WebSocket vs Server-Sent Events: Choosing the Right Protocol

Server-Sent Events Explained

Server-Sent Events (SSE) provide a simple, standards-based way to push updates from server to client over a regular HTTP connection. Unlike WebSockets, SSE is unidirectional — only the server sends data. This makes SSE ideal for live feeds, notifications, progress updates, and dashboards where the client only needs to receive data. SSE connections automatically reconnect if dropped, include built-in event IDs for resuming from the last received event, and work through HTTP proxies and firewalls that might block WebSocket connections.

When to Use Each Protocol

Choose SSE for unidirectional data flows where you only need to push updates from server to client. SSE is simpler to implement, works over standard HTTP, supports automatic reconnection, and is sufficient for most real-time features. Choose WebSockets when you need bidirectional communication — chat applications, collaborative editing, multiplayer games, or any feature where both client and server need to send messages. WebSockets provide lower latency for high-frequency bidirectional messaging but require more infrastructure for connection management and scaling.

• SSE for notifications: One-way server push with automatic reconnection and event IDs
• SSE for dashboards: Live data updates without the complexity of WebSocket infrastructure
• WebSocket for chat: Bidirectional messaging where both parties send messages frequently
• WebSocket for collaboration: Real-time document editing with cursor and change synchronization

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