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Top 23 C Osdev Projects
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There is already a "Windows Lite", and it's called ReactOS [0].
Except, the last thing we need is for Microsoft to own / embrace-extend-exterminate this. It's best that it's kept as an independent project, enabling developers to target the Windows API if they feel like it, while ensuring that they only target the Wine-compatible parts of it, which then enables their software to also run seamlessly on other platforms at no extra effort, and without requiring either the users or the devs to have to lock themselves into this ungodly telemetry-spying-ads-AI-.NET mess that the article talks about.
Microsoft, on the other hand, has zero to gain from making a Windows Lite variant themselves given their lifeline is exactly this telemetry-spying-ads-AI-.NET ecosystem; and they have zero to gain from absorbing ReactOS or similar projects, other than in order to eliminate them.
[0] https://reactos.org/
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AppSignal
AppSignal knows why the f*#k it crashed. Stop vibe-debugging. Every exception, every backtrace, grouped so you see patterns, not noise.
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ravynos
An open-source OS project that aims to provide source and binary compatibility with macOS® and a similar user experience.
Project mention: New OS aims to provide (some) compatibility with macOS | news.ycombinator.com | 2025-11-20 -
unikraft
A next-generation cloud native kernel designed to unlock best-in-class performance, security primitives and efficiency savings.
Unikernels with POSIX compatibility.
Each application gets its own fine grained security.
https://github.com/unikraft/unikraft
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Project mention: Show HN: Ant – A JavaScript Runtime and Ecosystem | news.ycombinator.com | 2026-07-11
on linux its kvm, on darwin its hypervisor.framework, the memory is not upfront, by default 256mb is lazy allocated, and ~35mb are used by both ant + the vm. the kernel is https://nanos.org with patches to get ant+networking running smoothly
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brutal
🏢 An operating system inspired by brutalist design that combines the ideals of UNIX from the 1970s with modern technology and engineering
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RetrOS-32
A x86 32bit Hobby Operatingsystem with graphics, multitasking, networking and 32bit C-Compiler for i386 architecture.
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SaaSHub
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PatchworkOS
A modular, non-POSIX operating system for x86_64, built from scratch in C and assembly. Intended to be educational and experimental while rigorously following a Plan9-style "everything is a file" philosophy, featuring a from-scratch ACPI AML parser, EEVDF scheduler and a pseudo-capability namespace based security model.
Project mention: PatchworkOS: An OS for x86_64, built from scratch in C and assembly | news.ycombinator.com | 2025-12-06 -
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Project mention: NanoShell: A preemptively multi-tasked 32-bit OS with a windowed GUI | news.ycombinator.com | 2026-07-01
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kernel
Portable asynchronous microkernel with multiprocessor priority scheduling and Unix-like abstractions (by lux-operating-system)
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lytlnyblOS
lytlnyblOS (little nibble OS) is a small, from scratch 32-bit operating system that comes with a complete guide book to teach beginners practically about OS development.
Project mention: Show HN: A beginner-friendly guide to building an operating system from scratch | news.ycombinator.com | 2026-09-17 -
Project mention: Show HN: Anos – a hand-written ~100KiB microkernel for x86-64 and RISC-V | news.ycombinator.com | 2026-04-03
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SaaSHub
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NOTE:
The open source projects on this list are ordered by number of github stars.
The number of mentions indicates repo mentiontions in the last 12 Months or
since we started tracking (Dec 2020).
C Osdev discussion
C Osdev related posts
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Show HN: Bare-Metal RTOS(TamgaOs) for Cortex-M7 (STM32H753ZI) Port
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ReactOS
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Using GNU toolchain for Windows kernel-mode drivers
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An initial investigation into WDDM on ReactOS
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Microsoft are removing mechanisms for creating a local account in Windows Setup
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Why is Windows still tinkering with critical sections? – The Old New Thing
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NanoVMs
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A note from our sponsor - AppSignal
www.appsignal.com | 9 Oct 2026
Index
What are some of the best open-source Osdev projects in C? This list will help you:
| # | Project | Stars |
|---|---|---|
| 1 | reactos | 18,155 |
| 2 | raspberry-pi-os | 13,937 |
| 3 | ravynos | 7,050 |
| 4 | unikraft | 3,884 |
| 5 | nanos | 3,199 |
| 6 | brutal | 1,110 |
| 7 | RetrOS-32 | 813 |
| 8 | WingOS | 769 |
| 9 | cavOS | 738 |
| 10 | opuntiaOS | 662 |
| 11 | ghost | 648 |
| 12 | PatchworkOS | 446 |
| 13 | mos | 393 |
| 14 | NanoShellOS | 263 |
| 15 | buddy_alloc | 252 |
| 16 | Ethereal | 213 |
| 17 | Dreamos64 | 213 |
| 18 | NesUEFI | 204 |
| 19 | kernel | 190 |
| 20 | fox32 | 141 |
| 21 | lytlnyblOS | 113 |
| 22 | anos | 112 |
| 23 | MoonOS | 109 |
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