How to check that a Windows or Office key is genuine
A key is genuine when Windows or Office activates with it. After activation, open Settings › System › Activation for Windows, or File › Account in Word for Office: the status should show as activated. Before buying, ask for an invoice and a written activation guarantee.
What Microsoft calls “genuine”
For Microsoft, genuine Windows is “published by Microsoft, properly licensed, and supported by Microsoft or a trusted partner”. Microsoft also lists signs of authenticity: the Certificate of Authenticity (COA), the proof of licence label and the hologram.
Checking a Windows licence in three steps
Look at the activation status
Open Settings › System › Activation. The status should show that Windows is activated.
Display the licence information
In the command prompt, type
slmgr /dli. The command shows the licence information for the installed edition, without administrator rights.Check the end date
Type
slmgr /xpr. Microsoft notes that this date is mainly useful for KMS clients (business activation), because retail and MAK activation is perpetual.
Checking an Office licence
Open Word or Excel, then File › Account. Under “Product Information”, the words “Product Activated” confirm that the key was accepted. The Office 2024 activation guide covers the steps.
What a test does not prove
Microsoft’s validation is an online check: it confirms that the copy is genuine and that the essential licensing files are intact. Our advice: do not enter a new key into a third-party “key checker” website. Only activation on Microsoft’s servers confirms it.
If the check fails
Microsoft lists three common causes of validation failure:
- A repair: a technician may have activated Windows with a different key. Re-entering your original key may fix the problem.
- Several PCs: a standard licence covers a single PC. For several computers, you need one key per computer or a volume licence.
- A used or auction copy: Microsoft advises asking the seller for the COA and the original disc.
On a non-genuine copy, Microsoft says notifications appear. Critical security updates keep arriving, but other updates are reserved for genuine copies. Error codes are explained in our activation errors guide.
Six questions to ask a seller
- Is the key new or used?
- For which edition (Home, Pro…) and which version?
- How many PCs is the licence valid for? According to Microsoft, a standard licence covers just one.
- Is an invoice provided, in the buyer’s name?
- What happens if activation fails: replacement or refund, and within what time?
- Is the download from Microsoft’s servers?
A seller who does not answer one of these questions clearly deserves caution.
For a business: keep a record
Our advice: for each computer, keep the invoice, the key and the machine name. In case of an audit, a PC change or a repair, you can find in a minute which key belongs to which computer. On delivery, our emails group all the keys of an order.
Before you buy: five points to check
- The seller: Microsoft says the safest option is to buy directly from Microsoft or from a trusted reseller.
- An invoice in the buyer’s name.
- A written activation guarantee: at Licenciel, a key that is refused is replaced or refunded (Our guarantees).
- The right type of licence: read our Retail, OEM and volume guide.
- The official download: the software installs from Microsoft’s servers.
If you think you bought counterfeit software, or know a seller that offers it, Microsoft lets you report it confidentially on its “How to Tell” website.