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

> tslib@2.8.1 ships CommonJS and ESM builds. Dual package — require() works on every Node.js version we test; import works too.

Runtime library for TypeScript helper functions

Last verified Sep 9, 2026 against tslib@2.8.1.

tslib publishes both a CommonJS entry and a native ESM entry (ESM added in 1.14.0). require("tslib") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "tslib" works alongside it.

## What to do

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

## Facts

- Latest: 2.8.1 (Oct 31, 2024)
- Module format: Dual (CommonJS + ESM)
- Last CommonJS version: 2.8.1
- Native ESM since: 1.14.0
- TypeScript types: bundled
- Node engines: not declared
- Weekly downloads: 374.4M
- License: 0BSD

## Runtime test results for tslib@2.8.1

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

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

ES modules:

```js
import * as tslib from "tslib";
```

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

CommonJS:

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

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (45 versions; the newest 45 shown).

| Versions | Format | First published |
|---|---|---|
| 2.0.2 – 2.8.1 | Dual (CommonJS + ESM) | Oct 6, 2020 |
| 2.0.0 – 2.0.1 | CommonJS | May 13, 2020 |
| 1.14.0 – 1.14.1 | Dual (CommonJS + ESM) | Oct 6, 2020 |
| 1.0.0 – 1.13.0 | CommonJS | Jun 28, 2016 |

## Frequently asked

**Is tslib ESM-only?**

tslib@2.8.1 ships CommonJS and ESM builds. tslib publishes both a CommonJS entry and a native ESM entry (ESM added in 1.14.0). require("tslib") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "tslib" works alongside it.

**Can I require tslib?**

Yes. tslib ships a CommonJS entry alongside the native ESM entry. require("tslib") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun.

**Does tslib work in Bun?**

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

**Does tslib ship TypeScript types?**

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

## Links

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

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