408
4xx Client ErrorRequest Timeout
The server timed out waiting for the request.
408 Request Timeout means the server got tired of waiting for the client to finish sending its request and closed the connection. It's about the request arriving too slowly, not the server responding too slowly (that's 504 when a gateway is involved). Browsers often retry it silently, so 408s tend to surface in server logs before anyone notices them in a UI.
What 408 looks like on the wire
HTTP/1.1 408 Request Timeout Connection: close
About 4xx Client Error
The request has a problem the client needs to fix, like a bad URL, missing auth, or invalid input.
How to fix 408 Request Timeout
- Check for slow or flaky client connections, especially uploads over mobile networks.
- For large uploads, raise the server's request timeout (client_body_timeout in nginx, for example).
- Make sure the client isn't opening the connection early and sending the request much later.
Where it's defined
408 Request Timeout is defined in RFC 9110 §15.5.9. MDN's 408 reference covers browser behavior and examples.