If more than two people need to use a Windows Server through Remote Desktop at the same time (or non-administrators use it as a desktop), you enter the world of Remote Desktop Services (RDS) Client Access Licences (CALs). They’re separate from the Windows Server licence itself. Here’s what they are, which type to buy, and how to install them.

Licensing rules are set by Microsoft and change over time. Confirm details with Microsoft or your licence reseller before buying.

When do you need RDS CALs?

Scenario RDS CALs needed?
Up to 2 admins managing the server (“Remote Desktop for Administration”) No
More than 2 concurrent sessions Yes (RD Session Host role + CALs)
Users working in desktop apps on the server (shared desktop) Yes
Published RemoteApp programs Yes
Each person has their own separate Windows VPS, used by them only Not for RDS (each server’s own licence applies)

You also need a Windows Server CAL for users or devices accessing the server, in many scenarios. RDS CALs are in addition to those. Ask your reseller what applies to your setup.

Per User vs Per Device

Per User Per Device
Covers One named user, from any number of devices One device, used by any number of users
Best for People who connect from laptop, phone and home PC Shared workstations, kiosks, shift work
Tracking Assigned to users (needs Active Directory for enforcement/reporting) Issued to devices, and enforced by the licensing server

Most small teams connecting to a VPS from their own devices choose Per User.

Note: Per-User CALs in a workgroup (non-domain) server can’t be tracked by the licensing server, but you still need enough CALs to stay compliant.

Setting up RD Licensing (single server)

  1. Install roles: Server Manager → Add Roles → Remote Desktop Services → Remote Desktop Session Host and Remote Desktop Licensing (or use the RDS Quick Start deployment on a domain).
  2. Activate the licence server: open RD Licensing Manager (licmgr.exe) → right-click the server → Activate Server (automatic over the internet).
  3. Install CALs: right-click → Install Licenses, choose the agreement type (retail, Open, volume…), and enter the codes.
  4. Point the Session Host at the licence server, and set the mode (Per User / Per Device). Via Group Policy:

Computer Configuration → Administrative Templates → Windows Components → Remote Desktop Services → Remote Desktop Session Host → Licensing

  • “Use the specified Remote Desktop license servers” → the server’s name
  • “Set the Remote Desktop licensing mode” → Per User or Per Device
  1. Check with RD Licensing Diagnoser (lsdiag.msc). It should show no errors.

The grace period

After the Session Host role is installed, RDS works without CALs for a grace period (typically 120 days). After that, connections beyond the administrative allowance fail with licensing errors. Don’t rely on the grace period for production.

Common errors

Message Cause
“The remote session was disconnected because there are no Remote Desktop License Servers available” Grace period ended; licensing server not configured or not reachable
“No Remote Desktop client access licenses available” All Per-Device CALs issued; or wrong licensing mode
Licensing Diagnoser: “licensing mode not configured” Set the mode in Group Policy
CAL version mismatch CALs must match or exceed the Windows Server version of the Session Host

Cost-saving alternatives

  • One Windows VPS per user (common for traders): each user has full use of their own server, without shared RDS. See Windows VPS and forex VPS.
  • Web-based apps instead of desktop apps on a shared server.
  • Two-admin limit may simply be enough. See RDP multiple sessions.

Quick reference

Item Notes
Free admin sessions 2
More users RD Session Host + RDS CALs
CAL types Per User / Per Device
Tools RD Licensing Manager, Licensing Diagnoser
Grace period ~120 days, then CALs required

Related: Windows Server activation and Windows Server users and groups.

  • RDP
  • Windows Server
  • Licensing