Answers
Is buying an OEM key online legal?
Short answer
Yes in most countries — Microsoft sells OEM keys to system builders, and reselling unused, unbound OEM keys is permitted in the EU under the UsedSoft v Oracle ruling (CJEU C-128/11). In the US, OEM keys are legal once detached from the original system as part of a single transfer.
The longer explanation
Microsoft's End User License Agreement allows the original purchaser of a Windows OEM license to transfer it once, in its entirety, to another party. Unused keys that were never activated on a specific motherboard are treated under the EU first-sale doctrine as resellable goods.
Risk indicators when buying: keys priced under €15 for Windows 11 Pro, no email receipt, no invoice, marketplace sellers with no contact address. Legitimate resellers offer a money-back guarantee and a written replacement policy.
Primary sources we cite
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Why trust this answer
Written by licensing analysts who handle Microsoft Open, CSP and EU-resale transactions every day. We never paraphrase Microsoft contracts second-hand — every claim links to the actual EULA section, Microsoft Learn article, or court ruling it comes from. Found a discrepancy? Email research@licensevault.net and we will update the page within 48 hours.
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