Quick answer: RDS CALs are installed in Remote Desktop Licensing Manager: activate the licence server, choose Install licenses, enter the licence code from your order email, then set the session host to the matching licensing mode. Windows Server User and Device CALs are not typed into Windows at all; they're licence records you keep for compliance.
This guide covers Windows Server 2025 RDS User CALs, RDS Device CALs, Windows Server 2025 User CALs, Device CALs and the 2022 and 2019 versions.
Which CALs do I need?
| Licence | What it covers | Installed in Windows? |
|---|---|---|
| Windows Server User CAL | One person accessing the server from any device | No, keep as a record |
| Windows Server Device CAL | One device used by any number of people | No, keep as a record |
| RDS User CAL | One person using Remote Desktop sessions | Yes, in RD Licensing Manager |
| RDS Device CAL | One device connecting to Remote Desktop | Yes, in RD Licensing Manager |
Remote Desktop users need both a Windows Server CAL and an RDS CAL. CALs must be the same version as, or newer than, the server they access: 2025 CALs cover 2025, 2022 and 2019 servers.
Part 1: Windows Server User and Device CALs
- Save your order email and invoice with the CAL keys in a safe place.
- Note how many users or devices each purchase covers, and which server they're for.
- That's it. Windows Server doesn't ask for these keys; they prove you're licensed if you're ever audited.
Part 2: Install the Remote Desktop licence server
- Open Server Manager → Manage → Add Roles and Features.
- Choose Role-based or feature-based installation, select your server and tick Remote Desktop Services.
- On the Role Services page, tick Remote Desktop Licensing (and Remote Desktop Session Host if this server will host sessions), then install.
- Open Remote Desktop Licensing Manager (Server Manager → Tools → Remote Desktop Services).
- Right-click your server name and choose Activate Server. Select Automatic connection, enter your company details and finish the wizard. Microsoft's licence server activation guide covers web and phone alternatives.
Part 3: Install your RDS CALs
- In RD Licensing Manager, right-click the server and select Install licenses, then Next.
- Choose the licence program stated in your order email (for example License Pack (Retail Purchase) for a 25-character key) and select Next.
- Enter the licence code or agreement details from your order email.
- Select the product version (for example Windows Server 2025), the licence type (Per User or Per Device) and the quantity.
- Select Next. The wizard contacts the Microsoft Clearinghouse and installs the CALs. Select Finish.
Full details are in Microsoft's Install RDS client access licenses article.
Part 4: Set the licensing mode on the session host
The session host must use the same mode as your CALs and know where the licence server is.
- With an RDS deployment: Server Manager → Remote Desktop Services → Overview → Tasks → Edit Deployment Properties → RD Licensing. Choose Per User or Per Device and add the licence server.
-
Without a deployment (single server): run
gpedit.mscand open Computer Configuration → Administrative Templates → Windows Components → Remote Desktop Services → Remote Desktop Session Host → Licensing. Enable Use the specified Remote Desktop license servers (enter the server name) and Set the Remote Desktop licensing mode (Per User or Per Device).
Run RD Licensing Diagnoser (Server Manager → Tools → Remote Desktop Services) to confirm there are no warnings. See Microsoft's licensing session hosts page for more.
Troubleshooting
| Problem | Fix |
|---|---|
| "The remote session was disconnected because there are no Remote Desktop client access licenses available" | The licensing mode or licence server isn't set, or the mode doesn't match your CAL type. Check Part 4 and run RD Licensing Diagnoser. |
| Grace period warning | RDS works for 120 days without CALs. Install your CALs and set the licence server before it ends. |
| Licence code rejected | Pick the licence program stated in your order email, and check the product version matches your CALs. |
| Per User CALs show "issued: 0" | Normal in a workgroup. Per User CAL tracking needs Active Directory, but connections still work. |
Still stuck? Reply to your order email with a screenshot of RD Licensing Diagnoser.
Frequently asked questions
Per User or Per Device: which should I choose?
Choose Per User if people connect from several devices (laptop, home PC, phone). Choose Per Device when several shift workers share the same computers.
Can I use 2025 RDS CALs with a 2022 server?
Yes. Newer CALs cover older servers, but older CALs don't cover newer servers. The licence server itself must run the same or a newer Windows Server version as the CALs.
Do I need CALs with Windows Server Essentials?
No Windows Server CALs are needed for Essentials, which is limited to 25 users and 50 devices.
Useful links
| Link | What it's for |
|---|---|
| Install RDS CALs (Microsoft) | Official RD Licensing steps |
| Activate the licence server (Microsoft) | Licence server activation |
| RDS User CAL 5-pack | Buy RDS CALs |
| Windows Server install guide | Installing and activating the server |