Nmap Online Port Scanner by Hacker Target allows users to find open ports on Internet-facing systems. It enables testing of servers, firewalls, and network perimeters with accurate port status information. The scanner utilizes Nmap, a powerful network port scanner that tests network connectivity between different hosts and services. Nmap Online Port Scanner offers both free and advanced scanning options, with the ability to scan IPv4 and IPv6 addresses, hostnames, and IP ranges.