You can convert an MSI using Microsoft’s free MSIX Packaging Tool, a commercial packaging tool or an installer-authoring solution such as InstallShield. Microsoft’s tool captures an application installation to create a new package. InstallShield takes a project-based approach, converting an existing MSI through a Basic MSI project so that teams can continue to manage and rebuild the installer.
Converting an MSI to MSIX can help modernize an existing Windows application for current packaging and deployment workflows. The right conversion method depends on whether you need a quick, one-off repackage or a repeatable process that can be maintained as the application changes.
This guide explains the main conversion options, walks through the process step by step and covers common runtime compatibility issues. It also compares MSI and MSIX, including the situations where moving to MSIX makes sense and those where retaining MSI may be the better choice.
What is MSIX, and Why Convert From MSI?
MSIX is the modern successor to MSI for packaging Windows applications. Converting from MSI to MSIX can provide cleaner installs and uninstalls, more efficient updates and better support for modern deployment and management tools.
Conversion is not automatically the right choice for every application. Traditional installers may rely on behaviours that do not translate directly into the MSIX model, particularly when an application expects unrestricted access to system locations or makes changes at runtime. Microsoft’s Package Support Framework can apply targeted compatibility fixes without requiring changes to the application’s source code, although each converted package should still be tested in its intended deployment environment.
MSI vs MSIX: the key differences
MSI and MSIX are both Windows application packaging formats, but MSIX adds modern deployment, update and application management capabilities that were not part of the original Windows Installer model. The table below highlights the main differences.
| Feature | MSI | MSIX |
| Installation model | Traditional Windows Installer Package | Modern Windows app package |
| Updates | Supports both full package updates and smaller updates delivered through a Windows Installer patch | Support deferential updates |
| Uninstall | May leave files or registry entries behind | Designed for cleaner removal |
| Application identity | No package identity | Includes Windows package identity |
| Enterprise deployment | Widely supported | Supported by Intune, Configuration Manager, and other modern deployment tools |
| Microsoft Store support | Not supported directly | Supported |
| Runtime isolation | Limited | Include containerization and virtualization capabilities |
| Driver/Kernel Components | Supported | Limited/not suitable |
| Enterprise compatibility and complex installation behavior | Excellent | Good, but some legacy scenarios can be challenging |
Ways to convert MSI to MSIX
There are several ways to convert an MSI to MSIX, but the best option depends on whether you need a one-time repackage or a maintainable packaging process. Microsoft's free MSIX Packaging Tool is designed for repackaging existing applications, while tools such as InstallShield provide ongoing package management capabilities.
| Microsoft MSIX Packaging Tool | InstallShield | |
| Best for | One-off conversions and evaluation projects | Application packagers, enterprise IT teams and software vendors |
| Approach | Monitors and captures an application installation to create an MSIX package | Converts MSI files through a maintainable project-based workflow |
| Benefits | Free Microsoft tool with broad MSIX support | Supports ongoing installer maintenance, native MSIX creation and MSI-to-MSIX conversion |
| Limitations | Less suited to maintaining the package as part of an ongoing installer project | Commercial product |
How to convert and MSI to MSIX, step-by-step
Converting an MSI to MSIX involves assessing the application, selecting a conversion tool, creating the MSIX package, testing the converted application and addressing any compatibility issues before deployment.
- Assess the application requirements
Review how the application interacts with the operating system, including file system access, registry usage, services and drivers. Not every application will convert cleanly without additional compatibility work.
- Choose a conversion method
Select a tool based on your requirements. Microsoft's MSIX Packaging Tool is designed for repackaging existing applications, while InstallShield enables conversion within a maintainable installer project.
- Create the MSIX package
Use your chosen conversion tool to generate an MSIX package from the existing MSI. InstallShield's MSI to MSIX Conversion Wizard converts existing Windows Installer (.msi) files into an MSIX package through a Basic MSI project.
- Test the converted application
Install the MSIX package in a representative test environment and verify
installation, launch, updates and uninstallation behaviour. Run through key user workflows to identify any functionality issues.
- Resolve compatibility issues
If the application relies on behaviours that do not work correctly in the MSIX environment, investigate compatibility fixes, including Microsoft's Package Support Framework (PSF) where appropriate.
- Deploy the package
Once testing is complete, deploy the MSIX package using your preferred delivery method, such as Intune, Configuration Manager or the Microsoft Store.
Handling conversion issues (PSF fixups and runtime compatibility)
The most common MSI-to-MSIX conversion challenges occur when an application relies on behaviours that do not align with the MSIX packaging model. After conversion, some applications may experience issues related to file system access, registry writes, services or other runtime dependencies that were designed for a traditional MSI installation.
The first step is always thorough testing. Validate the converted application in a representative environment and work through common user scenarios to identify any functionality that behaves differently after packaging.
Where compatibility issues arise, Microsoft's Package Support Framework (PSF) can help by applying runtime fixes without requiring changes to the application's source code. PSF is particularly useful for applications that expect access to locations or resources that are handled differently under the MSIX model.
For teams managing applications over multiple releases, it is also important to treat conversion as an ongoing maintenance task rather than a one-time exercise. InstallShield includes support for PSF fixups and enhanced runtime compatibility features, helping organizations convert MSI packages while maintaining a repeatable packaging workflow.
When to convert to MSIX, and when to keep MSI
MSIX is typically the better choice for modern Windows application deployment, but MSI remains a practical option for some applications and environments. The decision depends on your deployment requirements, application architecture and long-term packaging strategy.
Consider converting to MSIX if:
- You want to deploy applications through modern management platforms such as Intune.
- You need cleaner installation and uninstallation behaviour.
- You want to take advantage of more efficient application updates.
- You're modernizing software delivery processes or preparing applications for Microsoft Store distribution.
- You're actively maintaining the application and want a packaging format aligned with Microsoft's future Windows packaging direction.
Consider keeping MSI if:
- The application relies on installer behaviours that do not translate easily to the MSIX model.
- You support customers or systems that depend on established MSI deployment workflows.
- Extensive testing reveals compatibility issues that outweigh the benefits of conversion.
- The application is stable, rarely updated and there's little business value in migrating it.
Convert MSI to MSIX with InstallShield
InstallShield can convert existing MSI files into MSIX packages while keeping the application in a maintainable installer project. Unlike repackaging approaches that create a standalone package, InstallShield's MSI to MSIX Conversion Wizard converts Windows Installer (.msi) files through a Basic MSI project, making it easier to update, rebuild and manage the installer over time.
InstallShield supports both native MSI and MSIX package creation, allowing teams to maintain support for existing deployment requirements while adopting modern packaging standards. Recent releases also include enhanced PSF fixup support to help address runtime compatibility challenges that can emerge during conversion.
For software vendors and enterprise packaging teams, this project-based approach can be particularly valuable when applications are updated regularly. Rather than treating MSI-to-MSIX conversion as a one-time exercise, InstallShield enables MSIX packaging to become part of the ongoing release process. It also supports command-line builds and automation interface integration with development workflows, helping teams automate packaging and release activities.
Ready to try MSI-to-MSIX conversion? Explore InstallShield's capabilities, download a free trial, or review the MSI to MSIX Conversion Wizard documentation for detailed implementation guidance.
Frequently Asked Questions
You can convert an MSI to MSIX by using a conversion tool, such as Microsoft's MSIX Packaging Tool or InstallShield. The process typically involves creating an MSIX package from the existing MSI, testing the converted application and resolving any compatibility issues before deployment.
MSI is Microsoft's traditional Windows Installer format, while MSIX is the modern Windows application packaging format. MSIX provides capabilities such as cleaner installs and uninstalls, differential updates, package identity and support for modern deployment tools including Intune and the Microsoft Store.
Yes. InstallShield includes an MSI to MSIX Conversion Wizard that converts existing Windows Installer (.msi) files into MSIX packages through a Basic MSI project. This allows organizations to maintain and update the installer as part of an ongoing release process.
Several tools support MSI-to-MSIX conversion, including Microsoft's free MSIX Packaging Tool and InstallShield. The best option depends on whether you need a one-time repackage or a maintainable packaging workflow.
It depends on your application and deployment requirements. MSIX is often a strong choice for organizations adopting modern Windows management and deployment practices, while MSI may remain the better option for applications with legacy dependencies or established deployment workflows.
The MSIX Packaging Tool is Microsoft's free application repackaging utility. It creates MSIX packages by monitoring an application's installation and capturing the resulting changes, making it a popular option for one-off migration projects.
There is no direct Microsoft tool that converts MSIX packages back to MSI. In most cases, organizations need to rebuild the installer in an MSI authoring tool or maintain parallel MSI and MSIX packages for different deployment requirements. For applications that still require MSI support, tools such as InstallShield can build and maintain both MSI and MSIX package formats.
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