A Windows-formatted external drive plugged into a Mac mounts, shows every file, and then refuses to accept a single byte. That is not a bug and not a licence restriction on Apple’s side — it is a deliberate limit, and understanding it tells you which of the three fixes is the right one for you.

What NTFS Is

NTFS is the default filesystem on Windows. It handles permissions, journaling, compression, encryption and very large volumes, and it has been the standard since Windows NT. A drive formatted NTFS is the normal state of any external disk that has been used on a Windows machine and never reformatted.

The problem is not that macOS cannot read it. Apple’s driver handles reads fine, which is why the files appear in Finder. The problem is the write path: NTFS metadata updates are intricate, the format is Microsoft’s, and Apple does not ship a write implementation it is willing to stand behind. So the volume mounts read-only, and the Finder offers no way to change that.

Three Ways Around It

Reformat the drive. The clean answer when the drive is yours and nothing on it needs to stay in Windows format. ExFAT is readable and writable on macOS, Windows and most Linux distributions, has no practical file size limit for normal use, and is the standard choice for a shared external disk. The cost is that reformatting erases the drive, and exFAT has weaker journaling than NTFS — pulling the cable mid-write can cost you the directory.

Use a third-party NTFS driver. Paragon NTFS and Tuxera NTFS are commercial drivers that implement full read-write support. Both are mature, both handle journaling properly, and both are the answer when the drive has to stay NTFS because other machines depend on it.

Remove the read-only restriction yourself. Mounty re-mounts an NTFS volume in read-write mode using macOS’s own driver with the flag cleared. It is free and it works. It is also the option with the least protection: you are using a driver Apple declined to expose for writing, so the failure mode is a damaged volume rather than a refused write.

Which One to Pick

Reformat to exFAT if the drive is only ever going to move between your own machines. It costs one erase and removes the problem permanently.

Buy a driver if the drive belongs to a Windows workflow you do not control — a shared archive, a client’s disk, a bootable Windows installer you maintain.

Use the free re-mount if it is a one-off: you need to copy files onto a drive today and will not touch it again. Back up whatever is on it first.

What to Check Before Any of This

Confirm what the volume actually is, rather than assuming:

diskutil list

That prints every attached disk with its filesystem type. A drive showing Windows_NTFS is the case this article is about. One showing ExFAT or MS-DOS FAT32 already works on both platforms and needs nothing.

FAT32 is worth a mention because it looks like a solution and is not — it caps individual files at 4 GB, which rules out most video and disk images.

Our guide to NTFS drivers for Mac compares the commercial options, and if the underlying problem is that the drive is simply full, freeing up storage is the more useful next step.

Frequently Asked Questions

Why does macOS support reading NTFS but not writing to it?

NTFS is Microsoft's filesystem and its write behaviour is documented only partially. Apple ships a read-only driver rather than a write path it cannot fully validate, so a Mac will mount an NTFS drive and show its contents without offering to modify them.

Is it safe to force write access with a free tool?

The free approach uses macOS's own NTFS driver with the read-only restriction removed. It works, but it bypasses the safety margin Apple chose, so a volume that is ejected mid-write or already has filesystem errors can be damaged. Have a backup before relying on it.