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

> classnames@2.5.1 is a CommonJS package. CommonJS — require() works on every Node.js version we test.

A simple utility for conditionally joining classNames together

Last verified Sep 9, 2026 against classnames@2.5.1.

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

## Facts

- Latest: 2.5.1 (Dec 29, 2023)
- Module format: CommonJS
- Last CommonJS version: 2.5.1
- TypeScript types: bundled
- Node engines: not declared
- Weekly downloads: 28.8M
- License: MIT

## Runtime test results for classnames@2.5.1

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

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

ES modules:

```js
import classnames from "classnames";
```

CommonJS:

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

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (30 versions; the newest 30 shown).

| Versions | Format | First published |
|---|---|---|
| 1.0.0 – 2.5.1 | CommonJS | Nov 5, 2014 |

## Frequently asked

**Is classnames ESM-only?**

classnames@2.5.1 is a CommonJS package. classnames ships CommonJS only. require("classnames") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "classnames" 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 classnames with ES module syntax?**

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

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

**Does classnames ship TypeScript types?**

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

## Links

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

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