Overview
When you need the server to push updates, these are the two main browser options. WebSockets open a single TCP connection both sides can write to anytime — the right tool for chat, multiplayer and collaborative editing. SSE is deliberately simpler: a long-lived HTTP response that streams events one way, with the browser's EventSource reconnecting automatically. If clients only need to receive (live feeds, notifications, progress bars), SSE is less to build and proxies/caches understand it; if clients also need to push, reach for WebSockets.
WebSockets vs Server-Sent Events: key differences
| WebSockets | Server-Sent Events | |
|---|---|---|
| Direction | Bi-directional (full duplex) | One-way (server → client) |
| Protocol | ws:// after HTTP upgrade | Plain HTTP (text/event-stream) |
| Reconnect | Manual (you implement it) | Automatic (built into EventSource) |
| Infra friendliness | Needs WS-aware proxies/LBs | Works through any HTTP proxy/CDN |
| Binary data | Yes | Text only (base64 for binary) |
When to use WebSockets
Chat, multiplayer games, collaborative editing, trading — anything where the client must send messages to the server in real time as well as receive them.
When to use Server-Sent Events
Live feeds, dashboards, notifications, progress/status updates and stock tickers where data only flows server→client and you want the simplest, most proxy-friendly option.
Verdict
Use SSE when traffic is one-way server→client — it is simpler, auto-reconnects and traverses existing HTTP infrastructure cleanly. Use WebSockets when you need true two-way, low-latency messaging. Don't default to WebSockets just because it sounds more powerful; SSE covers a large share of "real-time" needs.
Common questions
Are WebSockets or SSE better for real-time updates?
For one-way server-to-client streams (feeds, notifications), SSE is simpler and reconnects automatically. For two-way, interactive communication (chat, games), WebSockets are the right choice. Pick by whether the client needs to push.
Does SSE work over HTTP/2?
Yes, and HTTP/2 removes SSE's old per-domain connection limit, making it a strong, lightweight choice for server-push when you don't need a two-way channel.