Why do I not need to enter a key to install Win10 Pro?

When Win10 is installed, it is not the same as Win7/Win8. It is to upgrade from the old system to Win10. It is not necessary to enter the product key. After the upgrade, the system will be automatically activated. Of course, the premise is to upgrade from genuine Win7/Win8 to Win10). Why is that?

Microsoft has enabled a new activation mechanism called "Digital Recognition" in Win10 that allows Win7/Win8 users to upgrade without a product key. With the “Digital Recognition” mechanism, manual activation is required unless the motherboard of the
computer is updated or the Win10 system is newly installed.

Digital recognition can be applied to the following four situations:

1. When you plan to upgrade to a Win10 system on a qualifying device running Win7/8 system

2. You purchased the real Win10 system from the Windows Store and successfully activated it on the device.

3. You purchased the Win10 Pro upgrade from the Windows Store and successfully activated it on your device.

4. You are a member of Windows Insider and upgrade to the latest Win10 Insider preview on eligible devices that have previously run successfully activated Windows and Win10 previews

At the same time, Microsoft also gives the circumstances under which a key is required:

1. You purchased a copy of the Windows 10 physical system from an authorized retailer

2. You are authorized The retailer has purchased a copy of the Windows 10 digital system.

3. You have a volume licensing contract for Windows 10 or MSDN subscriptions.

4. You purchased a brand new device running Windows 10 system < Br>

This means that whether you purchase a Win10 system license from the store, you can reinstall without a product key. You can reinstall it as much as you like, and the system will automatically execute the activation process.