.MSIX

Windows app package

Introduction

An .msix file is a Windows app package in Microsoft’s MSIX format, used by the Microsoft Store and for installing apps directly. Windows installs it into a protected folder, keeps the app’s settings apart from the rest of the system, and can remove it completely. MSIX grew out of AppX, the format made for Windows 8 Store apps; AppX packages (.appx) have the same layout. Packages for several processors can be combined in a bundle, .msixbundle or .appxbundle.

Unlike an MSI package, which describes how to install a program, an MSIX holds the app’s files as they will be used.

Structure

An MSIX package is a ZIP archive with fixed entries beside the app’s own files:

  • AppxManifest.xml: the package’s identity (name, publisher, version and processor), the apps it contains, their tiles and the capabilities they need.
  • AppxBlockMap.xml: a hash of every 64 KB block of every file, so Windows can check the files and download only the changed blocks in an update.
  • AppxSignature.p7x: the publisher’s signature; Windows installs only signed packages.
  • [Content_Types].xml: the media types of the entries.

Links

Software

  • App Installer, built into Windows, which installs them
  • MSIX Packaging Tool, which repackages existing installers (Windows)
  • MakeAppx.exe and SignTool.exe, in the Windows SDK, which pack and sign them (Windows)
  • Visual Studio, which builds them for Windows apps (Windows)

Reference