Why Did My Correctly Formatted External Drive Become Read-Only on Mac and How to Fix It Safely

Dealing with a read-only external drive on your Mac can be frustrating, especially if the drive was working fine before. This issue can arise for various reasons, ranging from file system compatibility and permission settings to drive errors and even a physical lock switch. In this guide, we'll explore common causes and provide comprehensive solutions to fix the read-only issue without risking data loss.

Common Causes of Read-Only External Drives on Mac

There are several common reasons why your external drive may have become read-only on your Mac. Some of the most frequent issues include:

File System Compatibility: If your drive is formatted with a file system not fully supported by macOS, such as NTFS, it may be mounted as read-only. Permissions Issues: Certain permission settings on the drive might prevent write access. Drive Errors: Errors on the drive itself can cause it to malfunction and appear as read-only. Physical Lock Switch: Some external drives have a physical switch that locks the drive to read-only mode.

Comprehensive Solutions to Fix the Read-Only Issue

Fortunately, there are several steps you can take to address the read-only issue and attempt to resolve it without risking data loss. Here’s a detailed guide:

1. Verify File System

If your drive is formatted with a file system not fully supported by macOS, it may mount as read-only.

Open Disk Utility from the Applications > Utilities folder. Select your external drive in the sidebar. Check the format of the drive and ensure it is compatible with macOS. If it's NTFS, consider using third-party software like Paragon NTFS for Mac to enable read/write access or reformat the drive. Reformatting the drive will result in data loss, so proceed with caution. Use the option to initialize the drive and choose a format compatible with macOS.

2. Check and Adjust Permissions

Incorrect permissions settings on the drive can block write access.

Right-click the drive icon on your desktop and select Get Info. In the Info window, scroll to the Sharing Permissions section. Ensure that your user account has Read Write access. If not, click the lock icon to make changes and enter your admin password to authorize the changes.

3. Repair the Drive

Drive errors can cause it to malfunction and appear as read-only. Running a disk repair can fix these issues.

Open Disk Utility. Select your external drive from the sidebar. Click on First Aid. This will check for and repair any errors on the disk. Follow any prompts to repair the drive.

4. Check Physical Lock Switch (If Applicable)

If your external drive has a physical lock switch, ensure it is set to the unlocked position.

Examine the drive for a physical lock switch. Move the switch to the unlocked position if it is currently locked.

5. Mount the Drive with Read/Write Access via Terminal

If the drive is formatted correctly but still appears as read-only, you can try mounting it manually with read/write permissions using the Terminal.

Open the Terminal application from Applications > Utilities. Type the following command to list all drives:

diskutil list

Locate your external drive in the list (it will be something like /dev/disk2). Use the following command to mount the drive with read/write access:

sudo mount -o rw /dev/disk2s1 /Volumes/YourMountPoint

Replace /dev/disk2s1 with your drive identifier and /Volumes/YourMountPoint with your desired mount point.

Backup Your Data

Before making significant changes to correct the read-only issue, it's essential to back up your data if possible. Copy files to another drive or use cloud storage for a safe backup.

Conclusion

By following these steps, you should be able to identify the cause of the read-only status and resolve it without losing your data. If the issue persists, consider consulting a professional data recovery service for further assistance.