Over the years, many of our clients have had questions regarding server licensing, especially when it comes to Windows CALs. For this reason, today we will explain all the details needed to properly license your servers.
What are Windows Server CALs?
When a client purchases a Windows server, they receive a server license that allows them to install the operating system on a machine.
However, a server license by itself does not grant the legal right for other users to connect to that machine, whether they work for the company or not. Instead, each user requires a Client Access License (CAL).
A Server Client Access License (CAL) is therefore a license that grants users and devices the legal right to access a server running Microsoft server software.
Types of Windows CALs Available
User CALs
Ideal for employees who need network access from multiple devices.
Device CALs
A suitable option for environments where employees work in shifts or share the same device to access the server.
RDS CALs for Remote Desktop Services
Designed for users who access applications remotely.
User CALs allow a single user to access an unlimited number of devices. In contrast, Device CALs allow a single device to be used by an unlimited number of users. Unlike the previous two, RDS CALs are required specifically for Remote Desktop access.
We will now explain each type of Windows CAL in detail
- User CALs: Ideal for employees who need network access from multiple devices.
- Device CALs: A suitable option for environments with rotation or shift-based work, where several employees use the same device to access the server.
Naturally, a combination of both can be used depending on your needs.
RDS CALs: Intended for users who access applications remotely.
Important details to consider when purchasing Windows CALs
Ultimately, any user who accesses server resources must obtain the appropriate CAL licenses (User vs. Device), as well as RDS CALs if they connect remotely.
There are several important points to keep in mind. When purchasing a Windows Server 2019 operating system license, CALs must be acquired separately—they are not included with the operating system. One special consideration is that CALs are not required for unauthenticated access over the internet.
Recommendations to ensure long‑term investment continuity
To ensure the continuity of your investment in Windows CALs, it is recommended to purchase them with Software Assurance. This option provides additional benefits, such as updates and technical support, which can be valuable for your company in the long term.
Implementation of RDS with Windows CAL licenses
As an update to our post related to Windows CALs, I would like to expand with more details about licensing for Remote Desktop users, commonly known as RDS CALs (Remote Desktop Services CALs).
Each user or device that connects to a Remote Desktop Session Host requires a Client Access License (CAL).
Remote Desktop licenses are used to install, issue, and track RDS CALs, allowing users to access their desktop or the applications they regularly use from home or any other location. A valid RDS CAL issued by a licensing server is required in order to sign in to a Remote Desktop Session Host server.
There are two types of RDS CALs
- RDS Device CAL
- RDS User CAL
Differences between User CALs and Device CALs
I always use the same example because it is very illustrative. The device‑based model applies, for instance, when employees work in shifts and share the same device; in this case, the most cost‑effective option is to license the PC.
In contrast, the user‑based model is appropriate when each user has their own PC, making it the best option even for accessing the Remote Desktop Session Host.
- Device CAL: Assigned to each physical device and allows any user to access RDS services from that device. Temporary CALs assigned during the first logon are valid for 90 days. Permanent CALs are valid for a random period between 52 and 89 days before renewal.
- User CAL: Assigned to a user in Active Directory and allows that user to access RDS services from any device. CALs are valid for 60 days before renewal or 90 days before reassignment.
The Remote Desktop Session Host server determines whether an RDS CAL is required when a user or device connects. If needed, it requests an RDS CAL from the licensing server. If an appropriate CAL is available, it is issued to the client, allowing the connection to the session host and to the desktop or applications being accessed.
There is a 120‑day licensing grace period during which no licensing server is required. After this period, clients must have a valid RDS CAL issued by a licensing server in order to sign in to a Remote Desktop Session Host server.
To install RDS CALs, the machine running the Remote Desktop Licensing Manager must have Internet connectivity, although the licensing server itself does not require it.
RDS CAL version compatibility
You must install your RDS CAL on a compatible Remote Desktop licensing server. Any RDS licensing server can host licenses for all previous versions of Remote Desktop Services as well as the current version.
For example, an RDS licensing server running Windows Server 2022 can host licenses for all previous versions of RDS, whereas an RDS licensing server running Windows Server 2016 can only host licenses up to Windows Server 2016.
Integration of RDS with Microsoft Azure
The integration of Windows Server 2016 with Microsoft Azure significantly enhances Remote Desktop Services (RDS) by offering a range of benefits:
- Cost reduction: By using Microsoft Azure services, on‑premises infrastructure expenses can be reduced, as Azure provides cloud computing resources that can be scaled as needed.
- High availability: Azure services ensure that desktops and applications are available whenever required, increasing overall system stability.
- Improved security: Azure Multi‑Factor Authentication adds an additional layer of protection, safeguarding against unauthorized access.
- Optimized user experience: Users can access RDS using their existing identities, simplifying the login process and access to resources.
In summary, combining RDS with Azure delivers a robust and efficient solution for desktop and application delivery, leveraging the scalability and security of the Azure cloud.
Learn more about Windows CAL licensing
If you would like to explore Windows Server licensing and CALs in more detail, we encourage you to visit Microsoft’s official website. There you will find comprehensive information about the different types of licenses and the specific requirements for your organization.
Updated 2025 Note: Remember that starting with Windows Server 2022 and Office LTSC 2024, Microsoft has introduced new SKUs and changes to licensing conditions. If you are using earlier versions (such as Server 2016 or 2019), check whether your environment needs to be updated.
Contact ABD Consulting and IT Solutions to get assistance
At ABD Consulting and IT Solutions, we are here to help you navigate the complex world of licensing and software asset management.
If you have questions or need assistance determining the best licensing options for your company, feel free to contact us. We are committed to helping you make informed and strategic decisions that drive your business’s success.
