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KDE Software Compilation 4
KDE4 logo preview.svg
KDE 4.png
KDE Plasma Desktop 4.3
Developer(s) KDE
Initial release 11 January 2008[1]
Stable release 4.3.4 / 2009-12-01; 42 days ago
Preview release 4.4 RC1[2] / 2010-01-08; 4 days ago
Written in C++ and Qt4
Operating system Whole desktop: Unix-like with X11.
Applications only: Mac OS X v10.4/10.5, Windows XP/Vista
Available in Multilingual[3]
Development status Current
Type Desktop environment

KDE Software Compilation 4 (KDE SC 4) is the current series of releases of KDE's Desktop Environment, the KDE Software Compilation. The first major version (4.0) of this series was released on 11 January 2008,[1] and the latest major version (4.3) was released on 4 August 2009.[4]

The new series includes updates to several of the KDE technology stack's core components, notably a port to Qt 4. It contains a new multimedia API, called Phonon, a device integration framework called Solid and a new style guide and default icon set called Oxygen. It also includes the new desktop and panel user interface tool, called Plasma, which supports desktop widgets (called "Plasmoids"), replacing SuperKaramba. The port to Qt 4 will facilitate support for non-X11-based platforms, including Microsoft Windows and Mac OS X. One of the overall goals of KDE 4 is to be more easily portable to different operating systems. In line with KDE's increased scope, from version 4.4 the desktop environment will be known as the KDE Software Compilation.

Major releases (4.x) are scheduled for every six months, while minor bugfix releases (4.x.y) are released monthly.[5]


Major updates

This is a short overview of major changes in KDE 4. Not all of these changes are available in the first (4.0) release.



The port to the Qt 4 series is expected to enable KDE 4 to use less memory and be noticeably faster than KDE 3. The KDE libraries themselves have also been made more efficient. Qt 4 is available under the LGPL for Mac OS X and Windows, which will allow KDE 4 to run on those platforms. The ports to both platforms are in an early state. Both ports are trying to use as little divergent code as possible to make the applications function almost identically on all platforms. During Summer of Code 2007 an icon cache was created to decrease application start-up times for use in KDE 4.[6] Improvements were varied – Kfind, an application which used several hundred icons, started up in almost a quarter of the time it took previously.[7] Other applications and a full KDE session started up a little over a second faster.

Many applications in the Extragear and KOffice modules have received numerous improvements with the new features of KDE 4 and Qt 4. But since they follow their own release schedule, they were not all available at the time of the first KDE 4 release – these include Amarok, K3b, digiKam, KWord, and Krita.


The most noticeable changes for users are the new icons, theme and sounds provided by the Oxygen Project. These represent a break from previous KDE icons and graphics, which had a cartoonish look. Instead Oxygen icons opt for a more photorealistic style. The Oxygen Project builds on the Icon Naming Specification and Icon Theme Specification, allowing consistency across applications. The Oxygen team uses community help for better visuals in KDE 4, with both alternate icon sets and the winners of a wallpaper contest held by the Oxygen project being included in KDE 4.[8] There is also a new set of human interface guidelines for a more standardized layout.

Plasma provides the main desktop user interface and is a rewrite of several core KDE applications, like the desktop drawing and most notably the widget engine. Plasma will allow for a more customizable desktop and more versatile widgets.

KWin, the KDE Window Manager, now provides its own compositing effects, similar to Compiz.


Phonon is the name of the new multimedia API in KDE 4. Phonon is a different approach to multimedia backends than in previous versions of KDE. 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. This was done to provide a stable API for KDE 4 and to prevent it from depending on a single multimedia framework. Applications that use the Phonon API can be switched between multimedia frameworks seamlessly by simply changing the backend used in system settings. Trolltech 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.[9]

Solid is the hardware API in KDE 4. It functions similarly to Phonon as it doesn’t manage hardware on its own but makes existing solutions accessible through a single API. The current solution uses HAL, NetworkManager and BlueZ (the official Linux bluetooth stack), but any and all parts can be replaced without breaking the application, making applications using Solid extremely flexible and portable.

ThreadWeaver is a programming library to help applications take advantage of multicore processors and is included with kdelibs.

Kross is the new scripting framework for KDE 4. Kross itself is not a scripting language, but makes it easier for developers to add support for other scripting languages. Once an application adds support for Kross, any language Kross supports can be used by developers. New scripting languages can be added by creating a plugin for Kross, which benefits all applications using it.

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.[10] Strigi is the default search tool for KDE 4, chosen for its speed and few dependencies.[11] 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.[12]

KDE 4 uses CMake for its build system. Since previous versions of KDE were only on Unix systems, autotools were used, but a new build system was needed for builds on operating systems like Windows. CMake also dramatically simplified the build process. The autotools build system had become so complicated by KDE 3 that few developers understood it, requiring hours of work for simple changes. In early 2007 CMake was shown to compile the KDE 4 version of KDElibs 40 % faster than the autotools compiled KDE 3 version.[13]

DXS, previously known as GHNS (Get Hot New Stuff)[14] and now adopted by, is a web service that lets applications download and install data from the Internet with one click. It was used in the KDE 3 series but has been extended for use throughout KDE 4. One example was Kstars, that can use Astronomical data that is free for personal use but cannot be redistributed. DXS allows that data to be easily downloaded and installed from within the application instead of manually downloading it.

Akonadi is a new PIM framework for KDE 4 that will be included in later releases. Akonadi is a unification of previously separate KDE PIM components. In the past each application would have its own method for storing information and handling data. Akonadi itself functions as a server that provides data and search functions to PIM applications. It is also able to update the status of contacts. So if one application changes information about a contact, all other applications are immediately informed of the change.[15]

KDE 4.0

KDE 4.0 showing Dolphin, System Settings and Kickoff

The majority of development went into implementing most of the new technologies and frameworks of KDE 4. Plasma and the Oxygen style were two of the biggest user-facing changes.

Dolphin replaces Konqueror as the default file manager in KDE 4.0. This was done to address complaints of Konqueror being too complicated for a simple file manager. However Dolphin and Konqueror will share as much code as possible, and Dolphin can be embedded in Konqueror to allow Konqueror to still be used as a file manager.

Okular replaces several document viewers used in KDE 3, like KPDF, KGhostView and KDVI. Okular makes use of software libraries and can be extended to view almost any kind of document. Like Konqueror and KPDF in KDE 3, Okular can be embedded in other applications.


On 11 May 2007, KDE 4.0 Alpha 1 was released marking the end of the addition of large features to the KDE base libraries and shifting the focus onto integrating the new technologies into applications and the basic desktop. Alpha 1 included new frameworks to build applications with, providing improved hardware and multimedia integration through Solid and Phonon. Dolphin and Okular were integrated and a new visual appearance was provided through Oxygen icons.[16]

On 4 July 2007, Alpha 2 was released.[17] The release focused on integrating the Plasma desktop, improving functionality and stabilizing KDE.

On 2 August 2007, Beta 1 was released.[18] Major features included a pixmap cache – speeding up icon loading, KDE PIM improvements, improved KWin effects and configuration, better interaction between Konqueror and Dolphin and Metalink support added to KGet for improved downloads.

On 6 September 2007, Beta 2 was released with improved BSD and Solaris support.[19] The release included the addition of the Blitz graphic library – allowing for developers to use high performance graphical tricks like icon animation – and an overhaul of KRDC (K Remote Desktop Client) for Google’s Summer of Code. Plasma was also integrated with Amarok to provide Amarok’s central context view.

On 16 October 2007, Beta 3 was released.[20] The beta 3 release was focused on stabilizing and finishing the design of libraries for the release of the KDE Development Platform. Plasma received many new features including an applet browser. The Educational software received many improvements in Marble and Parley (formerly known as KVoctrain) with bugfixes in other applications. A program called Step, an interactive physics simulator, was produced as part of the Google Summer of Code.

On 30 October 2007, Beta 4 was released.[21] A list of release blockers was compiled,[22] listing issues that need to be resolved before KDE will start with the release candidate cycle for the desktop. The goals were to focus on stabilization and fixing the release blockers.

At the same time, the first release candidate of the KDE 4.0 Development Platform was released. The development platform contains all the base libraries to develop KDE applications, including "high-level widget libraries, a network abstraction layer and various libraries for multimedia integration, hardware integration and transparent access to resources on the network."[23]

On 20 November 2007, Release Candidate (RC) 1 was released.[24] This release was called a "Release Candidate" despite Plasma requiring further work and not being ready for release. On 11 December 2007, RC2 was released.[25] The codebase was declared feature-complete. Some work was still required to fix bugs, finish off artwork and smooth out the user experience.

Stable releases

KDE 4.0 was released on 11 January 2008. There were maintenance releases every month through to June,[5] which fix bugs and add some minor features such as resizable desktop panels.

KDE 4.0 was met with a mixed reaction. Despite being labeled as a stable release, it was intended for early adopters.[26] Continuing to use KDE 3.5 was suggested for users wanting a more stable, "feature complete" desktop.[27] The intent was for 4.0 to be a developers release. It was included in a number of distributions in order to promote the migration from KDE 3.5 among the Linux developers.

The message got lost among the release excitement, and as a result the release disappointed some end users. This resulted in a backlash over the introduction of 4.0. This is mainly due to the release miscommunication.[28]

KDE 4.1

KDE 4.1 showing Kickoff and Folder View.

KDE 4.1 was released on 29 July 2008.[29] 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.[30] Also introduced are GStreamer, QuickTime 7, and DirectShow 9 Phonon backends.[30] Plasma improvements include support for Qt 4 widgets and WebKit integration – allowing many Apple Dashboard widgets to be displayed.[30] There will also be ports of some applications to Windows and Mac OS X.[30]

New applications include:[30]

  • Dragon Player multimedia player (formerly Codeine)
  • KDE-PIM module, with some Akonadi functionality
  • Skanlite scanner application
  • Step physics simulator
  • Games – Kdiamond (a Bejeweled clone), Kollision, Kubrick, KsirK, KBreakout

KDE 4.2

KDE 4.2 showing KMail, Dolphin and the desktop.

KDE 4.2 was released on 27 January 2009. The release is considered a significant improvement in nearly all aspects above KDE 4.1 and a suitable replacement of KDE 3.5 for most users.[31]

KDE workspace improvements

The 4.2 release includes thousands of bugs fixes and has implemented many features that were present in KDE 3.5 but had been missing in KDE 4.0 and 4.1.[32] These include grouping and multiple row layout in the task bar, icon hiding in the system tray, panel autohiding, window previews and tooltips are back in the panel and task bar, notifications and job tracking by Plasma, and the ability to have icons on the desktop again by using a Folder View as the desktop background where icons now remain where they are placed.

New Plasma applets include applets for leaving messages on a locked screen, previewing files, switching desktop Activity, monitoring news feeds, and utilities like the pastebin applet, the calendar, timer, special character selector, a QuickLaunch widget, and a system monitor, among many others. The Plasma workspace can now load Google Gadgets. Plasma widgets can be written in Ruby and Python. Support for applets written in JavaScript and Mac OS X dashboard widgets has been further improved. Theming improvements in the Task Bar, Application Launcher, System Tray and most other Plasma components streamline the look and feel and increase consistency. A new System Settings module, Desktop Theme Details, gives the user control over each element of various Plasma themes. Wallpapers are now provided plugins, so developers can easily write custom wallpaper systems in KDE 4.2. Available wallpaper plugins in KDE 4.2 will be slideshows, Mandelbrot fractals, and regular static images.[32]

New desktop effects have been added such as the Magic Lamp, Minimize effect and the Cube and Sphere desktop switchers. Others, such as the desktop grid, have been improved. The user interface for choosing effects has been reworked for easy selection of the most commonly used effects. Compositing desktop effects have been enabled by default where hardware and drivers support them. Automatic checks confirm that compositing works before enabling it on the workspace.[32]

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. The converter plugin now also supports quickly converting between units of speed, mass and distances.[32]

Multi-screen support has been improved through the Kephal library, fixing many bugs when running KDE on more than one monitor.[32]

New and improved applications

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. The components "printer-applet" and "system-config-printer" are shipped with the kdeadmin and kdeutils module. Killbots is a new game shipped with the kdegames module.[32]

All applications have seen bugfixes, feature additions and user interface improvements. Dolphin now supports previews of files in toolbars and has gained a slider to zoom in and out on file item views. It can now also show the full path in the breadcrumb bar. Konqueror offers increased loading speed by prefetching domain name data in KHTML. A find-as-you-type bar improves navigation in webpages. KMail has a new message header list, and reworked attachment view. The KWrite and Kate text editors can now operate in Vi input mode, accommodating those used to the traditional UNIX editor. Ark, the archiving tool has gained support for password-protected archives and is accessible via a context menu from the file managers now. KRDC, the remote desktop client improves support for Microsoft’s Active Directory through LDAP. Kontact has gained a new planner summary and support for drag and drop in the free/busy view. KSnapshot now uses the window title when saving screenshots, making it easier to index them using search engines.[32]

KDE 4.3

KDE 4.3 desktop, showing Dolphin, KMail and a selection of desktop widgets.

KDE 4.3 is the current release and was released on 4 August 2009. Polishing KDE 4 was a focus of 4.3, with this release being described as incremental and lacking in major new features.[33][34] Integration with other technologies, such as PolicyKit, NetworkManager & Geolocation services, was another focus of this release.[35][36][37] KRunner’s interface has been overhauled. A much more flexible system tray has been developed. Many new Plasmoids have been added, including the Plasmoid – an initial take on the Social Desktop.[38] Plasma also receives more keyboard shortcuts.[33]

KDE SC 4.4

KDE Plasma Netbook will be making its debut in 4.4

KDE SC 4.4 is the upcoming release, scheduled for February 2010.

KDE SC 4.4 will be based on version 4.6 of the Qt toolkit.[39] KDE 4.4 will then also carry Qt’s performance improvements as well as Qt 4.6's new features, such as the new animation framework Kinetic.

KAddressBook will be replaced by a completely new application with the same name – previously tentatively called KContactManager.[40] Key features of the new KAddressBook are Akonadi integration and a streamlined user interface.

Another major new feature is an additional new Plasma interface, targeted towards netbooks.[41]

Kopete will be released as version 1.0.[42]

KAuth, a cross-platform authentication API, will make its début in KDE SC 4.4. Initially only PolicyKit is supported as back-end.[43]

KDE SC 4.5

KDE SC 4.5 is a future release, scheduled for June 2010. The most prominent feature targeted for this release is KMail 2.0. Key features of KMail 2.0 are Akonadi compatibility and refactoring it into a modular application.

Planned, but not yet confirmed, is the official deprecation of KPackage. KPackageKit will be replacing it.[44]

Release schedule

Date Event
2 April 2007 Subsystem Freeze
From this date forward, no new KDE subsystem or major changes can be committed to kdelibs.
1 May 2007 kdelibs soft API Freeze
The kdelibs API is "soft-frozen", meaning that changes can be made with the consent of the core developers.
11 May 2007 Alpha 1
1 June 2007 trunk/KDE is module frozen
Trunk is frozen for new or resurrected applications.
4 July 2007 Alpha 2
Initially due to be called Beta 1, it was decided to retain the alpha designation because this release wasn’t judged to be beta quality.
24 July 2007 Core Library API Freeze
2 August 2007 Beta 1
6 September 2007 Beta 2
Trunk is frozen for feature commits.
18 October 2007 Beta 3
24 October 2007 KDE 4 Release Freeze
Source and binary compatibility until KDE 5, hard freeze Platform & soft freeze Desktop.
30 October 2007 Beta 4
20 November 2007 Release candidate 1
KDE Development Platform released
11 December 2007 Release candidate 2
Only regressions or serious bugs can be fixed.
11 January 2008 KDE 4.0 released
4 June 2008 4.0.5 Maintenance release. Predated by 4.0.1 to 4.0.4.
29 April 2008 Alpha 1
19 May 2008 Feature Freeze
27 May 2008 Beta 1
24 June 2008 Beta 2
15 July 2008 Release candidate 1
29 July 2008 KDE 4.1 released
13 January 2009 4.1.4 Maintenance release. Predated by 4.1.1 to 4.1.3.
17 November 2008 Feature Freeze
26 November 2008 Beta 1
18 December 2008 Beta 2
13 January 2009 Release candidate 1
27 January 2009 KDE 4.2 released
2 June 2009 4.2.4 Maintenance release. Predated by 4.2.1 to 4.2.3.
4 May 2009 Feature Freeze
12 May 2009 Beta 1
9 June 2009 Beta 2
30 June 2009 Release candidate 1
9 July 2009 Release candidate 2
22 July 2009 Release candidate 3
4 August 2009 KDE 4.3 released
1 December 2009 4.3.4 Maintenance release. Predated by 4.3.1 to 4.3.3.
25 November 2009 Feature Freeze
4 December 2009 Beta 1
21 December 2009 Beta 2
8 January 2010 Release candidate 1
20 January 2010 Release candidate 2
9 February 2010 KDE SC 4.4 released
Feature Freeze - From herein, no new features are allowed.
All future dates are provisional.


  1. ^ a b "KDE 4.0 Release Announcement".  
  2. ^
  3. ^ "KDE Localization statistics".  
  4. ^ "KDE 4.3 Release Announcement".  
  5. ^ a b "KDE 4.1 - release team aims at July 2008".  
  6. ^ Google Summer of Code 2007 – Application Information
  7. ^ KDE Commit-Digest – 22nd July 2007
  8. ^ Oxygen Team Unveils Wallpaper Collection for KDE 4.0
  9. ^ Trolltech Hosting Phonon Backends in KDE Subversion Repository
  10. ^ Matt Rogers Blog:
  11. ^ The Road to KDE 4: Strigi and File Information Extraction
  12. ^ KDE Commit-Digest – 9th December 2007
  13. ^ The Road to KDE 4: CMake, a New Build System for KDE
  14. ^ Get Hot New Stuff! Project
  15. ^ aKademy 2006: Akonadi – The KDE 4.0 PIM Framework
  16. ^ KDE 4.0 Alpha 1 announcement
  17. ^ KDE 4.0 Alpha 2 announcement
  18. ^ KDE 4.0 Beta 1 announcement
  19. ^ KDE 4.0 Beta 2 announcement
  20. ^ KDE 4.0 Beta 3 Release Announcement
  21. ^ KDE 4.0 Beta 4 Release Announcement
  22. ^ Schedules/KDE4/4.0 Release Beta Goals - KDE TechBase
  23. ^ KDE 4.0 Platform Release Candidate 1 announcement
  24. ^ KDE 4.0 Release Candidate Announcement
  25. ^ KDE 4.0 Release Candidate 2 Announcement
  26. ^ Aaron Seigo: Talking Bluntly
  27. ^ KDE 4.0 released: rough, but ready for action
  28. ^ critics are wrong: KDE 4 doesn't need a fork
  29. ^ "KDE 4.1 Release Announcement".  
  30. ^ a b c d e "KDE 4.1 Release Goals".  
  31. ^ "KDE 4.2 Released; Short Interview: Aaron Seigo".  
  32. ^ a b c d e f g "KDE 4.2 Beta 1 announcement".  
  33. ^ a b Bruce Byfield. "The KDE 4.3 beta: KDE Returns to Incremental Releases".  
  34. ^ Steven J. Vaughan-Nichols. "A first look at KDE 4.3".  
  35. ^ Networkmanager in KDE4.
  36. ^ KDE 4 Network Management Applet
  37. ^ KDE 4.3 Beta 1 Release Announcement
  38. ^ Social Desktop Starts to Arrive
  39. ^
  40. ^
  41. ^
  42. ^
  43. ^
  44. ^
  45. ^ "KDE 4.0 Release Schedule".  
  46. ^ "KDE 4.1 Release Schedule".  
  47. ^ "KDE 4.2 Release Schedule".  
  48. ^ "KDE 4.3 Release Schedule".  
  49. ^ "KDE 4.4 Release Schedule".  

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