Ntfs2btrfs is a tool which does in-place conversion of Microsoft's NTFS filesystem to the open-source filesystem Btrfs, much as btrfs-convert does for ext2. The original image is saved as a reflink copy at image/ntfs.img, and if you want to keep the conversion you can delete this to free up space.

Although I believe this tool to be stable, please note that I take no responsibility if something goes awry!

You're probably also interested in WinBtrfs, which is a Btrfs filesystem driver for Windows.

Thanks to Eric Biggers, who successfully reverse-engineered Windows 10's "WOF compressed data", and whose code I've used here.

On Windows, from an Administrator command prompt:

ntfs2btrfs.exe D:\

Bear in mind that it won't work with your boot drive or a drive with a pagefile on it.

On Linux, as root:

ntfs2btrfs /dev/sda1

On Windows, go to the Releases page and download the latest Zip file.

For Linux:

• Arch (thanks to nicman23)
• Fedora (thanks to Conan-Kudo)
• Gentoo ebuild

For other distributions or operating systems, you will need to compile it yourself - see below.

• 20210402 (source code only release)

  • Fixes for compilation on non-amd64 architectures

• 20210105

  • Added support for NTFS compression
  • Added support for "WOF compressed data"
  • Fixed problems caused by sparse files
  • Miscellaneous bug fixes

• 20201108

  • Improved error handling
  • Added better message if NTFS is corrupted or unclean
  • Better handling of relocations

• 20200330

  • Initial release

On Windows, open the source directory in a recent version of MSVC, right-click on CMakeLists.txt, and click Compile.

On Linux:

cmake .
make

You'll also need libfmt installed - it should be in your package manager.

• Files
• Directories
• Symlinks
• Other reparse points
• Security descriptors
• Alternate data streams
• DOS attributes (hidden, system, etc.)

• Rollback to original NTFS image
• Windows' old extended attributes (you're not using these)
• Large (i.e >16KB) ADSes (you're not using these either)
• Preservation of LXSS metadata
• Preservation of the case-sensitivity flag
• Unusual cluster sizes (i.e. not 4 KB)
• Encrypted files

Yes, if the stars are right. See Quibble.