HTTP 499 Client Closed Request

What does HTTP 499 mean?

Nginx logs 499 when the client closed the connection before the server answered. The client never sees this code — it appears only in Nginx access logs. It usually means the upstream application was too slow and the user or a load balancer gave up.

4xx Client error: The request has a problem the client can fix: wrong URL, missing credentials, bad data or too many requests.

Common causes of a 499 error

• Slow upstream application or database queries.
• Load balancer timeout shorter than the backend’s.

How to fix 499 Client Closed Request

• Profile slow requests and add caching.
• Align timeouts across load balancer, proxy and app.

499 and SEO

Indicates slowness that also affects crawlers.

Example response

HTTP/1.1 499 Client Closed Request

How to return a 499 response

Node.js (Express)

res.status(499).json({ error: 'Client Closed Request' });

PHP

http_response_code(499);

Python (Flask)

return {'error': 'Client Closed Request'}, 499

Go (net/http)

w.WriteHeader(499)

nginx

return 499;

Related status codes

• 504 Gateway Timeout — A gateway or proxy did not get a response from the upstream server in time.
• 408 Request Timeout — The server timed out waiting for the client to send the request.
• 502 Bad Gateway — A gateway or proxy got an invalid response from the upstream server.

Check which status code a URL returns with the HTTP header checker.