System Properties

Java system properties can be used to change some behavior of FlatLaf.

They can be either passed at command line to any application that uses FlatLaf:

$ myapp -Dflatlaf.animation=false

Or set in Java code:

System.setProperty( "flatlaf.animation", "false" );

List of system properties used in FlatLaf:

Property Name	Description	Allowed Values	Default
flatlaf.uiScale	Specifies a custom scale factor used to scale the UI. If Java runtime scales (Java 9 or later), this scale factor is applied on top of the Java system scale factor. Java 8 does not scale and this scale factor replaces the user scale factor that FlatLaf computes based on the font. To replace the Java 9+ system scale factor, use system property `sun.java2d.uiScale`, which has the same syntax as this one. Since FlatLaf 1.1.2: Scale factors less than 100% are allowed.	e.g. `1.5`, `1.5x`, `150%` or `144dpi` (96dpi is 100%)	none
flatlaf.uiScale.enabled	Specifies whether user scaling mode is enabled.	`false` and `true`	`true`
flatlaf.uiScale.allowScaleDown since v1.1.2	Specifies whether values smaller than 100% are allowed for the user scale factor.	`false` and `true`	`false`
flatlaf.useUbuntuFont	Specifies whether Ubuntu font should be used on Ubuntu Linux. By default, if not running in a JetBrains Runtime, the Liberation Sans font is used because there are rendering issues (in Java) with Ubuntu fonts.	`false` and `true`	`false`
flatlaf.useWindowDecorations	Specifies whether native window decorations should be used when creating `JFrame` or `JDialog`. Setting this to `true` forces using native window decorations even if they are not enabled by the application. Setting this to `false` disables using native window decorations. This system property has higher priority than client property `JRootPane.useWindowDecorations` and UI default `TitlePane.useWindowDecorations`. (requires Windows 10/11)	`false` and `true`	none
flatlaf.useJetBrainsCustomDecorations	Deprecated: No longer used since FlatLaf 3.3. Specifies whether JetBrains Runtime custom window decorations should be used when creating `JFrame` or `JDialog`. Requires that the application runs in a JetBrains Runtime (based on OpenJDK). Setting this to `false` disables using JetBrains Runtime custom window decorations. Then FlatLaf native window decorations are used. (requires Windows 10/11)	`false` and `true`	`false` (since since v2; was `true` in since v1)
flatlaf.menuBarEmbedded	Specifies whether the menu bar is embedded into the window title pane if window decorations are enabled. Setting this to `true` forces embedding. Setting this to `false` disables embedding. This system property has higher priority than client property `JRootPane.menuBarEmbedded` and UI default `TitlePane.menuBarEmbedded`. (requires Windows 10/11)	`false` and `true`	none
flatlaf.useNativeLibrary since v3.2	Specifies whether FlatLaf native library should be used. Setting this to `false` disables loading native library, which also disables some features that depend on the native library.	`false` and `true`	`true`
flatlaf.nativeLibraryPath since v2	Specifies a directory in which the FlatLaf native libraries are searched for. The path can be absolute or relative to current application working directory. This can be used to avoid extraction of the native libraries to the temporary directory at runtime. If the value is `"system"` (supported since FlatLaf 2.6), then `System.loadLibrary(String)` is used to load the native library. This searches for the native library in classloader of caller (using `ClassLoader.findLibrary(String)`) and in paths specified in system properties `sun.boot.library.path` and `java.library.path`. If the native library can not be loaded from the given path (or via `System.loadLibrary(String)`), then the embedded native library is extracted to the temporary directory and loaded from there. The file names of the native libraries must be either: the same as in flatlaf.jar in package `com/formdev/flatlaf/natives` (required for `"system"`) or when downloaded from Maven central then as described here: Native Libraries distribution (requires FlatLaf 3.4) Note: Since FlatLaf 3.1 it is recommended to download the FlatLaf native libraries from Maven central and distribute them with your application in the same directory as `flatlaf.jar`. Then it is not necessary to set this system property. See Native Libraries distribution for details.	absolute or relative path	none
flatlaf.animation	Specifies whether animations are enabled.	`false` and `true`	`true`
flatlaf.useRoundedPopupBorder since v3.5.2	Specifies whether native rounded popup borders should be used (if supported by operating system). (requires Windows 11 or macOS)	`false` and `true`	`true`; except on macOS 14.4+ where it is `false`
flatlaf.useTextYCorrection	Specifies whether vertical text position is corrected when UI is scaled on HiDPI screens.	`false` and `true`	`true`
flatlaf.updateUIOnSystemFontChange since v2.5	Specifies whether FlatLaf updates the UI when the system font changes. If `true`, `SwingUtilities.updateComponentTreeUI(java.awt.Component)` gets invoked for all windows if the system font has changed. This is the similar to when switching to another look and feel (theme). Applications that do not work correctly when switching look and feel, should disable this option to avoid corrupted UI.	`false` and `true`	`true`
flatlaf.useSubMenuSafeTriangle since v3.5.1	Specifies whether safe triangle is used to improve usability of submenus.	`false` and `true`	`true`