Which CAL version do you need for which Windows Server? A CAL entitles access to servers of the same version and of all earlier versions, but not to newer ones. For Windows Server 2025 you therefore need version 2025 CALs. These are also valid for Windows Server 2022, 2019 and 2016. What counts is the newest server that a user or device accesses. The same rule applies to RDS CALs.
Quick decision
- Only Windows Server 2025: 2025 CALs.
- Windows Server 2022, no change planned: 2022 CALs are enough, 2025 CALs work as well.
- Mixed environment: CALs in the version of the newest server.
- Move to 2025 foreseeable: buy 2025 CALs right away; they cover the old server too.
- Windows Server 2016: 2019 CALs or newer fit as well.
Table: CAL version and server version
The rule is in Microsoft’s product terms: a user CAL or device CAL permits access to the corresponding version of the server software or to earlier versions.
| Server that is accessed | CAL 2025 | CAL 2022 | CAL 2019 | CAL 2016 |
|---|---|---|---|---|
| Windows Server 2025 | Yes | No | No | No |
| Windows Server 2022 | Yes | Yes | No | No |
| Windows Server 2019 | Yes | Yes | Yes | No |
| Windows Server 2016 | Yes | Yes | Yes | Yes |
The edition of the server plays no role. The same CAL is valid for Standard and Datacenter. What a CAL is and when you do not need one is described in
Windows Server CAL: when you need client access licenses.
Table: RDS CALs and session hosts
For RDS CALs, Microsoft publishes a separate compatibility table. It follows the same logic.
| Session host | RDS CAL 2025 | RDS CAL 2022 | RDS CAL 2019 | RDS CAL 2016 |
|---|---|---|---|---|
| Windows Server 2025 | Yes | No | No | No |
| Windows Server 2022 | Yes | Yes | No | No |
| Windows Server 2019 | Yes | Yes | Yes | No |
| Windows Server 2016 | Yes | Yes | Yes | Yes |
With RDS there is a second rule: RDS CALs are installed on a license server, and it must have the same Windows Server version as the RDS CALs or a newer one.
| License server | RDS CAL 2025 | RDS CAL 2022 | RDS CAL 2019 | RDS CAL 2016 |
|---|---|---|---|---|
| Windows Server 2025 | Yes | Yes | Yes | Yes |
| Windows Server 2022 | No | Yes | Yes | Yes |
| Windows Server 2019 | No | No | Yes | Yes |
| Windows Server 2016 | No | No | No | Yes |
If you buy RDS CALs 2025, you therefore need a license server with Windows Server 2025. More on this in RDS CAL: licensing Remote Desktop Services.
Mixed environments
In many businesses, several versions run side by side. Then the following applies:
- Per user or device, the newest server counts. If an employee accesses a file server with 2019 and an application server with 2025, she needs a 2025 CAL. A second CAL for the older server is not needed.
- Not everyone needs the newest version. If production only accesses the server with 2019, 2019 CALs are enough there. This requires that access to the newer server is technically ruled out. A new domain controller is usually used by everyone.
- The domain controller often decides. If a domain controller is moved up to Windows Server 2025, all users sign in to it. Then everyone needs 2025 CALs.
Virtual machines and host
For the CAL, the version of the Windows Server instance that is accessed counts, not that of the host. Microsoft gives an example in the licensing guide: if Windows Server 2022 runs on the host only as a hypervisor and Windows Server 2019 in all virtual machines, 2019 CALs are enough. The host that exclusively hosts and manages virtual machines does not itself require CALs.
As soon as a VM with the newer version is added and users access it, these users need the newer CAL. The server side is explained in
Licensing Windows Server and virtualization correctly.
What happens when you change versions
A change of the server version entails a change of the CALs:
- New server license: Microsoft points out that every upgrade to a newer Windows Server version requires its own license.
- New CALs in the version of the new server for everyone who accesses it.
- With Remote Desktop, new RDS CALs and a license server in a matching version.
Sample calculation in license quantities: an office with 20 employees replaces its server with Windows Server 2019 by a new one with one processor and 12 cores running Windows Server 2025. Needed are 16 core licenses of Windows Server 2025 Standard and 20 user CALs 2025. The 20 existing 2019 CALs are not valid for the new server. For the server version you specify, the
license calculator only selects CALs of this or a newer version.
Whether the change is worthwhile also depends on the end of support:
Windows Server end of support: all versions.
Typical cases
New 2025 server next to an old 2019 server. 30 employees access both. 30 CALs 2025 cover both servers. The old 2019 CALs are no longer needed for these employees.
Server stays on 2022, CALs are still missing. 2022 CALs are enough. If a move to 2025 is due in the coming years, 2025 CALs are the forward-looking choice because they remain valid after the move.
Windows Server 2016 with new employees. 2019, 2022 or 2025 CALs also fit 2016. Note that Windows Server 2016 reaches end of support on January 12, 2027. New CALs should therefore match the planned successor version.
Terminal server is moved from 2019 to 2025. Besides the Windows Server CALs 2025, you need RDS CALs 2025 and a license server with Windows Server 2025.
At VivaKeys
| Version | Windows Server CAL | RDS CAL |
|---|---|---|
| 2025 | User, Device | User, Device |
| 2022 | User, Device | User, Device |
| 2019 | User, Device | User, Device |
| 2016 | use CAL 2019 or newer | User, Device |
All client access licenses are in the CALs category. The licensing model as a whole is explained in
Licensing Windows Server: cores, VMs, CALs.
Frequently asked questions
Can I use Windows Server 2022 CALs for Windows Server 2025? No. CALs are valid for their own and for earlier server versions. For Windows Server 2025 you need 2025 CALs.
Are Windows Server 2025 CALs also valid for Windows Server 2022 and 2019? Yes. A 2025 CAL entitles access to Windows Server 2025 and to all earlier versions.
Is there a downgrade for RDS CALs? RDS CALs of a newer version work with session hosts of earlier versions. An RDS CAL 2025 therefore also covers a session host with 2022 or 2019. It does not work the other way round.
Do I need new CALs after upgrading the server? Yes, if the new server version is newer than your CALs. After moving from 2019 or 2022 to 2025, all users or devices that access the server need 2025 CALs.
Does the CAL have to match the edition, i.e. Standard or Datacenter? No. The Windows Server CAL is not tied to an edition. Only the version matters.
Which CAL do I need if the host has 2025 and the VMs have 2022? For access to the VMs, 2022 CALs are enough, as long as the host only hosts and manages virtual machines and nobody accesses services of the host.
Sources
Checked on 2026-11-10 against the publisher’s information:
- www.microsoft.com/licensing/terms/productoffering/WindowsServerStandardDatacenterEssentials/EAEAS
- www.microsoft.com/licensing/guidance/Windows-Server-2025
- learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/rds-client-access-license
- www.microsoft.com/en-us/licensing/product-licensing/client-access-license
- learn.microsoft.com/en-us/windows-server/get-started/upgrade-overview