UR — Small network tools
UR is a family of tiny public tools for IP and network work. Each app lives on its own host. Add a new entry to the catalog when another app ships.

URIP
urip.kr
Your public IP
Echoes the client address Cloudflare sees, plus optional geo and request metadata. Root returns plain text. Open /json, /xml, /yaml, /csv, /html, /headers, or /trace for the same lookup in another shape.
Open https://urip.kr
  https://urip.kr
  https://urip.kr/json
  https://urip.kr/html

URNET
urnet.kr
IPv4 subnet calculator
Calculates CIDR fields for /{ip}/{prefix}: mask, network, broadcast, host range, first-octet address class, and shop-floor size (Class A=/8, Class B=/16, Class C=/24). Same format paths as URIP under each lookup.
Open https://urnet.kr
  https://urnet.kr/192.168.0.1/24
  https://urnet.kr/192.168.0.10/8/json
  https://urnet.kr/10.0.0.1/16