Is SSE better than WebSockets?

SSE is better for one-way server-to-client updates because it is simpler, uses standard HTTP and includes automatic reconnection. WebSockets are better when the client must also send frequent messages or binary data over the same connection. Neither is universally better; the direction of communication usually decides.

Why do AI chat apps use Server-Sent Events?

Language model responses are generated token by token and flow only from server to client. SSE lets the server stream each chunk over a normal HTTP response, which works with existing authentication, proxies and serverless platforms. The user's next prompt is sent as a regular HTTP request, so full-duplex WebSockets are unnecessary.

Do WebSockets work through firewalls and proxies?

Usually, especially over secure wss connections on port 443, but some corporate proxies and older load balancers block or break connection upgrades. Libraries such as Socket.IO fall back to long polling when WebSockets fail. SSE tends to pass through infrastructure more easily because it is ordinary HTTP, provided responses are not buffered.

What about WebTransport and long polling?

Long polling, where the client repeatedly makes requests that the server holds open until data is available, works everywhere but is less efficient. WebTransport is an API built on HTTP/3 that supports bidirectional streams and unreliable datagrams, useful for gaming and media. It became Baseline in March 2026 and works in all current major browsers, though a WebSocket fallback is still wise for older browser versions.

WebSockets vs Server-Sent Events (SSE)

Quick verdict

WebSockets open a persistent, two-way connection where client and server can both send messages at any time, ideal for chat, multiplayer games and collaborative editing. Server-Sent Events (SSE) stream one-way updates from server to browser over ordinary HTTP, with automatic reconnection built in, ideal for notifications, live feeds and streaming AI responses. Choose by whether the client needs to talk back continuously.

They differ in direction and complexity. WebSockets upgrade an HTTP connection into a separate, full-duplex protocol. SSE keeps a normal HTTP response open and writes events to it as they occur. That difference affects infrastructure compatibility, scaling, reconnection logic and how much code you need to write.

WebSockets vs Server-Sent Events, side by side

Criterion	WebSockets	Server-Sent Events
Direction	Bidirectional, full duplex	One-way, server to client
Protocol	WebSocket protocol after an HTTP upgrade	Standard HTTP response with text/event-stream
Data types	Text and binary messages	UTF-8 text events
Reconnection	Implement yourself or via libraries	Built into the browser EventSource API
Message resume	Custom logic needed	Last-Event-ID header supports resuming streams
Infrastructure	Proxies and load balancers must support upgrades	Works through most HTTP infrastructure
Connection limits	Not tied to HTTP connection limits	Limited per domain on HTTP/1.1; fine on HTTP/2
Client to server	Same connection	Separate regular HTTP requests
Complexity	Higher; state, heartbeats, scaling sticky connections	Lower; plain HTTP endpoints
Best fit	Chat, games, collaboration, trading terminals	Notifications, dashboards, feeds, AI token streaming

Choose WebSockets when

Users send frequent messages back, as in chat, multiplayer games or collaborative editing.
You need binary data, such as audio frames or compact game state.
Latency for messages in both directions matters, for example in trading or live auctions.
You are building presence features like typing indicators and cursors.

Choose Server-Sent Events when

Updates flow mainly from server to client, such as notifications, scores or order tracking.
You are streaming language model responses token by token to a web interface.
You want to reuse existing HTTP authentication, routing and infrastructure.
Automatic reconnection and resuming missed events would save development effort.
The team wants the simplest real-time solution that meets the requirement.

Scaling real-time connections

Both technologies keep long-lived connections open, so servers must handle many concurrent connections and route messages to the right users across instances. A common approach uses a pub/sub layer such as Redis, NATS or Kafka so any server can deliver an event to a connected client. WebSockets usually need load balancers configured for connection upgrades and sometimes sticky sessions. SSE works over standard HTTP, though proxies must not buffer responses, and HTTP/2 removes old per-domain connection limits.

Managed services, such as Ably, Pusher, AWS API Gateway WebSocket APIs and Azure Web PubSub, offload connection handling when scale or reliability needs grow. They also handle global distribution and fallbacks, which are hard to build well in-house. Compare their limits on connections and message rates.

SSE for AI streaming and simple feeds

Server-Sent Events have become a standard way to stream responses from large language model APIs, since the server simply writes tokens as they are generated and the client appends them. For many applications that only need server push, SSE is easier to build, secure and debug than WebSockets. Libraries such as Socket.IO add fallbacks and rooms on top of WebSockets when full duplex is needed. Nexzem implements both, matching the technology to each feature's direction and scale.

Final verdict

Use WebSockets when clients and servers both need to send frequent messages with low latency, as in chat, gaming, collaboration and trading. Use Server-Sent Events when data flows mainly from server to client, such as notifications, live dashboards and AI response streaming, because SSE is simpler, works over plain HTTP and reconnects automatically. Many applications use SSE for most push features and reserve WebSockets for truly interactive ones.

Terms in this comparison

Get it built

WebSockets vs Server-Sent Events: Real-Time Options