HTTP status codes for troubleshooting

HTTP status codes describe the application layer; distinguish network reachability from the web-server response. DNS can resolve, TCP/TLS can connect, and HTTP can still return a redirect or error. Status code, Location, hostname, path and URL scheme describe different parts of the transaction.

How to investigate the web response

Check DNS, then TLS and the HTTP response without hiding the redirect chain. Compare the requested hostname with the actual target URL. A 4xx response generally describes the request or access, while 5xx indicates unsuccessful server-side handling, although a reverse proxy or CDN may be another participant in the path.

The detail that matters

HTTP status classes provide context: 2xx reports successful handling, 3xx redirects or related control flow, 4xx describes a client/request/access condition, and 5xx reports server-side failure. Codes such as 404, 429, 502 and 503 have different operational meanings and should not be grouped as generic downtime. For an external check of the site, use 2ip site information check.