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Is sinon-chai ESM-only? Can you require() it?

Extends Chai with assertions for the Sinon.JS mocking framework.

Last verified Sep 9, 2026 against sinon-chai@4.0.1. JSON

ESM-only ESM-only since 4.0.0 — last CommonJS version is 3.7.0

sinon-chai dropped its CommonJS build in 4.0.0 (July 2024). The last version you can require() on every Node.js version, including 18 and older, is 3.7.0, published May 25, 2021.

On Node.js 20.19+, 22.12+ and every newer release, require("sinon-chai") 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
4.0.1 (Aug 22, 2025)
Module format
ESM-only
Last CommonJS version
3.7.0
ESM-only since
4.0.0 (Jul 25, 2024)
TypeScript types
@types/sinon-chai
Node engines
not declared
Weekly downloads
835K
License
(BSD-2-Clause OR WTFPL)

Does sinon-chai@4.0.1 actually load? Runtime test results

Installed and executed on Sep 9, 2026 with require("sinon-chai") from a CommonJS file and import "sinon-chai" from an ES module.

Runtimerequire("sinon-chai")import "sinon-chai"
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 sinon-chai

ES modules (import)

import sinonChai from "sinon-chai";

CommonJS (require)

// Node.js 20.19+ / 22.12+ / newer (package has no top-level await):
const sinonChai = require("sinon-chai");

// Any Node.js version:
const sinonChai = await import("sinon-chai");

// Or pin the last CommonJS release:
// npm install sinon-chai@3.7.0

Module format by version

Derived from the type, main and exports fields of every stable release on npm (36 versions; the newest 36 shown).

VersionsFormatFirst published
4.0.0 – 4.0.1ESM-onlyJul 25, 2024
1.0.0 – 3.7.0CommonJSFeb 13, 2012

Frequently asked

Is sinon-chai ESM-only?

sinon-chai@4.0.1 is ESM-only. sinon-chai dropped its CommonJS build in 4.0.0 (July 2024). The last version you can require() on every Node.js version, including 18 and older, is 3.7.0, published May 25, 2021.

Which version of sinon-chai still supports CommonJS / require()?

3.7.0 is the last version of sinon-chai with a CommonJS build. Install it with "npm install sinon-chai@3.7.0". Every version from 4.0.0 on is ESM-only.

How do I use sinon-chai from a CommonJS file?

Use a dynamic import: const mod = await import("sinon-chai"). On Node.js 20.19+, 22.12+ and newer, a plain require("sinon-chai") also works for ESM packages that do not use top-level await. Alternatively pin sinon-chai@3.7.0.

Does sinon-chai work in Bun?

Yes. import "sinon-chai" loaded successfully in Bun 1.4 on Sep 9, 2026.

Does sinon-chai ship TypeScript types?

Not bundled. Install the community types with "npm install -D @types/sinon-chai".

Links

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