HTTP 401
An HTTP response indicating missing valid authentication. The server should provide a WWW-Authenticate challenge; it differs from a 403 permission refusal.
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Clear filtersHTTP 408
An HTTP status for the server timing out while waiting for the client's request. It differs from 504, involving a gateway waiting for another server.
Definition and sourcesHTTP 503
An HTTP status indicating temporary unavailability, such as overload or maintenance. Retry-After can suggest when the client should retry.
Definition and sourcesHTTP/2
An HTTP version with binary framing and multiple streams per connection. It can reduce communication overhead but does not solve application-performance problems.
Definition and sourcesHTTP/3
An HTTP version using QUIC rather than TCP. It changes transport and connection-establishment behaviour; benefits depend on network, client and infrastructure.
Definition and sources