An APFS volume that mounts as read-only lets you open and copy files, but it will not let you create, edit, rename, or delete them. The cause may be a damaged file system, an unclean disconnection, a locked volume, incorrect permissions, encryption, or a failing drive.
Start by checking the volume in Disk Utility and running First Aid. If First Aid cannot repair it, copy any accessible files to another drive before trying more advanced steps. Do not erase or reformat the volume until your important data is backed up.
Quick Answer
- Stop writing to the affected drive and copy important files elsewhere.
- Open Disk Utility, choose View > Show All Devices, select the APFS volume, and run First Aid.
- Restart your Mac and reconnect the drive directly, if it is external.
- Check whether the volume is locked, encrypted, or mounted read-only because of file-system errors.
- If needed, use Terminal to inspect and attempt a read-only repair.
- If repair fails, back up the data and erase or reformat the drive only after confirming that no files remain on it.
Why an APFS Volume Becomes Read-Only
APFS is Apple’s modern file system for internal Mac storage and many external drives. A volume can mount as read-only for several reasons:
- File-system errors: macOS may prevent changes to protect the volume from further damage.
- An interrupted write: Disconnecting a drive during a file transfer or losing power can leave the volume in an inconsistent state.
- A locked or encrypted volume: FileVault or APFS encryption may require authentication before writing is allowed.
- Physical drive problems: Bad sectors, a failing SSD, a defective cable, or an unstable enclosure can cause read-only mounting.
- Insufficient permissions: Your account may not have write access to a particular folder or volume.
- A system volume: Some macOS system volumes are intentionally protected and cannot be modified normally.
- Hardware write protection: Certain storage devices, adapters, or enclosures can expose a drive as read-only.
If only one folder refuses changes, the problem may be permissions. If the entire volume is read-only, file-system or hardware issues are more likely.
Before You Repair the Volume
Back up accessible files first
If you can open files on the volume, copy the most important data to another drive or to a trusted backup location before repairing it. A repair can make changes to the file-system directory, and a failing drive can stop working without warning.
Do not use the affected drive as the destination for the backup. If the drive contains valuable data and begins disconnecting, making unusual noises, or becoming extremely slow, minimize use and consider professional data recovery.
Check the connection
For an external drive:
- Quit apps that are using files on the drive.
- In Finder, click the Eject button next to the drive, if it is available.
- Disconnect the drive and reconnect it directly to your Mac.
- If possible, try another USB or Thunderbolt cable and another port.
- Avoid an unpowered hub while testing.
If the drive repeatedly disconnects, repair attempts may not complete. See our guide to fixing an external drive that keeps disconnecting from a Mac.
Fix an APFS Volume That Mounts as Read-Only
1. Confirm that the entire volume is read-only
Test more than one location before assuming the whole volume is affected.
- Open the volume in Finder.
- Try creating a temporary folder in its top level.
- Try copying a small, nonessential file to it.
- Check whether existing files can be renamed or deleted.
If you can write to some folders but not others, check permissions:
- Select the affected folder in Finder.
- Press Command-I.
- Expand Sharing & Permissions.
- Confirm that your user account has Read & Write access.
- Click the lock and authenticate if you need to change permissions.
Do not change permissions throughout an entire drive unless you understand the consequences. Incorrect permissions can prevent apps or other users from accessing files.
2. Unlock the volume
An encrypted APFS volume may need to be unlocked before macOS allows normal access.
- Open Disk Utility.
- Choose View > Show All Devices.
- Select the affected APFS volume in the sidebar.
- Look for an Unlock control in the toolbar or choose File > Unlock if that option is available.
- Enter the volume password when prompted.
You can also eject and reconnect the drive, then enter its password when macOS asks. If the volume unlocks successfully but remains read-only, continue with First Aid.
3. Run First Aid in Disk Utility
First Aid checks the volume’s directory structure and attempts repairs. It does not recover deleted files and cannot fix every hardware problem.
Warning: First Aid can modify file-system information. Make a backup first when possible, and close apps using the drive.
- Open Disk Utility from Applications > Utilities.
- Choose View > Show All Devices.
- In the sidebar, select the affected APFS volume, not only the physical disk.
- Click First Aid, then click Run.
- Wait for the operation to finish.
- Read the final message carefully.
If the volume is part of an APFS container, run First Aid on the volume first. If problems remain, run it on the APFS container and then the physical device. Disk Utility may ask you to unmount a volume. Save your work and close any apps using the drive before accepting.
Restart your Mac after a successful repair and test whether you can create a file.
4. Check for a read-only mount in Terminal
Disk Utility provides the safest visual method, but Terminal can show how macOS mounted the volume.
Open Terminal from Applications > Utilities, then run:
diskutil info /Volumes/YourVolumeName
Replace YourVolumeName with the exact name of the mounted volume. You can type the command up to the volume path, type a space, and drag the volume from Finder into the Terminal window to insert its path automatically.
Look for information such as:
- File System Personality: This should identify APFS.
- Mounted: Whether macOS currently has access to the volume.
- Read-Only Volume: Whether the volume is mounted without write access.
- Device Location: Whether it is internal or external.
To list APFS containers and volumes, run:
diskutil apfs list
These commands only display information; they do not change the drive. For more detail about reading this output, see how to check APFS containers and volumes in Terminal on a Mac.
5. Try unmounting and remounting the volume
A temporary mounting problem can sometimes be cleared by unmounting and remounting the volume.
First identify the volume identifier with:
diskutil list
Find the APFS volume and note its identifier, such as disk4s1. Then unmount it:
diskutil unmount /dev/disk4s1
Replace disk4s1 with your actual identifier. After it unmounts, remount it:
diskutil mount /dev/disk4s1
These commands do not erase the volume. They close the volume’s current mount and ask macOS to attach it again. Save all work and close files on the drive first, because unmounting can interrupt applications and may cause unsaved changes to be lost.
If macOS says the volume is busy, quit apps that may be using it and try again. Do not force an unmount while files are being copied or modified.
6. Run First Aid from macOS Recovery
If the affected volume is your internal startup storage, or if normal macOS cannot repair it because the volume is in use, run Disk Utility from macOS Recovery.
Warning: Recovery tools can still modify storage. Back up accessible data first, and do not erase the disk unless you are certain the backup is complete.
- Shut down your Mac.
- Start it in macOS Recovery using the startup procedure appropriate for your Mac.
- Choose Options when the recovery screen appears, then click Continue.
- Open Disk Utility.
- Choose View > Show All Devices.
- Run First Aid on the affected APFS volume, then the container and physical device if necessary.
- Quit Disk Utility and restart the Mac.
The exact startup steps differ between Apple silicon and Intel-based Mac computers. If you are unsure which procedure applies, use Apple’s current Recovery instructions rather than guessing.
7. Use APFS repair commands only when necessary
Terminal includes APFS-specific commands, but they should not be the first option for beginners. An incorrect identifier can target the wrong volume, and some repair operations require the volume to be unmounted.
Start with an inspection command:
diskutil apfs list
For a volume identifier such as disk4s1, you can ask Disk Utility to verify it:
diskutil verifyVolume /dev/disk4s1
This checks the volume without intentionally repairing it. Replace the identifier with the one shown for your drive.
If verification reports errors, use Disk Utility’s First Aid rather than experimenting with undocumented or forceful commands. Do not disable macOS security features or attempt to force a read-only volume to become writable before you know why it was mounted that way. Forcing write access can worsen file-system damage.
What to Do If First Aid Reports an Error
The result determines the next step.
“Operation successful” or no errors found
Restart the Mac, reconnect the drive, and test a temporary file. If it is still read-only, inspect the volume’s lock status, permissions, and mount information.
The volume could not be repaired
Copy all accessible data immediately. Then test the drive with a different cable, port, enclosure, or Mac if possible. If the same problem follows the drive, the drive or its file system is likely at fault.
Once your backup is verified, erase and reformat the drive in Disk Utility if you are willing to remove all existing data. Select the physical device, click Erase, choose an appropriate format, and confirm only after checking that the correct disk is selected.
Warning: Erasing deletes the volume’s files and cannot be treated as a repair that preserves data.
The disk is failing or cannot be read reliably
Repeated disconnects, very slow reads, I/O errors, or unusual sounds indicate a possible hardware failure. Stop repair attempts if the data is important. Professional recovery may be safer than repeated mounting and repair operations.
You can read files but cannot write to the drive
Confirm that the format is actually APFS and that the drive is not being shared through software or hardware that restricts writing. If the volume works normally on another Mac, the issue may involve the original Mac’s permissions, software, or connection.
Troubleshooting Common Problems
The volume is full
A completely full APFS volume may behave unpredictably and may not accept new files. Delete unnecessary data only after confirming that you have a backup. Emptying the Trash may be necessary to reclaim space.
Time Machine or another app is using the drive
Quit Time Machine-related activity, backup software, virtual machines, media libraries, and file-sync tools before unmounting or repairing. If an app keeps the volume busy, restart the Mac and run First Aid before reopening those apps.
The drive was formatted on another system
APFS is designed for Apple operating systems. A drive formatted with another file system may have different write limitations. If you need to use the drive with both Mac and Windows computers, review the format requirements before reformatting; changing formats erases the drive. Our guide to APFS versus exFAT on a Mac explains the main trade-offs.
The volume is read-only after every restart
That pattern usually points to persistent file-system errors, a failing drive, encryption or security restrictions, or a connection problem. Back up the data, run First Aid from Recovery, and test the drive with another cable or Mac. If the behavior continues, replace the drive after securing the data.
Frequently Asked Questions
Can I force an APFS volume to mount as writable?
You should not force write access without identifying the cause. macOS may mount a damaged volume as read-only to prevent additional corruption. Repair the volume, check the connection, and back up the data first.
Will First Aid delete my files?
First Aid is intended to verify and repair file-system structures, not erase personal files. However, any repair operation changes disk information, and a failing volume can deteriorate during use. Back up accessible files before running it.
Why is only one folder read-only?
The volume may be writable while that folder has restrictive permissions, belongs to another user, or is controlled by an app. Select the folder, press Command-I, and review Sharing & Permissions.
Can I repair the volume without erasing it?
Often, yes. Start with a backup, then use Disk Utility’s First Aid. If First Aid cannot repair the volume, continued attempts may increase risk. Secure the data before considering erasure or professional recovery.
Does read-only mounting always mean the drive is failing?
No. A locked volume, permissions issue, interrupted transfer, bad cable, or temporary file-system problem can produce the same symptom. Persistent errors, disconnections, and I/O failures make hardware trouble more likely.
Final Thoughts
Begin with a backup, check the connection, unlock the volume if necessary, and run First Aid in Disk Utility.