For a long time Windows PCs (OEMs) came with a product key sticker that was often placed outside of the machine or with your computer’s manuals, but now manufacturers are storing this license within the machine’s UEFI/BIOS and the information is automatically retrieved and applied when reinstalling the operating system. Certainly a better approach overall.
Additionally, Windows 10 introduced a “Digital Entitlement” element to Microsoft’s license which links your Windows key to an ID generated based on your PC’s hardware. But because your hardware can significantly change if you upgrade your hardware, this entitlement was expanded to become a “Digital License” when 2016’s Anniversary Update (1607) arrived.
This means your Windows 10 license now ties Windows keys to Microsoft accounts, letting you activate a copy of the operating system simply by logging in with valid online credentials.
So, if you have a newer Windows PC or you already log in using your Microsoft account, you generally shouldn’t have to search for your original Windows 10 key. We will explain that in better detail in a minute.
There may be other scenarios where you may still want to manually find a Windows key stored in your UEFI/BIOS, or prevent this key from automatically being applied during installation. Not to mention that different conditions apply for non-OEM retail keys, as well as those given to people who upgraded to Windows 10 for free. And in a worst case scenario, you might be trying to find the license for a copy of Windows that no longer boots.
Windows OEM keys vs. retail vs. free upgrade
OEM keys are shipped with a specific computer and can’t be transferred to another machine. Again, these should be auto-applied from your UEFI/BIOS when reinstalling Windows on a modern boxed PC, but you can also retrieve them manually.
Retail keys are purchased directly from Microsoft, Amazon etc. — these can be transferred to another machine and that process should happen automatically for a digital license, though you can also “uninstall” a Windows key from a given PC.
Those who upgraded to Windows 10 for free from Windows 7 and 8 don’t have a unique Windows 10 key. This can only be transferred to one other machine (not if you upgraded from an OEM key). Free upgrade licenses are a digital entitlement.