What is the EMSIXBUNDLE file format?
A file with the .emsixbundle extension is an encrypted MSIX app bundle for Windows 10 and 11. It is the protected form of a .msixbundle, the packaging format Microsoft introduced in 2018 to unify how Windows apps are built and delivered. A bundle groups several app packages, each compiled for a specific processor architecture such as x86, x64, ARM, or ARM64, or for a resource set like a language or image scale. The store or installer then hands each device only the package it needs.
The e prefix marks encryption. When a developer runs Microsoft's MakeAppx.exe tool with a key, the parts inside the bundle are sealed so end users cannot unpack them. This mirrors how .eappxbundle relates to the older .appxbundle. Game studios use this to keep art and audio assets out of reach, and enterprises use it to protect internal apps. Under the encryption it is still an Open Packaging Conventions ZIP container with a bundle manifest and a block map of SHA hashes.
Security & safety
RISK: MEDIUMAn .emsixbundle is a Windows app installer package, so it can contain executable code. Encryption protects the contents from extraction but says nothing about trust: installing one requires the decryption key or an enterprise certificate, and it should come from a source you trust. Only install signed bundles from known developers, since a malicious package could run code on your machine once deployed.
Format details
in a nutshellPrograms that open EMSIXBUNDLE files
Windows3 apps
MakeAppx.exe (Windows 10/11 SDK)
Free Run MakeAppx.exe unbundle /ep MyBundle.emsixbundle /d "C:\Out" /kf MyKeyFile.txt to decrypt and extract, or MakeAppx.exe decrypt /ep MyBundle.emsixbundle /p MyBundle.msixbundle /kf MyKeyFile.txt to convert it back to a plain bundle. Requires the encryption key.
Microsoft Visual Studio 2022
Freemium Install the Universal Windows Platform / Windows app development workload, which bundles the Windows SDK and MakeAppx.exe, then use the Developer Command Prompt to decrypt the file.
Windows App Certification Kit
Free Provides a standalone copy of MakeAppx.exe under App Certification Kit for decrypting and validating packages without the full SDK. Technical details
deep spec| Encoding | Binary; Open Packaging Conventions (OPC) container based on the ZIP format, with encrypted package parts |
| Container | OPC / ZIP archive holding one or more architecture-specific MSIX packages plus a block map and bundle manifest |
| Compression | DEFLATE per part (files compressed by detected type unless /nc is used); some parts stored uncompressed |
| Encryption | Yes. AES-based content encryption applied by MakeAppx.exe using either a key file (/kf) supplying a base64 32-byte key ID and 32-byte encryption key, or the global test key (/kt) |
| Structure | A bundle wraps several MSIX packages, each built for a specific processor architecture (x86, x64, ARM, ARM64) or resource dimension (language, image scale, DirectX level). Encryption seals these parts so end users cannot unpack them without the key. |
| Integrity | AppxBlockMap.xml stores per-block hashes (SHA256 by default; SHA384 or SHA512 optional) used for integrity verification |
| Platforms | Windows 10, Windows 11 |
| Notes | Encryption and decryption are only available through the MakeAppx.exe command-line tool; they are not exposed in the Visual Studio packaging wizard. Installing an encrypted bundle requires the corresponding decryption key or an enterprise certificate. |
| Typical size | Tens to hundreds of megabytes, depending on the number of bundled architectures and assets |
| Released | 2018 |
| Latest version | MSIX (Windows 10 SDK, October 2018 Update / RS5) |
| Specification | learn.microsoft.com |
EMSIXBUNDLE conversions
Community Q&A
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Frequently asked questions
How do I open an .emsixbundle file?
.msixbundle, which Windows can then install.Can I install an .emsixbundle without the key?
What is the difference between .emsixbundle and .msixbundle?
.msixbundle is the plain app bundle; .emsixbundle is the same bundle after MakeAppx.exe has encrypted its parts so end users cannot unpack them.How do I decrypt an .emsixbundle to a .msixbundle?
MakeAppx.exe decrypt /ep MyBundle.emsixbundle /p MyBundle.msixbundle /kf MyKeyFile.txt, supplying your key file. Use /kt instead of /kf if the bundle was encrypted with the global test key.
