Client usage

looking-glass-client [--help] [-f] [-F] [-s] [-S] [options...]

Command line options

A full list of command line options is available with the --help or -h options.

Example: looking-glass-client --help

Common options are listed below:

Short option


-f shmFile

use shmFile for IVSHMEM shared memory


automatically enter full screen


disable spice


disable host screensaver

Options may be provided in short form when available, or long form. Boolean options may be specified without a parameter to toggle their state.


  • looking-glass-client -F (short)

  • looking-glass-client win:fullScreen (long)

  • looking-glass-client -f /dev/shm/my-lg-shmem (short with parameter)

  • looking-glass-client app:shmFile=/dev/shm/my-lg-shmem (long with parameter)

Default key bindings

By default, Looking Glass uses the ScrLk key as the escape key for commands, as well as the input capture mode toggle; this can be changed using the -m switch if you desire a different key. Below are a list of current key bindings:




Toggle capture mode

ScrLk + Q


ScrLk + E

Toggle audio recording

ScrLk + R

Rotate the output clockwise by 90° increments

ScrLk + T

Show frame timing information

ScrLk + I

Spice keyboard & mouse enable toggle

ScrLk + O

Toggle overlay

ScrLk + D

FPS display toggle

ScrLk + F

Full screen toggle

ScrLk + V

Video stream toggle

ScrLk + N

Toggle night vision mode

ScrLk + F1

Send Ctrl + Alt + F1 to the guest

ScrLk + F2

Send Ctrl + Alt + F2 to the guest

ScrLk + F3

Send Ctrl + Alt + F3 to the guest

ScrLk + F4

Send Ctrl + Alt + F4 to the guest

ScrLk + F5

Send Ctrl + Alt + F5 to the guest

ScrLk + F6

Send Ctrl + Alt + F6 to the guest

ScrLk + F7

Send Ctrl + Alt + F7 to the guest

ScrLk + F8

Send Ctrl + Alt + F8 to the guest

ScrLk + F9

Send Ctrl + Alt + F9 to the guest

ScrLk + F10

Send Ctrl + Alt + F10 to the guest

ScrLk + F11

Send Ctrl + Alt + F11 to the guest

ScrLk + F12

Send Ctrl + Alt + F12 to the guest

ScrLk + M

Send mute to the guest

ScrLk +

Send volume up to the guest

ScrLk +

Send volume down to the guest

ScrLk + Insert

Increase mouse sensitivity in capture mode

ScrLk + Del

Decrease mouse sensitivity in capture mode

ScrLk + LWin

Send LWin to the guest

ScrLk + RWin

Send RWin to the guest

You can also find this list at any time by holding down ScrLk.

Configuration files

By default, Looking Glass will load config files from the following locations:

  • /etc/looking-glass-client.ini

  • ~/.looking-glass-client.ini

  • $XDG_CONFIG_HOME/looking-glass/client.ini (usually ~/.config/looking-glass/client.ini)

All config files are loaded in order. Duplicate entries override earlier ones. This means you can set a system-wide configuration in /etc/looking-glass-client.ini, and override specific options for just your user in ~/.looking-glass-client.ini, which is overlayed on top of the system-wide configuration.

When first launched, the Looking-Glass client will create the folder $XDG_CONFIG_HOME/looking-glass/ if it does not yet exist.

The format of config files is the commonly known INI format, for example:



; this is a comment

Command line arguments will override any options loaded from config files.

Overlay mode

The Overlay Mode lets you configure various runtime options for Looking Glass. These include:

  • EGL filters

  • Performance metrics options

  • Debug frame damage display

(see Configuration widget)

You can also reposition and resize enabled widgets, like the FPS/UPS display, and performance metrics.

Enter and exit Overlay Mode with ScrLk + O. ESC can also be used to exit. (see Default key bindings)

Modifications done to widgets in overlay mode are stored in $XDG_CONFIG_HOME/looking-glass/imgui.ini. Please do not manually edit this file while Looking Glass is running, as your changes may be discarded.

Configuration widget

The configuration widget is accessible through the overlay mode. The widget has multiple tabs that allow setting a variety of modes and parameters for Looking Glass at runtime.

Settings tab

  • Performance Metrics: A toggle for the performance metrics widget. Multiple graphs are available, and they will stack vertically.

  • EGL: Modify EGL settings, such as the algorithm used for scaling, and night vision mode.

Changes in the settings tab are not persistent, and will be reset back to their default values when the client is restarted.

EGL filters tab

The EGL filters tab contains options for toggling, configuring, and ordering post-processing filters. Each filter can be expanded to open its settings. Filters can also be re-ordered by dragging them up or down. Filters are applied from top to bottom. Keep this in mind when ordering them – for example, applying CAS before FSR might have different results than the reverse. Users are encouraged to experiment with the order and parameters to achieve optimal results. The currently available filters include:

  • Downscaler: Filter for downscaling the host resolution. Can be used to undo poor upscaling on the VM to better utilize AMD FSR (see below). The filter has a pixel-size setting that is used to set the effective downscaling ratio, and a configurable interpolation algorithm.

  • AMD FidelityFX Super Resolution (FSR): Spatial upscaling filter that works on low resolution frames from the guest VM and intelligently upscales to a higher resolution. The filter sharpness is tunable, and displays the equivalent AMD quality mode based on the resolution difference.

  • AMD FidelityFX Contrast Adaptive Sharpening (CAS): Filter that increases visual quality by applying a sharpening algorithm to the video. CAS can sometimes restore detail lost in a typical upscaling application. Has adjustable sharpness setting.

The filter settings and order can be saved to presets so that it can be restored at a later time. As filter settings are usually application specific, multiple presets can be defined for each case scenario. To save a preset, click on “Save preset as…” and enter a preset name. Presets are loaded by selecting them in the Preset name pull down. Presets are persistent and are stored on disk at $XDG_CONFIG_HOME/looking-glass/presets.


Please refrain from modifying any files under the presets folder. Those files are meant to be modified only by the Looking-Glass client.


Although presets are persistent, the client will not remember which preset was used last session, so a preset needs to be recalled once the client starts.

All command line options

| Long                   | Short | Value                  | Description                                                                             |
| app:configFile         | -C    | NULL                   | A file to read additional configuration from                                            |
| app:renderer           | -g    | auto                   | Specify the renderer to use                                                             |
| app:license            | -l    | no                     | Show the license for this application and then terminate                                |
| app:cursorPollInterval |       | 1000                   | How often to check for a cursor update in microseconds                                  |
| app:framePollInterval  |       | 1000                   | How often to check for a frame update in microseconds                                   |
| app:allowDMA           |       | yes                    | Allow direct DMA transfers if supported (see `` in the `module` dir)           |
| app:shmFile            | -f    | /dev/shm/looking-glass | The path to the shared memory file, or the name of the kvmfr device to use, e.g. kvmfr0 |

| Long                    | Short | Value                  | Description                                                          |
| win:title               |       | Looking Glass (client) | The window title                                                     |
| win:position            |       | center                 | Initial window position at startup                                   |
| win:size                |       | 1024x768               | Initial window size at startup                                       |
| win:autoResize          | -a    | no                     | Auto resize the window to the guest                                  |
| win:allowResize         | -n    | yes                    | Allow the window to be manually resized                              |
| win:keepAspect          | -r    | yes                    | Maintain the correct aspect ratio                                    |
| win:forceAspect         |       | yes                    | Force the window to maintain the aspect ratio                        |
| win:dontUpscale         |       | no                     | Never try to upscale the window                                      |
| win:intUpscale          |       | no                     | Allow only integer upscaling                                         |
| win:shrinkOnUpscale     |       | no                     | Limit the window dimensions when dontUpscale is enabled              |
| win:borderless          | -d    | no                     | Borderless mode                                                      |
| win:fullScreen          | -F    | no                     | Launch in fullscreen borderless mode                                 |
| win:maximize            | -T    | no                     | Launch window maximized                                              |
| win:minimizeOnFocusLoss |       | no                     | Minimize window on focus loss                                        |
| win:fpsMin              | -K    | -1                     | Frame rate minimum (0 = disable - not recommended, -1 = auto detect) |
| win:ignoreQuit          | -Q    | no                     | Ignore requests to quit (i.e. Alt+F4)                                |
| win:noScreensaver       | -S    | no                     | Prevent the screensaver from starting                                |
| win:autoScreensaver     |       | no                     | Prevent the screensaver from starting when guest requests it         |
| win:alerts              | -q    | yes                    | Show on screen alert messages                                        |
| win:quickSplash         |       | no                     | Skip fading out the splash screen when a connection is established   |
| win:overlayDimsDesktop  |       | yes                    | Dim the desktop when in interactive overlay mode                     |
| win:rotate              |       | 0                      | Rotate the displayed image (0, 90, 180, 270)                         |
| win:uiFont              |       | DejaVu Sans Mono       | The font to use when rendering on-screen UI                           |
| win:uiSize              |       | 14                     | The font size to use when rendering on-screen UI                     |
| win:jitRender           |       | no                     | Enable just-in-time rendering                                        |
| win:showFPS             | -k    | no                     | Enable the FPS & UPS display                                         |

| Long                         | Short | Value               | Description                                                                      |
| input:grabKeyboard           | -G    | yes                 | Grab the keyboard in capture mode                                                |
| input:grabKeyboardOnFocus    |       | no                  | Grab the keyboard when focused                                                   |
| input:releaseKeysOnFocusLoss |       | yes                 | On focus loss, send key up events to guest for all held keys                     |
| input:escapeKey              | -m    | 70 = KEY_SCROLLLOCK | Specify the escape/menu key to use (use "help" to see valid values)              |
| input:ignoreWindowsKeys      |       | no                  | Do not pass events for the windows keys to the guest                             |
| input:hideCursor             | -M    | yes                 | Hide the local mouse cursor                                                      |
| input:mouseSens              |       | 0                   | Initial mouse sensitivity when in capture mode (-9 to 9)                         |
| input:mouseSmoothing         |       | yes                 | Apply simple mouse smoothing when rawMouse is not in use (helps reduce aliasing) |
| input:rawMouse               |       | no                  | Use RAW mouse input when in capture mode (good for gaming)                       |
| input:mouseRedraw            |       | yes                 | Mouse movements trigger redraws (ignores FPS minimum)                            |
| input:autoCapture            |       | no                  | Try to keep the mouse captured when needed                                       |
| input:captureOnly            |       | no                  | Only enable input via SPICE if in capture mode                                   |
| input:helpMenuDelay          |       | 200                 | Show help menu after holding down the escape key for this many milliseconds      |

| Long                   | Short | Value     | Description                                                         |
| spice:enable           | -s    | yes       | Enable the built in SPICE client for input and/or clipboard support |
| spice:host             | -c    | | The SPICE server host or UNIX socket                                |
| spice:port             | -p    | 5900      | The SPICE server port (0 = unix socket)                             |
| spice:input            |       | yes       | Use SPICE to send keyboard and mouse input events to the guest      |
| spice:clipboard        |       | yes       | Use SPICE to synchronize the clipboard contents with the guest      |
| spice:clipboardToVM    |       | yes       | Allow the clipboard to be synchronized TO the VM                    |
| spice:clipboardToLocal |       | yes       | Allow the clipboard to be synchronized FROM the VM                  |
| spice:audio            |       | yes       | Enable SPICE audio support                                          |
| spice:scaleCursor      | -j    | yes       | Scale cursor input position to screen size when up/down scaled      |
| spice:captureOnStart   |       | no        | Capture mouse and keyboard on start                                 |
| spice:alwaysShowCursor |       | no        | Always show host cursor                                             |
| spice:showCursorDot    |       | yes       | Use a "dot" cursor when the window does not have focus              |

| Long                   | Short | Value  | Description                                                                   |
| audio:periodSize       |       | 2048   | Requested audio device period size in samples                                 |
| audio:bufferLatency    |       | 13     | Additional buffer latency in milliseconds                                     |
| audio:micDefault       |       | prompt | Default action when an application opens the microphone (prompt, allow, deny) |
| audio:micShowIndicator |       | yes    | Display microphone usage indicator                                            |

| Long             | Short | Value | Description                                                               |
| egl:vsync        |       | no    | Enable vsync                                                              |
| egl:doubleBuffer |       | no    | Enable double buffering                                                   |
| egl:multisample  |       | yes   | Enable Multisampling                                                      |
| egl:nvGainMax    |       | 1     | The maximum night vision gain                                             |
| egl:nvGain       |       | 0     | The initial night vision gain at startup                                  |
| egl:cbMode       |       | 0     | Color Blind Mode (0 = Off, 1 = Protanope, 2 = Deuteranope, 3 = Tritanope) |
| egl:scale        |       | 0     | Set the scale algorithm (0 = auto, 1 = nearest, 2 = linear)               |
| egl:debug        |       | no    | Enable debug output                                                       |
| egl:noBufferAge  |       | no    | Disable partial rendering based on buffer age                             |
| egl:noSwapDamage |       | no    | Disable swapping with damage                                              |
| egl:scalePointer |       | yes   | Keep the pointer size 1:1 when downscaling                                |
| egl:preset       |       | NULL  | The initial filter preset to load                                         |

| Long                 | Short | Value | Description                                 |
| opengl:mipmap        |       | yes   | Enable mipmapping                           |
| opengl:vsync         |       | no    | Enable vsync                                |
| opengl:preventBuffer |       | yes   | Prevent the driver from buffering frames    |
| opengl:amdPinnedMem  |       | yes   | Use GL_AMD_pinned_memory if it is available |

| Long                  | Short | Value | Description             |
| wayland:warpSupport   |       | yes   | Enable cursor warping   |
| wayland:fractionScale |       | yes   | Enable fractional scale |

Host usage

By default the host application will simply work however there are some configurable options available. While the host application will accept command line arguments just as the client will it is more convenient to create the looking-glass-host.ini file with the desired configuration options.

This file must be placed in the same directory that the Looking Glass host application was installed for it to be found and used by the application

Capture interface


Currently we only provide support for the Windows host application, Linux options are not currently documented.

Currently under windows there are two capture interfaces available for use, by default the most compatible and commonly supported interface is selected however this can be changed via the ini file with the following configuration:


Where <INTERFACE> is one of dxgi or nvfbc

Microsoft DXGI Desktop Duplication

This interface (DXGI) is the default and most compatible capture interface for windows, unfortunately though it does suffer from several drawbacks over other options. DXGI capture can operate in two modes, DirectX 11 (default) or the experimental and unofficial DirectX 12 mode.

Due to the design of Microsoft’s DXGI API and the decision made to roll hardware cursor updates into the capture stream this interface can suffer from microstutters when the mouse is being moved/updated. This issue only affects guest applications that make use of the hardware cursor instead of compositing the cursor directly, as such titles that do not use a mouse (most FPV games) are not affected.

The other drawback of this API is the overall system overhead, however this can be mitigated by using the DirectX 12 backend. Please be aware though that this backend is not experimental because it’s new, but rather it’s a slight abuse/misuse of the DXGI API and allows us to bypass some Windows internals.

To enable the DirectX 12 backend the following configuration needs to be added to the looking-glass-host.ini configuration:



The option d3d12CopySleep is to work around the lack of locking this misuse of the API allows and you will need to tune this value to what suits your hardware best. The default value is 5ms as this should work for most, lowing it below 2ms is doubtful to be of practical use to anyone. If this value is too low you may see screen corruption which is usually most evident while dragging a window around on the Windows desktop.


Lowering d3d12CopySleep can improve the UPS however the UPS metric makes little sense when using the d3d12 backend as if this value is too low unchanged frames will be doubled up.

The disableDamage option may be needed to avoid screen corruption. Note that this will increase the bandwidth required and in turn the overall load on your system.

The DXGI capture interface also offers a feature that allows downsampling the captured frames in the guest GPU before transferring them to shared memory. This feature is very useful if you are super scaling for better picture quality and wish to reduce system memory pressure.

The configuration for this is fairly straightforward and is defined as set of rules to determine when to perform this downsampling. The format is as follows:


The rules are written as follows:


The LEVEL is the fractional scale level where 1 = 50%, 2 = 25%, 3 = 12.5%.


; Downsample anything greater then 1920x1080 to 50% of it's original size

; Downsample exactly 1920x1080 to 25% of it's original size, and anything greater
; then 1920x1080 to 50% of it's original size.

; Downsample anything greater or equal to 1920x1080 to 50% of it's original size

NVIDIA Frame Buffer Capture

Due to the NVIDIA SDK License agreement this GPU feature is only available on professional/workstation GPUs such as the Quadro series. It is known however that all NVIDIA GPUs are capable of this as both GeForce Experience and Steam are able to make use of it.

If you are able to make use/enable this this feature it offers lower overall system load and lower latency capture, and does not suffer from the mouse motion stutter issues that DXGI suffers from.

To enable it’s usage use the following configuration in the looking-glass-host.ini file:


If this feature is unavailable to you the host application will fail to start and the host log will contain an error stating that the feature is not available.

The NVFBC capture interface also offers a feature much like DXGI to allow downsampling the captured frames in the guest GPU before transferring them to shared memory. However unlike DXGI which is limited to fractional scaling, NvFBC is able to scale to any arbitrary resolution.

The configuration for this is fairly straight forward and is defined as set of rules to determine when to perform this downsampling. The format is as follows:


The rules are written as follows:



; Downsample exactly 3840x2160 to 1920x1080

; Downsample anything greater then 1920x1080 to 1920x1080

; Downsample 3840x2160 to 1920x1080, or 3840x2400 to 1920x1200

This capture interface also looks for and reads the value of the system environment variable NVFBC_PRIV_DATA if it has been set, documentation on its usage however is unavailable.