.msi

What is a .msi file?

MSI is a Windows installer package — containing everything needed to install, update, or remove software via the Windows Installer service.

Use caution
Type System
By Microsoft
MIME application/x-msi

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What is it

You downloaded software for Windows and the installer is an .msi file instead of an .exe. MSI (Microsoft Software Installer) is the structured installer format managed by the Windows Installer service. It provides cleaner installs, reliable uninstalls, repair capabilities, and support for enterprise deployment via Group Policy.

The difference between MSI and EXE installers is standardisation. An EXE installer can do anything — there's no enforced structure. An MSI follows a defined database schema: tables describing files, registry entries, shortcuts, services, and installation sequences. This structure means Windows can reliably uninstall every file and registry entry an MSI installed, and system administrators can deploy MSI packages silently across thousands of machines. Enterprise IT loves MSI.

Double-click to install, or run `msiexec /i package.msi` from the command line. For silent installation: `msiexec /i package.msi /quiet`. Administrative installs (extracting files without running): `msiexec /a package.msi`. As with any installer, only run MSI files from trusted sources — they execute with elevated privileges and can modify system files.

Technical details
Full Name
Windows Installer Package
MIME Type
application/x-msi
Developer
Microsoft
Magic Bytes
D0 CF 11 E0
Safety
.msi requires caution. MSI files install software on your computer. Only install from trusted sources.
What opens it
Windows Installer (runs natively)
FREE Windows
FAQ
What's the difference between MSI and EXE installers?
MSI is a structured, standardised installer managed by the Windows Installer service — it supports clean uninstall, repair, and enterprise deployment. EXE installers are freeform executables with no enforced structure. MSI is more reliable but less flexible.
How do I silently install an MSI?
Run `msiexec /i package.msi /quiet /norestart` from an admin command prompt. This is how IT departments deploy software across networks. Add `/log install.log` to capture installation details.
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