The tool
What it can and cannot tell you
| Check | This tool | Microsoft activation servers |
|---|---|---|
| 25 characters in 5 groups | Yes | Yes |
| Only valid key characters (no A E I L O S U Z 0 1 5) | Yes | Yes |
| Known public generic / KMS placeholder | Yes | Yes |
| Edition the key belongs to | Only for known placeholders | Yes |
| Whether the key is genuine | No | Yes |
| Whether it has already been used | No | Yes |
Microsoft's product keys are cryptographically signed and the signature can only be verified by Microsoft. Any website that claims to tell you a key is "genuine" from the characters alone is guessing — including us, which is why this tool stops at the format.
Generic and KMS keys
Microsoft publishes two kinds of keys openly. Generic installation keys let you install Windows and choose an edition without owning a licence yet — the PC then shows "Windows is not activated" until a real key or digital licence is applied. KMS client setup keys (GVLKs) point a corporate PC at the organisation's own activation server; on a home PC they do nothing. Both are legitimate tools from Microsoft and both are regularly sold on marketplaces as "Windows 11 Pro key — instant delivery". The checker knows the common ones and tells you when you have been handed one.
How to really verify a key
- Check activation statusSettings → System → Activation. "Active" with a digital licence linked to your Microsoft account is the goal.
- See the edition and channelIn an administrator Command Prompt run slmgr /dli. "RETAIL channel" means a retail licence; "VOLUME_KMSCLIENT" means a KMS client key — not a licence.
- Confirm the partial keyThe same dialog shows the last five characters of the installed key, so you can confirm the key you bought is the one in use.
- Check OfficeFile → Account shows the product and "Product Activated". For deeper detail run cscript ospp.vbs /dstatus from the Office installation folder.
Bought a key that passes every check and still will not activate? See activation help — or, if it came from us, tell us and we replace it.
Privacy
The checker runs entirely in your browser. The key you type is not sent to our server, stored, or logged; there is no analytics on this page. You can confirm this with your browser's network inspector — the page makes no requests after it loads.