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About ReactOS

ReactOS® is an effort by the ReactOS Foundation to create a Free Software replacement for Microsoft Windows® that is compatible with existing hardware and software!

What Is ReactOS

ReactOS is a free and open-sourced operating system based on the Windows NT architecture, providing support for existing applications and drivers, and an alternative to the current dominant consumer operating system.

It would be perhaps important to start by saying what ReactOS -isn't-. It is not another wrapper built on Linux, like WINE. It does not attempt or plan to compete with WINE; in fact, the user-mode part of ReactOS is almost entirely WINE-based and our two teams have cooperated closely in the past. ReactOS is also not "yet another OS". It does not attempt to be a third player, like SkyOS or any other alternative OS out there. People are not meant to uninstall Linux and use ReactOS instead; ReactOS is a replacement for Windows users who want a Windows replacement that behaves just like Windows.

While ReactOS' source availability and current usage is mostly intended for programmers to expand and improve on, you don't need to be a rocket scientist to use it, and in its final state will be a consumer friendly OS. If you've used Windows before, you'll find yourself in a familiar environment with ReactOS. The learning curve, if any, should be minimal, since ReactOS duplicates many of the Windows graphical environment applets, control panels and dialogs (Windows 2000/XP/2003).

Focus at present is on developing ReactOS to a stage where it is capable of running most Windows drivers and applications "out of the box." This does not mean that ReactOS will stop there, however; as new features are added to Windows, our developers be striving to incorporate such new features in future versions of ReactOS. Once the compatibility level has been reached, we may even choose to improve ReactOS beyond its Windows roots. These changes would be external from the main OS, and totally compatible with Windows, but they would add an extra advantage. For example, one of our goals is to have built-in POSIX compatibility, much like Windows Services for Unix. It could also be as simple as natively supporting multiple desktops however, instead of requiring a powertoy.

ReactOS® is a registered trademark of the ReactOS Foundation.
Windows® NT™ is a registered trademark of Microsoft Corporation.


Change your OS, not your software!

The ReactOS project reimplements a state-of-the-art and open NT-like operating system based on the NT architecture. It comes with a WIN32 subsystem, NT driver compatibility and a handful of useful applications and tools.

ReactOS combines the power and strengths of the NT kernel - which is well known for its extensibility, portability, reliability, robustness, performance and compatibility – with Win32 compatibility.


Despite statements to the contrary, NT is secure by design. It was the first mainstream operating system with a proper implementation of a very flexible security model based on access control lists.

Recent NT-based operating systems from Redmond, especially XP, got a bad reputation for their weak default security settings; mainly to simplify the transition from Win9x for both users and legacy applications. This decision alone invalidated many of the security features in NT. ReactOS will incorporate proper default security settings.

ReactOS has been designed for high security; it doesn't share some of the common security flaws with other operating systems.

On a closer view, real computer viruses (which are normal applications) are not as widespread anymore. Most malicious applications are scripts that target common network software like browsers and email applications and software with built-in scripting support like various Office products. Obviously, more widespread systems with a large user base are more likely to be attacked by bad software writers than minor systems like Macintosh and Linux.


In short, ReactOS is designed to be powerful and lightweight. You can think of the term "lightweight" in the good old fashion of Win95, a consistent user interface and small bundle of very common and useful tools. Although lightweight, ReactOS offers a lot in comparison to Windows 95, with an up-to-date experience as well as built from scratch on a rock solid NT core.


The code of ReactOS is licensed under GNU GPL 2.0+

'Free' as in 'free speech' and as in 'free beer'

ReactOS is free and open source software, the source code of the whole system is available for free. Most parts are licensed under GNU General Public License, some modules have other licenses like BSD .


Open your windows to freedom

ReactOS has been written from scratch since 1996, a rock solid NT re-implementation, and therefore a reliable and robust operating system for tasks ranging from embedded micro computer to personal computer, workstations to server cluster, mainframes and super computers. ReactOS incorporates many design decisions from other operating system families like UNIX, VMS, OS/2 and of course NT and is meant as 'the' new platform that serves all.


ReactOS – the XP successor people asked for

The ReactOS operating system design is able to provide portability across families of processors, such as Intel x86 and even provide portability across different processor architectures, such as CISC and RISC. There is only one single OS core, the kernel; porting ReactOS to other architectures only involves porting the hardware abstraction layer, the lowest part that talks directly with the platform hardware.


ReactOS is flexible and extensible by design. ReactOS is probably one of the most versatile operating system platform, especially thanks to its NT kernel and the open source nature. ReactOS can be extended with the help of so called "subsystems" to provide support for legacy applications from other platforms. For example, a POSIX subsystem would provide compatibility layer with various flavors of UNIX applications.

Object Based

ReactOS is not an object-oriented system in the strictest sense of the term, but it does use objects to represent internal system resources. Software objects are a combination of computer instructions and data that model the behavior of things, real or imagined, in the world.

UNIX file metaphor is sooooo 1970s

UNIX operating systems adhere to the file metaphor, and devices such as printers, storage devices, keyboards and monitors all appear as ordinary files to both programmers and regular users. This simplifies many routine tasks, and is a key component in the extensibility of the system. The file metaphor has several downsides and it is known as a bottleneck of UNIX-like operating systems. ReactOS capitalizes on this metaphor and expands it. It uses an object metaphor that is pervasive throughout the architecture of the system. Not only are all of the things in the UNIX file metaphor viewed as objects by ReactOS, but so are things such as processes and threads, shared memory segments, the global registry database and even access rights.

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