# Socket.IO

> MIT realtime library with fallbacks, not a hosted product

**Category:** Comms  
**Pricing:** open-source  
**URL:** https://socket.io  
**GitHub:** https://github.com/socketio/socket.io  
**Added:** 2026-09-03

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## The Hook

Socket.IO is still the WebSocket library people actually ship when the connection has to survive a proxy.

## What's Good

MIT. Engine.IO fallbacks (WebSocket, HTTP long-polling), rooms, acknowledgements, binary. Client and server that have been in production for a decade-plus. No product pricing page because there is no product — you run the server.

## The Catch

You bring the host. Horizontal scale needs Redis (or equivalent) adapter. This is not LiveKit and not a managed pub-sub. CORS, sticky sessions, and polling surprises remain your bugs.

## Verdict

The MIT socket library. Free as in you run it.