Buying & activation guide
Windows Retail vs OEM: what buyers should check
Retail and OEM describe different license channels and terms. Neither label alone proves authenticity. Always read the actual license terms and buy from a source you trust.
Retail licenses
Retail licenses are generally sold directly to end users. Transfer rights depend on the applicable license terms, so check the terms for your specific product and country before moving a license to another device.
OEM licenses
OEM licenses are intended for device manufacturers and system builders and are commonly associated with the device on which they are first installed. Do not assume an OEM license can be transferred like a retail license.
Volume or unauthorized keys are not a substitute
A volume-licensing key, shared key, activation bypass, or modified installer is not the same as an individual Retail license. Ask exactly what license channel is being supplied.
A practical pre-purchase checklist
Confirm the Windows edition, license channel, device limit, activation method and support terms. Keep your invoice and delivered key private. If any of these details are missing, ask before ordering.
Official reference: Microsoft Windows support.