{"data":{"slug":"socket-io","name":"Socket.IO","tagline":"MIT realtime library with fallbacks, not a hosted product","category":"comms","categoryName":"Comms","url":"https://socket.io","github":"https://github.com/socketio/socket.io","pricing":"open-source","hook":"Socket.IO is still the WebSocket library people actually ship when the connection has to survive a proxy.","whatsGood":"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.","theCatch":"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.","addedAt":"2026-09-03","featured":false,"domain":"Comms","subSpecialty":"Realtime","capabilities":["websockets","realtime"],"surfaces":["Self-host"],"ecosystem":["Node.js","Browser"],"licenseModel":"OSS/MIT","githubStars":63206},"related":[{"slug":"livekit","name":"LiveKit","tagline":"Apache-2.0 realtime rooms, SFU, and agents"},{"slug":"chatwoot","name":"Chatwoot","tagline":"MIT-core support inbox you can self-host for $0/agent"},{"slug":"plunk","name":"Plunk","tagline":"AGPL-3.0 transactional email, workflows, and broadcasts"},{"slug":"centrifugo","name":"Centrifugo","tagline":"Apache-2.0 Go realtime server binary, not in-process Socket.IO"},{"slug":"liveblocks","name":"Liveblocks","tagline":"Hosted collab rooms; Free $0 pauses at the cap"}],"links":{"self":"/api/gems/socket-io","html":"/gems/socket-io","markdown":"/gems/socket-io.md","category":"/api/gems?category=comms","categoryPage":"/stacks/comms"}}