Overview
Before WebSockets, the way to get near-real-time updates was long polling: the client makes an HTTP request the server holds open until it has data, then the client immediately re-requests. It works through any firewall or proxy and needs no special protocol, but every message costs a fresh round trip and a connection setup. WebSockets replace that with one upgraded TCP connection both sides can push over instantly — far lower latency and overhead for chatty, bidirectional traffic — at the cost of stateful connections your infrastructure must support.
Long Polling vs WebSockets: key differences
| Long Polling | WebSockets | |
|---|---|---|
| Latency | A round trip per message | Near-instant push |
| Connection | Repeated short HTTP requests | One long-lived socket |
| Overhead | High (headers + reconnect each time) | Low after handshake |
| Compatibility | Works everywhere, no upgrade | Needs WS-aware proxies/LBs |
| Direction | Effectively server → client | Full duplex |
When to use Long Polling
Legacy environments or restrictive networks where WebSockets are blocked, low-frequency updates, or when you want the simplest possible HTTP-only fallback.
When to use WebSockets
High-frequency, low-latency, two-way messaging — chat, multiplayer, live collaboration — where the persistent connection pays for itself.
Verdict
Use WebSockets for genuine real-time, bidirectional traffic; they are more efficient and lower latency. Keep long polling as a fallback for clients or networks that can't hold a WebSocket. Many libraries (e.g. Socket.IO) negotiate WebSockets first and fall back to long polling automatically.
Common questions
Is long polling still used?
Yes — mainly as a fallback when WebSockets or SSE are unavailable (old browsers, strict corporate proxies). For new real-time features, WebSockets or SSE are preferred; long polling is the compatibility safety net.
Why are WebSockets more efficient than long polling?
Long polling reopens a connection and resends HTTP headers for every message and incurs a round trip; WebSockets keep one connection open and push small framed messages with minimal overhead.