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

> setprototypeof@1.2.0 is a CommonJS package. CommonJS — require() works on every Node.js version we test.

A small polyfill for Object.setprototypeof

Last verified Sep 9, 2026 against setprototypeof@1.2.0.

setprototypeof ships CommonJS only. require("setprototypeof") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "setprototypeof" also works because Node.js and Bun can import CommonJS from ES modules, but only the default export is guaranteed; named imports depend on Node's static analysis of the module.

## What to do

1. require("setprototypeof") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun.
2. From ES modules use the default import: import setprototypeof from "setprototypeof"; then destructure. Named imports only work when Node.js can statically detect the exports.
3. TypeScript: types are bundled; install nothing extra.

## Facts

- Latest: 1.2.0 (Jul 18, 2019)
- Module format: CommonJS
- Last CommonJS version: 1.2.0
- TypeScript types: bundled
- Node engines: not declared
- Weekly downloads: 92.0M
- License: ISC

## Runtime test results for setprototypeof@1.2.0

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

| Runtime | require("setprototypeof") | import "setprototypeof" |
|---|---|---|
| Node.js 18 | works | 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 setprototypeof

ES modules:

```js
import setprototypeof from "setprototypeof";
```

CommonJS:

```js
const setprototypeof = require("setprototypeof");
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (7 versions; the newest 7 shown).

| Versions | Format | First published |
|---|---|---|
| 1.0.0 – 1.2.0 | CommonJS | Feb 4, 2015 |

## Frequently asked

**Is setprototypeof ESM-only?**

setprototypeof@1.2.0 is a CommonJS package. setprototypeof ships CommonJS only. require("setprototypeof") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "setprototypeof" also works because Node.js and Bun can import CommonJS from ES modules, but only the default export is guaranteed; named imports depend on Node's static analysis of the module.

**Can I import setprototypeof with ES module syntax?**

Yes. import setprototypeof from "setprototypeof" works in Node.js and Bun because they support importing CommonJS modules. Named imports work only when Node.js can statically detect the exports.

**Does setprototypeof work in Bun?**

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

**Does setprototypeof ship TypeScript types?**

Yes. setprototypeof bundles its own type declarations; no @types package is needed.

## Links

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

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