Categories of Status Codes

HTTP status codes are grouped into five categories, based on the first digit:

• 1xx (Informational): These codes indicate that the request was received and the server is continuing to process it. You don't usually see these codes directly in your browser.

  • Example: 100 Continue.

• 2xx (Successful): These codes mean that the request was successful. The server received the request, understood it, and processed it without any problems.

  • Example: 200 OK (the most common success code), 201 Created (for successful resource creation), 204 No Content (successful request, but no content to return).

• 3xx (Redirection): These codes indicate that the client needs to take additional action to complete the request. The requested resource has moved, either temporarily or permanently.

  • Example: 301 Moved Permanently, 302 Found (temporary redirect), 307 Temporary Redirect, 308 Permanent Redirect.

• 4xx (Client Error): These codes indicate that there was a problem with the client's request. The request might be malformed, unauthorized, or the requested resource might not exist.

  • Example: 400 Bad Request, 401 Unauthorized, 403 Forbidden, 404 Not Found (the most famous error code!), 405 Method Not Allowed.

• 5xx (Server Error): These codes indicate that there was a problem on the server's side. The server failed to fulfill a valid request.

  • Example: 500 Internal Server Error, 502 Bad Gateway, 503 Service Unavailable, 504 Gateway Timeout.