Windows Server Core Licensing

Since Windows Server 2016, Microsoft relies on core licensing.

In this article, all important information, that is required for the licensing of Windows Server, is included.

It is possible to test the latest server version up to 180 days for free.

A corresponding download can be found in Microsoft Evaluation Center.

Click here for our Microsoft software in the Thomas-Krenn online shop

Windows Server licensing

Since Windows server 2016, it must be distinguished between Essentials and Standard/Datacenter . Every system running a Windows Server instance must be licensed, whether it is physical or virtualized.

Windows Server Essentials

For the Essentials Edition, the licensing model remains "per CPU / per server".

Essentials still has the limitation that a maximum of two CPUs may be installed.

An Essentials license includes two CPUs. Therefore, only one Essentials license needs to be assigned per server.

Windows Server Standard and Datacenter

For the Standard and Datacenter Edition, a core licensing is required. It must be noted how much active, physical kernels possesses a CPU.

To obtain two virtual licenses for the Standard Edition and unlimited licenses for the Datacenter Edition, the following three rules must be observed:

Rule #1: Every physical processor is scored based on at least 8 cores

Rule #2: Every physical server is scored based on at least 16 cores

Rule #3: All physical and active cores must be licensed in accordance with Rule #1 and Rule #2

If you want to increase virtualization rights for the Standard Edition, you must double the number of licenses for 4 VMs, triple them for 6 VMs, quadruple them for 8 VMs, and so on.

Basis and additional licenses

There are so-called basis licenses and additional licenses. The basis licenses are available with 16 or 24 cores. Additional licenses are available with 2, 4 or 16 cores.

The following chart shows that additional licenses are required only when there are 4 or more CPUs or more than 8 cores.

You are still unsure? No problem!

In the Thomas-Krenn online shop, you do not need to worry about the core licensing yourself.

Our online configurator automatically calculates the correct number of licenses, so that your new Windows server system is licensed correctly.

If you have questions on the licensing, do not hesitate to contact us.

Software assurance

Of course, you can also purchase software assurance for the new server operating system.

Did you know? Software assurance for OEM!

Within 90 days, you can buy a software assurance for your OEM Windows Server license

An OEM license becomes a volume license when combined with software assurance. You have the same advantages as a volume license customer.

Even after the SA expires, the OEM license remains a volume license, so you will continue to benefit from it.

Benefits you can enjoy through software assurance:

• License mobility - all 90 days right of reassignment of the license
• free upgrade to a new version of Windows Server
• Windows Virtual Desktop access licenses (VDA)
• and more...

Windows Server Access Licenses(CAL)

Windows Server Access Licenses - CALs (Client Access Licence) - are required for the access on systems with Windows Server operating system:

For every user or every device, you require a CAL. If the user or the device accesses a Windows Server via remote desktop, a RDS-CAL is required additionally.

CAL is tied to the latest version of Windows Server, which means that to license a user's access to a Windows Server 2025, you need a Windows Server 2025 User CAL for that user.

In this scenario, you must not use an older Windows Server CAL!

All important information about the topic access licenses/CALs, can be found directly at Microsoft.

Did you know? There are OEM-CALs!
Every OEM-CAL (Windows-Server-CAL and RDS-CAL) allows the access on every Windows server, regardless of the manufacturer, regardless of whether the Windows Server was licensed through OEM or volume licensing.

You can purchase additional OEM CALs at any time in the Thomas-Krenn online shop: Microsoft software.

Downgrade right

Every Windows Server license includes an unlimited downgrade right, whether OEM or volume licenses.

With your Windows Server license, you have the right to install all underlying Windows Server versions and editions.

With a Windows Server 2025 Standard license, for example, you may install Windows Server 2016 Standard or Windows Server 2019 Essentials, but not, for example, Windows Server 2019 Datacenter.

To exercise this downgrade right, all you need is an installation medium as well as an installation product key (Windows key) of the operating system that should be installed.

There are so-called downgrade kits that include these installation mediums as well as product keys. You can also purchase these directly from Thomas-Krenn.

All important information on the downgrade topic can be found at Microsoft.

More information

• Microsoft Licence Guide (www.microsoft.com)
• Windows Server (EN) (www.microsoft.com)
• Windows Server 2025 Pricing Information

(www.thomas-krenn.com)

• Windows Server 2025 Differences Between Editions (www.wiki.thomas-krenn.com)
• Thomas-Krenn Webinar on Windows Server 2025 Licensing] (www.thomas-krenn.com)

Author: Armin Oberneder Armin Oberneder has been working for Thomas-Krenn.AG for over 7 years now. He is currently employed in the consulting team and thus takes care of all customer-specific inquiries concerning servers, storage, virtualization and networks. In the past years Armin has specialized in Windows Server, Software-Defined-Technologies and Network Technology. Due to these specializations, he also ensures that our customers are helped as quickly as possible in the event of problems by means of a ticket system, by telephone or in writing via e-mail.

Translator: Alina Ranzinger Alina has been working at Thomas-Krenn.AG since 2024. After her training as multilingual business assistant, she got her job as assistant of the Product Management and is responsible for the translation of texts and for the organisation of the department.