408 Request Timeout means the server did not receive a complete request message within the time it was prepared to wait. Servers send it on idle keep-alive connections, or when a client starts a request but sends the headers or body too slowly. The server then closes the connection; a client that still has a request in transit may repeat it on a new connection.
Do not confuse it with 504 Gateway Timeout, where a gateway waits too long for an upstream server, or with nginx's 499, which is logged when the client gives up first.
Example response
HTTP/1.1 408 Request Timeout
Date: Fri, 06 Nov 2026 10:15:32 GMT
Connection: close
Content-Type: text/html
Content-Length: 54
<html><body><h1>408 Request Timeout</h1></body></html>SEO and redirect checking
Occasional 408s are harmless. Frequent 408s for crawlers suggest that the server's request timeouts are too short or that the server is overloaded, which can reduce crawling. A redirect checker sends complete requests immediately, so it rarely gets a 408; if it does, the server or a proxy in front of it is struggling.
Common causes and use cases
- A slow mobile connection uploads a request body too slowly.
- A keep-alive connection stayed idle longer than the server's timeout.
- Very short header or body timeouts in a load balancer or server, such as
client_header_timeoutandclient_body_timeoutin nginx. - Protection against slow-request attacks (Slowloris) cuts off slow clients.