Find your Windows product key

Product keys and Windows activation in 2026

Windows activation still relies on a 25-character product key to verify that your copy of the operating system is genuine. Without a valid key, Windows runs in a reduced-functionality state: the desktop watermark appears, personalisation settings are locked, and Microsoft may restrict certain security features over time. Keys originate from a variety of sources — retail purchases, digital downloads through the Microsoft Store, volume licensing agreements, Microsoft 365 developer subscriptions, and original equipment manufacturer (OEM) licences pre-loaded by the PC maker. Microsoft first introduced product activation with Windows XP as an anti-piracy measure, and while the underlying goal hasn't changed, the mechanics have evolved considerably since then.

On modern hardware shipped with Windows 10 or Windows 11, the product key is almost never printed on a sticker. Instead it lives silently inside the firmware, embedded in the ACPI tables of the motherboard. This means that if you reinstall Windows on the same machine — or upgrade from Windows 10 to Windows 11 — activation typically happens automatically, without you ever needing to type a key. That said, there are situations where you need to retrieve the key manually: migrating to a new motherboard, troubleshooting an activation failure, or verifying what edition of Windows your licence entitles you to run.

It is perfectly legitimate to reinstall and reactivate Windows on the PC for which the product key is licensed as many times as you need to.

Edition of Windows

Your product key does more than prove ownership — it also determines which edition of Windows you are licensed to run. A Home key cannot activate a Pro installation, and a Pro key will not unlock Enterprise features. This distinction matters when you are reinstalling from scratch, because the Windows 11 installer will ask you to choose an edition before it downloads or applies the image. If you select the wrong edition and activate with your stored key, Windows will refuse the key or activate the wrong feature set. Retrieving your original key first removes the guesswork.

Product keys stored in your PC's firmware

TL;DR — On any PC shipped with Windows 8 or later, the product key is stored in the Advanced Configuration and Power Interface (ACPI) firmware tables, specifically in a table called the MSDM (Microsoft Data Management) table. This is non-volatile memory on the motherboard, completely separate from your hard drive or SSD, so it survives a full disk wipe. Retrieving it takes a single command.

Microsoft's shift to digital licensing — introduced alongside Windows 10 — adds another layer. Once a licence has been activated on a particular piece of hardware, Microsoft's servers link the licence to a hardware fingerprint. On Windows 11 machines that have been online at least once, you can often reactivate simply by signing in with the Microsoft account that was associated with the original activation, even if the firmware key is no longer readable. The firmware key and the digital licence work in parallel, so it is worth knowing how to access both.

How to retrieve your original product key

Windows (PowerShell — recommended for Windows 10 and Windows 11)

The wmic command used in older guides still works on Windows 10, but it has been deprecated and is absent from Windows 11 by default. Use PowerShell instead, which is available on both Windows 10 and Windows 11 without installing anything extra. Open PowerShell as Administrator and run:

PS C:\> (Get-WmiObject -query 'select * from SoftwareLicensingService').OA3xOriginalProductKey
XXXXX-XXXXX-XXXXX-XXXXX-XXXXX

If the command returns a blank line, your machine uses a digital licence tied to your Microsoft account rather than a readable firmware key. In that case, sign in to account.microsoft.com/devices to view and manage your linked licences.

Windows (Command Prompt — legacy, Windows 10 only)

If you are still running Windows 10 and prefer the older approach, the following still works — but be aware that wmic is removed in clean Windows 11 installations:

C:\> wmic path softwarelicensingservice get OA3xOriginalProductKey
OA3xOriginalProductKey
XXXXX-XXXXX-XXXXX-XXXXX-XXXXX

Linux

If you have booted from a Linux live environment — useful when Windows itself will not start — you can read the MSDM firmware table directly. On Debian-based distributions including Ubuntu:

$ sudo apt install binutils
$ sudo strings /sys/firmware/acpi/tables/MSDM
[sudo] password for youraccount:
MSDMU
COMPUTERMFR
XXX
XXXXX-XXXXX-XXXXX-XXXXX-XXXXX

The 25-character string at the end of the output is your original OEM product key. This approach works regardless of whether Windows is installed, making it particularly handy for disaster recovery scenarios.

Checking your digital licence via your Microsoft account

If your device runs Windows 11 and was activated with a Microsoft account, the firmware key may return blank because the licence is held server-side rather than embedded in a readable ACPI string. In this case, visit Settings > System > Activation to confirm that a digital licence is linked to your account. You can also view all devices associated with your Microsoft account at account.microsoft.com/devices. When you reinstall Windows 11 on the same hardware and sign in with the same Microsoft account during setup, activation completes automatically without requiring a key at all.

References

• Wikipedia — Microsoft Product Activation
• Wikipedia — ACPI (Advanced Configuration and Power Interface)
• Microsoft Support — Activate Windows 10 and Windows 11
• Microsoft Account — Manage your devices and digital licences