Quick fix: Enable sideloading: Settings → Privacy & security → For developers → toggle Developer Mode on. Then double-click the .appx or .appxbundle file. App Installer launches. Click Install. Or via PowerShell: Add-AppxPackage -Path C:\file.appx.

You have an .appx, .appxbundle, .msix, or .msixbundle file from a developer or beta program. You want to install it without going through Microsoft Store. Sideloading is the manual install path. Enable Developer Mode and use App Installer or PowerShell.

Symptom: Need to install a UWP app from an .appx/.appxbundle file (sideload) instead of Microsoft Store.
Affects: Windows 11 (and Windows 10).
Fix time: ~5 minutes.

What causes this

UWP / Microsoft Store apps are packaged as .appx, .appxbundle, .msix, or .msixbundle files. Microsoft Store handles install for catalog apps. For developer beta builds, internal corporate apps, or apps not in Store, you sideload the package file directly. Requires enabling sideloading or Developer Mode.

Method 1: Enable Developer Mode and install via double-click

The standard route.

Open Settings → Privacy & security → For developers.
Toggle Developer Mode on. (Or: toggle Sideload apps on for less aggressive option.)
Confirm dialog. Windows enables sideloading.
Locate the .appx (or .appxbundle, .msix) file.
Double-click. App Installer launches. Shows: app name, publisher, version, capabilities.
Click Install.
App installs. Appears in Start menu like any other app.
For signed apps from trusted publishers: install completes without warning. For unsigned/self-signed: Windows shows trust warning. Click Trust this package.

This is the standard sideload.

Method 2: PowerShell Add-AppxPackage

For scripted install or when double-click fails.

Open Terminal (Admin).

Install the package:

Add-AppxPackage -Path "C:\path\to\file.appx"

For .appxbundle or .msixbundle: same command. Add-AppxPackage handles all variants.

For installs requiring dependencies (other AppX): use -DependencyPath:

Add-AppxPackage -Path "app.appx" -DependencyPath "dependency1.appx","dependency2.appx"

For development install (overwrites in place, no version check):
```
Add-AppxPackage -Path "app.appx" -DisableDevelopmentMode -Register
```
This uses the unpacked AppxManifest.xml; useful for testing.
To list installed AppX packages: Get-AppxPackage | Format-Table Name, Version.
To remove: Get-AppxPackage MyApp | Remove-AppxPackage.

This is the scriptable path.

Method 3: For signed enterprise packages

For corporate-distributed apps.

For enterprise-signed packages: install via Intune Configuration Profile (managed PCs) or via direct sideload after enabling.
To install signing certificate first (if not from public CA): Import-Certificate -FilePath cert.cer -CertStoreLocation Cert:\LocalMachine\TrustedPeople.
For unattended bulk deploy: PowerShell script with multiple Add-AppxPackage calls. Run via SCCM or Intune deployment.
For per-user install vs. all-users: Add-AppxPackage -Path app.appx -ForAllUsers. Requires admin.
For provisioned apps (install at first user logon for new users): Add-AppxProvisionedPackage -Online -PackagePath app.appx -SkipLicense.
For enterprise sideloading without Developer Mode: register an LOB (Line of Business) trusted store. gpedit.msc → Computer Configuration → Administrative Templates → Windows Components → App Package Deployment → Allow all trusted apps to install → Enabled.

This is the right path for enterprise app distribution.

How to verify the fix worked

App appears in Start menu.
Run Get-AppxPackage AppName in PowerShell. Returns package info with Status: Ok.
Launch app. Works as expected.

If none of these work

If install fails: Signature error 0x80073CFF: package not signed by trusted authority. Install signing cert in Trusted Root Certification Authorities, or self-trust the cert. Dependency error: app needs other AppX packages. Find dependencies in publisher’s docs, install with -DependencyPath. Version error 0x80073D02: app already installed with higher version. Remove existing first: Get-AppxPackage AppName | Remove-AppxPackage. For .msix instead of .appx: same install commands work. MSIX is the newer format with better certificate handling. For corporate PCs with Group Policy restricting sideload: check policy via gpresult /h C:\result.html. Contact IT to allow sideloading.

Bottom line: Settings → Privacy & security → For developers → Developer Mode on. Double-click .appx file, App Installer handles it. Or PowerShell Add-AppxPackage -Path. For enterprise: Group Policy + signed packages.