ipConnecting to your own device
Localhost is a special name referring to the local device. Common loopback addresses are 127.0.0.1 for IPv4 and ::1 for IPv6. Connections to them normally do not reach another computer on the public internet. A geolocation lookup should not be expected to return a real city.
The role of the port
In localhost:3000, 3000 is the port on which a local application listens. Several services can run on different ports on one device. Sending that URL to a friend does not share your application: their browser will try port 3000 on their own device. Sharing requires an appropriate deployment or access method.
Pay attention to the bind address
A service bound only to 127.0.0.1 is not directly accessible from the local network. Listening on all interfaces broadens exposure and requires firewall consideration. Making a development server reachable is not equivalent to deploying a production-ready, authenticated service.
Sending a local link to someone else
A working localhost:3000 on your computer does not mean another user can open that link. Their localhost is their own machine. Use an authorized deployment method to share a preview. If access fails, determine the listening interface and firewall policy first rather than indiscriminately exposing every interface.
Further reading
Special-use domain names — RFC 6761 ↗Put it into practice
Inspect one public IP, or compare a list of addresses with the bulk lookup tool. Location results are approximate.
Single lookup ↗ Bulk lookup ↗