How to install a Windows Store app in Windows 8

In this article on our web site we explained how to install a Windows Desktop app (desktop application) in a Microsoft Windows 8 system. In this article we will discuss how to install a Windows Store app in Windows 8.
Installation of a Windows Store app

A Windows Store app (former "Metro-style app") is a new type of application that only runs on Windows 8. They can not be installed using traditional installation techniques; a complete new technique is used to install a Windows Store app.
One big difference compared to an installation of a desktop app (desktop application) is that no separate setup program / self-extractor need to be deployed with the setup package. In fact, it is not even possible to do that. Instead, you create a "passive" package that contains all necessary files to run the app, and that you submit to Windows Store. Users will download your app from the Windows Store as an app package, and Windows will use the information in the app package to install the app. Windows also handles the uninstallation of the app and make sure that all traces of the app are gone from the device after uninstallation. Windows take 100% care of the installation and uninstallation process.
Always installed per-user

Another difference compared to a desktop app installation is that a Windows Store app is always installed per-user basis. For a desktop app you can choose if you want to install the app per-machine or per-user, but a Windows Store app is always installed per-user. When an app is installed per-user, only the user that installed the app can access it.
The Windows Store app package format (APPX format)
All files that are necessary for a successful installation of a Windows Store app are stored in a APPX package. An APPX package is a compressed package that is based on ZIP and OPC technologies, and contains the app’s payload files plus the information that is needed to validate, deploy, manage, and update the app. The filename extension for an APPX package file is .appx.
OPC (Open Packaging Conventions) is a container-file technology created by Microsoft to store a combination of XML and non-XML files together in a single file. For example a DOCX file (Microsoft Word) uses this technology to build a word processor document. Read more on Wikipedia.
A Windows Store app package / APPX package contain these four main parts:
App payload App code files and assets (files that you author when you create your app)
App manifest App manifest file (AppxManifest.xml)
App block map App package’s block map file (AppxBlockMap.xml)
App signature App package’s digital signature file (AppxSignature.p7x)
n App payload are the payload files (code files and assets) that you author when you create your app.
n App manifest is a XML-based manifest file that contains the information Windows needs to deploy, display, and update the app; for example information about package identity, package dependencies, required capabilities, visual elements, and extensibility points.
n App block map is a block map file that lists all the app files contained in the package along with associated cryptographic hash values (for each file) that Windows uses to validate file integrity and to optimize an update of the app.
n App signature is the app package’s digital signature file and ensures that the package and contents haven't been modified after they were digitally signed.
The image below shows what can be inside a created APPX package:
Inside an APPX package
Declarative install

The deployment and installation of a Windows Store app is an entirely declarative process that relies on the XML-based manifest in the app package. The manifest is used to specify the desired integration with the operating system. By using this method Windows will have full control over both the installation and uninstallation of the app, and will make sure that installation / uninstallation behaves in the same way in different Windows 8 devices.
Where is a Windows Store app installed?
A Windows Store app is always installed to the following folder: \Program Files\WindowsApps. The WindowsApps folder is hidden by default. And if you makes the folder visible you may notice that you don't have access to the folder (you will probably get a permission denied warning message). You can change the permission settings for the folder by following the steps described in the The 'WindowsApps' folder in Windows 8 article on our web site.
Digitally signed
A Windows Store app will always be digitally signed before it is deployed to customers (if it is uploaded to Windows Store). You don't need to sign your app yourself; instead Windows Store will sign your app with a certificate containing your registered developer name. The signing process will occur when you upload your APPX package to Windows Store. The digital signature / digital certificate assures that the app has not been changed in any way after deployment to Windows Store.
You can also sign your app package manually, on your own. This may be necessary when you test your app or create apps for Enterprise use. Signing can be made via Visual Studio or by using standard tools for signing (for example the SignTool tool from Microsoft).
An app can not be installed if it is not digitally signed and the signature validated. So this is a compulsory step.
How to create an APPX package
You can create an APPX package (Windows Store app package) by using the Create App Packages wizard in Visual Studio. Detailed information about how to use the wizard can be found on the Creating an app package web page on MSDN. An APPX package can also be created by using a separate tool: App packager (MakeAppx.exe). Instructions on how to use this tool is available on the App packager (MakeAppx.exe) web page on MSDN.
More information
There is more useful information available in the App packages and deployment article on Microsoft's web site. Also the Designing a simple and secure app package blog post (posted by the Windows 8 engineering team) on MSDN Blogs contains useful information about creation of APPX packages.

See also:
How to install a desktop application / desktop app in Windows 8
Related products:
SamLogic Visual Installer
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The information in this article is also valid for Windows 8.1.

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Article written by: Mika Larramo