408

What 408 means

The server gave up waiting for the client to finish sending. This is distinct from 504, where the server was waiting on something upstream — here the incomplete party is the client. It is comparatively rare in normal browsing.

Common causes

• •A slow or interrupted upload.
• •A client that opened a connection and never sent a complete request.
• •An aggressive server-side request timeout.
• •Slowloris-style behaviour, whether malicious or from a broken client.

How to fix it

Check the server's request timeout against realistic upload sizes on slow connections. If a legitimate file upload trips it, the timeout is too low rather than the client being at fault.

Why 408 is rare in browsers but common in APIs

Most people never see a 408 while browsing, because browsers send requests promptly and completely. It shows up far more in API traffic and file uploads, where a client may open a connection and then send slowly, or stall partway through a body.\n\nKeep-alive muddies this further. A server may return 408 on an idle persistent connection it has decided to reclaim, and a well-behaved client simply opens a new connection and retries. That kind of 408 is routine housekeeping rather than an error worth alerting on.\n\nLoad balancers add their own idle timeouts, often shorter than the application's. If 408s appear in a specific environment only, compare the idle timeout at every hop — the shortest one wins, and it is rarely the one you configured.

Often confused with

← All HTTP status codes