@5.0.0. JSON

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

@vitest/spy has been ESM-only since its first stable release. There is no version you can require() on Node.js 18 or older.

On Node.js 20.19+, 22.12+ and every newer release, require("@vitest/spy") works anyway: Node can load synchronous ES modules through require(). Verified on Node 20, 22, 24, 26. Node.js 18 and older still fail with ERR_REQUIRE_ESM.

Latest
5.0.0 (Sep 3, 2026)
Module format
ESM-only
Last CommonJS version
none
ESM-only since
0.27.0 (Jan 9, 2023)
TypeScript types
Bundled
Node engines
not declared
Weekly downloads
86.8M
License
MIT

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

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

Runtimerequire("@vitest/spy")import "@vitest/spy"
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✓ works✓ works

How to import @vitest/spy

ES modules (import)

import spy from "@vitest/spy";

CommonJS (require)

// Node.js 20.19+ / 22.12+ / newer (package has no top-level await):
const spy = require("@vitest/spy");

// Any Node.js version:
const spy = await import("@vitest/spy");

Module format by version

Derived from the type, main and exports fields of every stable release on npm (132 versions; the newest 60 shown).

VersionsFormatFirst published
2.1.5 – 5.0.0ESM-onlyNov 13, 2024

Frequently asked

Is @vitest/spy ESM-only?

@vitest/spy@5.0.0 is ESM-only. @vitest/spy has been ESM-only since its first stable release. There is no version you can require() on Node.js 18 or older.

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

None. @vitest/spy has always been ESM-only. Use import, or await import("@vitest/spy") from CommonJS.

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

Use a dynamic import: const mod = await import("@vitest/spy"). On Node.js 20.19+, 22.12+ and newer, a plain require("@vitest/spy") also works for ESM packages that do not use top-level await.

Does @vitest/spy work in Bun?

Yes. import "@vitest/spy" loaded successfully in Bun 1.4 on Sep 9, 2026.

Does @vitest/spy ship TypeScript types?

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

Links

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