You need one RDS CAL per person (user CAL) or per machine (device CAL) that opens a Remote Desktop session on the server, regardless of the number of simultaneous connections. Choose user if your staff connect from several devices, device if several people take turns on the same machines. And on top of that, plan for standard Windows Server CALs: they are two separate licences.
Windows Server CAL vs RDS CAL: what is the difference?
| Licence | What it allows | When it is required |
|---|---|---|
| Windows Server licence | Installing and running the operating system on the server | Always |
| Windows Server CAL | Accessing server services: files, printing, Active Directory | For every user or device that connects to the server (Standard and Datacenter editions) |
| RDS CAL | Opening a Remote Desktop session or a RemoteApp application | In addition to the Windows Server CAL, for every user or device that uses RDS |
Without the RDS role, Windows Server allows two simultaneous Remote Desktop sessions, reserved for administration. They require no RDS CAL, but cannot be used to let users do their everyday work.
RDS CAL per user or per device: which should you choose?
| Criterion | User CAL | Device CAL |
|---|---|---|
| Assigned to | A named person | A physical machine |
| Ideal case | Remote working, laptop + desktop + tablet | Shared machines: reception, workshop, shift teams |
| Active Directory | Required for licence tracking | Optional, works in a workgroup |
| Technical enforcement | Tracked in the directory, not blocked: compliance is your responsibility | Strict: the licence server refuses a machine beyond the number of CALs |
A server in a workgroup, without a domain, cannot track user CALs. In that setup, common in very small businesses, buy device CALs or set up a domain. The mode is chosen once for the session host: you do not mix the two types on the same server.
How many RDS CALs do you need?
You count people or machines, not simultaneous connections. Three examples:
- Accounting firm, 12 staff who connect from the office and from home: 12 RDS user CALs. Device CALs would need one per PC, so at least 24.
- Warehouse, 6 terminals used by 20 operators in rotation: 6 RDS device CALs, instead of 20 user CALs.
- External contractor who connects once a month: they need a CAL too. Occasional access is the most common oversight during an audit.
Add the same number of Windows Server CALs to this total, if you do not already have them.
Which CAL version for which server?
The rule: the RDS CAL must be the same version as the session host, or newer. An RDS 2022 CAL covers a 2022, 2019 or 2016 host; an RDS 2019 CAL covers a 2019 or 2016 host, but not a 2022 host. The licence server itself must run a version at least equal to that of the CALs it issues. Microsoft sets out these compatibilities in its documentation on RDS client access licences.
In practice, our RDS user CAL for Windows Server 2019 is suitable for a 2019 or 2016 session host. If you plan to migrate to Windows Server 2022 in the short term, take that into account before buying.
How do you install RDS CALs on the server?
- In Server Manager, add the Remote Desktop Licensing role service.
- Open Remote Desktop Licensing Manager, right-click the server, then Activate Server (“Automatic connection” method).
- Right-click > Install Licenses. Choose the licence programme stated in your delivery email, enter the key, then the version, the type (user or device) and the quantity.
- Tell the session host where to find the licences. In
gpedit.msc: Computer Configuration > Administrative Templates > Windows Components > Remote Desktop Services > Remote Desktop Session Host > Licensing. Enable “Use the specified Remote Desktop license servers” and “Set the Remote Desktop licensing mode”. - Check with the licensing diagnosis tool (
lsdiag.msc): it should show the licence server and the number of CALs available, with no warnings.
Step 4 is the one people forget. The server then works normally during the 120-day grace period, then suddenly refuses all connections overnight, even though the CALs are properly installed. If your users are blocked with the message “no Remote Desktop license servers available”, start there.
Frequently asked questions
Are RDS CALs included with Windows Server?
No. Neither the Standard nor the Datacenter edition includes them. They are bought separately, like Windows Server CALs; everything is grouped in our Windows Server and CAL collection.
Does Windows Server Essentials need CALs?
The Essentials edition does not require Windows Server CALs, up to 25 users. However, it is not designed to host a multi-user RDS service: for that use, go for Windows Server 2019 Standard or a newer edition.
Can user CALs be converted to device CALs?
The type is fixed at purchase. Remote Desktop Licensing Manager offers a conversion under certain volume licensing programmes, but it is not a general right: it is better to choose correctly from the start.
What happens at the end of the grace period?
After 120 days without a configured licence server, the session host refuses user connections. The two administration sessions remain accessible with mstsc /admin, which lets you fix the configuration.
Is an RDS CAL tied to a specific server?
It is installed on a licence server, which can serve several session hosts. If the server is replaced, the licences are migrated from Remote Desktop Licensing Manager. Installing the operating system itself is covered in our guide Windows Server 2019 Standard: download, install and activate.