# Is mocha ESM-only? Can you require() it?

> mocha@12.0.0 is ESM-only. ESM-only since 12.0.0 — last CommonJS version is 11.8.0.

Classic, reliable, trusted test framework for Node.js and the browser

Last verified Sep 9, 2026 against mocha@12.0.0.

mocha dropped its CommonJS build in 12.0.0 (August 2026). The last version with a plain require()-able CommonJS entry is 11.8.0, published Aug 2, 2026; it declares support for Node.js ^18.18.0 || ^20.9.0 || >=21.1.0.

On Node.js 20.19+, 22.12+ and newer, require("mocha") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. Node.js 18 has no require(esm), and mocha@12.0.0 declares Node.js ^20.19.0 || >=22.12.0, so 18 is outside its supported range anyway.

mocha@12.0.0 declares engines "^20.19.0 || >=22.12.0", so Node.js 18 is outside its supported range regardless of module format.

## What to do

1. On Node.js 20.19+, 22.12+ and newer, require("mocha") 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 mocha = await import("mocha"). That works on every Node.js version the package supports (^20.19.0 || >=22.12.0).
3. If you need a synchronous require() or run Node.js 18: npm install mocha@11.8.0, the last CommonJS release (published Aug 2, 2026); it declares Node.js ^18.18.0 || ^20.9.0 || >=21.1.0.
4. mocha@12.0.0 declares engines "^20.19.0 || >=22.12.0", so Node.js 18 is unsupported regardless: upgrade Node.js or pin an older release.
5. TypeScript: npm install -D @types/mocha

## Facts

- Latest: 12.0.0 (Aug 31, 2026)
- Module format: ESM-only
- Last CommonJS version: 11.8.0
- ESM-only since: 12.0.0 (Aug 31, 2026)
- TypeScript types: @types/mocha
- Node engines: ^20.19.0 || >=22.12.0
- Weekly downloads: 13.3M
- License: MIT

## Runtime test results for mocha@12.0.0

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

| Runtime | require("mocha") | import "mocha" |
|---|---|---|
| Node.js 18 | fails (ERR_REQUIRE_ESM) | fails (ERR_REQUIRE_ESM) |
| 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 mocha

ES modules:

```js
import * as mocha from "mocha";
```

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

CommonJS:

```js
// Node.js 20.19+, 22.12+ and newer (verified):
const mocha = require("mocha");

// Any Node.js version the package supports (^20.19.0 || >=22.12.0), from an async function:
async function main() {
  const mocha = await import("mocha");
}

// Or pin the last CommonJS release (declares Node.js ^18.18.0 || ^20.9.0 || >=21.1.0):
// npm install mocha@11.8.0
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (209 versions; the newest 60 shown).

| Versions | Format | First published |
|---|---|---|
| 12.0.0 | ESM-only | Aug 31, 2026 |
| 7.2.0 – 11.8.0 | CommonJS | May 23, 2020 |

## Frequently asked

**Is mocha ESM-only?**

mocha@12.0.0 is ESM-only. mocha dropped its CommonJS build in 12.0.0 (August 2026). The last version with a plain require()-able CommonJS entry is 11.8.0, published Aug 2, 2026; it declares support for Node.js ^18.18.0 || ^20.9.0 || >=21.1.0.

**Which version of mocha still supports CommonJS / require()?**

11.8.0 is the last version of mocha with a CommonJS build; it declares Node.js ^18.18.0 || ^20.9.0 || >=21.1.0. Install it with "npm install mocha@11.8.0". Every version from 12.0.0 on is ESM-only.

**How do I use mocha from a CommonJS file?**

From a CommonJS file, use a dynamic import inside an async function: const mocha = await import("mocha"). That works on every Node.js version the package supports (^20.19.0 || >=22.12.0). On Node.js 20.19+, 22.12+ and newer, require("mocha") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. Alternatively pin mocha@11.8.0 (declares Node.js ^18.18.0 || ^20.9.0 || >=21.1.0).

**Does mocha work in Bun?**

Yes. import "mocha" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

**Does mocha ship TypeScript types?**

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

## Links

- [mocha on npm](https://www.npmjs.com/package/mocha)
- [Source repository](https://github.com/mochajs/mocha)
- [HTML version](https://canirequire.com/package/mocha/)
- [JSON version](https://canirequire.com/package/mocha.json)

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