Nullsoft Scriptable Install System (NSIS) is a script-driven installation system for Microsoft Windows with minimal overhead backed by Nullsoft, the creators of Winamp. NSIS has become a widely used alternative to commercial and proprietary products like InstallShield, with users including Amazon, Dropbox, Ubisoft, BitTorrent, and McAfee.NSIS is free software released under a combination of free software licenses, primarily the zlib license.