Along with the release of Windows 10 SDK Preview Build 10166, Microsoft has announced the launch of a side-loading app tool for Windows 10 Mobile.

The new application deployment tool enables developers to deploy a Universal Windows application from Windows 10 PC to any smartphone powered by Windows 10 Mobile operating system.

Basically, users will be able to deploy an .AppX to a device connected via USB or available on the same subnet without requiring access to the complete Visual Studio solution.

This tool is especially useful for developers who want to create apps on the Universal Windows Platform (UWP) and test them on a physical device because they will be able to use WinAppDeployCmd.exe to deploy their apps.

The Windows 10 Application Deployment (WinAppDeployCmd) is a command line utility, which is also bundled in the Visual Studio solution, but you can also get it when you install Windows 10 SDK on your PC.
A quicker way to solve issues when Visual Studio can't help

Keep in mind that the stand-alone tool is only installed on the PC if you download Windows 10 SDK preview version 10166 or newer, since previous versions don't bundle this tool.

It's also worth mentioning that WinAppDeployCmd for Windows 10 does not require you to install Visual Studio 2015. Microsoft has also confirmed that the side-loading tool will be included in the RTM version of the Windows 10 SDK as well.

In order to deploy an application to a device, you must enable it for development by upgrading to Windows 10 Mobile preview build 10149 emulator.

Then, head over to Settings / Update & security / For developers / Developer mode, and enable side-load scenarios using WinAppDeployCmd.exe.

If you want more details on how to side-load your app, you can watch the video below, but you can also read more in the related MSDN topic.