Widgets are the basic elements of a graphical user interface, such as buttons, scrollbars, tabs, and menus. A widget style is a plugin or a small program that instructs KDE how widgets are displayed. Since widgets are the very basic parts of an interface, they are frequently accessed and must be able to respond very quickly. This is why widget styles must come as source code to be compiled or as binary packages to be installed, just like window decorations. Please refer to your distribution's documentation on how to compile from source or install binary packages.

Once a widget style has been installed, it will be added to the list of available styles in the Style module in the KDE Control Center. The Style tab allows you to select a widget style from the list and to configure it if the style has a Configure... feature. Different styles have different options. A preview of the selected style is available at the lower portion of the tab. The Effects tab controls different visual effects for some widgets like comboboxes and tooltips. The Toolbar tab gives some options on the general appearance of toolbars.

Additional widget styles can be found in the different KDE subsections of the Themes/Styles of kde-look.org. Take note that styles come in source code or binary package forms. They are not KDE theme files.