Nmap Online is described as 'Nmap online is dedicated to report the very fast nmap scan results, with a focus on nmap tool installed on back side. In easy steps you will scan your target from web interface by Browser' and is an app in the Security & Privacy category. There are four alternatives to Nmap Online for Linux, Mac, Windows, BSD and SaaS. The best alternative is Nmap, which is both free and Open Source. Other great apps like Nmap Online are Zenmap (Free, Open Source), ZMap (Free, Open Source) and Rumble Network Discovery (Freemium).
Zenmap is the official cross-platform GUI for the Nmap Security Scanner. It is free and runs on Linux, Windows, Mac OS X, etc. Zenmap aims to make Nmap easy for beginners to use while providing advanced features for experienced Nmap users.
ZMap is a fast single packet network scanner designed for Internet-wide network surveys. On a typical desktop computer with a gigabit Ethernet connection, ZMap is capable scanning the entire public IPv4 address space in under 45 minutes.
Rumble is a network discovery platform that enumerates the network topology, identifies devices, and creates an asset inventory. Rumble runs discovery scans via a locally installed agent or using the standalone Rumble Scanner on the command-line.