Free software desktops such as Gnome and KDE are built on top of toolkits that provide support for the graphic elements. Gnome is built on the GTK toolkit. GTK is an important component of many GUI-based Linux systems, and a new release of GTK eventually has implications for all Linux users working in Gnome and other GTK-based desktop systems.

GTK4 [1] was released at the end of 2020, and components that rely on GTK4 have quickly followed, starting with Gnome 40 in March 2021. Recent distributions such as Fedora 34 [2] and Arch Linux already include Gnome 40. Other distributions such as Ubuntu 21.04 [3] include the GTK4 libraries in their package sources but don't use the GTK4-based desktop yet.

In practice, however, GTK4's influence in these distributions is still not very noticeable. For example, the Gnome desktop's extensions app does not look noticeably different, even though it has now been ported to GTK4: It uses the usual widgets, such as buttons, search fields, and fold-out dialogs. If you look at the Widget Factory (see the "Widget Factory" box), a test program that organizes all common widgets in a window, you probably won't notice any outstanding innovations at first glance. However, if you take a look at the animated GTK cube video on the main Widget Factory page, you can see one of the biggest changes between GTK3 and GTK4. Mousing over the video reveals the typical pause and start playback media player buttons. This cube video demonstrates that you now can put graphics or other media elements in the background of almost all window elements [4].

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