Chapter 15: Status codes
Based on an HTTP request from the client, the server returns a response that includes a status code. The current set of status codes is defined by RFC 9110. A status code is represented as a three-digit number in the range of 100 to 599, where the first digit indicates the category. Although the RFC only requires compliance with the category, I strongly recommend using the extended set of status codes to provide more precise details about the outcome of the request.
HTTP status codes can be categorized as follows:
1xx- informational2xx- success3xx- dditional action required to complete the request4xx- client errors5xx- server errors