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ReactOS

ReactOS

Open Source & Free Software AlternativesOperating Systems
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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

Illustration for ReactOS