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

The assert module from Node.js, for the browser.

Last verified Sep 9, 2026 against assert@2.1.0. JSON

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

assert ships CommonJS only. require("assert") works everywhere. import "assert" 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.

Latest
2.1.0 (Sep 7, 2023)
Module format
CommonJS
Last CommonJS version
2.1.0
TypeScript types
@types/assert
Node engines
not declared
Weekly downloads
16.1M
License
MIT

Does assert@2.1.0 actually load? Runtime test results

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

Runtimerequire("assert")import "assert"
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✓ works✓ works

How to import assert

ES modules (import)

import assert from "assert";

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 assert = require("assert");

Module format by version

Derived from the type, main and exports fields of every stable release on npm (16 versions; the newest 16 shown).

VersionsFormatFirst published
0.4.9 – 2.1.0CommonJSJun 30, 2011

Frequently asked

Is assert ESM-only?

assert@2.1.0 is a CommonJS package. assert ships CommonJS only. require("assert") works everywhere. import "assert" 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 assert with ES module syntax?

Yes. import assert from "assert" 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 assert work in Bun?

Yes. import "assert" loaded successfully in Bun 1.4 on Sep 9, 2026.

Does assert ship TypeScript types?

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

Links

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