NSIs

NSIS stands for Nullsoft Scriptable Install System, a free and open-source system for creating Windows installers. It was developed by Nullsoft, the company behind Winamp, and first released in the late 1990s. NSIS provides a script-based language that lets developers describe installation logic and user interface, producing a single small executable installer.

Features include a compact installer runtime, a flexible scripting language, support for multiple UI pages (License, Directory, InstallFiles, Finish), and the ability to create or uninstall files, registry entries, shortcuts, services, and checks. It supports multiple languages, customizable installer themes, and can perform silent or unattended installations. Data compression options (including LZMA and zlib) help shrink the installer size.

NSIS is extensible through a plugin interface; plugins written in C/C++ (and sometimes other languages) can extend installer functionality. The system also supports external executables, custom install actions, and patching or updating installers. Build work is done with the makensis compiler from scripts; the resulting installer is a Windows executable.

Platforms: NSIS targets Windows; installers built with NSIS run on Windows and can be distributed to end users on that platform. The project is maintained by an active community and is widely used in both open-source and commercial software distributions. Licensing: NSIS is released under its own permissive NSIS License, allowing free use, modification, and redistribution with some attribution and trademark considerations.