Editing application settings
The application settings dialog allows users to customize application behavior.
After starting Slicer, it can be accessed clicking in menu:
Application startup script can be used to launch any custom Python code when Slicer application is started.
Select which type of modules to not load at startup. It is also possible to start Slicer by temporarily disabling those modules (not saved in settings) by passing the arguments in the command line.
For example, this command will start Slicer without any CLI loaded:
Directory where modules can store their temporary outputs if needed.
Additional module paths
List of directories scanned at startup to load additional modules. Any CLI, Loadable or scripted modules located in these paths will be loaded.
Module folders of extensions are included in this list. To remove modules of an extension, it is recommended to use the Extensions Manager instead of just removing its module paths.
It is also possible to start Slicer by temporarily adding module paths (not saved in settings) by passing the arguments in the command line.
For example this command will start Slicer trying to load CLIs found in the specified directory:
Slicer.exe --additional-module-paths C:\path\to\lib\Slicer-X.Y\cli-modules
List of modules loaded, ignored or failed to load in Slicer. An unchecked checkbox indicates that module should not be loaded (ignored) next time Slicer starts. A text color code is used to describe the state of each module:
Black: module successfully loaded in Slicer
Gray: module not loaded because it has been ignored (unchecked)
Red: module failed to load. There are multiple reasons why a module can fail to load.
Look at startup log outputs to have more information. If a module is not loaded in Slicer (ignored or failed), all dependent modules won’t be loaded. You can verify the dependencies of a module in the tooltip of the module.
You can filter the list of modules by untoggling in the advanced (>>) panel the “To Load”, “To Ignore”, “Loaded”, “Ignored” and “Failed” buttons.
Module that is shown when Slicer starts up.
List of modules that appear in the Favorites toolbar:
To add a module, drag&drop it from the Modules list above. Then use the advanced panel (>>) to reorganize/delete the modules within the toolbar.
The overall theme of Slicer is controlled by the selected Style:
Slicer (default): it sets the style based on theme settings set by the operating system. For example, on Windows if dark mode is turned on for apps, then the
Dark Slicerstyle will be used upon launching Slicer. Currently, automatic detection of dark mode is not available on Linux, therefore use needs to manually select
Dark Slicerstyle for a dark color scheme.
Light Slicer: application window background is bright, regardless of operating system settings.
Dark Slicer: application window background is dark, regardless of operating system settings.
Enable the following features:
Module selection toolbar: Modules associated with the Testing category are visible by default.
Reload & Testmodule panel section is displayed for scripted modules. It includes controls for reloading, testing and editing scripted modules as well as restarting the application.
Information for Advanced Users
Settings file location
Settings are stored in *.ini files. If the settings file is found in application home directory (within organization name or domain subfolder) then that .ini file is used. This can be used for creating a portable application that contains all software and settings in a relocatable folder. Relative paths in settings files are resolved using the application home directory, and therefore are portable along with the application.
If .ini file is not found in the application home directory then it is searched in user profile:
Deleting the *.ini files restores all the settings to default.
There are two types of settings:
user specific settings and
user and revision specific settings.
User specific settings
This file is named
Slicer.ini and it stores settings applying to all versions of Slicer installed by the current user.
To display the exact location of this settings file, open a terminal and type:
Slicer.exe --settings-path | more
or enter the following in the Python console:
User and revision specific settings
This file is named like
Slicer-<REVISION>.ini and it stores settings applying to a specific revision of Slicer installed by the current user.
To display the exact location of this settings file, enter the following in the Python console:
Application startup file
Each time Slicer starts, it will look up for a startup script file named
.slicerrc.py. Content of this file is executed automatically at each startup of Slicer.
The file is searched at multiple location and the first one that is found is used. Searched locations:
Application home folder (
Path defined in
User profile folder (
You can find the path to the startup script in Slicer by opening in the menu: Edit / Application Settings. ‘’Application startup script’’ path is shown in the ‘’General’’ section (or running
getSlicerRCFileName() command in Slicer Python console).
Runtime environment variables
The following environment variables can be set before the application is started to fine-tune its behavior:
PYTHONNOUSERSITE: if it is set to
1then import of user site packages is disabled. For example, this will prevent Slicer to reuse packages downloaded/built by Anaconda.
QT_SCALE_FACTOR: see Qt documentation. For example, font size can be reduced by running
set QT_SCALE_FACTOR=0.5in the command console and then starting Slicer in that console.
QT_ENABLE_HIGHDPI_SCALING: see Qt documentation
QT_SCALE_FACTOR_ROUNDING_POLICY: see Qt documentation
QTWEBENGINE_REMOTE_DEBUGGING: port number for Qt webengine remote debugger. Default value is
SLICER_OPENGL_PROFILE: Requested OpenGL profile. Valid values are
core(core profile), and
compatibility(compatibility profile). Default value is
compatibilityon Windows systems.
SLICER_BACKGROUND_THREAD_PRIORITY: Set priority for background processing tasks. On Linux, it may affect the entire process priority. An integer value is expected, default =
20on Linux and macOS, and
SLICERRC: Custom application startup file path. Contains a full path to a Python script. By default it is
~/.slicerrc.py(where ~ is the user profile a.k.a user home folder).
SLICER_EXTENSIONS_MANAGER_SERVER_URL: URL of the extensions manager backend with the
/apipath. Default value is retrieved from the settings using the key
SLICER_EXTENSIONS_MANAGER_FRONTEND_SERVER_URL: URL of the extension manager frontend displaying the web page. Default value is retrieved from the settings using the key
SLICER_EXTENSIONS_MANAGER_SERVER_API: Supported value is
Girder_v1. Default value is hard-coded to
Qt built-in command-line options
Slicer application accepts standard Qt command-line arguments that specify how Qt interacts with the windowing system.
Examples of options:
-qwindowgeometry geometry, specifies window geometry for the main window using the X11-syntax. For example:
-display hostname:screen_number, switches displays on X11 and overrides the
-platform windows:dpiawareness=[0|1|2], sets the DPI awareness on Windows.
-widgetcount, prints debug message at the end about number of widgets left undestroyed and maximum number of widgets existed at the same time.
-reverse, sets the application’s layout direction to
To learn about the supported options:
Since the Slicer launcher is itself a Qt application and the Qt built-in command-line options are expected to only be passed to
the launched application
SlicerApp-real and not the Slicer launcher, the list of arguments to filter is specified in the Main.cpp found in the