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About Transform Files

Transform files (.MST) let you customize an MSI without editing the original package. They store only the differences between the base MSI and your changes.

In Master Packager, transforms are useful for preserving vendor packages while still applying properties, feature changes, registry updates, and other installation settings.

Why use transform files​

  • Preserve the vendor MSI, which makes future updates or replacements easier.
  • Apply settings during installation and repair, unlike command-line properties that apply only during installation.
  • Work well with enterprise deployment tools.

Limitations​

  • You cannot add files directly to a transform. Store files in external CAB files instead.
  • You cannot modify some areas, such as Summary Information, through an MST.
  • Some vendor MSI packages do not behave correctly with transforms and may need repackaging first.

Create a transform​

  1. Open the MSI in Master Packager.
  2. Choose New Transform to start recording changes.
  3. Make the required changes, such as properties, features, or registry entries.
  4. Save the transform as an .MST file.

Create, Apply and Remove Transform Files - Master Packager

The saved .MST contains only the recorded changes. In Master Packager, you can attach it to an installer so installation, uninstallation, and repair automatically use it.

Apply a transform​

In Master Packager​

  • Add the .MST when you include an MSI in the installer list.
  • Master Packager automatically applies the transform for installation, uninstallation, and repair.

From the command line​

msiexec /i setup.msi TRANSFORMS=custom.mst

To apply multiple transforms, separate them with semicolons:

msiexec /i setup.msi TRANSFORMS=base.mst;custom.mst

Remove a transform​

  • Rerun the MSI without the TRANSFORMS property.
  • In Master Packager, remove the transform entry from the installer configuration.
  • For embedded transforms, open the MSI in Master Packager and delete the embedded .MST.

Best practices​

  • Do not edit vendor MSI files directly when a transform is sufficient.
  • Use a transform instead of command-line properties when the setting must persist during repair.
  • Test transforms on different operating system languages and editions.
  • Rebuild non-standard MSI packages before applying transforms if vendor packaging causes problems.
  • Use Response Transform when you want to capture installer dialog changes instead of removing files or registry entries manually.
tip

For Adobe Reader and similar vendor packages, transforms are the standard way to preconfigure enterprise options such as disabled updates or auto-launch behavior.