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

> leven@4.1.0 is ESM-only. ESM-only since 4.0.0 — last CommonJS version is 3.1.0.

Measure the difference between two strings using the Levenshtein distance algorithm

Last verified Sep 9, 2026 against leven@4.1.0.

leven dropped its CommonJS build in 4.0.0 (August 2021). The last version with a plain require()-able CommonJS entry is 3.1.0, published Apr 4, 2019; it declares support for Node.js >=6.

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

## What to do

1. On Node.js 20.19+, 22.12+ and newer, require("leven") 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 leven = await import("leven"). That works on every Node.js version the package supports (^12.20.0 || ^14.13.1 || >=16.0.0).
3. If you need a synchronous require() or run Node.js 18: npm install leven@3.1.0, the last CommonJS release (published Apr 4, 2019); it declares Node.js >=6.
4. TypeScript: types are bundled; install nothing extra.

## Facts

- Latest: 4.1.0 (Sep 11, 2025)
- Module format: ESM-only
- Last CommonJS version: 3.1.0
- ESM-only since: 4.0.0 (Aug 10, 2021)
- TypeScript types: bundled
- Node engines: ^12.20.0 || ^14.13.1 || >=16.0.0
- Weekly downloads: 57.5M
- License: MIT

## Runtime test results for leven@4.1.0

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

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

ES modules:

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

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 leven = require("leven");

// Any Node.js version the package supports (^12.20.0 || ^14.13.1 || >=16.0.0), from an async function:
async function main() {
  const leven = await import("leven");
}

// Or pin the last CommonJS release (declares Node.js >=6):
// npm install leven@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 – 4.1.0 | ESM-only | Aug 10, 2021 |
| 1.0.0 – 3.1.0 | CommonJS | Aug 9, 2014 |

## Frequently asked

**Is leven ESM-only?**

leven@4.1.0 is ESM-only. leven dropped its CommonJS build in 4.0.0 (August 2021). The last version with a plain require()-able CommonJS entry is 3.1.0, published Apr 4, 2019; it declares support for Node.js >=6.

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

3.1.0 is the last version of leven with a CommonJS build; it declares Node.js >=6. Install it with "npm install leven@3.1.0". Every version from 4.0.0 on is ESM-only.

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

From a CommonJS file, use a dynamic import inside an async function: const leven = await import("leven"). That works on every Node.js version the package supports (^12.20.0 || ^14.13.1 || >=16.0.0). On Node.js 20.19+, 22.12+ and newer, require("leven") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. Alternatively pin leven@3.1.0 (declares Node.js >=6).

**Does leven work in Bun?**

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

**Does leven ship TypeScript types?**

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

## Links

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

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