An external hard drive is a portable storage device that can be connected to a computer using a USB or other type of connection. It provides additional storage capacity for your computer, allowing you to store large files that might not fit on your computer’s internal hard drive.

External hard drives can be used to back up your important files, transfer files from one computer to another, or expand the amount of storage you have available for your computer. They can be either solid-state drives (SSDs) or hard disk drives (HDDs), and they come in various capacities ranging from a few gigabytes to several terabytes. 

Generally, an external hard drive will be detectable and recognizable after being attached to your Mac, making it easy to copy files from your Mac to the external hard drive. But sometimes, transferring files from your Mac to an external hard drive may not work.

What do you do when you can’t copy files from a Mac to an external hard drive? In this article, we will elaborate on some possible reasons why this might happen and several troubleshooting solutions that you can try to get your files transferred.

Why Are You Unable to Copy Files from a Mac to an External Hard Drive?

Several things can cause the failure to copy data from your Mac to an external hard drive. We’ve analyzed some potential reasons in this section.

  1. Connectivity issue: The external hard drive isn’t properly connected to your Mac, leading to a poor connection between it and the external hard drive.
  1. Full disk space: The external hard drive may not have enough space to store the files you’re trying to copy.
  1. Read-only file system: The external hard drive could be formatted as New Technology File System (NTFS), a proprietary file system developed by Microsoft. Since Mac OS doesn’t have native support for the system, it will have read-only access to your external hard drive.
  1. Permission issue: The read-only permission setting is a hindrance that restricts you from copying files from a Mac to your external hard drive.
  1. Corrupted external hard drive: The external hard drive you’re trying to copy files to could be corrupted.

What to Do If You Can’t Copy Files from a Mac to an External Hard Drive

First off, ensure that the two devices are connected properly. The Mac won’t recognize the external drive if the connection is loose, resulting in your inability to copy data to the external drive.

Perform a basic examination of the Mac port (a physical interface on the Mac that allows you to connect external devices, such as a monitor, a keyboard, a mouse, or an external hard drive) and the USB cable. If this is not the underlying cause, you must try some remedies to resolve this issue.

Solution 1: Check If There Is Enough Space on the External Hard Drive

One possibility is that your drive is full. When this happens, you will receive an alert when you try to add files to the drive.

Hence, ensure you have enough free space on the external hard drive to hold the files you’re trying to copy.
You can check how much free space is available on your external hard drive by navigating to the Apple logo > About This Mac > Storage tab. If the drive is already full, you can delete unnecessary data to make space for the new files.

Check to See if There Is Enough Space on the External Hard Drive

Solution 2: Check If the External Hard Drive Has a Mac-Compatible File System

A file system is a method and data structure computer operating systems (OSs) use to store, organize, and retrieve files on a storage device, such as a hard drive, solid-state drive, or flash drive. The file system provides a structure for organizing and accessing files and directories on the storage device, and it manages the allocation and storage of data on the device.

Some file systems are Mac-compatible, such as APFS (the default file system used for Macs running macOS 10.13 or later versions), HFS+, exFAT, and FAT32 while some file systems like NTFS can’t be fully supported by Mac.

To find out what file system the external hard drive uses, access Disk Utility by going to Launchpad > Other > Disk Utility. After that, choose the drive from Disk Utility’s left sidebar to view its format in the right pane.

Check if the External Hard Drive Has a Mac-Compatible File System

If your external hard drive is formatted as the NTFS file system and you’re trying to copy files from your Mac, you may encounter issues because the Mac will see the NTFS formatted drive as read-only.

To fix this, you’ll need to format the external hard drive to a file system that your Mac supports, such as FAT32 or exFAT. To do this, launch Disk Utility, select the external hard drive you’d like to format from the left sidebar, click the Erase button from the top menu of Disk Utility, and then follow the prompts to complete the process.   

Alternatively, you can use some NTFS for Mac utilities to mount your external hard drive in read-write mode. That is the most straightforward way to solve the read-only drive issue without losing any data because the NTFS for Mac utility will grant you full read-write access to your NTFS drive on macOS, allowing you to copy, delete, rename, transfer, and edit files stored on the NTFS drive.

Solution 3: Check If the External Hard Drive Has a Read-Only Permission Setting on Mac

If you’re unable to copy files to an external hard drive, it’s likely that you don’t have the correct permissions to access the external hard drive. To fix that, you’ll need to open the Info Window on your Mac to grant yourself read-write access to the external hard drive.

Step 1: Right-click the external hard drive and then select the Get Info option from the context menu.

Step 2: Scroll down to the Sharing & Permissions area at the bottom of the Info pane to see the permissions that each user has on the disk. If you have read-only permission, then move on to the next step.

Check if the External Hard Drive Has a Read-Only Permission Setting on Mac

Step 3: Click the yellow Lock icon at the bottom right corner to enter the correct password.

Step 4: Choose the username associated with the account you are using to access the drive and then change Read Only to Read & Write.

Read & Write

Solution 4: Run the First Aid Program to Repair the Corrupted External Hard Drive

After trying the fixes mentioned above, are you still unable to copy files to your external hard drive? In that case, your drive might be corrupted. If a drive is corrupted, it may be difficult or impossible to access the files stored on it, let alone move files to the corrupt drive. Given this scenario, run First Aid in Disk Utility to check and repair the corrupted external hard drive.

Step 1: Click Finder from the Dock, select Applications from the left sidebar, and then find and open Disk Utility under the Utilities menu.

Step 2: Choose the corrupted drive under External and move to the top toolbar to click the First Aid menu.

Step 3: Click the Run button to confirm your choice.

Step 4: Wait for the repair process to be completed and then click Done.

Run the First Aid Program to Repair the Corrupted External Hard Drive

Conclusion

You now know some of the reasons why you cannot copy files from your Mac to an external hard drive and their fixes. The tips and steps can help you copy your files to your external hard drive.