TL;DR
If you’re building an AI chat app, go with Server-Sent Events (SSE). It’s purpose-built for streaming responses in real time, incredibly lightweight, and much easier to scale and maintain. WebSockets do have advantages in complex, truly bidirectional scenarios—like games or video chat—but for most AI chat use cases, they’re overkill and come with extra cost and complexity. SSE is faster to implement, cheaper to run, and better aligned with how AI responses work. Stick with the tool that fits the job.
If you’re building an AI-powered chat app, the default instinct might be to reach for WebSockets. After all, they’re built for real-time, bidirectional communication. But when it comes to streaming AI responses, scaling efficiently, and keeping infrastructure simple, Server-Sent Events (SSE) is the clear winner.
Let’s talk about why SSE is the better choice—and why you probably don’t need WebSockets at all.
AI Chats don’t need full-duplex communication
In most AI chat apps, users send a message and wait for a response from the AI. That’s it.
You don’t need the server to listen for incoming messages while simultaneously pushing data back and forth like a multiplayer game. You just need to:
- Receive a message
- Stream the response back as it’s generated
SSE is built for this: one-way, real-time communication from server to client. It’s simpler, more efficient, and matches the flow of AI chats perfectly.
SSE makes AI responses feel instant and natural
SSE lets your server stream data as it becomes available—letter by letter, word by word, just like ChatGPT does. Users see the AI “typing” in real-time, improving the perceived speed and responsiveness.
No extra configuration. No reconnection logic. SSE handles it all automatically.
This feels fast and fluid—exactly what users want.
WebSockets get expensive fast
Persistent WebSocket connections eat memory and CPU—even when idle.
For a small chat app with 1,000 users, WebSockets might seem manageable, using about 70 KiB per connection — that’s roughly 68 MiB in total. But if you scale to 100,000 users, memory jumps to over 6.68 GiB. As connections grow, you’ll need bigger servers and face escalating costs for connections that often remain idle.
SSE uses standard HTTP. It’s lightweight. Stateless. Easier to cache, debug, scale, and secure.
SSE works everywhere WebSockets struggle
WebSockets rely on a special “upgrade” handshake that many proxies and firewalls don’t handle well. That means connections can get dropped, blocked, or refused without warning.
SSE, by contrast:
- Uses plain old HTTP (works on ports 80 and 443)
- Has built-in reconnection if the connection drops
- Plays nice with proxies, load balancers, and corporate networks
It’s just more reliable.
Simpler to build, simpler to maintain
WebSockets need:
- A custom protocol handler
- A connection manager
- Reconnection logic
- More infrastructure
SSE needs:
- A single HTTP endpoint
- A loop to stream data
That’s it.
You can get an SSE chat stream working in minutes with plain JavaScript or simple Node.js middleware like express-sse. No event hubs, no connection managers, no exotic load balancers.
When WebSockets make more sense than SSE
WebSockets do have some clear strengths over SSE, and there are situations where they’re the better choice.
Most notably, WebSockets support full two-way (bidirectional) communication, making them ideal for use cases where both the client and server need to send data back and forth continuously. This is crucial in real-time multiplayer games, voice or video chat (VoIP) applications, and collaborative tools like shared whiteboards or live document editing.
WebSockets also support binary data, so if you need to send images, audio, or other non-text content, SSE simply won’t cut it.
However, these benefits come at the cost of more complex implementation, manual reconnection handling, and potential issues with firewalls or proxies. Despite these tradeoffs, if your application genuinely demands fast, persistent, low-latency, two-way communication — including support for media files — WebSockets may still be the preferred choice.