HDX features managed through the registry

Note:

Editing the registry incorrectly can cause serious problems that might require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of the Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.

To open the Registry Editor, run regedit.exe on the server. Then navigate to the registry key to add or edit the settings.

Devices

Bloomberg keyboards

Citrix Virtual Apps and Desktops support the Bloomberg model 4 and model 3 starboard keyboard. By default, the support for the enhanced Bloomberg keyboard is disabled.

To enable support for the Bloomberg keyboard, set the following registry value on the client machine before you start a connection:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ICAClient\GenericUSB
• Value name: EnableBloombergHID
• Value type: DWORD
• Value data: 0 = Disable, 1 = Enable

For more information, see Bloomberg keyboard.

Mapped client drives

As a security precaution, when a user logs in to Citrix Virtual Apps and Desktops, by default, the server maps client drives without user run permission. To enable users to run executable files residing on mapped client drives, override this default by editing the registry on the server.

To allow access, edit the following registry value (create CDMSettings if it doesn’t exist):

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Citrix\CDMSettings
• Value name: ExecuteFromMappedDrive
• Value type: DWORD
• Value data: 1 = Allow permission, 0 = Deny permission on mapped drives

The change takes effect for sessions connected after you edit the registry.

Citrix Virtual Apps and Desktops 7 2006 is the first version to contain this registry location. Earlier versions of Citrix Virtual Apps and Desktops used a different registry location.

For more information, see Client Drive Mapping.

Microsoft Surface Pro and Surface Book pens

Citrix Virtual Apps and Desktops support standard pen functionality with Windows Ink-based applications. By default, this feature is enabled.

To disable or enable this feature, set the following registry value:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\Citrix Virtual Desktop Agent\PenApi
• Value name: DisablePen
• Value type: DWORD
• Value data: 1 = Disable, 0 = Enable

For more information, see Microsoft Surface Pro and Surface Book pens.

Windows Image Acquisition application allow list

This setting lets you control which applications on the VDA can access the Windows Image Acquisition scanner redirection.

By default, no applications have access to Windows Image Acquisition.

To adjust Windows Image Acquisition for applications on the VDA, create the following registry setting:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix

• Value name: WIAAllowedProcesses

  Select and right-click WIAAllowedProcesses. Choose New > Multi-String Value and rename the new value to AllowProcesses.

• Value data: Enter the full path and process name for each application that can access Windows Image Acquisition. Provide each application on a new line.

Any changes to this setting take effect the next time you launch a session on the VDA.

General

Configure Rendezvous version

To configure the version of Rendezvous to use, set the following:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\VirtualDesktopAgent
• Value type: DWORD
• Value name: GctRegistration

• Value data:

  • 1 - To enable V2
  • 0 - To enable V1

Configure automatic logon to the VDA

This setting lets you enable or disable the Always prompt for password Microsoft policy setting on the Windows 10 single-session OS and multi-session OS VDAs.

If Always prompt for password is enabled, users must enter credentials on the VDA when they start a remote session. If this setting is disabled, users automatically connect to the remote session without providing credentials on the VDA.

By default, the Microsoft policy setting is disabled. To enable or disable the Always prompt for password setting, set the following registry value on the VDA:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\Portica
• Value name: AutoLogon
• Value type: DWORD
• Value data:
  • 1 - Disables the Microsoft policy setting and lets users automatically sign in to a remote session.
  • 0 – Enables the Microsoft policy setting and prompts users to provide credentials when they launch a remote session.

Disable timeout warning

By default, users with inactive or idle sessions receive a warning message two minutes before their session automatically disconnects.

This setting disables and removes the warning message for users reaching the idle session timeout limit on the following:

• Windows Server 2004
• Windows 10 multi-session 2004 or later multi-session OS

To remove the warning, set the following registry value on the VDA:

• Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\Winstations\ICA-CGP
• Value name: fEnableTimeoutWarning
• Value type: DWORD
• Value data: 1 = Disable the warning message, 0 = Enable the warning message

To display the warning message, delete the registry value or set it to 0.

EDT MTU Discovery

MTU Discovery allows EDT to automatically determine the Maximum Transmission Unit (MTU) when establishing a session. Doing so prevents EDT packet fragmentation that might result in performance degradation or failure to establish a session.

This setting is enabled by default. To disable EDT MTU Discovery, configure the following registry value and restart the VDA.

• Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\Wds\icawd
• Value name: MtuDiscovery
• Value type: DWORD
• Value data: 0

This setting is machine-wide and affects all sessions connecting from a supported client.

Enable loss tolerant mode

You can access adaptive audio using the loss tolerant mode for bidirectional audio service for Citrix Workspace app for Windows, Multi-user VDA, and Desktop VDA. This setting is disabled by default. To enable loss tolerant mode, depending on the machine you are using, configure the following registry value and restart the respective machine.

For Citrix Workspace app for Windows client,

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\ClientAudio
• Value name: EdtUnreliableAllowed
• Value type: REG_SZ
• Value data: 1

For TS VDA,

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Citrix\Audio
• Value name: EdtUnreliableAllowed
• Value type: DWORD
• Value data: 1

For WS VDA,

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\Audio
• Value name: EdtUnreliableAllowed
• Value type: DWORD
• Value data: 1

General content redirection

Add URL types for host to client redirection

By default, we support redirection of the following URL types: HTTP, HTTPS, RTSP, RTSPU, PNM, and MMS. You can add URL types to the list by creating the following registry key and values on the Windows client.

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Policies\Citrix\ICA Client\SFTA
• Value name: ExtraURLProtocols
• Value type: REG_SZ
• Value data: Specify the required URL types separated by semicolon. Include everything before the authority portion of the URL. For example: ftp://;mailto:;customtype1://;custometype2://

You can add URL types only for Windows clients. Clients missing this registry setting reject redirection back to the Citrix session. The client must have an application installed and configured to handle the specified URL types.

For more information, see Host to client redirection.

Client folder redirection

Client folder redirection changes the way client-side files are accessible on the host-side session. Consider that you enable client folder redirection on the server and the user configures it on the user device. In this case, the portion of the local volume specified by the user is redirected.

To enable client folder redirection on the server, set the following registry value:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\Client Folder Redirection
• Value name: CFROnlyModeAvailable
• Value type: DWORD
• Value data: 1

For more information, see Client folder redirection.

Host to client redirection for a specific set of websites

To enable host to client redirection for a specific set of websites, set the following registry value on the server VDA.

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\SFTA
• Value name: ValidSites
• Value type: REG_MULTI_SZ
• Value data: Specify any combination of fully qualified domain names (FQDNs). Type multiple FQDNs on separate lines. Include the FQDN only, without protocols (http:// or https://). An FQDN can include an asterisk (*) as a wildcard character in the leftmost position only. This wildcard matches a single level of domain, which is consistent with the rules in RFC 6125. For example:

www.example.com

*.example.com

For more information, see Host to client redirection.

Local application behavior on logoff and disconnect

By default, local applications continue to run when a user logs off or disconnects from the virtual desktop. After reconnection, local applications are reintegrated if they are available on the virtual desktop. To configure local application behavior on logoff and disconnect, set the following registry value in the hosted desktop:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\wow6432node\Citrix\Client Hosted Apps\Policies
• Value name: Session State
• Value type: DWORD
• Value data:
  • 1 - Local applications continue to run when a user logs off or disconnects from the virtual desktop. Upon reconnection, local applications are reintegrated if they are available in the virtual desktop.
  • 3 - Local applications close when a user logs off or disconnects from the virtual desktop.

For more information, see Local App Access and URL redirection.

Remove URL types from the default list for host to client redirection

To remove URL types from the default redirection list, create the following registry key and values on the server VDA.

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\SFTA

• Value name: DisableServerFTA
• Value type: DWORD

• Value data: 1

• Value name: NoRedirectClasses
• Value type: REG_MULTI_SZ
• Value data: Specify any combination of the values: http, https, rtsp, rtspu, pnm, or mms. Type multiple values on separate lines. For example:

http

https

rtsp

For more information, see Host to client redirection.

Server VDA default browser configuration

You can enable host to client redirection to supersede any default browser configuration on the Server VDA. If a web URL is not redirected, the Citrix launcher passes the URL to the browser configured in the command_backup registry key. The key points to Internet Explorer by default, but you can modify it to include the path to a different browser.

• Internet Explorer (Default)

  • Key: HKEY_CLASSES_ROOT\http\shell\open\command_backup
  • Value name: Default
  • Value type: REG_SZ

  • Value data: "c:\program files\internet explorer\iexplore.exe" "%1"

  • Key: HKEY_CLASSES_ROOT\https\shell\open\command_backup`
  • Value name: Default
  • Value type: REG_SZ
  • Value data: "c:\program files\internet explorer\iexplore.exe" "%1"

• Google Chrome

  • Key: HKEY_CLASSES_ROOT\http\shell\open\command_backup
  • Value name: Default
  • Value type: REG_SZ

  • Value data: "C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" "%1"

  • Key: HKEY_CLASSES_ROOT\https\shell\open\command_backup
  • Value name: Default
  • Value type: REG_SZ
  • Value data: "C:\Program Files (x86)\Google\Chrome\Application\chrome.exe" "%1"

• Microsoft Edge

  • Key: HKEY_CLASSES_ROOT\http\shell\open\command_backup
  • Value name: Default
  • Value type: REG_SZ

  • Value data: "C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe" "%1"

  • Key: HKEY_CLASSES_ROOT\https\shell\open\command_backup
  • Value name: Default
  • Value type: REG_SZ
  • Value data: "C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe" "%1"

The Local App Access for published applications

Local App Access seamlessly integrates locally installed Windows applications into a hosted desktop environment without switching from one desktop to another. To provide access to published applications, set the following registry value on the server:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\DesktopStudio
• Value name: ClientHostedAppsEnabled
• Value type: DWORD
• Value data: 1 = Enable, 0 = Disable

For more information, see Local App Access and URL redirection.

Graphics

GPU acceleration for CUDA or OpenCL applications

GPU acceleration of CUDA and OpenCL applications running in a user session is disabled by default.

To use the CUDA acceleration POC features, enable the following registry setting:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\CtxHook\AppInit_Dlls\Graphics Helper
• Value name: CUDA
• Value type: DWORD
• Value data: 00000001

To use the OpenCL acceleration POC features, enable the following registry setting:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\CtxHook\AppInit_Dlls\Graphics Helper
• Value name: OpenCL
• Value type: DWORD
• Value data: 00000001

For more information, see GPU acceleration for Windows multi-session OS

Progressive mode

Progressive mode is disabled by default. You can change the progressive mode state with the following registry value:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\Graphics
• Value type: REG_DWORD
• Value name: ProgressiveDisplay
• Value data:
  • 0 = Always off (Disables progressive mode. This value is the default.)
  • 1 = Automatic (Toggle based on network conditions.)
  • 2 = Always on

For more information, see Progressive mode.

Note:

Progressive mode has been deprecated. Thinwire is an alternative option that optimizes image delivery and maintains cache efficiency while providing nearly all of the benefits of the progressive mode.

Windows Presentation Foundation (WPF) rendering

HDX 3D Pro allows graphics-heavy applications running in Windows Multi-session OS sessions to render on the server’s graphics processing unit (GPU). By moving Windows Presentation Foundation (WPF) rendering to the server’s GPU, graphics rendering does not slow the server’s CPU.

To enable WPF application rendering using the server’s GPU, create the following setting in the registry of the server running Windows multi-session OS:

1. Open the Registry Editor on the VDA and navigate to the following key:

   HKLM\Software\Citrix\CtxHook\AppInit_DLLs\Graphics Helper

2. Create or edit the following registry values:

   • [REG_DWORD] AdapterHandle = 0x00000001
   • [REG_DWORD] DevicePath = 0x00000001
   • [REG_DWORD] Flag = 0x00000412
   • [REG_DWORD] WPF = 0x00000001

3. Create a sub-key with the executable name of your WPF app. For example, if your app is called “mywpfapp.exe”, create the following key:

   HKLM\Software\Citrix\CtxHook\AppInit_DLLs\Graphics Helper\mywpfapp.exe

4. Reboot the server for the setting to take effect.

For more information, see GPU acceleration for Windows multi-session OS and the blog on Getting the best out of WPF apps on Windows multi-session OS.

Multimedia

Avoid echo during multimedia conferences

Citrix Virtual Apps and Desktops provide an echo cancellation option that minimizes any echo. This feature is enabled by default. To disable echo cancellation, you can change one of the following registry settings:

• Key:
  • 32-bit: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\ClientAudio
  • 64-bit: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\ICA Client\Engine\Configuration\Advanced\Modules\ClientAudio
• Value name: EchoCancellation
• Value type: String/REG_SZ
• Value data: False

For more information, see Audio features.

Audio limitation

After you install an audio device on your client, enable the audio redirection, and start an RDS session, the audio files might not play audio. As a workaround, add the following registry key on the RDS machine and then restart the machine:

• Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SCMConfig
• Value name: EnableSvchostMitigationPolicy
• Value type: DWORD
• Value data: 0

For more information, see Audio features.

Browser content redirection and DPI

When using browser content redirection with the DPI (scaling) set to anything over 100% on the user’s machine, the redirected browser content screen is incorrectly displayed. To avoid the issue, disable browser content redirection GPU acceleration for Chrome by creating the following registry value on the user’s machine:

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Citrix\HdxMediaStream
• Value name: GPU
• Value type: DWORD
• Value data: 0

For more information, see Browser content redirection and DPI.

High-definition webcam resolution

If the media type negotiation fails, HDX falls back to the default VGA resolution (640 x 480 pixels). You can use registry keys on the client to configure the default resolution. Before setting the following registry keys, ensure that the camera supports the specified resolution.

• Key: HKEY_CURRENT_USER\SOFTWARE\Citrix\HDXRealTime
• Width
  • Value name: DefaultWidth
  • Value type: DWORD
  • Value data: desired width in decimal (for example 1280)
• Height
  • Value name: DefaultHeight
  • Value type: DWORD
  • Value data: desired height in decimal (for example 720)

Microsoft Teams fallback mode

If Microsoft Teams fails to load in optimized VDI mode (“Citrix HDX Not Connected” in Teams/About/Version), the VDA falls back to legacy HDX technologies, such as webcam redirection and client audio and microphone redirection. If you are using a Workspace app version/platform OS that does not support Microsoft Teams optimization, fallback registry keys do not apply.

To control the fallback mechanism, set one of the following registry values on the VDA:

• Key (only one needed):
  • Computer setting: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Teams
  • User setting: HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\Teams
• Value name: DisableFallback
• Value type: DWORD
• Value data: 1 = Disable fallback mode, 2 = Enable audio only

If the value isn’t present or is set to 0, fallback mode is enabled. This feature requires Microsoft Teams version 1.3.0.13565 or later. For more information, see Optimization for Microsoft Teams.

Optimization for Microsoft Teams with Citrix App Layering

If using Citrix App Layering to manage VDA and Microsoft Teams installations in different layers, create an empty registry key named PortICA on Windows before installing Microsoft Teams with the ALLUSER=1 flag from the command line. Leave the default value name, type, and data.

• Key for 32-bit Version of Registry Editor: HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Citrix\PortICA
• Key for 64-bit Version of Registry Editor: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\PortICA

For more information, see Optimization for Microsoft Teams.

Single sign-on with Integrated Windows Authentication for browser content redirection

This setting provides single sign-on to a web server configured with Integrated Windows Authentication (IWA) within the same domain as the VDA. To enable single sign-on, set the following registry value to 1:

• Key:

  • HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\HdxMediastream

  or

  • HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Citrix\HdxMediastream
• Value name: WebBrowserRedirectionIwaSupport
• Value type: DWORD
• Value data: 1

For more information, see Single sign-on with Integrated Windows Authentication.

User-agent request header

The user-agent header helps identify HTTP requests sent from browser content redirection. This setting can be useful when you configure the proxy and firewall rules. For example, if the server blocks the requests sent from browser content redirection, you can create a rule that contains the user-agent header to bypass certain requirements. Only Windows devices support the user-agent request header.

By default, the user-agent request header string is disabled. To enable the user-agent header for client-rendered content, use the Registry editor.

On each Citrix Workspace app for Windows client, set one of the following registry settings:

• Key:
  • 32-bit: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\HdxMediaStream
  • 64-bit: HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Citrix\HdxMediaStream
• Value name: EnableCefUserAgentString
• Value type: DWORD
• Value data: 1

After you add the registry value, the user-agent header contains the CitrixBCR/2102.1 text, where 2102.1 is the Citrix Workspace app for Windows version.

Webcam software compression

If a webcam supports hardware encoding, HDX video compression uses the hardware encoding by default. Hardware encoding might consume more bandwidth than software encoding. To force software compression, add the following value on the client:

• Key: HKEY_CURRENT_USER\SOFTWARE\Citrix\HdxRealTime
• Value name: DeepCompress_ForceSWEncode
• Value type: DWORD
• Value data: 1

For more information, see HDX webcam video compression.

Webcam video compression

HDX webcam video compression sends the H.264 video directly to the video conferencing application running in the virtual session. To optimize VDA resources, HDX webcam compression doesn’t encode, transcode, and decode webcam video. This feature is enabled by default.

To disable direct video streaming from the server to the video conferencing app, set the following registry value in the VDA.

• Key: HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\HdxRealTime
• Value name: OfferH264ToApp
• Value type: DWORD
• Value data: 0

For more information, see HDX webcam video compression.

Webcam video compression frame rate

To adjust the preferred video frame rate, edit the following registry value on the client:

• Key: HKEY_CURRENT_USER\SOFTWARE\Citrix\HDXRealTime
• Value name: FramesPerSecond
• Value type: DWORD
• Value data: 15

If the webcam doesn’t support the specified frame rate, the application uses 15 FPS by default.

For more information, see HDX webcam video compression.