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

> psl@1.15.0 ships CommonJS and ESM builds. Dual package — require() works on every Node.js version we test; import works too.

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Last verified Sep 9, 2026 against psl@1.15.0.

psl publishes both a CommonJS entry and a native ESM entry (ESM added in 1.11.0). require("psl") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "psl" works alongside it.

## What to do

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

## Facts

- Latest: 1.15.0 (Dec 2, 2024)
- Module format: Dual (CommonJS + ESM)
- Last CommonJS version: 1.15.0
- Native ESM since: 1.11.0
- TypeScript types: bundled
- Node engines: not declared
- Weekly downloads: 36.7M
- License: MIT

## Runtime test results for psl@1.15.0

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

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

ES modules:

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

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

CommonJS:

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

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (52 versions; the newest 52 shown).

| Versions | Format | First published |
|---|---|---|
| 1.13.0 – 1.15.0 | Dual (CommonJS + ESM) | Nov 21, 2024 |
| 1.12.0 | CommonJS | Nov 21, 2024 |
| 1.11.0 | Dual (CommonJS + ESM) | Nov 21, 2024 |
| 1.0.0 – 1.10.0 | CommonJS | Oct 14, 2014 |

## Frequently asked

**Is psl ESM-only?**

psl@1.15.0 ships CommonJS and ESM builds. psl publishes both a CommonJS entry and a native ESM entry (ESM added in 1.11.0). require("psl") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "psl" works alongside it.

**Can I require psl?**

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

**Does psl work in Bun?**

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

**Does psl ship TypeScript types?**

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

## Links

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

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