If your USB drive is read-only on a Mac, you can access the drive, but can't save, copy, delete, rename, or modify files on it. This issue usually results from an NTFS file system, permission restrictions, disk errors, insufficient storage space, or drive recognition problems.
This guide just explains how to identify the cause and safely choose the correct fix. After the fixing, most USB drives can be made writable again without losing data.
Note: If the USB drive can't be accessed on a Mac due to BitLocker encryption, unmountable issue, connection problems, or others, follow this guide: How to Fix USB Drive Not Readable on Mac
First, identify why your USB drive is read-only on Mac
Before trying any fixes, identify the cause first.
| What Happens | Possible Causes | Recommend Solutions |
| You can open the USB drive, but you can't copy, save, delete, or rename files on it. | The USB drive is formatted with NTFS. macOS can read NTFS but cannot write it by default. | Do not format! Use an NTFS driver to gain read-write access without data loss. |
| You can open the USB drive, but you can't copy, save, delete, or rename files on it. | You only have read permission for the USB drive. | Adjust "Read only" to "Read & Write" in Sharing & Permissions settings. |
| You can access the USB drive, but you can't add or move files to it. | The USB drive is almost full and can't store more files. | Free up more space by deleting unnecessary files or moving them to a different location. |
| You can't even access the USB drive You can only open the drive The USB drive doesn't show up | macOS fails to recognize the USB drive properly. | Reconnect the drive and restart the Mac. |
| You can't even access the USB drive You can only open the drive | The USB drive has minor software errors. | Run First Aid in Disk Utility to check and repair the drive |
Tips: To find the right fix quickly, right-click your external drive in Finder or on the desktop, choose Get Info, and check the Format.
If your USB drive is NTFS-formatted, macOS can read files from it but cannot write to it by default. In this case, use iBoysoft NTFS for Mac to mount the USB drive in full read-write mode. Then, you can write to it seamlessly.
Case 1: The USB drive is formatted with the NTFS file system
If you can open files but cannot copy, save, edit, rename, or delete files on the drive, the drive is likely formatted as a read-only file system on Mac, like NTFS. NTFS is Microsoft's proprietary file system. macOS can read NTFS drives by default.
Some USB sticks are formatted with the Microsoft NTFS file system by default for Windows compatibility.
This is one of the most common reasons why a USB drive appears read-only or is not writable on a Mac.
Check your USB drive's format
- Right-click the USB drive in the Finder sidebar or on the desktop.
- Select Get Info.
- In the Format section, check if it shows Unknown (ms_ntfs).
If it is, it indicates that your USB drive is formatted with Microsoft NTFS.
Enable the NTFS USB drive write support on a Mac
Way 1. Use an NTFS for Mac tool
If the drive contains files, do not format the drive, as formatting will erase everything. Instead, use an NTFS for Mac tool.
iBoysoft NTFS for Mac can mount NTFS external drives in full read-write mode without reformatting. It works as a seamless Mac NTFS mounter, allowing you to edit, rename, copy, paste, and delete files on your Windows NTFS USB drive within a macOS environment as if it were a native Mac drive.
#Compatible with macOS Tahoe 26 - macOS High Sierra 10.13#Support Apple Silicon & Intel Mac
Steps:
- Free download and install iBoysoft NTFS for Mac on your computer.
- Connect the read-only USB stick to your Mac, then launch iBoysoft NTFS for Mac.
- Click Enable Writable and choose a mode - Simple Mode or Advanced Mode, according to your preferences.
If you select Advanced Mode, you'll be asked to install an NTFS driver by iBoysoft and enable System Extensions to gain full disk access. Just follow the onscreen instructions and finish the installation. - Your USB drive will be mounted in read-write mode automatically.
Now, you can write, modify, transfer, and delete files on that drive.
You can also check this video guide to learn how to read and write NTFS drives on Mac using iBoysoft NTFS for Mac.
Way 2. Reformat the drive to a macOS-compatible format
If the drive contains no important data and you don't need Windows compatibility, you can reformat it with a macOS fully compatible file system:
- APFS
- Mac OS Extended (Journaled)
- exFAT (also Windows-compatible)
- FAT32 (also Windows-compatible)
Note that formatting a disk will erase all data stored on it, so be careful before starting!
Steps:
- Connect the read-only drive to your Mac computer.
- Open Disk Utility, then select the malfunctioning drive in the left sidebar.
- Click the Erase button at the top, set the format of the USB drive as APFS, MS-DOS (FAT), Mac OS Extended (Journaled), or ExFAT, and click Erase.
When the formatting process is completed, disconnect the drive and restart your Mac, then reconnect your USB drive. The drive is writable on Mac now.
Complete guide to solving WD My Passport read-only problem on Mac, to change permissions on WD My Passport from write-protected, to unlock read-only WD My Passport on macOS.
Case 2: Your USB drive permission is read-only
If your USB drive is formatted in a Mac-compatible system (like FAT32, exFAT, or APFS) but you still can't copy files to the drive on a Mac, the drive's sharing permissions might be restricted or write-protected.
In this case, you only need to remove write protection from the USB in the permission settings. Then, your USB drive will become writable again.
How to change USB drive read-only permissions on Mac
- Connect the read-only USB drive to your Mac.
- Find the USB drive icon on your Mac desktop, right-click on it, then select Get Info.
Or, you can simply select the drive icon, and then press Command + I, it works the same.
- In the Get Info window, click the arrow next to Sharing & Permissions. (Seeing the message "You can only read" on your external hard drive on Mac?)
- Click the Lock icon, and enter your admin password to unlock for changes.
- Tick the checkbox next to "Ignore ownership on this volume." Or, change your privilege to "Read & Write."
After that, check if you can access and edit files on your USB flash drive. If not, safely eject the drive, restart the Mac, connect the USB drive to your Mac, and try again.
Case 3: The USB drive is almost full
If you can open and delete files on the USB drive but can't copy files to it, the USB drive may be full.
I failed to add 10 GB of videos to my USB drive and mistakenly thought that the drive was read-only. Afterward, I noticed that the drive is full. So, checking the drive storage is also necessary to troubleshoot this issue.
Check the USB drive's available storage space
- Right-click the USB drive on the desktop or Finder sidebar.
- Select Get Info.
- In the Capability and Available sections, see how much storage space the USB drive has.
Free up more space on the USB drive
If the drive doesn't have much available space, delete the useless files on it, or move the files to your Mac or another external drive.
Case 4: The USB drive isn't properly recognized by your Mac
A USB drive may appear read-only if macOS does not mount it correctly because of:
- Temporary system errors
- Previous improper ejection
- Too quick insertion
- Faulty USB adapters, USB hubs, or USB ports
- Unstable connection
So, you can:
- Safely eject the drive and then reconnect it to your Mac properly and slowly.
- Try another USB port or adapter.
- Restart your Mac to refresh the system.
Case 5: The USB drive has file system issues
If the drive suddenly becomes read-only after a crash, power interruption, forced removal, or system freeze, file system corruption may be preventing write operations. When this happens, you can't delete files from the USB drive on the Mac, nor can you add new ones.
In this case, to get rid of the Mac OS USB read-only issue caused by internal errors, you can run Disk Utility First Aid and see if the problem still exists.
Important: Back up files on the USB drive first
Before running First Aid, make sure important files are backed up or recovered. Repairing a damaged file system may modify metadata structures and reduce the chances of recovering lost files later.
Copy files on the drive to your Mac or another external drive as a backup.
Run First Aid to repair the USB drive
First Aid in Disk Utility can help you repair some minor existing errors on the read-only drive.
Here's how:
- Make sure the read-only USB is connected to your Mac.
- Navigate to Mac Launchpad > Others, and double-click on Disk Utility to open it.
- In the Disk Utility window, select your malfunctioning USB drive in the left column.
- Click on the First Aid tab at the top pane, a dialogue box appears, then click Run.
- Until the First Aid process is completed, safely eject and reconnect the drive to the Mac.
- Check if you can write to your USB pen drive now.
Reformat the USB drive after backup
If the issue persists, don't worry, back up your files on the USB drive and then format it in Disk Utility.
- Open Disk Utility.
- Select the USB drive.
- Click Erase on the top toolbar.
- Rename the drive if needed and choose one of the formats:
APFS: macOS only
Mac OS Extended (Journaled): macOS only, especially for older Macs
exFAT: macOS and Windows compatibility
FAT32: macOS and Windows compatibility, usually for storage devices of less than 32 GB - Click Erase.
Why is your USB drive read-only on a Mac?
It is necessary to know why your USB thumb drive becomes read-only on your Mac. Generally speaking, this problem can be caused by the following reasons:
- USB drive permission is read-only
- The USB flash drive is formatted as an NTFS file system
- The USB thumb drive is corrupted, or it contains unknown errors
- macOS doesn't recognize the USB drive properly
- The USB drive is almost full and can't store any other data
Do note that the reasons behind the Mac USB drive read-only issue vary in different situations; we've just listed some of them. But whatever your case is, the ways in this post can help you out.
If your USB drive is from Toshiba, read this article to learn the 5 best ways to resolve the "Toshiba external hard drive read-only" issue on Mac.
FAQ
- QWhy can't I copy files to my USB drive on Mac?
-
A
If you can view files but cannot copy new files to the drive, the drive may be NTFS-formatted, write-protected, full, or affected by permission restrictions.
- QWhy can't I delete files from a USB drive on Mac?
-
A
This usually happens when the drive is mounted in read-only mode or your account lacks write permission.
- QHow do I make a USB drive writable on Mac without formatting?
-
A
If the drive is NTFS-formatted, use an NTFS driver for Mac. If it uses a Mac-compatible file system, check permissions, connection status, and disk errors before considering formatting.