When you copy files to or edit documents on an external hard drive on a Mac, the following message appears:
The operation can't be completed because you don't have the necessary permission.
Conventionally, you can right-click the external drive and go to the Get Info field to change permissions. However, you only find that you can't change permissions on the external drive on your Mac. Why? We can help you. Please read on to get the answers and workarounds.
| Situation | Solution |
| See "You have custom access" in Get Info | 1. Check if the drive is NTFS in the General section of the Get Info window. 2. If it is, use iBoysoft NTFS for Mac to automatically mount the read-only drive to read & write on your Mac. |
| See " You can only read" in Get Info | 1. Go to Time Machine preferences to stop using the drive as the backup disk. 2. Or, add a volume to the drive in Disk Utility to enable it to store other files. |
| You are a guest user | 1. Click the lock at the bottom of the Get Info window. 2. Enter the admin account to activate the right to change disk permissions. |
| Not in any above situation | 1. Update the Mac. 2. Reconnect the external drive. |
Check what you see (Identify your case first)
When you can't change permissions on the external hard drive on the Mac, you may be in one of the scenarios.
Case 1: See "You have custom access" in Get Info
If you see the words "You have custom access" in the Sharing & Permissions section of the Get Info window, check if the external hard drive is formatted with NTFS.
NTFS is a proprietary file system for Windows, while macOS only has read permission for it.
If it is, you indeed can't change a read-only file system on a Mac to read and write.
Case 2: See "You can only read" in Get Info
If you see the prompt "You can only read" in Sharing & Permissions and have no options available to change the drive's permissions, the external drive is probably a Time Machine backup disk.
By default, the Time Machine backup drive is locked in read-only mode and can only be used to store backups. Thus, you can't change the drive's permissions.
Case 3: You are a guest user of the external drive
In Get Info, you can see your permissions to the external drive and find that you are a guest user.
Usually, guest users can't see external drives on a Mac. But in some situations, guest users can see the external drives, but only with read-only privilege, and can't change the permissions.
Case 4: After the above checks, you still can't change permissions on the drive
Your Mac may have system errors, blocking you from changing the permissions to the drive.
Tell others the reasons why they can't change permissions for an external drive on a Mac.
Can't change permissions on an external drive on Mac, how to fix
If you can't change the permissions on the external hard drive or can't access it on your Mac, you can follow the step-by-step methods below to make the external drive readable and writable on your Mac.
Option 1. If the drive is NTFS: use iBoysoft NTFS for Mac to enable its read-write access
If Get Info shows only "You have custom access" and there's no option to change permissions or check "Ignore ownership on this volume," view the drive format under General.
If the drive is formatted as NTFS, the issue is not related to macOS permissions. macOS can only read NTFS drives but cannot write to them by default. Therefore, changing Sharing & Permissions will not enable write access.
To copy, edit, delete, or move files on an NTFS drive without reformatting it, use iBoysoft NTFS for Mac. It automatically mounts NTFS drives in full read-write mode on a Mac.
Here's how:
- Free download, install, and open iBoysoft NTFS for Mac.
- Ensure your NTFS drive is connected to your Mac.
- The drive will immediately and automatically be mounted in read-write mode.
After that, you can directly edit or delete files on the drive, or copy files from your Mac to the external drive.
Share this easy-to-use NTFS for Mac tool to help others change read-only NTFS drives to read & write on a Mac.
Option 2. If it is a Time Machine backup disk: add a volume or stop using it for backups
If you can only read the external hard drive on your Mac and there's no option to change permissions in Get Info, the external drive is usually a Time Machine backup disk. You can usually see the Time Machine icon on the drive.
To change the read-only Time Machine drive to read-write permission, you can add a volume to the external drive in Disk Utility. Then, you can use the Time Machine drive to store other files and backups freely.
- Open Disk Utility by clicking Launchpad > Other.
- Click the View button > Show All Devices.
- Select the backup volume from the sidebar and click the + button on the toolbar to add a volume to the drive.
- Enter a name, choose a format, and click Add.
Or, you can:
Terminate the disk as the Time Machine backup drive.
Then, the read-only external drive will become read-write again.
Option 3. If you are a guest user: use the administrator account to change permissions
As a guest user for this Mac, you can only use the administrator account to change permissions when the external drive is set to read-only for customers.
- Right-click the external drive and choose Get Info.
- Click the lock button at the bottom of the Get Info window for changes. At this time, a pop-up will ask for the admin account. Just enter it.
- Change the privilege next to your account to Read & Write.
Fix 4. If permissions still cannot be changed: update your Mac
May be the system has bugs, making the permissions for the external drive can't be changed.
You can update your Mac, reconnect the drive, and then, check if the issue is solved.
If this post helps you access and write to the external drive on your Mac, share the solutions with others who also can't change permissions on external hard drives on their Macs.
FAQ
- Q How do I change permissions on my external hard drive in Mac?
-
A
To change permissions on an external hard drive in Mac:
1. Right-click the drive.
2. Select Get Info.
3. Scroll down to the Sharing & Permissions section.
4. Change the permission next to your account or group.
- QWhy can't I access my external hard drive on Mac?
-
A
The causes may include:
Your external drive is locked.
Your external drive is encrypted.
Your external drive is corrupted.