In API design, what does the status code indicate?

In API design, the status code serves as a critical indicator of the outcome of an HTTP request. When a client makes a request to an API, the server responds with a status code that reflects whether the operation was successful or if an error occurred.

Status codes are categorized into several classes based on the first digit of the code:

• 1xx codes indicate informational responses.

• 2xx codes indicate success, with 200 being a common response for a successful request.

• 3xx codes relate to redirections.

• 4xx codes denote client errors, such as a 404 Not Found or 403 Forbidden.

• 5xx codes signify server errors, indicating that something failed on the server side.

This consistent use of status codes allows clients to quickly determine the result of their requests programmatically, enabling appropriate error handling and flow control.

While the other options pertain to various aspects of API design, they do not encapsulate the primary purpose of a status code. The type of resource is usually indicated in the response body or endpoint structure, the data format is typically specified in the headers, and the size of the data being transferred is not directly related to the status code itself.