If you can't copy and paste (or drag and drop) items from the Mac to your external drive as usual, the problem is usually caused by one of the following:
| Symptom | Possible Cause | Recommended Fix |
| You can open the drive, but you cannot copy files to it | NTFS-formatted drive | Use NTFS for Mac software |
| The drive says you only have read permission | Read-only permissions to the drive | Change drive permissions in Get Info |
| Copying stops or fails halfway unexpectedly The external hard drive freezes when copying files on the Mac | System bugs Insufficient storage space | Restart the Mac Free up more space |
| Drive disconnects or disappears randomly | Unstable connection | Try another cable/port |
| The drive only shows up in Disk Utility, but in an unmounted state, and cannot be mounted manually | File system corruption | Recover data before running First Aid or reformatting |
Follow the safe troubleshooting steps in this guide, and then you can copy files from your Mac to an external hard drive again.
Before you fix it: avoid data loss
Before troubleshooting the drive, keep these precautions in mind:
- If the external drive contains important files, recover or back up the data before running First Aid repeatedly or reformatting the drive. Repair and formatting operations may change the file system structure and reduce the chance of successful recovery.
- If the drive is NTFS-formatted, formatting is usually unnecessary. You can use an NTFS for Mac tool.
These precautions can help reduce the risk of permanent data loss.
Check whether the drive is NTFS
NTFS is Microsoft's default file system for Windows. macOS can typically read NTFS drives, but cannot write to them natively.
As a result, you can open files but not copy, move, edit, delete, or create files on the NTFS drive on your Mac.
To check if you have a read-only file system on the external drive:
- Open Finder > Applications > Utilities > Disk Utility.
- Select the external drive.
- Check the format displayed under the drive name.
If it is an NTFS drive, use iBoysoft NTFS for Mac to enable full read-write access without requiring you to erase or reformat the drive.
With write access enabled, you can:
- Copy files to NTFS drives on a Mac
- Move files between your Mac and the drive
- Edit existing files
- Create folders
- Delete files
However, NTFS software does not resolve problems caused by:
- Physical drive damage
- File system corruption
- Insufficient storage space
- Faulty cables or ports
- BitLocker encryption issues
If any of these conditions exist, continue with the troubleshooting steps below.
Check the external hard drive's permissions on Mac
If the drive uses macOS-compatible APFS, HFS+, exFAT, or FAT32 but remains read-only, its permissions may be restricting access.
To verify permissions:
- Right-click the external hard drive.
- Select "Get Info" from the menu.
- Scroll to Sharing & Permissions.
You can see the disk's privileges for each user.
If your account does not have Read & Write privileges, change the permissions on your Mac:
- Click the bottom padlock and enter the admin password to unlock it.
- Select the user name of the account that you currently log into on the Mac under the Sharing & Permissions section.
- Expand the privilege of this user and choose "Read & Write".
After resetting the permissions on the external hard drive, you can put items on it freely. If you can't change permissions on the external hard drive on your Mac, re-check if the drive is set as a Time Machine backup disk.
Restart your Mac
Temporary macOS glitches can interfere with file operations.
Restarting your Mac refreshes system processes and may resolve copy-and-paste, Finder, or external drive communication issues.
Go to: Apple menu > Restart
After restarting, reconnect the drive and test file transfers again.
Check the available storage space of the external drive
It is also possible that your external hard drive is full. So, when you put large files and folders into it, a prohibitive symbol shows up to indicate that you can't do that.
To check available storage:
- Open Disk Utility.
- Select the external drive.
- Review available capacity.
If the external disk is almost full:
- Delete unnecessary files
- Move old files elsewhere
- Use another drive for temporary storage
Then try copying your files again.
Check the disk connections
A loose cable, damaged USB adapter, or faulty port can interrupt communication between your Mac and the external drive.
Try the following:
- Disconnect and reconnect the drive
- Connect the drive directly instead of through a USB hub
- Try another USB-C or USB-A port
- Use a different cable if available
- Test the drive on another Mac or PC
If the drive frequently disconnects, spins up and down repeatedly, or disappears from Finder, the issue may be hardware-related.
Repair the drive with First Aid
File system errors can prevent external drives from working properly on a Mac or even from being mounted in Disk Utility, let alone accepting new data.
To run Disk Utility First Aid to check and repair the errors on the disk:
- Open Launchpad on the dock > Other > Disk Utility.
- Select the external hard drive on the left sidebar.
- Click "First Aid" on the top toolbar in the Disk Utility window.
- Click "Run" on the confirmation dialogue window and wait until the process is done.
After First Aid finishes, try copying files again.
Recover data and then reformat the external drive (last resort)
If you're still unable to copy files from Mac to the external hard drive after running Disk Utility First Aid, the disk may be seriously corrupted. You have to reformat it to make it work again.
But formatting a disk will erase all data on it. If you have important data on it, you need to use iBoysoft Data Recovery for Mac to recover the files. This professional data recovery tool can help you restore files from unmounted, inaccessible, and corrupted external hard drives, USB drives, and other storage devices with simple clicks.
Recover data from the external drive
- Free download, install, and open iBoysoft Data Recovery for Mac.
- Select your problematic external drive from the app's main interface and click "Search for Lost Data".
- Preview the results after the scanning process is done.
- Choose the desired files and click "Recover" to save these files to a different destination.
Reformat the external hard drive on your Mac
- Open Launchpad > Other > Disk Utility.
- Select the drive.
- Click Erase > Run.
Why can't you copy files from a Mac to an external hard drive?
The reasons for this problem are multifarious.
Reasons why you can't copy or move an item to an external drive on a Mac:
- Poor or faulty disk connections, such as the external hard drive spinning up/down constantly.
- The external drive is not compatible with your Mac.
- Read-only permission for the external hard drive.
- Drag and drop is not working on your Mac.
- Copy and paste is not working on your Mac.
- The disk storage space is full.
- The external hard drive is corrupted.
- macOS bugs.
- The external hard drive is damaged.
Read this article to learn different ways to copy files from your Mac to an external hard drive. It also tells you what to do if you can't transfer files to an external hard drive on a Mac.
FAQ
- QWhy can I read files but not copy files to my external hard drive on Mac?
-
A
There are two main reasons. One is that your external hard drive is formatted with NTFS. Microsoft NTFS is used for Windows and only provides read support on Mac. The other is that the external hard drive's permission on your Mac is read-only.
- QCan I copy files to an NTFS drive on Mac without formatting it?
-
A
Yes. You can use NTFS for Mac software, like iBoysoft NTFS for Mac, to enable write access without erasing or reformatting the drive.
- Q How do I know if my external drive is NTFS?
-
A
Open Disk Utility, select the drive, and check the format listed in the drive information panel.