Inside MSIX
Demystifying MSIX Architecture, Development, Deployment and Troubleshooting
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Staging Part 1 – Sharing is Caring
A key phase in installing a package is staging the package: When a package is staged for the first time, deployment performs several actions, including: Deployment secures these directories with strict permissions, typically granting users Read and potentially Execute access - but notably not Write access. This ensures one user cannot modify the contents of a package in a manner that would compromise their own environment - or anyone else's. Because MSIX guarantees the immutability of the pkgdir after staging, it can be safely shared across all users on the system - regardless of who installed the p...
Deployment Operations, Requests and Queue
The PackageManager API submits requests to the deployment engine for processing. Each request represents an instruction for the deployment system to carry out a defined set of actions, collectively referred to as a deployment operation. The operation associated with a request depends primarily on the API used to initiate it and, in some cases, its parameters. Internally, the deployment pipeline models its work as a series of deployment operations derived from an API called and its arguments. For example, PackageManager.MovePackageToVolumeAsync() submits a request to perform a Move Package operation. In most cas...
Package Identity
An MSIX package identity is composed of a five-part tuple that uniquely identifies a package. It consists of the following attributes: Together, these fields form the canonical identity of a package. Programmatically, this identity can be represented using APIs such as Windows.ApplicationModel.PackageId or the PACKAGE_ID structure. Why Package Full Name? Working directly with the individual identity fields is often inconvenient. To simplify common scenarios, Windows defines an opaque string representation that encapsulates the entire five-part identity: the Package Full Name. This canonical form provi...
Is This a Packaged Process?
Sometimes you need to know whether the current process has package identity. Certain Windows features require it, and behaviors can differ—both technically and culturally. For example, classic Windows applications often store settings in the registry, whereas packaged applications typically use ApplicationData.LocalSettings. So how can your code determine whether it is running with package identity — that is, whether it is a packaged process? Terminology Let's begin with clear and unambiguous definitions: We deliberately say process rather than application. The distinction matters: applications have pro...
There is no Install – it’s ‘Stage’ and ‘Register’
"Is ContosoParts.msix installed?" is a common - but misleading - question The term install is not a formal concept in MSIX. This may seem paradoxical for a deployment technology, but it makes perfect sense once you understand MSIX deployment’s core architecture. Deployment Requests A caller makes a deployment request to the deployment engine via the PackageManager API to perform some activity. This may involve adding a package to the system, removing one, or performing another management operation. Deployment requests include: The system queues the request in the deployment engine’s memory for process...
