Which HTTP status code indicates a successful request?

The status code indicating a successful request is 200. This code signifies that the request was successfully received, processed, and understood by the server, and that the server has returned the requested information. The 200 status code is part of the standard response codes defined in the HTTP protocol, where different codes indicate the result of a client's request.

In contrast, other status codes indicate different scenarios: 100 is an informational response, which means the server has received the initial part of the request and is awaiting the rest; 404 indicates that the requested resource could not be found on the server; and 500 signals an internal server error, meaning there was an unexpected condition on the server preventing it from fulfilling the request. Thus, 200 is the only status code that directly confirms a successful action completed by the server in response to the client's request.