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

> optimist@0.6.1 is a CommonJS package. CommonJS — require() works on every Node.js version we test.

Light-weight option parsing with an argv hash. No optstrings attached.

Last verified Sep 9, 2026 against optimist@0.6.1.

optimist ships CommonJS only. require("optimist") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "optimist" 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("optimist") 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 optimist from "optimist"; then destructure. Named imports only work when Node.js can statically detect the exports.
3. TypeScript: npm install -D @types/optimist

## Facts

- Latest: 0.6.1 (Feb 6, 2014)
- Module format: CommonJS
- Last CommonJS version: 0.6.1
- TypeScript types: @types/optimist
- Node engines: not declared
- Weekly downloads: 2.7M
- License: MIT/X11

## Runtime test results for optimist@0.6.1

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

| Runtime | require("optimist") | import "optimist" |
|---|---|---|
| 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 optimist

ES modules:

```js
import optimist from "optimist";
```

CommonJS:

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

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (39 versions; the newest 39 shown).

| Versions | Format | First published |
|---|---|---|
| 0.0.1 – 0.6.1 | CommonJS | Dec 21, 2010 |

## Frequently asked

**Is optimist ESM-only?**

optimist@0.6.1 is a CommonJS package. optimist ships CommonJS only. require("optimist") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "optimist" 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 optimist with ES module syntax?**

Yes. import optimist from "optimist" 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 optimist work in Bun?**

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

**Does optimist ship TypeScript types?**

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

## Links

- [optimist on npm](https://www.npmjs.com/package/optimist)
- [Source repository](http://github.com/substack/node-optimist)
- [HTML version](https://canirequire.com/package/optimist/)
- [JSON version](https://canirequire.com/package/optimist.json)

---

For scripts and AI agents: any package is at https://canirequire.com/package/<name>/index.md (Markdown) or https://canirequire.com/package/<name>.json (JSON); the site index is https://canirequire.com/llms.txt. Fetch the URL directly; no search needed.