The primary registry keys for managing Remote Desktop Services (RDS) Client Access Licenses (CALs) are used to configure the licensing mode and specify the license server. Core RDS Licensing Registry Keys Licensing Mode : Defines "Per User" ( ) or "Per Device" ( ) settings.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\Licensing Core Specified License Server : Defines the server(s) issuing CALs.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TermService\Parameters\LicenseServers\SpecifiedLicenseServers Policy-Based Settings : Configures licensing via GPO.
HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services Microsoft Learn License Remote Desktop session hosts | Microsoft Learn
Remote Desktop Services (RDS) Client Access License (CAL) system does not use a single "registry key" as a serial number. Instead, the registry is primarily used to manage the licensing mode , identify license servers , or reset the grace period 1. The "Grace Period" Registry Key
The most commonly referenced registry key regarding RDS licensing is the one that tracks the 120-day grace period. Once this period ends, users can no longer connect without a valid CAL.
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\GracePeriod The "Timebomb"
: Inside this key, there is typically a binary entry starting with L$RTMTIMEBOMB
. Deleting this entry resets the 120-day timer, though this requires taking ownership of the registry folder first.
: This is usually a temporary fix for administrators to restore connectivity while they troubleshoot or wait for license procurement. 2. Configuring the Licensing Mode
If your server is failing to recognize installed licenses, it may be because the Licensing Mode
(Per User vs. Per Device) is not correctly set in the registry. Microsoft Learn
The registry keys for Remote Desktop Services (RDS) Client Access Licenses (CALs) differ depending on whether you are configuring the session host, managing the licensing server, or troubleshooting a client device. 1. Configure Licensing Mode and Server
These keys are used on the RD Session Host to specify how it finds and communicates with the license server. Group Policy-Defined Settings:
Registry Path: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows NT\Terminal Services Value: LicensingMode (DWORD) 2 = Per Device 4 = Per User
Value: LicenseServers (String) — The FQDN of your license server. Local/Manual Configuration:
Registry Path: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\Licensing Core Value: LicensingMode (DWORD) — Same values as above.
License Server Path: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TermService\Parameters\LicenseServers
Value: SpecifiedLicenseServers (Multi-String) — Contains the list of license servers. 2. Reset RDS Grace Period rds cal license registry key
If your 120-day evaluation period has expired and you need to reset it for testing, you must delete the "Timebomb" key.
Registry Path: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\GracePeriod
Action: Delete the L$RTMTIMEBOMB... binary value. Note that you must take ownership of the GracePeriod folder to delete this entry. 3. Clear Client-Side Licensing Errors
If a client PC receives a "licensing protocol" error, deleting the local license cache often forces a fresh request. Guidance for troubleshooting RDS Licensing - Windows Server
If you've spent any time managing Windows Servers, you know the Remote Desktop Services (RDS) licensing process can be a headache. The RDS CAL License registry keys are the "hidden gears" that keep remote connections running—or bring them to a grinding halt. 🛠️ The "Big Three" Registry Keys
While most admins use Group Policy, the registry is where the real configuration lives. The Mode Selector (LicensingMode):
Path: HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\Licensing Core
The Secret Code: Setting this to 2 tells the server to look for Per Device CALs; setting it to 4 switches it to Per User. The Address Book (SpecifiedLicenseServers):
Path: HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\LicenseServers
Purpose: This tells your Session Host exactly which server is holding the "tickets" (licenses). Without this, your server is essentially shouting into a void. The Infamous "Time Bomb" (L$RTMTIMEBOMB):
Path: HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\GracePeriod
The Catch: This key tracks the 120-day grace period. If it expires, users get kicked out. Many admins in lab environments delete this key to "reset" the clock, though Microsoft warns this isn't for production use. 🚦 Pro-Tip: When to Use Them
Registry edits are usually a "last resort" for troubleshooting RDS licensing. Use them if:
Group Policy isn't applying correctly (check with gpresult /H).
You're working on a Workgroup server where Group Policy isn't available.
The RD Licensing Diagnoser shows a "No license server available" error despite correct settings.
⚠️ Warning: Always back up your registry before diving in. Deleting the wrong subkey in Terminal Server can lead to a full OS reinstallation.
Here is text related to "RDS CAL license registry key," broken down by context. This includes technical locations, troubleshooting advice, and important warnings. The primary registry keys for managing Remote Desktop
Once your RDS host obtains a CAL from a license server, it stores the token locally to avoid re-querying the license server for every user connection. This data resides under:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\LicensingCore\IssuedLicenses
Manipulating this key can resolve “blacklisted” or corrupted CAL entries.
Symptom: RDS session host shows “Per User” mode, but users get a temporary license expiration warning.
Check:
LicensingMode = 4 (Per User).Cause: Per User CALs are not auto-applied — they require tracking in AD or manual installation. Registry only stores the mode preference.
Fix: Ensure Per User CALs are actually installed on the license server (RD Licensing Manager → Install Licenses).
| Aspect | Detail |
|--------|--------|
| Per‑User CAL tracking | Not fully stored in registry – uses AD or local DB (LSERVER\edb.log) |
| Registry editing | Not supported for daily license management; use RD Licensing Manager |
| Manual license entry | Do NOT manually add CALs via registry – use licmgr.exe or Import-LicensingPack |
| Temp licenses | Stored in same LicenseKeyStore with expiration set |
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM.RCM and select Export..reg file to a safe location.If you want, I can produce:
Managing RDS Client Access Licenses (CALs) via the registry is often necessary when Group Policy or the Server Manager GUI fails to apply settings correctly. You can configure the licensing mode and the license server address directly through the Registry Editor. 1. Configure the RDS Licensing Mode
This registry key tells the RD Session Host whether to look for Per User or Per Device CALs.
Registry Path: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\Licensing Core
Action: Locate or create a DWORD (32-bit) value named LicensingMode. Values: 2 — Per Device mode. 4 — Per User mode. 2. Specify the RD License Server
If your Session Host cannot find the license server, you can manually point to it using the registry.
Registry Path: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TermService\Parameters\LicenseServers
Action: Create a new Key (folder) under LicenseServers named with the FQDN or IP Address of your license server.
Note: You can also use the Microsoft Learn guide to verify if the server is properly configured via PowerShell as an alternative to registry edits. 3. Clear Cached Grace Period (Troubleshooting)
If you are seeing "The Remote Desktop trial period has expired" even after installing licenses, you may need to delete the cached grace period key to force a refresh.
Registry Path: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\GracePeriod
Action: You must first take ownership and grant yourself "Full Control" permissions for this key. Once done, delete the L$RTMTIMEB... binary value inside.
Reboot: A restart is required for this change to take effect and for the server to reach out to the specified license server. 4. Verify Activation When to Contact Support
After making registry changes, use the RD Licensing Manager tool to confirm the server status.
Open Server Manager > Tools > Remote Desktop Services > Remote Desktop Licensing Manager.
The server should show a green checkmark if it is activated and communicating correctly. License Remote Desktop session hosts | Microsoft Learn
The primary registry keys for managing Remote Desktop Services (RDS) Client Access Licenses (CALs) are used to configure the licensing mode, specify license servers, or troubleshoot the 120-day grace period. 1. Core Licensing Configuration
Located at HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\Licensing Core, the LicensingMode DWORD sets the mode (2 for Device, 4 for User). License servers are specified under HKLM\SYSTEM\CurrentControlSet\Services\TermService\Parameters\LicenseServers. 2. Group Policy and Troubleshooting License Remote Desktop session hosts | Microsoft Learn
In the fluorescent-lit hum of the Server Room, a junior admin named Leo stared at a flickering monitor. It was 4:45 PM on a Friday. He was trying to get a new Remote Desktop Session (RDS) host online, but every user who tried to log in was met with a cold, digital wall: “The remote session was disconnected because there are no Remote Desktop License Servers available.”
Leo had installed the licenses. He had activated the server. Yet, the server was acting like it had amnesia.
"It’s the registry," whispered Sarah, the senior lead, appearing like a ghost behind him. "The server is looking for a map it can't find."
She leaned over and opened regedit. They dove into the belly of the machine, navigating the hive:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\Licensing Core
"Look here," she pointed to the LicensingMode key. "It’s set to 5. That’s the ghost code. It doesn't know if it wants Per User or Per Device."
With a few keystrokes, they flipped the value to 4 (Per User). But the beast still wouldn't budge. Sarah knew they had to clear the "Grace Period" debris—the digital cobwebs left behind from when the server was free and young.
They navigated to:HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\GracePeriod "The gatekeeper key," Leo muttered.
Windows didn't want them there. It protected that key with ironclad permissions. Sarah right-clicked, seized Ownership from the SYSTEM, and granted herself full control. With a final, decisive click, she deleted the binary blob sitting inside. "Now," Sarah said, "give it a heartbeat."
Leo restarted the services. The progress bar crawled. He held his breath and tried a test login. Instead of an error, the desktop bloomed into view—icons, taskbars, and all. The registry key had been turned, the lock had clicked, and the users were finally home.
Here’s a technical review covering the RDS CAL license registry key in Windows Server, focusing on its purpose, location, typical use cases, risks, and best practices.
A common administrative task involving the registry is resetting the RDS Grace Period. When a Remote Desktop Session Host is activated, it enters a grace period (usually 120 days) before it requires CALs. If this period expires and you are troubleshooting license installation, you may need to reset this timer.
Registry Key Location:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\RCM\GracePeriod
Procedure:
To reset this, an administrator must delete the GracePeriod key. However, Windows protects this key with specific permissions.
regedit.GracePeriod key and select Permissions.GracePeriod key (it will be a long binary string).