Responses
Status code families
Use the first digit of an HTTP status code to quickly distinguish information, success, redirection, client errors, and server errors.
HTTP status codes are grouped into five families:
1xx: the exchange is still in progress.2xx: the request succeeded.3xx: another location or a cached response is involved.4xx: the request cannot be fulfilled as sent.5xx: the server failed while handling a valid request.
The family gives you a useful first diagnosis. A 404 and a 401 mean different things, but both tell you to investigate the request or client context. A 500 points you toward server logs instead.
Do not treat every non-200 response as failure. 201, 204, 301, and 304 can all be correct outcomes.
Lesson completed