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ReactOS 0.4.13
developer ReactOS team & contributors
License (s) Open Source (including GNU GPL )
Current  version 0.4.13 of April 9, 2020
(135 days ago)
ancestry ReactOS
Architecture (s) x86 ; x64 in development (formerly also PowerPC and ARM )
compatibility Windows NT
Others Languages: German and much more

ReactOS ( English react "react" and operating system "operating system"), also called ROS for short , is a software project for the development of a free operating system of the same name. The project is still in the alpha stage . Its aim is to create full binary compatibility with Windows .


ReactOS has the goal to kernel of Windows NT to be compatible, so it should be possible, programs and device drivers for Windows NT and its successors such as XP , Server 2003 and 7 to use. Among other things, the Win32 programming interface is simulated for this purpose.

The operating system was largely licensed under the GNU GPL , but some of its components are under the LGPL or under the BSD license .

One problem with achieving binary compatibility with Windows is that some API calls that are used by many programs are not publicly documented. In addition, almost all parts have to be reprogrammed for ReactOS, since nothing can be taken over from Linux or BSD or used in any other way. An exception, however, are the Unix-independent libraries of the Wine project, so that they are adopted in ReactOS.

ReactOS and the Win32 API in different operating systems


2007: ReactOS 'then project coordinator Alexei Bragin (left) presents ReactOS to the nationalist hardliner known as Wiktor Alksnis , Rodina party (right).

The project was launched in 1996 as "FreeWin95" and should only be compatible with Windows 95 programs. It followed on from a comparable project that had the aim of reprogramming MS-DOS and became known as an open source project with the name FreeDOS . Today it is a usable DOS replica, but not compatible with today's Windows software. After FreeWin95 got stuck in a lengthy specification phase, Jason Filby, as project coordinator, revived the project in 1998, which has since been known as ReactOS. The compatibility with Windows NT was defined as a new project goal.

For a long time, the ReactOS team was busy developing the kernel , so that hardly any success was visible. With the appearance of version 0.2, ReactOS offered a graphical user interface for the first time . This made the press more aware of ReactOS. Support for Java , OS / 2 and DOS programs was put on the agenda, but has not yet been pursued. An implementation of the Internet protocol family , based on the FreeBSD IP stack , was already usable.

The first € 4000 donation campaign was started on January 8, 2007 and ended on February 11, 2007 with a total of € 4450. The money will mainly be used for server maintenance and increasing the awareness of ReactOS. The programmers hope to attract new developers and testers through increasing public interest in the project.

The project was presented for the first time on February 25, 2007 at the annual meeting of European developers of free software in Brussels ( FOSDEM ).

At the beginning of 2009, the previous roadmap was replaced by a new plan up to version 0.5. The development of free NTFS drivers has been announced for version 0.5. ReactOS code was used in other projects such as Captive to enable write access to the proprietary NTFS file system .

On January 16, 2010, Alexei Bragin, then coordinator of the project, spoke about conceptual weaknesses of the Win32 subsystem and designed an alternative 32-bit subsystem to come closer to a functioning system. The Win32 subsystem, whose software design is closer to Windows than that of Wine , is to be temporarily supplemented by a new subsystem based on Wine source code (as opposed to outdated versions in the current Win32 subsystem) instead of developing it from scratch. The previous graphics driver is not affected by the innovation. Compared to X Window from Wine, it enables more efficient graphics calls with system calls to the Win32k kernel mode.

In 2014, the new desktop environment ReactOS Explorer - a free replica of Windows Explorer  - was released. This replaced the ( English ) as ROS explorer or old explorer predecessor indicated that the original Windows Explorer and the even older file manager was ajar. ReactOS updates are released every three months.

Google Summer of Code

ReactOS has been participating in the Google Summer of Code (GSoC) project since 2006 . At GSoC 2011, four ReactOS projects were completed, including a TCP / IP driver based on lwIP ( lightweight IP ) and a GDI font driver .

A € 30,000 donation campaign was started on May 1, 2012 and ended at the end of the year with a total donation of € 14,392.

Project thorium Core Cloud Desktop

On December 23, 2013, a cloud computing project based on ReactOS, called Thorium Core Cloud Desktop, was started on to raise $ 120,000 , which failed with only around 40 percent funding by the end of the two-month campaign.

ReactOS Community Edition project

A second crowdfunding campaign ran on Indiegogo from April 2 to June 1, 2014 to finance a ReactOS Community Edition with a target donation of US $ 50,000. For the three most popular Windows applications and devices chosen by the community, the money is intended to enable full compatibility. The campaign was completed as a partial success for an amount of $ 25,141.

Awards and grants

At the 2011 Seliger meeting, the ReactOS project won the prize for the best presentation, endowed with 100,000 rubles . In June 2013, ReactOS was named SourceForge Project of the Month.

Lobbying in Russia

From 2007 until its dissolution in 2015, the Russian ReactOS Foundation made several attempts to position ReactOS as a possible way out of Russia's dependence on foreign software providers. However, these tests did not show any results.

The most detailed meeting took place in 2007 with the nationalist hardliner Viktor Alksnis , who at that time represented the Rodina party in the federal Duma .

In 2011, representatives of the foundation took advantage of a visit by then President Medvedev to a school to familiarize him with the project. In 2012, ReactOS was presented to the now re-elected Vladimir Putin at the Seliger meeting.

On April 1, 2015, developer and foundation representative Alexei Bragin took part in an expert meeting of the Russian Ministry of Telecommunications on the subject of protection against imported software. There the “Project for the development of a client operating system based on ReactOS” presented by Bragin took second of three places in the client operating system area.


version publication Remarks
Older version; no longer supported: 0.1.0 February 2, 2003 first version that can be installed from CD, without graphical user interface ; File operations such as copying and deleting do not yet work reliably
Older version; no longer supported: 0.2.0 January 25, 2004 Beginning of the graphical user interface based on Windows Explorer and the taskbar ; unstable
Older version; no longer supported: 0.2.2 April 28, 2004 Improvements to the graphical user interface and its stability
Older version; no longer supported: 0.2.5 January 5, 2005 more stable kernel and many small improvements
Older version; no longer supported: 0.2.6 April 10, 2005 next 1.x first well-known games ( Deus Ex , Unreal Tournament ) via software rendering bootable
Older version; no longer supported: 0.2.7 August 21, 2005 Comparison of the header file structure with Windows, localization; For compatibility reasons it reports as Windows 2000 SP4 instead of NT 4.0
Older version; no longer supported: 0.2.8 October 30, 2005 Preparatory steps for USB , installing programs, correcting display errors on the surface
Older version; no longer supported: 0.2.9 December 22, 2005 improved hardware detection and ACPI , improved API support
Older version; no longer supported: 0.3.0 August 28, 2006 improved support of the network ( Internet protocol ) and plug and play (PnP) and much more
Older version; no longer supported: 0.3.1 March 10, 2007 many bug fixes, Winlogon implementation, better boot manager
Older version; no longer supported: 0.3.3 September 12, 2007 Bug fixes, Win32 kernel modules partly rewritten, changes to the DirectX system; Version 0.3.2 was skipped
Older version; no longer supported: 0.3.4 January 22, 2008 Compatibility with NT 5.2 ( Windows 2003 ) improved, user mode DLLs from Wine project synchronized, new remote desktop client, runs better, regionalization, PnP drivers for mouse and keyboard , translations
Older version; no longer supported: 0.3.5 June 30, 2008 Better integration of the user mode DLLs and the Win32 subsystem, Unicode porting from the ICU project , improvements in security, stability and compatibility (including of Visual Studio compilations) as well as additions to regionalization and translations
Older version; no longer supported: 0.3.6 August 6, 2008 Support of the ARM architecture , the beginning of the × 64 support, APC, timer, memory manager, improvements to the Win32 subsystem, synchronization of user-mode DLLs with Wine, improved memory management, network
Older version; no longer supported: 0.3.7 November 4, 2008 Kernel improvements, stack, Win32 subsystem, and × 64 processor architecture
Older version; no longer supported: 0.3.8 February 4, 2009 Corrections to the kernel services, in the Win32 subsystem, in device drivers, synchronization with Wine, RTL improvements, enhancements in system applications and in the build system
Older version; no longer supported: 0.3.9 April 26, 2009 lower memory requirement (32  MB ), improved network stack, security check in the object manager, increased driver compatibility, audio support through kernel streaming, extension of the command line interpreter, GDI and character processing corrected
Older version; no longer supported: 0.3.10 July 5, 2009 Better audio support, SATA hard drive support, extended USB support for mouse and keyboard, support for additional network cards and a drawing program
Older version; no longer supported: 0.3.11 December 16, 2009 new memory management, better Windows compatibility, especially with Firefox 3 and
Older version; no longer supported: 0.3.12 October 20, 2010 Corrections to memory management, hardware access and kernel mode, improvements to device drivers, d. H. the standard drivers, which only support the most important functions of essential hardware for the purpose of downward compatibility.
Older version; no longer supported: 0.3.13 March 22, 2011 Improved memory and audio mixer management as well as graphics support, greater support for SATA devices
Older version; no longer supported: 0.3.14 February 7, 2012 WLAN support (up to WEP ), increase in network throughput and stability with the new TCP / IP driver LwIP, support for desktop themes; ReactOS can now be created with MSVC
Older version; no longer supported: 0.3.15 May 30, 2013 USB 2.0 support (including with EHCI ) for input devices and mass storage devices; improved SATA support
Older version; no longer supported: 0.3.16 February 6, 2014 CSRSS updated, network card driver (RTL8139 chips), integrated theme, Wine library version 1.7.1
Older version; no longer supported: 0.3.17 November 6, 2014 early version of NTVDM , better hardware support
Older version; no longer supported: 0.4.0 February 16, 2016 Improvements in the area of ​​audio, SATA and WLAN. Implementation of the free ext2 driver ext2fsd
Older version; no longer supported: 0.4.1 17th May 2016 u. a. better support of the Btrfs file system , shared folders in virtual machines (such as VirtualBox and VMware )
Older version; no longer supported: 0.4.2 16th August 2016 u. a. GUI optimization, support for multiple Unix file systems
Older version; no longer supported: 0.4.3 November 16, 2016 u. a. new Winsock library, better application compatibility
Older version; no longer supported: 0.4.4 16th February 2017 u. a. better printer support
Older version; no longer supported: 0.4.5 18th May 2017 u. a. Office 2010 support, shell32 and explorer improvements
Older version; no longer supported: 0.4.6 1st September 2017 u. a. Extension of the explorer to include compatibility settings in application links and many bug fixes
Older version; no longer supported: 0.4.7 December 6, 2017 u. a. Driver for Ext2 , Ext3 , Ext4 , Btrfs , ReiserFS , FFS and NFS ; With the CDFS / ISO-9660 driver, ISO images can now be mounted ( mounted ) without a CD drive .
Older version; no longer supported: 0.4.8 April 16, 2018 Support also for programs created for Windows Vista, Windows 7, Windows 8 and Windows 10.
Older version; no longer supported: 0.4.9 23rd July 2018 Zip format support, Wine update: version 3.3, bug fixing when copying large files.
Older version; no longer supported: 0.4.10 November 6, 2018 Operating system start from Btrfs partitions, Wine update: Version 3.9
Older version; no longer supported: 0.4.11 4th March 2019 Update capability, bidirectional text input (Arabic, Hebrew), manifest / DLL checks for more applications, Wine 3.17
Older version; no longer supported: 0.4.12 23 September 2019 Driver for file system, CD and network cards, PXE start, emulation with Wine 4
Current version: 0.4.13 April 9, 2020 new USB stack, accessibility menu, improved XBOX compatibility, file explorer: search function, faster boot with FAT file system
Old version
Older version; still supported
Current version
Current preliminary version
Future version

General bug fixes, synchronization of the DLL libraries of the Wine project and driver updates are carried out with every released version.


The source of ReactOS is primarily in C written. The (ReactOS) Explorer and the sound system are implemented in C ++ . The project uses MinGW for translation (or compilation ) and works with its developers.


Where it makes sense, ReactOS uses source code from other open source projects such as Haiku, WINE and FreeBSD to provide a more stable system.


Integration and use of Wine in the operating system

In ReactOS parts of the Wine used -project that the Win32 - API implement. Since Wine is based on Linux, the Windows components NTDLL, USER32, KERNEL32, GDI32 and ADVAPI are rewritten for ReactOS.

Network driver

As part of the Google Summer of Codes 2011, a student developed a network stack based on lwIP. Previously, ReactOS used the FreeBSD network stack , which was found to be unstable in ReactOS.


Parts of the USB driver were taken over from Haiku .

File system (Btrfs)

ReactOS has been supporting the Linux file system Btrfs since 2018 . The free file system driver WinBtrfs was used to support the file system .

Virtual machines and drivers

To install ReactOS an ISO image of the ReactOS BootCD is required. ReactOS should always be in a virtual machine - such as B. Oracle's VirtualBox , VMWares Workstation or QEMU - as well as natively on computers with x86 processors . To support the development of the so-called ReactOS was UniATA - driver started that with the aid of a Serial ATA interface across operating systems can be addressed. The ROS , Haiku and Mesa 3D developers are working together in a Google Summer of Code project in 2011 in order to be able to use the USB driver across operating systems.

Online community

There are IRC chats and discussion forums for exchange between users and developers in English and German. In Germany, this online community is supported by ReactOS Deutschland e. V. represents. The ReactOS Foundation listed in the ReactOS Wiki in Saransk, Russia, was dissolved in 2015. Some of the developers are regularly on the Chemnitzer Linux days or Linuxtage represented in Berlin. The developers meet once a month in the chat, a summary of the minutes is published on the official website. About the Jira -Weboberfläche anyone can bug reports or suggestions (English bug reports or feature requests ) submitted.


The project is in the alpha phase. It is not yet intended for everyday use. The developers recommend installing it in a virtual machine . QEMU , VirtualBox and VMware are officially supported .

Hardware support has been limited so far. Apart from drivers for operation in a virtual machine , only a few drivers from device manufacturers are considered stable. In-house developments from some of Microsoft's software subsystems such as the Speech API are not yet available. Others, such as B. Sound system, have only been partially implemented so far (e.g. no MIDI). Standard applications that work stably include VLC media player , Softmaker Office 2006 and Firefox as well as basic utilities (e.g. 7-Zip ) and games such as Paintball 2, Quake III Arena , Globulation 2 or Civilization II .

ReactOS currently only offers very limited support for multi-core processors (SMP); almost all calculations are only carried out on one core.

Hardware requirements

ReactOS is content with older hardware. It supports 86 processors of Pentium generation or later. ReactOS requires 96 MB of RAM, but the developers recommend 256 MB. 650 MB storage space is required for installation. 5 GB or more is recommended for testing. The graphics card must be VGA compatible and implement the VESA BIOS Extension 2.0.

Legal issues

To avoid copyright infringement and legal conflicts, ReactOS must not be a derivative work from the Windows model. Therefore the further development was stopped for a short time on January 26th, 2006. To ensure that the procedures used to re-implement undocumented Windows functions through reverse engineering do not violate US copyright law, the source code was checked by a code audit up to December 2007 .

It was disputed whether and how the development of the operating system should be continued during the audit. At the beginning of February, a clear majority was in favor of a procedure in which development on the old code would be continued in parallel to the audit. According to this plan, version 0.4 would only contain checked source code. The plan favored by a smaller group of developers, however, envisaged the complete blocking of old code and the deletion of ReactOS publications from download servers. The further development should therefore only have been carried out on checked code, which led to delays of several months, but would have maximized legal certainty. During this phase, several developers left the project.

Previously, in November 2004, legal conflicts arose for the first time with a project that plagiarized the source code . Therefore the formation of a "Legal Defense Fund" was planned, with which legal interests of ReactOS should be represented.

Web links

Commons : ReactOS  - album with pictures, videos and audio files
Commons : ReactOS screenshots  - collection of images, videos and audio files

Individual evidence

  1. ReactOS license ( Memento of July 8, 2011 in the Internet Archive ), accessed on March 4, 2012.
  2. Release 0.4.13 . April 9, 2020 (accessed April 10, 2020).
  3. a b ReactOS ports (English) - ReactOS-Wiki ; last change on October 22, 2014.
  4. roadmap of the project (English)
  5. Arwinss presentation (English) - Presentation of the project coordinator Aleksey Bragin. January 16, 2010, accessed June 6, 2013.
  6. ARWINSS - The new Windows subsystem for ReactOS / Windows ( Memento from July 7, 2011 in the Internet Archive ; PDF; 900 kB) - Presentation about Arwinss (English)
  7. Newsletter No. 68 ( Memento of July 8, 2011 in the Internet Archive ) of January 22, 2010.
  8. Enjoy the New ReactOS Explorer (English) - ReactOS Community , on November 26, 2014.
  9. a b ReactOS Explorer (English) - Page in the ReactOS Wiki , last change on August 16, 2016 (accessed on December 11, 2016)
  10. Google Summer of Code 2006. Retrieved October 18, 2013 (English): “ This is a page lists the students and organizations that participated in the Google Summer of Code 2006 program. [...] ReactOS "
  11. TCP / IP driver replacement for ReactOS, using lwIP. (No longer available online.) Google, archived from the original on March 21, 2012 ; accessed on August 9, 2011 .
  12. Cameron Gutman: ReactOS is now using lwIP for TCP. August 7, 2011, accessed August 9, 2011 .
  13. ^ A personal appeal from ReactOS Project Coordinator Aleksey Bragin , accessed April 15, 2013.
  14. List of donors ( Memento from December 30, 2013 in the Internet Archive ) Status: December 24, 2012, accessed on April 15, 2013.
  15. Aleksey Bragin, Steven Edwards: Thorium Core Cloud Desktop. , December 23, 2013, accessed December 24, 2013 .
  16. ReactOS: The free Windows XP replica fulfills user requirements. In: heise open. Retrieved January 31, 2015 .
  17. reactos community edition on indiegogo (English, June 1, 2014)
  18. Russian president asked to Fund Windows Open Source Clone. Jordan Open Source Association, September 12, 2011, accessed on June 18, 2013 (English): “ At the forum, ReactOS won“ The Best Presentation ”award and a grant of 100000 rubles (approximately 2400 JDs). In addition, around twenty large investors became interested in the project. "
  19. Sourceforge POTM June 2013. SourceForge , June 17, 2013, accessed June 17, 2013 : “ Well I don't want to spread too many rumors, but I can say that we do have something in the works. If all goes well, it's going to be announced within a week. While I cannot go into too many details, I can say that it involves Kickstarter and what we believe to be a viable commercial product based off of ReactOS. "
  20. Виктор Имантович Алкснис wrote: 2007-06-06 16:38:00 Виктор Имантович Алкснис v_alksnis2 2007-06-06 16:38:00: ЗнакомствоOS стопроctкомствоOS. Retrieved April 8, 2019 .
  21. Russian President Medvedev asked to fund Windows clone. In: BBC News . September 13, 2011, accessed September 14, 2011 .
  22. Z98: ReactOS Presented to President Putin. In: ReactOS News. August 5, 2012, accessed June 23, 2013 .
  23. Russia declares ReactOS a favorite Windows alternative , Heise, June 23, 2015.
  24. Протокол экспертной оценки проектов по импортозамещению инфраструктурного программного обеспечения, соответствующего пунктам 4-8 плана импортозамещения программного обеспечения, утвержденного приказом Минкомсвязи России от 1 апреля 2015 г. №96 «Об утверждении плана импортозамещения программного обеспечения»:. Retrieved February 20, 2019 (Russian).
  25. Newsletter No. 41 ( Memento of July 8, 2011 in the Internet Archive ) of May 15, 2008.
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  27. Information from the newsletter ( memento of July 8, 2011 in the Internet Archive ) of November 4, 2008.
  28. Information from the news ( memento of July 8, 2011 in the Internet Archive ) on February 4, 2009.
  29. Information from the news ( memento of July 8, 2011 in the Internet Archive ) of April 26, 2009.
  30. ChangeLog-0.3.12 (English) - ReactOS JIRA , last changed on October 27, 2010; u. a. with ' Legacy HAL ' (see also " hardware abstraction layer ") and ' legacy device [driver] s ' literally "inherited devices [drivers] "
  31. ReactOS 0.3.13 published ( Memento from July 7, 2011 in the Internet Archive ) - Reported to ReactOS , from March 22, 2011.
  32. Windows replica: ReactOS 0.3.13 improves graphics support - Article at , March 28, 2011, accessed on June 6, 2013.
  33. ReactOS 0.3.14 published ( Memento from March 1, 2014 in the Internet Archive ) - public announcement by ReactOS , from February 7, 2012.
  34. Windows replica: ReactOS 0.3.14 receives new network stack and WLAN - Article at February 8, 2012, accessed June 6, 2013.
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  43. ChangeLog-0.4.6 - ReactOS Wiki. Retrieved September 3, 2017 .
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  59. Terry Hancock: What if copyright didn't apply to binary executables? Free Software Magazine , August 29, 2008; archived from the original on January 25, 2016 ; Retrieved January 25, 2016 : "" ReactOS aims to run actual Windows binary executable programs. This means that ReactOS must implement the entire Windows environment. Functions must do exactly what their Windows counterparts would do. In other words, like our notional parallel stew recipes, ReactOS and Windows should be functionally identical. In order to avoid copyright prosecution, though, ReactOS must be expressively completely distinct and non-derivative from Windows. This is a careful tightrope walk! ReactOS is a free, clean room re-implemented drop -in replacement for WindowsReactOS is a free, clean room re-implemented drop-in replacement for Windows So, consider this, especially regarding extremely simple library calls: is it legal for ReactOS to produce identical binary code to Windows? ""
  60. FOSDEM interview with Aleksey Bragin ( Memento from January 10, 2010 in the Internet Archive ) (2007, English)
  61. ReactOS Newsletter No. 11 ( Memento of July 8, 2011 in the Internet Archive ) of February 2, 2006.
  62. Ekush Emulator And its License Pains on OSNews by Eugenia Loli (November 10, 2004)
  63. Ekush OS - stolen source code / copyright violation ( Memento of November 14, 2004 in the Internet Archive )
  64. EKUSH The Next Generation Operating System ( Memento from June 19, 2004 in the Internet Archive ) on