Microsoft sells the same software under several very different license models. Knowing which kind of key you are holding — retail, OEM, MAK or KMS — tells you what you are allowed to do with it and what happens when your hardware changes. Here is the plain-language version.

The four key types

Retail (FPP)

Bought individually, activates one device, and — importantly — is transferable. If you retire a PC, you may deactivate and move a retail license to a new machine. This is the most flexible license a small buyer can own.

OEM

Ships preinstalled on a new PC and is legally tied to that motherboard forever. Cheaper than retail, but when the machine dies, the license dies with it. Fine for a device you plan to run into the ground; a poor fit if you upgrade hardware often.

MAK — Multiple Activation Key

A volume-licensing key issued to organizations. One MAK carries a pool of activations — it might be good for 50, 500 or 5,000 machines, and a counter on Microsoft's side decrements with every activation. Each activated machine stays permanently activated, even offline afterwards.

KMS — Key Management Service

Also volume licensing, but instead of contacting Microsoft, machines activate against a KMS server inside the organization's own network — and must renew every 180 days. Great for a corporate LAN; useless for a laptop that never touches that network again.

MAK in practice: the honest pros and cons

  • Pro: permanent activation, no renewal check-ins, works fine for remote and offline machines.
  • Pro: one key to manage across many installs instead of a spreadsheet of 200 retail keys.
  • Con: the activation pool is finite. Reinstalling Windows consumes another activation unless the organization requests a reset.
  • Con: volume licenses are governed by the agreement between Microsoft and the organization that bought them. Rights, transferability and support all flow from that agreement — not from the key itself.
Tip: if a seller offers a “volume” key, ask what happens when you need to reinstall. A trustworthy seller answers that question directly and backs it with a replacement policy.

Which should you buy?

  1. One or two personal machines: retail. Full flexibility, cleanest ownership story.
  2. A fleet on a corporate network: KMS through a proper volume agreement.
  3. Many machines, scattered or offline: MAK through a volume agreement.
  4. Budget build you will never upgrade: OEM is acceptable — go in with eyes open about the motherboard tie.

How to tell what you have

Run slmgr /dli in an elevated prompt. The description line names the channel: RETAIL, OEM_DM, VOLUME_MAK or VOLUME_KMSCLIENT. Worth checking before you buy a “retail” key from an unfamiliar source.

Our store lists the license channel on every product page, so you know exactly what you are buying. See our Windows and Office licenses — all delivered instantly by email.