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

> onetime@8.0.0 is ESM-only. ESM-only since 6.0.0 — last CommonJS version is 5.1.2.

Ensure a function is only called once

Last verified Sep 9, 2026 against onetime@8.0.0.

onetime dropped its CommonJS build in 6.0.0 (April 2021). The last version with a plain require()-able CommonJS entry is 5.1.2, published Aug 9, 2020; it declares support for Node.js >=6.

On Node.js 22.12+ and newer (onetime@8.0.0 declares Node.js >=22), require("onetime") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 22, 24 and 26. Node.js 18 has no require(esm), and onetime@8.0.0 declares Node.js >=22, so 18 is outside its supported range anyway.

onetime@8.0.0 declares engines ">=22", so Node.js 18, 20 are outside its supported range regardless of module format.

## What to do

1. On Node.js 22.12+ and newer (onetime@8.0.0 declares Node.js >=22), require("onetime") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 22, 24 and 26.
2. From a CommonJS file, use a dynamic import inside an async function: const onetime = await import("onetime"). That works on every Node.js version the package supports (>=22).
3. If you need a synchronous require() or run Node.js 18: npm install onetime@5.1.2, the last CommonJS release (published Aug 9, 2020); it declares Node.js >=6.
4. onetime@8.0.0 declares engines ">=22", so Node.js 18, 20 are unsupported regardless: upgrade Node.js or pin an older release.
5. TypeScript: types are bundled; install nothing extra.

## Facts

- Latest: 8.0.0 (Feb 2, 2026)
- Module format: ESM-only
- Last CommonJS version: 5.1.2
- ESM-only since: 6.0.0 (Apr 8, 2021)
- TypeScript types: bundled
- Node engines: >=22
- Weekly downloads: 162.3M
- License: MIT

## Runtime test results for onetime@8.0.0

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

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

ES modules:

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

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

CommonJS:

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

// Any Node.js version the package supports (>=22), from an async function:
async function main() {
  const onetime = await import("onetime");
}

// Or pin the last CommonJS release (declares Node.js >=6):
// npm install onetime@5.1.2
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (15 versions; the newest 15 shown).

| Versions | Format | First published |
|---|---|---|
| 6.0.0 – 8.0.0 | ESM-only | Apr 8, 2021 |
| 0.1.0 – 5.1.2 | CommonJS | Dec 13, 2013 |

## Frequently asked

**Is onetime ESM-only?**

onetime@8.0.0 is ESM-only. onetime dropped its CommonJS build in 6.0.0 (April 2021). The last version with a plain require()-able CommonJS entry is 5.1.2, published Aug 9, 2020; it declares support for Node.js >=6.

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

5.1.2 is the last version of onetime with a CommonJS build; it declares Node.js >=6. Install it with "npm install onetime@5.1.2". Every version from 6.0.0 on is ESM-only.

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

From a CommonJS file, use a dynamic import inside an async function: const onetime = await import("onetime"). That works on every Node.js version the package supports (>=22). On Node.js 22.12+ and newer (onetime@8.0.0 declares Node.js >=22), require("onetime") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 22, 24 and 26. Alternatively pin onetime@5.1.2 (declares Node.js >=6).

**Does onetime work in Bun?**

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

**Does onetime ship TypeScript types?**

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

## Links

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

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