5xx Server Error Status Codes
These status codes indicate that the server is aware it has encountered an error or is otherwise incapable of performing the request.
TL;DR
5xx errors mean the server made a mistake. Unlike 4xx errors, the client's request was valid, but the server failed to fulfill it due to an error on the server side.
Understanding 5xx Errors
Server error responses indicate that the server is aware it has encountered an error or is otherwise incapable of performing the request. These errors are the server's fault, not the client's.
Complete List of 5xx Status Codes
500
Internal Server Error
Generic server error when no specific error code is appropriate.
501
Not Implemented
The server does not support the functionality required to fulfill the request.
502
Bad Gateway
The server received an invalid response from the upstream server.
503
Service Unavailable
The server is temporarily unable to handle the request.
504
Gateway Timeout
The server did not receive a timely response from the upstream server.
505
HTTP Version Not Supported
The server does not support the HTTP protocol version used in the request.
511
Network Authentication Required
The client needs to authenticate to gain network access.