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.msi

Windows Installer
Windows Installer 5.0 running on Windows 7.png
Help screen of Windows Installer 5.0 running on Windows 7
Developer(s) Microsoft
Initial release 31 August 1999; 17 years ago (1999-08-31)
Stable release
5.0 / 22 July 2009; 7 years ago (2009-07-22)
Operating system Microsoft Windows 2000 and later
Platform IA-32, x86-64, Itanium
Type Installer
License Freeware
Windows Installer Package
Filename extension .msi, .msp
Internet media type application/x-ole-storage
Developed by Microsoft
Type of format Archive
Container for Installation information and an optional .cab file payload
Extended from COM Structured Storage
Open format? No

Windows Installer (previously known as Microsoft Installer,codename Darwin) is a software component and application programming interface (API) of Microsoft Windows used for the installation, maintenance, and removal of software. The installation information, and optionally the files themselves, are packaged in installation packages, loosely relational databases structured as COM Structured Storages and commonly known as "MSI files", from their default filename extensions. Windows Installer contains significant changes from its predecessor, Setup API. New features include a GUI framework and automatic generation of the uninstallation sequence. Windows Installer is positioned as an alternative to stand-alone executable installer frameworks such as older versions of InstallShield and NSIS.

Before the introduction of Windows Store, Microsoft encouraged third parties to use Windows Installer as the basis for installation frameworks, so that they synchronize correctly with other installers and keep the internal database of installed products consistent. Important features such as rollback and versioning depend on a consistent internal database for reliable operation. Furthermore, Windows Installer facilitates the principle of least privilege by performing software installations by proxy for unprivileged users.

A package describes the installation of one or more full products and is universally identified by a GUID. A product is made up of components, grouped into features. Windows Installer does not handle dependencies between products.


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