What is an RDS CAL and when do you need it? An RDS CAL (Remote Desktop Services client access license) is the client access license for Remote Desktop sessions on a Windows Server. Every user or device that connects to a session host needs an RDS CAL, in addition to the Windows Server CAL. The RDS CAL must have the version of the session host or be newer, and it is installed on a Remote Desktop license server.
Quick decision
| Situation | What you need |
|---|---|
| Employees work in sessions on a terminal server | 1 Windows Server CAL and 1 RDS CAL per user or device |
| Published applications (RemoteApp) | as above |
| Desktops are hosted on Windows Server with other technology | RDS CALs as well |
| Access only to file shares or the domain | Windows Server CALs only |
| Session host with Windows Server 2025 | RDS CALs 2025 |
What the RDS CAL covers
Microsoft distinguishes between base client access licenses and additive client access licenses. The Windows Server CAL is the base for every access. The RDS CAL is an additive license for an advanced feature, namely Remote Desktop Services. It does not replace the base.
| License | Purpose | Who needs it |
|---|---|---|
| Core licenses (Standard or Datacenter) | running the session host | the server |
| Windows Server CAL | access to the server | every user or device that accesses it |
| RDS CAL | Remote Desktop session or hosted interface | every user or device that uses sessions |
The product terms also make clear: the RDS CAL is needed even when Windows Server provides a graphical user interface through a technology other than Remote Desktop Services. If you publish sessions on Windows Server using another vendor’s solution, you therefore still need the RDS CALs.
What the base CAL is, is explained in
Windows Server CAL: when you need client access licenses.
Per user or per device
Like Windows Server CALs, RDS CALs come in two types. Microsoft describes the differences like this:
| Feature | RDS CAL per device | RDS CAL per user |
|---|---|---|
| Assignment | permanently assigned to the device | to a user in Active Directory |
| Tracking | by the license server, also without Active Directory | by the license server, not possible in a workgroup |
| Temporary RDS CAL | at first sign-in, valid for 90 days | not provided |
| Validity of the issued RDS CAL | random, 52 to 89 days, then renewal | 60 days, then renewal |
| Revocation | up to 20% of the RDS CALs | not possible |
| Overallocation | technically not possible | technically possible, but a license violation |
Important for RDS CALs per user: the license server does not enforce the number. It issues licenses even when more users access the server than RDS CALs are installed. The responsibility for having enough RDS CALs lies with the administrator. Remote Desktop Licensing Manager creates reports for this.
Rule of thumb as with the base CALs: per user if everyone has their own devices; per device for shift work on shared computers. How to weigh the two in detail:
User CAL or device CAL.
License server and grace period
RDS CALs are not installed on the session host but on a Remote Desktop license server. This is a Windows Server role that can run alongside other roles on an existing server. When a connection is made, the session host checks whether an RDS CAL is needed and requests it from the license server if necessary.
- Grace period: after the session host is set up, a period of 120 days runs in which no license server is needed. After that, clients can only sign in if a license server issues valid RDS CALs.
- Setting the mode: on the session host you define whether it requests RDS CALs per user or per device. The mode must match the type of RDS CALs purchased.
- Version of the license server: it must have the same Windows Server version as the RDS CALs or a newer one. RDS CALs 2025 can only be installed on a license server with Windows Server 2025.
Versions: which RDS CAL for which session host
| 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 |
Newer RDS CALs are valid for older session hosts, older ones not for newer hosts. The complete tables including the license server are in
Which CAL version fits which server.
Sample calculations in license quantities
Terminal server for 25 employees. One server with one processor and 16 cores, with two virtual machines on it (domain controller with license server, session host). You need:
- 16 core licenses of Windows Server Standard,
- 25 Windows Server user CALs,
- 25 RDS user CALs.
Production with 8 terminals and 30 employees in shifts. Everyone works only at the terminals in sessions: 8 Windows Server device CALs and 8 RDS device CALs.
40 employees, 12 of them with Remote Desktop. All 40 sign in to the domain, 12 additionally work from home on the session host: 40 Windows Server user CALs and 12 RDS user CALs.
In the license calculator, enable the option for Remote Desktop for this. For the RDS CALs it adopts the type and number of the Windows Server CALs. If only some of the employees use Remote Desktop, enter the different number.
Typical cases
Tax consultancy with working from home. 10 employees work alternately in the office and at home in sessions. 10 user CALs and 10 RDS user CALs. RDS CALs per user fit because everyone accesses the server from several devices.
Two session hosts behind a load balancer. The RDS CAL applies per user or device, not per session host. 25 users need 25 RDS user CALs, even if two hosts share the load. The server side, by contrast, requires licenses for both hosts or VMs, see
Licensing Windows Server and virtualization correctly.
Small business with Essentials. According to Microsoft, Windows Server Essentials does not support the Remote Desktop Session Host role. If you need a terminal server, take Standard.
Workstations from the cloud instead of a terminal server. If you do not want to run your own session host, you can look into Cloud PCs, see
Windows 365 Business explained.
At VivaKeys
| Version | RDS User CAL | RDS Device CAL |
|---|---|---|
| 2025 | RDS 2025 User CAL | RDS 2025 Device CAL |
| 2022 | RDS 2022 User CAL | RDS 2022 Device CAL |
| 2019 | RDS 2019 User CAL | RDS 2019 Device CAL |
| 2016 | RDS 2016 User CAL | RDS 2016 Device CAL |
The base CALs and all other 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
Do I need a Windows Server CAL as well as the RDS CAL? Yes. The RDS CAL is an additive license. Every user or device with Remote Desktop sessions needs both.
Which RDS CAL do I need for Windows Server 2025? Version 2025 RDS CALs. Older RDS CALs do not work with a session host running Windows Server 2025.
What is the difference between an RDS user CAL and an RDS device CAL? The RDS user CAL covers one user with any devices, the RDS device CAL one device with any users. The session host must be set to the matching mode.
How do I activate RDS CALs? You install the RDS CALs in Remote Desktop Licensing Manager on an activated license server. The license server needs the same Windows Server version as the RDS CALs or a newer one.
How long does a session host work without RDS CALs? Microsoft names a grace period of 120 days in which no license server is needed. After that, sign-ins are only possible with valid RDS CALs.
Can I use RDS 2025 CALs with an older session host? Yes. RDS CALs 2025 are also valid for session hosts with Windows Server 2022, 2019 and 2016. The license server must then have Windows Server 2025.
Are my RDS CALs also valid in the cloud, for example at AWS or Azure? The product terms allow the use of RDS user CALs on Azure and with certain partners only with Software Assurance. Without Software Assurance, RDS CALs are intended for your own licensed servers.
Sources
Checked on 2026-11-10 against the publisher’s information:
- learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/rds-client-access-license
- www.microsoft.com/licensing/terms/productoffering/WindowsServerStandardDatacenterEssentials/EAEAS
- www.microsoft.com/licensing/guidance/Windows-Server-2025
- www.microsoft.com/licensing/guidance/Base-and-Additive-CALs
- learn.microsoft.com/en-us/windows-server/remote/remote-desktop-services/rds-license-session-hosts
- www.microsoft.com/en-us/licensing/product-licensing/windows-server