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Is socket.io ESM-only? Can you require() it?

node.js realtime framework server

Last verified Sep 9, 2026 against socket.io@4.8.3. JSON

Dual (CommonJS + ESM) Dual package — both require() and import work

socket.io publishes both a CommonJS entry and a native ESM entry (ESM added in 3.0.0). require("socket.io") and import "socket.io" both work on every supported Node.js version and in Bun.

Latest
4.8.3 (Dec 23, 2025)
Module format
Dual (CommonJS + ESM)
Last CommonJS version
4.8.3
Native ESM since
3.0.0
TypeScript types
Bundled
Node engines
>=10.2.0
Weekly downloads
16.2M
License
MIT

Does socket.io@4.8.3 actually load? Runtime test results

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

Runtimerequire("socket.io")import "socket.io"
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✓ works✓ works

How to import socket.io

ES modules (import)

import socketIo from "socket.io";

CommonJS (require)

const socketIo = require("socket.io");

Module format by version

Derived from the type, main and exports fields of every stable release on npm (150 versions; the newest 60 shown).

VersionsFormatFirst published
3.0.0 – 4.8.3Dual (CommonJS + ESM)Nov 5, 2020
1.5.1 – 2.5.1CommonJSOct 24, 2016

Frequently asked

Is socket.io ESM-only?

socket.io@4.8.3 ships CommonJS and ESM builds. socket.io publishes both a CommonJS entry and a native ESM entry (ESM added in 3.0.0). require("socket.io") and import "socket.io" both work on every supported Node.js version and in Bun.

Can I require socket.io?

Yes. socket.io ships a CommonJS entry, so require("socket.io") works on every Node.js version, alongside the native ESM entry for import.

Does socket.io work in Bun?

Yes. import "socket.io" loaded successfully in Bun 1.4 on Sep 9, 2026.

Does socket.io ship TypeScript types?

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

Links

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