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

> scheduler@0.27.0 is a CommonJS package. CommonJS — require() works on every Node.js version we test.

Cooperative scheduler for the browser environment.

Last verified Sep 9, 2026 against scheduler@0.27.0.

scheduler ships CommonJS only. require("scheduler") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "scheduler" 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("scheduler") 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 scheduler from "scheduler"; then destructure. Named imports only work when Node.js can statically detect the exports.
3. TypeScript: npm install -D @types/scheduler

## Facts

- Latest: 0.27.0 (Oct 1, 2025)
- Module format: CommonJS
- Last CommonJS version: 0.27.0
- TypeScript types: @types/scheduler
- Node engines: not declared
- Weekly downloads: 152.8M
- License: MIT

## Runtime test results for scheduler@0.27.0

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

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

ES modules:

```js
import scheduler from "scheduler";
```

CommonJS:

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

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (44 versions; the newest 44 shown).

| Versions | Format | First published |
|---|---|---|
| 0.1.0 – 0.27.0 | CommonJS | Jan 11, 2011 |

## Frequently asked

**Is scheduler ESM-only?**

scheduler@0.27.0 is a CommonJS package. scheduler ships CommonJS only. require("scheduler") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "scheduler" 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 scheduler with ES module syntax?**

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

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

**Does scheduler ship TypeScript types?**

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

## Links

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

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