ReactOS
Verified working Sep 19, 2026
An open-source operating system built for Windows app compatibility.
ReactOS is a free operating system project that reimplements Windows-compatible system behavior in open source form. The site provides downloads, nightly builds, development documentation, bug reporting, project news, and community channels for users and contributors.
Why it stands out
- Targets Windows application and driver compatibility rather than being a Unix-like desktop clone.
- Fully open-source project with public code, build instructions, bug tracking, and contribution paths.
- Long-running community effort with decades of development history and public progress updates.
- Offers both release downloads and nightly builds for users who want newer fixes quickly.
Good to know
- ReactOS aims for Windows compatibility, but users should verify specific apps, drivers, and hardware before depending on it.
- The newest fixes may require using nightly builds instead of the main release download.
- Support appears to be community-based through chat, forums, mailing lists, and issue tracking rather than commercial support.
Under the radar: Before filing a compatibility bug, check the linked Testman results and try a current nightly build; the issue may already be exposed by automated tests or fixed after the latest release.
Photos
Developers, testers, and open-source OS enthusiasts can try Windows-oriented software in a non-Microsoft environment. Test an application or driver against ReactOS before reporting compatibility issues. Follow project progress through news posts, Jira, GitHub, and the wiki. Download stable releases or nightly builds for experimenting with newer fixes. Join chat, forums, or mailing lists to contribute testing, documentation, or code.
Downloadable ReactOS releases and nightly builds; GitHub source repository; Jira bug tracker; Testman test infrastructure; wiki and build/contribution documentation; screenshots, FAQ, news, forums, chat, and mailing lists.
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Similar sites elsewhere
- WineHQ — winehq.org
- FreeDOS — freedos.org
- Haiku — haiku-os.org
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