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, 7).
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 and you have to be ready to encounter some problems. Different things may not work well and it can corrupt the data present on your hard disk. It is HIGHLY recommended to test ReactOS on a virtual machine or on a computer with no sensitive or critical data!
Up-to-date versions for Windows and for Unix/GNU-Linux are available from our download page at: ["Build Environment"](https://reactos.org/wiki/Build_Environment).
Alternatively one can use Microsoft Visual C++ (MSVC) version 2019+. Building with MSVC is covered here: ["Visual Studio or Microsoft Visual C++"](https://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.
Starting with 0.4.10, ReactOS can be installed using the BtrFS file system. But consider this as an experimental feature and thus regressions not triggered on FAT setup may be observed.
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.
__NOTE:__ The bug tracker is _not_ for discussions. Please use our [official chat](https://chat.reactos.org/) or our [forum](https://reactos.org/forum/).
__Legal notice__: If you have seen proprietary Microsoft Windows source code (including but not limited to the leaked Windows NT 3.5, NT 4, 2000 source code and the Windows Research Kernel), your contribution won't be accepted because of potential copyright violation.
You can also support ReactOS by [donating](https://reactos.org/donate/)! We rely on our backers to maintain our servers and accelerate development by [hiring full-time devs](https://reactos.org/contributing/#paid-jobs).
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.
