Server-Sent Events (SSE) offer a simpler alternative to WebSockets for one-way server-to-browser data streaming over plain HTTP. Using the browser's built-in EventSource API, clients can receive real-time updates with automatic reconnection and no extra libraries. The post covers the SSE protocol format, a minimal Node.js server implementation, a Cloudflare Workers equivalent using ReadableStream, and a comparison with WebSockets. SSE is highlighted as the mechanism behind token-by-token streaming in AI chat apps like those using OpenAI, Anthropic, and Gemini APIs. Key limitations include one-way data flow and HTTP/1.1 connection limits (mitigated by HTTP/2).
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How it worksThe clientThe serverOn Cloudflare WorkersWhy this matters right nowSSE vs WebSocketsLimits worth knowing237 Impressions1 Comment