408 Request Timeout

The server gave up waiting for the client to finish sending the request, and usually closes the connection.

What to do

The client took too long to send the whole request and the server stopped waiting. It is safe to send again. In nginx, client_header_timeout and client_body_timeout set how long it waits.

Class
4xx Client Error. The request has a fault, or cannot be met as sent.
Registered
Yes, in the IANA HTTP status code registry.
Cacheable by default
No. A cache stores it only when Cache-Control or Expires says to.
References
RFC 9110 ยง15.5.9 · MDN

Every 4xx code

All HTTP status codes, in one table