reactos/reactos
FreeA free Windows-compatible Operating System
FreeFree tier
About reactos/reactos
ReactOS is an open-source operating system designed to be compatible with applications and drivers written for the Microsoft Windows NT family (NT4, 2000, XP, 2003, Vista, 7). Currently focused on Windows Server 2003 compatibility, the project also targets future Windows NT releases. ReactOS is licensed under GNU GPL 2.0 and is in alpha development stage, meaning it is not yet stable for production use and may corrupt data. It can be built from source using the ReactOS Build Environment (RosBE) or Microsoft Visual C++ (MSVC) 2019+, and bootable CD images can be generated with the ninja bootcd command. Daily binary builds are available for testing.
Key Features
Compatible with Windows NT family (NT4, 2000, XP, 2003, Vista, 7) applications and drivers
Open source under GNU GPL 2.0 license
Focus on Windows Server 2003 compatibility with plans for future NT releases
Alpha quality – under heavy development
Buildable from source using RosBE or Microsoft Visual C++ 2019+
Generates bootable CD image (bootcd.iso) via ninja command
Daily binary builds available for testing
Pros & Cons
Pros
- Completely free and open source under GPL 2.0
- Aims to run Windows applications and drivers natively
- Active development with a large community (17.8k stars on GitHub)
- Supports multiple build environments (RosBE, MSVC, Clang)
Cons
- Alpha quality – unstable and may cause data loss; not recommended for production
- Incomplete compatibility with all Windows software and drivers
- Limited hardware support and potential performance issues
- Installation only on FAT16/FAT32 partitions
Best For
Running Windows applications on an open-source operating systemTesting and development of Windows-compatible softwareLearning operating system internals and Windows NT architectureCompatibility testing for Windows drivers and applicationsBuilding and contributing to an open-source OS project
FAQ
What is ReactOS?
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).
Is ReactOS stable?
No, ReactOS is currently in alpha quality, meaning it is under heavy development and may not work well. It can corrupt data on your hard disk, so it is highly recommended to test it on a virtual machine or a computer without sensitive data.
How can I build ReactOS from source?
ReactOS can be built using the ReactOS Build Environment (RosBE) on Windows or Unix/Linux, or using Microsoft Visual C++ (MSVC) version 2019 or later. Run the configure script (configure.cmd or configure.sh) and then use ninja to build modules or the entire system.
Where can I download prebuilt binaries?
Fresh binary builds of bootable CD images are available from the 'Daily builds' page linked in the repository's README.
What license does ReactOS use?
ReactOS is licensed under GNU General Public License version 2 (GNU GPL 2.0).