What is MSI?

MSI (Microsoft Installer) files are database files containing all information needed to install software on Windows. They include program files, registry changes, shortcuts, file associations, and uninstall information. MSI packages can be deployed silently via Group Policy, support administrative installations, and provide automatic rollback if installation fails.

MSI is used by Windows for software distribution in enterprise environments, application updates via Windows Update, and standardized software installation. The format supports conditional installation (based on OS version, existing software, etc.), repair/modify capabilities, and centralized management through Active Directory. MSI replaced older .exe installer formats as the Windows standard.

Did you know? MSI files can be deployed to thousands of computers simultaneously via Group Policy!

History

Microsoft created Windows Installer to provide a standardized, reliable installation system for the Windows platform, replacing inconsistent .exe installers.

Key Milestones

  • 1999: Windows Installer 1.0 released
  • 2001: Version 2.0 with Windows XP
  • 2005: Version 3.0 with major features
  • 2008: Version 4.5 with Windows Vista
  • 2012: Version 5.0 with Windows 8
  • Present: Standard Windows installation format

Key Features

Core Capabilities

  • Database Format: Structured installation data
  • Silent Install: Unattended deployment
  • Rollback: Automatic failure recovery
  • Repair: Fix corrupted installations
  • Group Policy: Enterprise deployment
  • Versioning: Update management

Common Use Cases

Enterprise

Software deployment

Distribution

Application installers

Updates

Software patches

IT Management

Centralized installation

Advantages

  • Standardized Windows installation
  • Silent deployment support
  • Automatic rollback on failure
  • Enterprise management via Group Policy
  • Repair and modify capabilities
  • Consistent uninstall process
  • Windows Update integration

Disadvantages

  • Windows-only format
  • Complex to create
  • Requires administrator rights
  • Limited customization vs .exe
  • Larger file sizes
  • Steeper learning curve

Technical Information

Format Specifications

Specification Details
File Extension .msi, .msp (patch), .msm (merge module)
MIME Type application/x-msi
Format Type Structured storage (COM)
Database Relational database format
Platform Windows only
Typical Size 5-500 MB

Common Tools

  • Creation: WiX Toolset, InstallShield, Advanced Installer
  • Editing: Orca, InstEd, MSI Editor
  • Deployment: Group Policy, SCCM, PDQ Deploy
  • Analysis: Orca, SuperOrca, msiexec (command-line)