Windows Server Licensing Guide: Editions, Cores and CALs

This Windows Server licensing guide explains how Windows Server is sold and licensed: the Essentials, Standard and Datacenter editions, the versions from 2016 to 2025, core licensing, client access licenses (CALs) and Remote Desktop Services CALs. By the end you will know which edition and version fit your business, and what to check in Microsoft's terms before you buy.

IMPORTANT: This guide is general information. Microsoft sets the licensing rights of each edition, including its virtualization rights, and its licensing terms decide what your setup needs. Check Microsoft's Windows Server licensing guidance for your case.

IMPORTANT: The Windows Server keys in our shop are RETAIL Licenses. Each key activates the edition named on its product page, on 1 server. Other editions and versions are separate products.

1. Windows Server editions: Essentials, Standard and Datacenter

Windows Server comes in editions. They run the same operating system family, but each one is designed for a different size of business and a different way of using servers. This is how Microsoft describes them:

• Essentials: a cloud-connected first server designed for small businesses with up to 25 users and 50 devices. We sell it for Windows Server 2019 and Windows Server 2016.
• Standard: ideal for physical or minimally virtualized environments.
• Datacenter: ideal for highly virtualized datacenters and cloud environments.

Standard and Datacenter are sold for versions 2025, 2022, 2019 and 2016. Each edition is a separate product with its own page and its own key: a Standard key does not activate Datacenter, and an Essentials key does not activate Standard.

The most important difference between Standard and Datacenter is virtualization: Microsoft gives each edition different rights to run virtual machines on the same licensed server. Microsoft states those rights, so read its licensing guidance for your setup.

2. Windows Server versions: 2016, 2019, 2022 or 2025

The version is the release of Windows Server. A newer version gets security updates for longer and supports newer features, but your applications must support it. Microsoft's support dates:

• Windows Server 2025: mainstream support until November 13, 2029; extended support until November 14, 2034.
• Windows Server 2022: mainstream support ended on October 13, 2026; extended support until October 14, 2031.
• Windows Server 2019: mainstream support until January 9, 2024; extended support until January 9, 2029.
• Windows Server 2016: mainstream support until January 11, 2022; extended support until January 12, 2027.

Dates are in US Pacific Time and were last reviewed in October 2026. During extended support, Microsoft publishes security updates, so check the end date against your plans. A server you want to keep for five years should not run a version whose extended support ends in a few months.

As a rule of thumb: choose the version your applications support, and if you have no constraint, the newest one that fits your hardware. Details for each version:

• Windows Server 2025: the newest release, with the longest support horizon. See 2025 Standard and 2025 Datacenter.
• Windows Server 2022: a widely deployed version that many applications already support. See 2022 Standard and 2022 Datacenter.
• Windows Server 2019: a solid choice when your software is certified for it. See 2019 Standard, 2019 Datacenter and 2019 Essentials.
• Windows Server 2016: only for matching an existing 2016 environment or for short horizons, because its extended support ends on January 12, 2027. See 2016 Standard, 2016 Datacenter and 2016 Essentials.

3. Core licensing: what "activate all cores" means

Since Windows Server 2016, Microsoft licenses the Standard and Datacenter editions by the number of physical cores in the server, instead of by processor. Microsoft sets minimums: a license for at least 8 cores per physical processor and at least 16 cores per server. Your server's hardware decides how many core licenses Microsoft's terms require, so count the physical cores of your server and check the terms.

Our Windows Server keys activate all cores of the server. That means the key does not limit the cores that Windows Server uses on the machine where you activate it.

4. What is a CAL?

A client access license (CAL) is a license that gives a person or a device the right to access the services of a Windows Server. There are two kinds, and the idea is the same for both:

• User CAL: covers one person, from any device.
• Device CAL: covers one device, whoever uses it.

Whether your setup needs CALs, and which ones, is defined by Microsoft's licensing terms: check them for the edition and the version you plan to use.

5. RDS CALs: licenses for Remote Desktop

Remote Desktop Services (RDS) lets people connect to a Windows Server session host and work with apps and desktops that run on the server. The access to that session host uses RDS CALs, which are separate products from Windows Server. We sell them in packs of 50, as User CALs or Device CALs.

Two rules matter when you buy:

• The version rule: an RDS CAL pack works with its own Windows Server version or an earlier one, never a later one. A 2022 pack works with 2022, 2019 and 2016 session hosts, but not with 2025.
• The count: count the people (User CALs) or the devices (Device CALs) that will connect, and divide by 50, rounding up. For example, 120 people need three packs.

Choose the pack for your version:

• Windows Server 2025: RDS 50 User CALs and RDS 50 Device CALs
• Windows Server 2022: RDS 50 User CALs and RDS 50 Device CALs
• Windows Server 2019: RDS 50 User CALs and RDS 50 Device CALs
• Windows Server 2016: RDS 50 User CALs and RDS 50 Device CALs

Not sure whether User or Device CALs fit better? Read RDS User CALs vs Device CALs. Need several packs? Request a quote. Once you have your pack, follow How to Install RDS CALs on Windows Server 2022 and 2025, and if Remote Desktop shows a licensing error, read Fix: No Remote Desktop License Servers Available.

6. How to choose your edition and version

Go through these questions in order:

• Do you have up to 25 users and 50 devices and need one first server? Look at Essentials, for 2019 or 2016.
• Is your environment physical or lightly virtualized? Standard is the edition Microsoft describes for that.
• Do you run many virtual machines or build a private cloud? Datacenter is the edition Microsoft describes for highly virtualized environments.
• Do your people use remote desktops? Add RDS CAL packs for your version (section 5).
• Which version do your applications support? Use that one, and check its support end date (section 2).
• Do you also need a database? Read our SQL Server licensing guide.

If you are running an evaluation copy of Windows Server and want to keep it, follow How to Convert Windows Server Evaluation to a Full License. For a fresh installation, see How to Install Windows Server 2022 and Activate It with a Product Key or How to Install Windows Server 2019.

7. How your license is delivered

Right after your payment is confirmed, we email you a secure link to your license, and your invoice comes with the order. You reveal your license with the "Get my license" button when you are ready to use it, not before: revealed licenses can't be cancelled or refunded. If a license doesn't work, tell us within 24 hours of revealing it and we will replace it right away. Your statutory rights are not affected.

RETAIL Licenses are single-use: one key activates once. If you later reinstall the software or the operating system, or change the server's hardware, that activation can't be used again, and our warranty doesn't cover it. Read How our licenses work for the details of each license type.

8. Frequently asked questions