Two technologies dominate real-time web communication: WebSockets (bidirectional, full-duplex) and Server-Sent Events (SSE, one-directional server-to-client). Both solve the problem of pushing data from server to client without the client polling. They take different approaches with different trade-offs — and the right choice depends heavily on the application's communication pattern.
Server-Sent Events: Simple but One-Way
SSE is a standard HTTP/1.1 feature (no protocol upgrade required) that enables servers to push events to clients over a persistent HTTP connection. The client opens an EventSource connection; the server sends events formatted as text ("data: payload ") whenever it has something to push. SSE automatically reconnects on connection loss. The simplicity is an advantage: SSE works through most corporate proxies and firewalls that block WebSocket upgrades, making it more reliable in restricted network environments. It also benefits from HTTP/2 multiplexing when available.
The limitation is one-directionality: SSE is server-to-client only. Client-to-server communication requires a separate HTTP POST request for each message. For applications where clients send infrequent data (live feeds, notification streams, dashboard updates), this is fine. For bidirectional real-time chat, it creates overhead and complexity.
WebSockets: Bidirectional and Low-Overhead
WebSockets provide full-duplex communication: both client and server can send messages independently at any time after the initial handshake. This is the natural model for chat: when either participant types a message, it goes directly through the open WebSocket connection without requiring a new HTTP request. The overhead per message is dramatically lower than separate HTTP requests: WebSocket frames have 2–14 bytes of header overhead versus several kilobytes for HTTP.
The Right Choice
For anonymous chat with bidirectional real-time messaging, WebSockets are clearly superior to SSE. The bidirectionality is not a nice-to-have — it is the fundamental communication model. SSE's simplicity advantage matters less when the platform already requires WebSocket-compatible infrastructure for matching and session management. The practical choice comes down to: use SSE for unidirectional feeds (online count notifications, system announcements), WebSockets for conversational messaging — a hybrid approach that many production platforms use.