Which HTTP status code indicates authentication failure (incorrect password) for a REST API request?

HTTP status code 401 (Unauthorized) is used when the client needs to authenticate to get the requested response. This specifically means the client's credentials (like a password) are missing or incorrect, leading to an authentication failure. HTTP status code 200 (OK) indicates that the request has succeeded. HTTP status code 302 (Found) is a redirection message, meaning the resource has been temporarily moved to a different URI. HTTP status code 504 (Gateway Timeout) indicates that the server, while acting as a gateway or proxy, did not receive a timely response from an upstream server. These codes do not signify an authentication failure.