What is the significance of HTTP status codes starting with 500?

HTTP status codes starting with the digit 5 (e.g., 500, 501, 503) indicate server errors. This means that the server encountered a problem and was unable to process the client's request correctly.

Main characteristics:

• 500 Internal Server Error — a general server error when it cannot fulfill the request for an unknown reason.
• 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 an upstream server.
• 503 Service Unavailable — the server is temporarily unavailable (overload, maintenance).
• 504 Gateway Timeout — the server did not receive a timely response from another server.

Thus, 5xx codes indicate problems on the server side, not the client side.