[7] The series included updates to several of the KDE Platform's core components, notably a port to Qt 4.

This was made possible by the port to Qt 4, which facilitated support for non-X11-based platforms, including Microsoft Windows and Mac OS X.

However, tests reveal that KDE 4.4 has the highest memory utilization on default Ubuntu installations when compared to GNOME 2.29, Xfce 4.6, and LXDE 0.5.

[8] Qt 4 is available under the LGPL for Mac OS X and Windows, which allows KDE 4 to run on those platforms.

During Summer of Code 2007 an icon cache was created to decrease application start-up times for use in KDE 4.

Many applications in the Extragear and KOffice modules have received numerous improvements with the new features of KDE 4 and Qt 4.

This is because Phonon only functions as a wrapper, abstracting the various multimedia frameworks available for Unix-like operating systems into runtime switchable backends that can be accessed through a single API.

Applications that use the Phonon API can be switched between multimedia frameworks seamlessly by simply changing the backend used in System Settings.

Nokia adopted Phonon for multimedia use in Qt 4.4 and are developing backends for Gstreamer, Windows and OS X in the KDE SVN repository under the LGPL.

It functions similarly to Phonon as it does not manage hardware on its own but makes existing solutions accessible through a single API.

Decibel is a Telepathy-based communication framework, which was expected to be fully used by Kopete by KDE 4.2, but which is reported to be postponed indefinitely.

[16] In concert with other software like Soprano, an RDF storage framework, and the NEPOMUK specification, Strigi will provide the beginnings of a semantic desktop in KDE 4.

Users can tag files with additional information through Dolphin, which Strigi can index for more accurate searches.

The autotools build system had become so complicated by KDE 3 that few developers understood it, requiring hours of work for simple changes.

[18] DXS, previously known as GHNS (Get Hot New Stuff)[19] and now adopted by freedesktop.org, is a web service that lets applications download and install data from the Internet with one click.

Alpha 1 included new frameworks to build applications with, providing improved hardware and multimedia integration through Solid and Phonon.

A program called Step, an interactive physics simulator, was produced as part of the Google Summer of Code.

Despite the criticism, reviewers such as Ars Technica’s Ryan Paul noted that the visual style "is very attractive and easy on the eyes" and "exhibits a relatively high level of polish" and that "the underlying technologies still have a lot of very serious potential".

[40] KDE 4.1 includes a shared emoticon theming system which is used in PIM and Kopete, and DXS, a service that lets applications download and install data from the Internet with one click.

Theming improvements in the Task Bar, Application Launcher, System Tray and most other Plasma components streamline the look and feel and increase consistency.

[43] KRunner – the "Run command…" dialog – has extended functionality through several new plugins, including spellchecking, Konqueror browser history, power management control through PowerDevil, KDE Places, Recent Documents, and the ability to start specific sessions of the Kate editor, Konqueror and Konsole.

[43] Multi-screen support has been improved through the Kephal library, fixing many bugs when running KDE on more than one monitor.

[43] New applications include PowerDevil, a power management system for controlling various aspects of mobile devices.

A new printing configuration system brings back a number of features users have been missing in KDE 4.0 and 4.1.

KSnapshot now uses the window title when saving screenshots, making it easier to index them using search engines.

KDE SC 4.6 was released on 26 January 2011 and has better OpenGL compositing[59] along with the usual myriad of fixes and features.

This version updated KWin in order to be compatible with OpenGL ES 2.0, which will enhance its portability to mobile and tablet platforms.

Marble, the virtual globe software, now supports voice navigation, a map creation wizard, as well as many new plugins.

[65] Other KWin features are: QML based Window switcher (Tabbox),[66] AnimationEffect class and initial Wayland support.

Many of the default Plasma widgets were rewritten in QML, and Nepomuk, Kontact and Okular received significant speed improvements.