Frequently asked questions
Does this tool use a paid or commercial lookup API?
No. It uses server-native networking or official Internet infrastructure such as DNS, IANA, registry services or the DOI resolver, depending on the tool.
Why can a lookup fail even when the input is valid?
Authoritative services can rate-limit requests, shared hosting can block some outbound ports, DNS may be temporarily unavailable, or the target server may refuse the connection.
Are private network targets allowed?
Tools that make direct HTTP or TLS connections block private, loopback, link-local and reserved IP ranges.