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Frequently Asked Questions[edit]


How does Looking Glass work?[edit]

Please see the following video that covers this:


Why is my UPS (Updates Per Second) so low?[edit]

There are several reasons why this can happen, the most common is your capture resolution. At the time of this writing, the windows capture methods struggle to capture high resolutions under certain circumstances, as a general rule of thumb anything greater then 1200p (1920x1200) starts to suffer from performance issues.

Another cause can be how the game or application you are running is configured. Because of the way windows integrate with the WDM (Windows Desktop Manager) running applications in "Full Screen" mode may in some cases cause a large performance penalty. Try switching to windowed full-screen mode, the difference in performance can be like night and day. Titles known to be affected by this are Fallout76, The BattleField Series and SCUM.

Some titles do some strange things at early initialization that cause capture performance issues. One such title is the Unigine Valley benchmark where the capture rate is limited to 1/2 the actual rate. For an unknown reason to both myself and the Unigine developers a simple task switch (alt+tab) in and out resolves the issue. This is not a Looking Glass bug.

Is my GPU supported?[edit]

Your guest GPU almost certainly supports DXGI. Use DxDiag to confirm that you have support for WDDM 1.2 or greater.

The server-side (guest) probing error "Capture is not possible, unsupported device or driver" indicates NVidia duplication has failed, not that DXGI has failed. You can make the error go away by specifying "-c DXGI"

Why do I need Spice if I don't want a Spice display device?[edit]

You don't need Display Spice enabled. Looking Glass has a Spice client built in to provide some conveniences, but you can disable it with the "-s" argument.

Note that without Spice, you will not be sending mouse/keyboard events to the guest.

Where is the host application for Linux?[edit]

The "Windows host application" is actually the display server, which runs in the guest VM. The only thing that needs to run in your Linux host OS is the `looking-glass-client` application


The mouse doesn't stay aligned with the host.[edit]

This is due to windows mouse acceleration, it can be disabled with the following registry magic: http://donewmouseaccel.blogspot.com.au/2010/03/markc-windows-7-mouse-acceleration-fix.html

Contrary to the title this works just fine on Windows 10

Some other things to try:

  • Have you tried pressing Scroll Lock to toggle mouse capture mode?
  • Try keeping the client window the same size as the guest's resolution.

The cursor position doesn't update until I click[edit]

Make sure you have removed the Virtual Tablet Device from the Virtual Machine. Due to the design of windows absolute pointing devices break applications/games that require cursor capture and as such Looking Glass does not support them.


Looking Glass does not handle audio at all, nor will it ever. If you're having audio problems please look to Qemu for help.


The Windows Logon Screen, Shutdown, UAC Dialogs, Ctrl+Alt+Del, LockScreen do not work.[edit]

These screens are on the "Secure Desktop", Microsoft has intentionally limited access to capture this screen to prevent malware attempting to capture information from these screens that might be sensitive. There is little we can do here unless Microsoft are willing to let us sign the host application as an 'Accessibility' program.

Users of NVIDIA cards that support the NVidia Capture API (Quadro, Tesla, etc) will find this limitation only applies to the Windows Logon Screen and Shutdown Screens, the NvFBC capture API is able to capture the "Secure Desktop" outside of Microsoft's control.

The Windows host program doesn't work as a service[edit]

As of Windows Vista, Microsoft deprecated the ability for services to interact with the user's desktop, and as of Windows 10 this is enforced. There is nothing we can do about this.

Please see Windows Host Application for how to setup a scheduled task to launch the application at login.

NvFBC (NVIDIA Capture API) doesn't work[edit]

Unfortunately, NVIDIA deemed fit to only allow owners of "Professional Cards", and their own software (ShadowPlay) the right to use the NVIDIA Capture API. There is little we can do about this other than to complain to NVIDIA.