Sideloading installs and runs unverified extensions in Microsoft Edge. With this policy, you can specify whether unverified extensions can be sideloaded in Microsoft Edge. If enabled or not configured, sideloading of unverified extensions in Microsoft Edge is allowed. If disabled, sideloading of unverified extensions in Microsoft Edge is not allowed. Extensions can be installed only through Microsoft store (including a store for business), enterprise storefront (such as Company Portal) or PowerShell (using Add-AppxPackage). When disabled, this policy does not prevent sideloading of extensions using Add-AppxPackage via PowerShell. To prevent this, in Group Policy Editor, enable Allows development of Windows Store apps and installing them from an integrated development environment (IDE), which is located at: Computer Configuration > Administrative Templates > Windows Components > App Package Deployment Supported versions: Microsoft Edge on Windows 10, version 1809 Default setting: Disabled or not configured Related policies: - Allows development of Windows Store apps and installing them from an integrated development environment (IDE) - Allow all trusted apps to install Fix: (1) GPO: Computer Configuration\Administrative Templates\Windows Components\Microsoft Edge\Allow Sideloading of extension (2) REG: HKEY_LOCAL_MACHINE or HKEY_CURRENT_USER\Software\Policies\Microsoft\MicrosoftEdge\Extensions!AllowSideloadingOfExtensions