canirequire

canirequire › ESM-only › is-wsl

Is is-wsl ESM-only? Can you require() it?

Check if the process is running inside Windows Subsystem for Linux (Bash on Windows)

Last verified Sep 9, 2026 against is-wsl@3.1.1. JSON

ESM-only ESM-only since 3.0.0 — last CommonJS version is 2.2.0

is-wsl dropped its CommonJS build in 3.0.0 (August 2023). The last version you can require() on every Node.js version, including 18 and older, is 2.2.0, published May 3, 2020.

On Node.js 20.19+, 22.12+ and every newer release, require("is-wsl") works anyway: Node can load synchronous ES modules through require(). Verified on Node 20, 22, 24, 26. Node.js 18 and older still fail with ERR_REQUIRE_ESM.

Latest
3.1.1 (Feb 15, 2026)
Module format
ESM-only
Last CommonJS version
2.2.0
ESM-only since
3.0.0 (Aug 8, 2023)
TypeScript types
Bundled
Node engines
>=16
Weekly downloads
117.6M
License
MIT

Does is-wsl@3.1.1 actually load? Runtime test results

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

Runtimerequire("is-wsl")import "is-wsl"
Node.js 18✗ failsERR_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✓ works✓ works

How to import is-wsl

ES modules (import)

import isWsl from "is-wsl";

CommonJS (require)

// Node.js 20.19+ / 22.12+ / newer (package has no top-level await):
const isWsl = require("is-wsl");

// Any Node.js version:
const isWsl = await import("is-wsl");

// Or pin the last CommonJS release:
// npm install is-wsl@2.2.0

Module format by version

Derived from the type, main and exports fields of every stable release on npm (9 versions; the newest 9 shown).

VersionsFormatFirst published
3.0.0 – 3.1.1ESM-onlyAug 8, 2023
1.0.0 – 2.2.0CommonJSApr 16, 2017

Frequently asked

Is is-wsl ESM-only?

is-wsl@3.1.1 is ESM-only. is-wsl dropped its CommonJS build in 3.0.0 (August 2023). The last version you can require() on every Node.js version, including 18 and older, is 2.2.0, published May 3, 2020.

Which version of is-wsl still supports CommonJS / require()?

2.2.0 is the last version of is-wsl with a CommonJS build. Install it with "npm install is-wsl@2.2.0". Every version from 3.0.0 on is ESM-only.

How do I use is-wsl from a CommonJS file?

Use a dynamic import: const mod = await import("is-wsl"). On Node.js 20.19+, 22.12+ and newer, a plain require("is-wsl") also works for ESM packages that do not use top-level await. Alternatively pin is-wsl@2.2.0.

Does is-wsl work in Bun?

Yes. import "is-wsl" loaded successfully in Bun 1.4 on Sep 9, 2026.

Does is-wsl ship TypeScript types?

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

Links

Other esm-only packages

Similar popularity