nanokrnl: a Windows kernel, from scratch, in your browser

The end of an era. Many of us spent the last 20 or 30 years on low-level systems, emulation, and reverse engineering; a Windows kernel booting in a browser tab feels like full circle.

Both halves are written from scratch: nanokrnl, an NT-compatible kernel in Rust, and nanox, the ~60 KB x86-64 emulator that boots it in your browser and runs real, unmodified Windows binaries (cmd.exe, more.com, null.sys) on its own syscalls.

By Matt Suiche (@msuiche), Fable 5, Opus 4.8. Shout out to Fabrice Bellard.

C:\ Command Prompt (nanokrnl) 

    
    

      
      
      
      
      
      
      Boot runs the real cold boot; Fast Boot resumes a saved snapshot instantly.
    

    

      idle
      …
    

  








  

    
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WINAMP PLAYLIST

  







  
Resource Monitor×

  

    
CPU (emulation throughput)

    
    
speed0 MIPS

    
Memory

    
    
nanox RAM0 MB

    
JS heapn/a

  







  
Explorer: H:\×

  

    
H:\ (9P host share) · drag a file onto the page to add it

    
  










  
readme.txt×

  
Type directly into the console once you see C:\>. These run real Microsoft binaries on the kernel's own syscalls:
     dir, set, ver, whoami, vol, echo hi, more hello.txt, where cmd.exe, cmd /c dir, redirect with dir > out.txt then type out.txt, or crash for a BSOD.
     Enter sends the line. The kernel runs its self-tests first, so the prompt takes a few seconds.