Editing Windows Installer (section)

{{Short description|Software}}
{{About|the [[Microsoft Windows]] component|the installation of the operating system itself|Windows Setup}}
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{{primary sources|date=August 2024}}
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{{Infobox software
| name = Windows Installer
| screenshot = Windows Installer.png
| caption = Help screen of Windows Installer 5.0 running on [[Windows 11]]
| developer = [[Microsoft]]
| released = {{Start date and age|1999|08|31|df=yes}}
| discontinued = yes
| latest release version = 5.0
| latest release date = {{Start date and age|2009|07|22|df=yes}}<ref name="release_history">{{cite web |url=http://msdn.microsoft.com/en-us/library/aa371185.aspx |title=Released Versions of Windows Installer |work=[[Microsoft Developer Network]] |publisher=[[Microsoft]] |access-date=3 November 2012}}</ref>
| operating system = [[Microsoft Windows]]
| platform = [[IA-32]], [[x86-64]], [[ARM32]], [[ARM64]], [[Itanium]]
| included with = [[Windows 2000]] and later
| genre = [[Installer]]
| license = [[Freeware]]
}}
{{Infobox file format
| name = Windows Installer Package<ref>{{cite web|url=http://filext.com/file-extension/msi |title=File Extension .MSI Details |publisher=Filext.com |access-date=2013-04-24}}</ref>
| logo = 
| icon = 
| iconcaption = 
| screenshot = 
| caption = 
| extension = .msi, .msp
| mime = application/x-ole-storage
| type code = 
| uniform type = 
| conforms to = 
| magic = 
| owner = [[Microsoft]]
| genre = [[Archive (computing)|Archive]]
| container for = Installation information and an optional [[Cabinet (file format)|.cab]] file payload
| contained by = 
| extended from = [[COM Structured Storage]]
| extended to = 
| standard = 
| open = No
| url = 
}}

'''Windows Installer''' (<code>msiexec.exe</code>, previously known as '''Microsoft Installer''',<ref>{{cite web| url=http://blogs.msdn.com/robmen/archive/2003/11/25/56510.aspx|title=Inside the MSI file format|date=2003-11-25|first=Rob| last=Mensching|website=MSDN Blogs|archive-url=https://web.archive.org/web/20090115213653/http://blogs.msdn.com/robmen/archive/2003/11/25/56510.aspx | archive-date=2009-01-15 | access-date=2017-02-15}}</ref> [[List of Microsoft codenames|codename]] '''Darwin''')<ref>{{cite web|url=http://blogs.msdn.com/robmen/archive/2003/10/11/56487.aspx|title=The story of Orca|date=2003-10-11|first=Rob|last=Mensching|website=MSDN Blogs|archive-url=https://web.archive.org/web/20081223050952/http://blogs.msdn.com/robmen/archive/2003/10/11/56487.aspx | archive-date=2008-12-23|access-date=2017-02-15}}</ref><ref>{{cite web|url=https://blogs.msdn.microsoft.com/chrsmith/2005/07/01/windows-installer-the-net-framework-the-bootstrapper-and-you/|title=Windows Installer, The .NET Framework, The Bootstrapper, and You|date=2005-07-01| first=Chris|last=Smith|website=MSDN Blogs|access-date=2017-02-15}}</ref> is a [[software component]] and [[application programming interface]] (API) of [[Microsoft Windows]] used for the [[Installation (computer programs)|installation]], maintenance, and removal of software. The installation information, and optionally the files themselves, are packaged in [[Package (package management system)|''installation packages'']], loosely [[relational database]]s structured as [[COM Structured Storage]]s and commonly known as "MSI files", from their default [[filename extension]]s. The packages with the file extensions <code>mst</code> contain Windows Installer "Transformation Scripts", those with the <code>msm</code> extensions contain "Merge Modules" and the file extension <code>pcp</code> is used for "Patch Creation Properties".<ref>{{cite web|url=https://devblogs.microsoft.com/setup/identifying-windows-installer-file-types/|title=Identifying Windows Installer File Types|first=Heath|last=Stewart|date=2006-02-27|access-date=2020-04-22}}</ref> Windows Installer contains significant changes from its predecessor, Setup API. New features include a [[GUI]] [[Software framework|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 [[Nullsoft Scriptable Install System|NSIS]].

Before the introduction of [[Microsoft Store]] (then named 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 (data management)|rollback]] and [[version control|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.