ReactOS™ is an Open Source effort to develop a quality operating system that is compatible with applications and drivers written for the Microsoft® Windows™ NT family of operating systems (NT4, 2000, XP, 2003, Vista, Seven).
The ReactOS project, although currently focused on Windows Server 2003 compatibility, is always keeping an eye toward compatibility with Windows Vista and future Windows NT releases.
***ReactOS is currently an Alpha quality operating system. This means that ReactOS is under heavy development, things may not work well and it can corrupt the data present on your hard disk. It is recommended to test ReactOS on a virtual machine or on a computer with no sensitive or critical data!***
To build the system it is strongly advised to use the _ReactOS Build Environment (RosBE)._
Up-to-date versions for Windows and for Unix/GNU-Linux are available from our download page at: ["Build Environment"](http://www.reactos.org/wiki/Build_Environment).
Alternatively one can use Microsoft Visual C++ (MSVC) version 2010+. Building with MSVC is covered here: ["Visual Studio or Microsoft Visual C++"](https://www.reactos.org/wiki/CMake#Visual_Studio_or_Microsoft_Visual_C.2B.2B).
To build ReactOS you must run the `configure` script in the directory you want to have your build files. Choose `configure.cmd` or `configure.sh` depending on your system. Then run `ninja <modulename>` to build a module you want or just `ninja` to build all modules.
If you discover a bug in ReactOS search on JIRA first - it might be reported already. If not report the bug providing logs and as much information as possible.
You can also support ReactOS by [donating](https://reactos.org/donating)! We rely on our backers to maintain our servers and accelerate development by [hiring full-time devs](https://reactos.org/node/785).
ReactOS is a Free and Open Source operating system based on the Windows architecture,
providing support for existing applications and drivers, and an alternative to the current dominant consumer operating system.
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 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.
The main development is done on [GitHub](https://github.com/reactos/reactos). We have an [alternative mirror](https://git.reactos.org/?p=reactos.git) in case GitHub is down.
