How Many Users Can a WebSocket Server Really Handle?
Unlike HTTP, WebSocket keeps a connection open for as long as the client stays on the page. That means the server must hold memory and resources for every open connection continuously. As concurrent users grow, memory usage and message-processing load scale roughly linearly — until a single server hits its limit.
This calculator takes your concurrent connection count, memory per connection, messages per second per user, and average message size, then estimates total memory usage and required bandwidth. It also assumes a single server can comfortably handle around 10,000 concurrent connections and suggests a recommended server count based on that. Real limits vary with server specs, event loop design, and message handling logic, so treat this as a reference figure.
For services with many concurrent users, optimizing how connections are kept alive matters a lot. Extending heartbeat intervals, batching messages, and automatically closing idle connections can meaningfully cut memory and bandwidth usage. If traffic growth is expected, it's safer to plan a horizontal scale-out architecture with multiple servers behind a load balancer ahead of time.
FAQ
It varies by server spec and app architecture, but this calculator uses 10,000 as a common baseline default.
Adjusting heartbeat intervals, closing idle connections, and batching messages all reduce per-connection resource usage.
Yes — as message frequency and size grow, network bandwidth usage grows with them, so it should be considered together.