Socket.IO

Socket.IO is the default answer when someone asks "how do I add real-time to my app." It wraps WebSockets with automatic fallbacks, reconnection logic, and room-based broadcasting. Thirteen years in, it still works and still ships.

For chat apps, live dashboards, collaborative editors, or multiplayer games — Socket.IO gets you there fast. The API is dead simple: emit an event on one side, listen on the other. ws is lighter if you only need raw WebSockets. Ably and Pusher handle the infrastructure for you but charge per message. If you're already on Supabase, its Realtime channels might be enough.

Best for indie hackers who need real-time features without managing WebSocket infrastructure. The ecosystem is massive — adapters for Redis, Postgres, MongoDB for horizontal scaling.

The catch: Socket.IO adds overhead compared to raw WebSockets. At serious scale (100k+ connections), you'll feel it. The protocol isn't standard WebSocket, so non-JS clients need special libraries. And if you're building something latency-critical like a trading platform, go lower-level.