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

A simple utility for conditionally joining classNames together

Last verified Sep 9, 2026 against classnames@2.5.1. Markdown · JSON

CommonJS CommonJS — require() works on every Node.js version we test

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.
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

Does classnames@2.5.1 actually load? Runtime test results

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

Runtimerequire("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 (import)

import classnames from "classnames";

Named imports from a CommonJS package only work when Node.js can statically detect them. If a named import fails, use the default import and destructure.

CommonJS (require)

const classnames = require("classnames");

Module format by version

Derived from the type, main and exports fields of every stable release on npm, corrected where a runtime test of that version contradicted them (30 versions; the newest 30 shown).

VersionsFormatFirst published
1.0.0 – 2.5.1CommonJSNov 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

Other commonjs packages

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