The WebSocket vs polling calculator compares bandwidth usage for real-time applications. Enter your message frequency, size, and concurrent connections to see which approach uses less bandwidth and what the latency tradeoffs are.
Traffic Parameters
E.g., 0.1 = every 10s, 1 = every second, 10 = 10/sec
Payload size only (e.g., JSON event data)
How often clients check for updates
Results update automatically
Approach Comparison
| Feature | WebSocket | HTTP Polling | SSE |
|---|---|---|---|
| Direction | Bidirectional | Request-Response | Server → Client only |
| Protocol overhead/msg | 2-10 bytes | 800-1,200 bytes | ~200 bytes (reconnect) |
| Latency | ~1-5ms | 0 to poll-interval | ~1-5ms |
| Firewall/proxy friendly | Sometimes blocked | Always works | Always works |
| CDN caching | No | Yes (GET) | No |
| Load balancer sticky | Required | Not needed | Required |
| Implementation complexity | Medium | Low | Low-Medium |
How to Choose Between WebSocket and Polling
The right choice depends on your update frequency, message size, and infrastructure constraints. This calculator helps you quantify the bandwidth tradeoff.
Use WebSockets When
Messages are frequent (more than ~1 per 10 seconds per client), you need low latency (under 100ms), or you need bidirectional communication (multiplayer games, collaborative editing, live trading). WebSockets have dramatically lower per-message overhead, making them far more efficient for high-frequency real-time data.
Use HTTP Polling When
Updates are infrequent (checking every 30+ seconds), you're behind CDN or proxies that may block WebSockets, or you need the simplicity of stateless HTTP. For low-frequency checks like job status or email notifications, polling with a generous interval is simpler to implement and the bandwidth difference is negligible.
Consider Server-Sent Events (SSE)
SSE is the sweet spot for server-push scenarios: lower implementation complexity than WebSockets, works over standard HTTP/2, automatic reconnection built into the browser. If you only need server-to-client data (notifications, live dashboards, AI response streaming), SSE is often the best choice.
Frequently Asked Questions
Is this WebSocket vs polling calculator free?
Yes, completely free. All calculations run in your browser.
What is the main advantage of WebSockets over polling?
WebSockets eliminate the HTTP overhead of repeated request-response cycles. A WebSocket connection has ~2 bytes of framing overhead per message versus ~800-1,200 bytes of HTTP headers per polling request. For high-frequency real-time data (>1 message/second per client), WebSockets are dramatically more bandwidth-efficient.
When is HTTP polling better than WebSockets?
HTTP polling is simpler, uses CDN-friendly infrastructure, and works better behind restrictive proxies and corporate firewalls that block WebSocket upgrades. For low-frequency updates (checking for changes every 30+ seconds), polling may be simpler to implement and operate with negligible bandwidth difference.
What is Server-Sent Events (SSE) and how does it compare?
SSE (EventSource) is a one-way push channel from server to client over HTTP. It has lower overhead than polling but is unidirectional — only server can push. SSE is ideal for notifications, live feeds, and dashboards where the client doesn't need to send data frequently. WebSockets support bidirectional communication.
What is long polling and how does it differ from regular polling?
Regular polling sends a request every N seconds whether or not there's new data. Long polling sends a request and the server holds it open until new data arrives (or a timeout), then responds. Long polling reduces unnecessary requests but still has full HTTP overhead per event. WebSockets have persistent bidirectional connection with minimal framing overhead.
How does message size affect the WebSocket vs polling decision?
For small, frequent messages (like cursor positions or status updates), WebSocket's minimal framing (2-10 bytes) is far more efficient than polling's 800+ byte HTTP headers. For large, infrequent payloads (like loading a full dashboard every 30 seconds), the HTTP overhead is proportionally negligible and polling is simpler.