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

> mimic-fn@5.0.0 is ESM-only. ESM-only since 4.0.0 — last CommonJS version is 3.1.0.

Make a function mimic another one

Last verified Sep 9, 2026 against mimic-fn@5.0.0.

mimic-fn dropped its CommonJS build in 4.0.0 (April 2021). The last version with a plain require()-able CommonJS entry is 3.1.0, published Jul 24, 2020; it declares support for Node.js >=8.

On Node.js 20.19+, 22.12+ and newer, require("mimic-fn") 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("mimic-fn") fails with ERR_REQUIRE_ESM.

**Deprecated:** Renamed to mimic-function

## What to do

1. On Node.js 20.19+, 22.12+ and newer, require("mimic-fn") 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 mimicFn = await import("mimic-fn"). That works on every Node.js version the package supports (>=12).
3. If you need a synchronous require() or run Node.js 18: npm install mimic-fn@3.1.0, the last CommonJS release (published Jul 24, 2020); it declares Node.js >=8.
4. TypeScript: types are bundled; install nothing extra.
5. This package is deprecated: Renamed to mimic-function

## Facts

- Latest: 5.0.0 (Nov 5, 2023)
- Module format: ESM-only
- Last CommonJS version: 3.1.0
- ESM-only since: 4.0.0 (Apr 7, 2021)
- TypeScript types: bundled
- Node engines: >=12
- Weekly downloads: 99.7M
- License: MIT

## Runtime test results for mimic-fn@5.0.0

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

| Runtime | require("mimic-fn") | import "mimic-fn" |
|---|---|---|
| Node.js 18 | fails (ERR_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 mimic-fn

ES modules:

```js
import * as mimicFn from "mimic-fn";
```

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 mimicFn = require("mimic-fn");

// Any Node.js version the package supports (>=12), from an async function:
async function main() {
  const mimicFn = await import("mimic-fn");
}

// Or pin the last CommonJS release (declares Node.js >=8):
// npm install mimic-fn@3.1.0
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (9 versions; the newest 9 shown).

| Versions | Format | First published |
|---|---|---|
| 4.0.0 – 5.0.0 | ESM-only | Apr 7, 2021 |
| 1.0.0 – 3.1.0 | CommonJS | Oct 19, 2016 |

## Frequently asked

**Is mimic-fn ESM-only?**

mimic-fn@5.0.0 is ESM-only. mimic-fn dropped its CommonJS build in 4.0.0 (April 2021). The last version with a plain require()-able CommonJS entry is 3.1.0, published Jul 24, 2020; it declares support for Node.js >=8.

**Which version of mimic-fn still supports CommonJS / require()?**

3.1.0 is the last version of mimic-fn with a CommonJS build; it declares Node.js >=8. Install it with "npm install mimic-fn@3.1.0". Every version from 4.0.0 on is ESM-only.

**How do I use mimic-fn from a CommonJS file?**

From a CommonJS file, use a dynamic import inside an async function: const mimicFn = await import("mimic-fn"). That works on every Node.js version the package supports (>=12). On Node.js 20.19+, 22.12+ and newer, require("mimic-fn") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. Alternatively pin mimic-fn@3.1.0 (declares Node.js >=8).

**Does mimic-fn work in Bun?**

Yes. import "mimic-fn" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

**Does mimic-fn ship TypeScript types?**

Yes. mimic-fn bundles its own type declarations; no @types package is needed.

## Links

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

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