IP Address Inspector

An address that's only valid inside a single network segment. IPv4 uses 169.254.0.0/16 when a host fails to get a DHCP lease; IPv6 uses fe80::/10 for neighbour discovery and is set automatically by every interface.

RFC 5737 reserves those three /24 blocks (and 2001:db8::/32 for IPv6) for examples in documentation and training material — they're guaranteed never to appear on the public internet, which makes them safer than picking a real-looking IP that might exist.

DNS PTR records — they map an IP back to a hostname. IPv4 reverses the octets and appends .in-addr.arpa; IPv6 reverses every hex nibble and appends .ip6.arpa. The reverse zones are delegated to whoever owns the address space.

Neither reliably. Carrier-grade NAT puts thousands of subscribers behind one address, mobile networks rotate them, VPNs and proxies stand in for them, and geolocation databases resolve to a registration address that can be a different city or country from the user. An address is useful as a routing fact and as one weak signal among others; treating it as an identity is where investigations go wrong.

Because the address on your interface is usually private — assigned inside your network — while the address a site records is the public one your router or your provider translates to on the way out. Everything behind that router shares it. A VPN adds another layer, replacing the public address with the exit node's, which is why the answer changes when you connect one.