HTTP 511 Network Authentication Required (RFC 6585) indicates the client needs to authenticate to gain network access. This is the status code for captive portals — the WiFi login pages at hotels, airports, and coffee shops. When you connect to a WiFi network that requires authentication, the network intercepts your HTTP requests and returns 511 with the login page. This is distinct from 401 (server authentication) — 511 is about network-level access.
Response includes the status code, standard headers (including Content-Type), and a small diagnostic JSON body describing the request and returned status.
Simulator URL (copy in the app after load — not a normal link):
https://httpstatus.com/api/status/511
Example request:
curl -i "https://httpstatus.com/api/status/511"The client needs to authenticate to gain network access.
On this code, Inspector focuses on semantics, headers, and correctness warnings that commonly affect clients and caches.
HTTP 511 Network Authentication Required represents a specific server-side condition that requires different handling than other 5xx errors. Understanding the precise cause helps operations teams diagnose and resolve issues faster. Monitoring systems should distinguish 511 from other 5xx codes for accurate alerting and diagnosis.
// Handle 511 Network Authentication Required
process.on('unhandledRejection', (reason) => {
console.error('Unhandled rejection:', reason);
});
app.use((err, req, res, next) => {
console.error(`${req.method} ${req.url}:`, err.stack);
res.status(err.status || 500).json({
error: process.env.NODE_ENV === 'production'
? 'Internal Server Error'
: err.message,
requestId: req.id
});
});from fastapi import FastAPI, Request
from fastapi.responses import JSONResponse
import logging
logger = logging.getLogger(__name__)
@app.exception_handler(Exception)
async def server_error_handler(request: Request, exc: Exception):
logger.error(f'{request.method} {request.url}: {exc}',
exc_info=True)
return JSONResponse(
status_code=511,
content={'error': 'Network Authentication Required', 'request_id': request.state.id}
)@ControllerAdvice
public class GlobalErrorHandler {
private static final Logger log = LoggerFactory.getLogger(
GlobalErrorHandler.class);
@ExceptionHandler(Exception.class)
public ResponseEntity<ErrorResponse> handleException(
Exception ex, HttpServletRequest req) {
log.error("{} {}: {}", req.getMethod(),
req.getRequestURI(), ex.getMessage(), ex);
return ResponseEntity.status(511)
.body(new ErrorResponse("Network Authentication Required",
"An unexpected error occurred"));
}
}func errorMiddleware(next http.Handler) http.Handler {
return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
defer func() {
if err := recover(); err != nil {
log.Printf("%s %s: %v\n%s",
r.Method, r.URL, err, debug.Stack())
w.WriteHeader(511)
json.NewEncoder(w).Encode(map[string]string{
"error": "Network Authentication Required",
})
}
}()
next.ServeHTTP(w, r)
})
}