What Is an MSI File?

How to open, edit, and convert MSI files

A file with the .MSI file extension is a Windows Installer Package file. It's used by some versions of Windows when installing updates from Windows Update, as well as by other installer tools.

An MSI file holds all the information necessary for installing the software, including the files that should be installed and where on the computer those files should be installed to.

"MSI" originally stood for the title of the program that works with this format, which was Microsoft Installer. However, the name has since changed to Windows Installer, so the file format is now the Windows Installer Package file format.

MSI files in a folder

MSU files are similar but are Windows Vista Update Package files used by Windows Update on some versions of Windows, and installed by the Windows Update Standalone Installer (Wusa.exe).

How to Open MSI Files

Windows Installer is what the Windows operating system uses to open MSI files when they're double-clicked. It doesn't need to be installed to your computer or downloaded from anywhere because it's built-in to Windows. Just opening the MSI file should invoke Windows Installer so you can install the files that are contained within it.

MSI files are packed in an archive-like format, so you can actually extract the contents with a file unzip utility like 7-Zip. If you have that or a similar program installed (most of them work similarly), you can right-click the MSI file and choose to open or extract the file to see all the files that are stored inside.

Using a file unzip tool is also useful if you want to browse the MSI files on a Mac. Since the MSI format is used by Windows, you can't just double-click it on a Mac and expect it to open.

Extracting the parts that make up an MSI file does not mean that you can "manually" install the software — the MSI will do it for you automatically.

How to Convert an MSI File

To convert MSI to ISO is possible only after you extract the files to a folder. Use a file unzip tool like we described above so that the files can exist in a regular folder structure. Then, with a program like WinCDEmu installed, right-click the folder and select Build an ISO image.

Another option is to convert MSI to EXE, which you can do with Ultimate MSI to EXE Converter. The program is simple to use: select the MSI file and choose where to save the EXE file. There aren't any other options.

Introduced in Windows 8 and similar to MSI, APPX files are app packages that run on the Windows OS. Visit Microsoft's website if you need help converting MSI to APPX. Also, see the tutorial at CodeProject.

How to Edit MSI Files

Editing MSI files isn't as straightforward and easy as editing most other file formats like DOCX and XLSX files because it's not a text format. However, Microsoft offers the Orca program as part of the Windows Installer SDK that edits an MSI file.

Use Orca in a standalone format without the whole SDK. Technipages has a copy you can download. After you install Orca, right-click an MSI file and choose Edit with Orca.