Activation helps verify that your copy of Windows is genuine and hasn’t been used on more devices than the Microsoft Software License Terms allow.
Most computers today come with a digital license, a method of activation in Windows 10 that doesn’t require you to enter a product key.
However older computers and new custom builds will require a product key. A product key is a 25-character code that looks like this and is usually printed on a colored sticker somewhere on the device,
PRODUCT KEY: XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
To enter the product key, select the Start button, and then select Settings > Update & Security > Activation > Update product key > Change product key.
