# Is web-streams-polyfill ESM-only? Can you require() it?

> web-streams-polyfill@4.3.0 ships CommonJS and ESM builds. Dual package — require() works on every Node.js version we test; import works too.

Web Streams, based on the WHATWG spec reference implementation

Last verified Sep 9, 2026 against web-streams-polyfill@4.3.0.

web-streams-polyfill publishes both a CommonJS entry and a native ESM entry (ESM added in 4.0.0). require("web-streams-polyfill") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 8. import "web-streams-polyfill" works alongside it.

## What to do

1. Nothing to change. require("web-streams-polyfill") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 8. import * as webStreamsPolyfill from "web-streams-polyfill" works alongside it; use named imports for what the ESM entry exports.
2. TypeScript: types are bundled; install nothing extra.

## Facts

- Latest: 4.3.0 (May 15, 2026)
- Module format: Dual (CommonJS + ESM)
- Last CommonJS version: 4.3.0
- Native ESM since: 4.0.0
- TypeScript types: bundled
- Node engines: >= 8
- Weekly downloads: 53.5M
- License: MIT

## Runtime test results for web-streams-polyfill@4.3.0

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

| Runtime | require("web-streams-polyfill") | import "web-streams-polyfill" |
|---|---|---|
| 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 web-streams-polyfill

ES modules:

```js
import * as webStreamsPolyfill from "web-streams-polyfill";
```

Namespace import shown because the ESM entry may have no default export; use named imports for what it exports.

CommonJS:

```js
const webStreamsPolyfill = require("web-streams-polyfill");
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (35 versions; the newest 35 shown).

| Versions | Format | First published |
|---|---|---|
| 4.0.0 – 4.3.0 | Dual (CommonJS + ESM) | Feb 28, 2024 |
| 1.0.0 – 3.3.3 | CommonJS | Mar 2, 2016 |

## Frequently asked

**Is web-streams-polyfill ESM-only?**

web-streams-polyfill@4.3.0 ships CommonJS and ESM builds. web-streams-polyfill publishes both a CommonJS entry and a native ESM entry (ESM added in 4.0.0). require("web-streams-polyfill") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 8. import "web-streams-polyfill" works alongside it.

**Can I require web-streams-polyfill?**

Yes. web-streams-polyfill ships a CommonJS entry alongside the native ESM entry. require("web-streams-polyfill") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. The package declares Node.js >= 8.

**Does web-streams-polyfill work in Bun?**

Yes. import "web-streams-polyfill" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

**Does web-streams-polyfill ship TypeScript types?**

Yes. web-streams-polyfill bundles its own type declarations; no @types package is needed.

## Links

- [web-streams-polyfill on npm](https://www.npmjs.com/package/web-streams-polyfill)
- [Source repository](https://github.com/MattiasBuelens/web-streams-polyfill)
- [HTML version](https://canirequire.com/package/web-streams-polyfill/)
- [JSON version](https://canirequire.com/package/web-streams-polyfill.json)

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