I have a 2TB Seagate Expansion drive that shows up as HFS, but I can’t write to it.
The permissions can’t be changed, and attempts to reformat or fix it haven’t worked.
I’ve tried stopping mds_stores in Activity Monitor and running First Aid multiple times, but the issue persists.
The drive itself works—I can copy files from it to my Mac—but I can’t copy anything back onto it. I’m looking for a workaround since it’s becoming really frustrating.
Have you really checked the file system?
I know that the NTFS-formatted drive has this issue like you said: can read but not write.
Please check the file system in Disk Utility, if it is NTFS, it’s highly recommended to use NTFS driver tool(without reformatting).
iBoysoft NTFS for Mac is a good choice, have a try.
Sounds like your drive might be formatted in HFS+ but set as read-only for some reason.
If you only need it on macOS, try backing up your data and reformatting it in Disk Utility to “Mac OS Extended (Journaled)” or even APFS on Mac. That should restore full read/write access.
Or read this post: Can’t save or write to external hard drive on Mac.
If the disk was originally formatted on another machine, it’s possible macOS is just mounting it read-only because of file system corruption. Since you’ve already tried First Aid, I’d suggest using Terminal:
diskutil verifyVolume /Volumes/YourDriveName
diskutil repairVolume /Volumes/YourDriveName
If that still fails, reformatting might be the only permanent fix.
Or you can check the drive’s permissions. Sometimes, external drives mount as read-only if ownership is enforced. In Finder, right-click the drive → Get Info → scroll down to Sharing & Permissions, and make sure “Ignore ownership on this volume” is checked. Then eject and reconnect the drive.