KMS activation and MAK keys explained for Microsoft licenses

KMS activation and MAK activation are the two classic ways to activate Microsoft volume licenses. If you know how an installation was activated, you often also know which sales channel the license came from. This article explains KMS, MAK and Active Directory-based activation, gives the thresholds documented by Microsoft and shows what the activation method reveals about the license type.

Three channels, three activation routes

According to Microsoft, its software is obtained through three main channels: retail, original equipment manufacturer (OEM) and volume licensing agreements. Each channel has its own activation methods.

With retail, every purchased copy comes with one unique product key. Activation is mostly done online, and activation by telephone is also available. With OEM, the hardware vendor activates Windows by associating the operating system with the firmware or BIOS of the computer. This OEM activation exists only for computers bought through OEM channels with Windows preinstalled. For volume licenses, KMS, MAK and Active Directory-based activation are available. This applies, for example, to Windows Server and Microsoft Office from volume agreements.

KMS: activation through a server on your own network

KMS uses a client-server model. For activation, the clients connect to a KMS host on the local network. By default, the host uses TCP on port 1688.

For the host to activate clients, enough of them must ask. Clients activate if the count is 25 or higher. For servers and for volume editions of Microsoft Office, the threshold is five.

A KMS activation is valid for 180 days. By default, the clients try to renew it every seven days. The key for the KMS host comes from the Volume Licensing Service Center (VLSC), from the Open, Open Value, Select, Enterprise and Services Provider License agreements.

MAK: one-time activation with Microsoft

The Multiple Activation Key (MAK) is used for one-time activation. It runs through Microsoft's online activation services, by telephone or through a VAMT proxy. No server on your own network is needed.

Each MAK has a preset number of activations, based on a percentage of the licenses the organization has purchased. If the number runs short, it can be increased by calling Microsoft. The source does not state the percentage, so we do not give a figure here.

Active Directory-based activation

With this method, computers activate through their connection to the company domain. This requires that the computers can reach the domain and run a currently supported version of Windows. The activation stays valid for up to 180 days after the last contact with the domain. By default, it is renewed every seven days.

How to tell whether you hold a volume license

The activation method gives hints about the license type:

• If a device reports to a KMS host on your own network, that points to a volume license. According to Microsoft, the key for the host comes from the VLSC of the volume agreements.
• If a key was activated once online or by telephone and is meant for several installations, it is a MAK and therefore volume activation.
• If one copy comes with exactly one key of its own, it is a retail key.
• If Windows is preinstalled at the factory and tied to the firmware, it is OEM.

Windows clients are a special case: according to Microsoft, licenses from volume programs such as Open License, Select License and Enterprise Agreements cover upgrades to Windows client operating systems only.

What this means for used licenses

The activation method tells you how an installation was activated. It is not proof of the license itself. Whether a license may be passed on is a separate question, which we cover in our article on volume and individual licenses.

For used volume licenses we therefore supply evidence: first placing on the market in the EEA, a deletion confirmation from the previous holder and a complete chain of acquisition. The Court of Justice names product keys as a possible technical protection measure for rights holders (paragraph 79 of the judgment in C-128/11). If you want to know which license type you have in use, we can help you classify it through our enquiry form.

Read more: Volume or individual license: differences and transferability and Microsoft volume licensing at a glance.