When you install Windows 10 21H1, you'll need to activate it using a valid product key. This key helps verify that your copy of Windows is genuine and ensures you receive updates and support from Microsoft. Without a valid activation key, you'll face limitations, such as:
Guide to Activating Windows 10 Version 21H1 Windows 10 21H1 reached its on December 13, 2022. While Microsoft no longer provides "free" activation keys to the general public, there are several legitimate ways to activate this version using existing licenses or official troubleshooting tools. 1. Reusing an Existing Digital License windows 10 21h1 activation key free