List of free, open source operating systems

Updated: October 27, 2025

  1. OpenBSD
  2. Linux
  3. FreeBSD
  4. NetBSD
  5. Dragonfly BSD
  6. Qubes OS
  7. Haiku
  8. Redox
  9. ReactOS
  10. AROS
  11. FreeDOS
  12. BASIC-DOS
  13. Blog series: Writing an OS in Rust
  14. skiftOS
  15. RetrOS-32
  16. Tock
  17. Hubris
  18. Essence
  19. Subgraph OS
  20. Ares
  21. osv.io
  22. axle OS
  23. Snowdrop OS
  24. vekos
  25. Essence
  26. Barrelfish
  27. ToaruOS
  28. MyraOS
  29. Mezzano
  30. House
  31. Minoca OS
  32. Kerla
  33. SOS
  34. PowerNex
  35. Interim OS
  36. KolibriOS
  37. MINIX
  38. RISC OS
  39. HelenOS
  40. GeckOS/A65 V2.0
  41. Serenity
  42. GNU Hurd
  43. Plan 9
  44. Harvey
  45. illumos
  46. AquilaOS
  47. NuttX
  48. Sculpt
  49. Biscuit
  50. Xv6