HackerTarget.com is described as 'Security Vulnerability Scanning based on Open Source Tools. With 12 different types of security scans available for Free' and is a vulnerability scanner in the security & privacy category. There are five alternatives to HackerTarget.com, not only websites but also apps for a variety of platforms, including Mac, Windows, Linux and Android apps. The best HackerTarget.com alternative is SecApps, which is free. Other great sites and apps similar to HackerTarget.com are sploit.io, HostedScan Security, SubdomainRadar and GRC Port Scan.
GRC Port scan is too limited