NTFSTool writes Windows drives on a Mac through FSKit, with a macOS 26 catch
NTFSTool’s current open-source edition uses Apple’s user-space FSKit to write NTFS disks. Physical-disk writing needs macOS 26; a Windows-hibernated disk deliberately stays read-only.
The drive is readable in Finder, but adding a file is another matter. NTFSTool’s current edition addresses that NTFS gap with an FSKit driver, avoiding the older kernel-extension setup.
The version requirement decides whether it solves your problem. The README says “write support needs macOS 26 or later,” even though the app itself can run on macOS 15.6. The old Electron/FUSE edition lives on a separate archived branch and is no longer maintained.
Setup means enabling the file system extension in System Settings under General, Login Items & Extensions, then File System Extensions. The app may ask you to eject and reconnect a drive so macOS can mount it through the new driver.
A drive left hibernated by Windows, including its Fast Startup state, remains read-only. The maker treats that as protection against disk corruption and gives instructions for shutting Windows down completely. Trying to force past the refusal would defeat the part of the design protecting the files.
The next thing worth checking is an ordinary file round trip on a backed-up test disk: write on the Mac, eject properly and read it back in Windows.