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