KWin Rules


KWin allows the end-user to define rules to alter the behavior of an application's windows.

Plasmoids, Workspaces can also be affected.

For example, when an application is started, it can be forced to always run on Virtual Desktop #2. Or a defect in an application can be worked-around by using a rule to, say, always force the window on top of all others.

This page will define the different settings and the attributes. For the impatient folks, working examples will be listed. Whenever possible, screen shots will be used to show example settings.

KWin Rule Editor


Invoking the Editor

There are several ways one can invoke the Rules editor. Below are a couple:

  • Right-click on the title-bar of any window, choose Configure Window Behavior ... and in the Configure window, select Window Rules or
  • Configure Desktop -> Window Behavior -> Window Rules



The editor is composed of four tabs:

  1. Window matching
  2. Size & Position
  3. Arrangement & Access
  4. Appearance & Fixes

As the name implies, Window matching is used to specify criteria to match one or more windows. The other three tabs are used to alter the characteristics of the matching windows.



KWin evaluates the rules when an application starts and after editing rules. Any matching rule's attribute(s) override the application's corresponding attribute(s).


In the Window Rules window, the rules are listed in the order in which they are processed.

The rule at the top of the list is processed first, followed by the next rule until the end of the list is reached.


In the event two rules match a window and affect the same attribute, the first rule in the list takes precedence.

Window Matching


The Window Matching tab provides a series of matching-criteria fields used to identify application windows:

  • Window class (application) - This window and all its children windows.
    • and Match whole window class
  • Window role - a window within the application (e.g. Main Window)
  • Window types - Normal Window, Dialog Window, etc. The different types are presented.
  • Window title - self-explanatory.
  • Machine (hostname) - Useful when identifying a window which is logging on to a specific remote machine.
While it's possible to manually enter the above information, the preferred method is to use the Detect Window Properties button.

For each field, the following operators can be applied against the field value:

  • Unimportant
  • Exact Match
  • Substring Match
  • Regular Expression - Qt's regular expressions are implemented. For additional information, perform a web search with qt regex nokia.
Detect Window Properties

The Detect Window Properties function simplifies the process of entering the matching-criteria.

  1. For the application you'd like to create a rule, start the application.
  2. Next, set the number of seconds of delay before the Detect Window Properties function starts. The default is zero seconds.
  3. Click on Detect Window Properties and
  4. When the mouse-cursor turns to cross-hairs, place it inside the application window and left-click.
  5. A new window is presented with information about the selected window:
    • Class
    • Role
    • Type
    • Title
    • Machine (hostname)

The information is used to back-fill the Window Matching criteria.

By using a combination of the information, you can tailor whether the rule will be generic and apply to the entire class or certain windows, say a particular Type of window, within the class.

Window Attributes


Force a Window on a Desktop

Force a Window on all Desktops

Suppress a Window showing on Pager

Force a Window to the Top

Good for knotes

Multiple Rules per Application

e.g. Thunderbird on one desktop and composition window on any

This page was last edited on 22 January 2021, at 22:44. Content is available under Creative Commons License SA 4.0 unless otherwise noted.