How do I open an MSIX file without installing it?

Drop it on the box above. The manifest, capabilities, signature and files are read in the browser. An MSIX is also a ZIP, so renaming a copy to .zip lets any archive program list the files, but not explain them or check the signature.

What is the difference between .msix and .appx?

APPX came first, with Windows 8 and the early Store apps; MSIX (2018) is its successor and also packages ordinary desktop programs. They are built the same way, a ZIP with AppxManifest.xml, a block map and a signature, and this page reads both, and their bundles.

What does "restricted capability" mean?

A capability Microsoft only allows in the Store for a reason it approves, because it reaches beyond the app's own space: running as a full desktop program, reading every file you can, installing other apps or services. Outside the Store nobody checks, so it is worth reading the list.

Why does Windows say the publisher certificate could not be verified?

Windows does not trust the certificate the package was signed with: usually a developer's self-made test certificate. This page shows that certificate (marked self-signed) so you can see who it names. Whether to trust it is your call; most people should not install such a package.

Can it open .emsix or .eappx files?

No. Those are packages encrypted by the Microsoft Store for its own downloads, and only Windows can read them. The page says so if you open one.

Is the package uploaded anywhere?

No. The package is read by this browser tab on your own device, and nothing is sent anywhere.

Stays on your computer How this works

Free MSIX viewer: see inside a Windows app package

Open an .msix, .appx, .msixbundle or .appxbundle to see the app's name, publisher and version, the capabilities it asks for with the restricted ones marked, the file types and links it opens, who signed it and whether it has been changed since, and every file inside. The file is opened in your browser and is not uploaded, and nothing in it is installed or run.

Drop a .msix file here, or click to choose oneIt is opened by your browser, on this computer. Nothing is uploaded.

About the MSIX viewer

MSIX is how Windows 10 and 11 package apps: the Microsoft Store, winget and many developers' download pages hand them out as .msix files, and older ones as .appx. A bundle (.msixbundle or .appxbundle) holds one package per processor or language. Double-clicking one opens App Installer, which offers to install it; seeing what it is without installing takes PowerShell or the MSIX Packaging Tool, and neither is on a Mac or a phone. (An .msi installer is a different format: the MSI viewer opens those.)

This page reads the package's AppxManifest.xml, block map and signature, and works out again every fingerprint the signature covers, so a package changed after signing is caught and the changed part named. A bundle's packages open one at a time, from inside the bundle. It is free to use, with no account and no upload limit, and it runs entirely in your browser: nothing is uploaded, and while the page stays open, a feature you have already used keeps working offline.

What you can see

The package name, publisher, version and processor (x64, x86, Arm64 or neutral), and the logo
Every capability it asks for, in plain words, with restricted ones such as runFullTrust and broadFileSystemAccess marked first
The Windows versions it needs and the packages it depends on (such as the VC++ runtime or Windows App SDK)
Its apps: the program each starts, whether it is a desktop program or a sandboxed app, and the file types, links and typed commands it registers
What it adds to Windows: startup tasks, services, File Explorer menus, fonts, firewall rules and the like
Who signed it (the certificate's name, issuer, dates and thumbprint), whether the signature is intact, and whether every file is still exactly as signed
For bundles and Store upload files: each package with its processor and languages, opened in place
What the size is made of, and every file as a folder tree, with pictures shown and any file saved on its own

How to check a package before installing it

Drop the file on the box above, or click the box and choose it.
Read the publisher and the signing certificate: the name should be the company you expected, and the package should be unchanged since it was signed.
Look at the capabilities. runFullTrust is common for ordinary desktop programs and means the app can do anything your account can; restricted capabilities beyond that deserve a reason.
Check "Runs on" against your Windows version (Settings > System > About).

Viewing is safe; installing is a choice

Opening a package here only reads it: nothing is installed or run. Installing an app from outside the Microsoft Store is like running any downloaded setup file: it is as trustworthy as whoever made it. Windows only installs a signed package whose certificate it trusts, and this page shows who signed it, but it does not check Windows' list of trusted certificate authorities, and a signature proves who signed, not that the app is harmless.

How to install an MSIX on Windows

App Installer: on Windows 10 (1809 and later) and Windows 11, double-click the .msix or .msixbundle and choose Install. If nothing happens, get App Installer from the Microsoft Store.
PowerShell:Add-AppxPackage -Path .\app.msix installs it for your account; add -DependencyPath with any framework packages it needs. Get-AppxPackage lists what is installed.
A test or self-signed package installs only once its certificate is trusted on the computer (imported into Trusted People or Trusted Root), or in developer mode. Only do that for a package whose maker you know.
Mac, Linux, Android, iPhone: an MSIX does not install outside Windows, but this page reads it on any of them.

Questions

How do I open an MSIX file without installing it?: Drop it on the box above. The manifest, capabilities, signature and files are read in the browser. An MSIX is also a ZIP, so renaming a copy to .zip lets any archive program list the files, but not explain them or check the signature.
What is the difference between .msix and .appx?: APPX came first, with Windows 8 and the early Store apps; MSIX (2018) is its successor and also packages ordinary desktop programs. They are built the same way, a ZIP with AppxManifest.xml, a block map and a signature, and this page reads both, and their bundles.
What does "restricted capability" mean?: A capability Microsoft only allows in the Store for a reason it approves, because it reaches beyond the app's own space: running as a full desktop program, reading every file you can, installing other apps or services. Outside the Store nobody checks, so it is worth reading the list.
Why does Windows say the publisher certificate could not be verified?: Windows does not trust the certificate the package was signed with: usually a developer's self-made test certificate. This page shows that certificate (marked self-signed) so you can see who it names. Whether to trust it is your call; most people should not install such a package.
Can it open .emsix or .eappx files?: No. Those are packages encrypted by the Microsoft Store for its own downloads, and only Windows can read them. The page says so if you open one.
Is the package uploaded anywhere?: No. The package is read by this browser tab on your own device, and nothing is sent anywhere.