A disk or volume may be connected to your Mac but unavailable in Finder. In that case, you may need to mount it in Disk Utility. When you are finished using an external disk, you should unmount or eject it before disconnecting it to reduce the risk of data loss.
Quick Answer
To mount a disk in Disk Utility:
- Open Disk Utility from Applications > Utilities.
- Choose View > Show All Devices.
- Select the unmounted volume in the sidebar.
- Click Mount in the toolbar.
To unmount a disk:
- Select the volume in Disk Utility.
- Click Unmount in the toolbar.
- Wait until it disappears from the desktop and Finder.
Mounting makes a volume available to macOS. Unmounting makes it unavailable without physically disconnecting it. Ejecting usually unmounts the volume and prepares an external disk for safe removal.
What “Mount” and “Unmount” Mean
A disk is a physical storage device, such as an internal SSD, external hard drive, USB flash drive, or memory card. A volume is a usable storage area on that disk. One physical disk can contain multiple volumes.
When macOS mounts a volume, it makes the volume available to the system. You can then open it in Finder, browse its files, and save data to it. Mounted volumes usually appear in the Finder sidebar and, depending on your Finder settings, on the desktop.
Unmounting removes the volume from active use while leaving the disk connected. The volume is no longer available in Finder, but you can usually mount it again without reconnecting the device.
Unmounting is not the same as erasing or formatting. It does not delete files or change the disk’s partition structure.
Before You Mount or Unmount a Disk
Before changing a disk’s mounted state:
- Make sure the correct disk or volume is selected.
- Close files stored on that volume.
- Quit apps that may be using the disk.
- Do not disconnect an external disk while files are being copied.
- Do not use Erase, Partition, or other destructive options unless you intentionally plan to delete or modify the disk.
Unmounting a volume can make open files unavailable and may interrupt an active transfer. Save your work first.
How to Mount a Disk in Disk Utility
Use these steps when a connected disk or volume does not appear in Finder or is listed in Disk Utility but is not available.
1. Open Disk Utility
Open Finder, then select Applications in the sidebar. Open the Utilities folder and double-click Disk Utility.
You can also press Command-Space, type Disk Utility, and press Return.
2. Show the complete device list
In the Disk Utility menu bar, choose View > Show All Devices.
This view displays the physical storage device, its containers, and the volumes inside them. A volume may be hidden from the normal view if it is not currently mounted.
The sidebar is generally arranged in a hierarchy:
- Physical disk: The actual internal or external storage device.
- Container: A storage structure used by some file systems, including APFS.
- Volume: The individual usable storage area.
Select the volume you want to make available. If you are unsure, check the name and capacity shown in the main window before continuing.
3. Select the unmounted volume
In the sidebar, click the volume that is not available in Finder. It may appear dimmed or may lack the usual mounted-volume indicators.
Avoid selecting the physical disk if your goal is simply to make one volume available. The volume is usually the correct item to mount.
4. Click Mount
Click Mount in the Disk Utility toolbar.
If the button is not visible, choose File > Mount from the menu bar. Disk Utility may ask for an administrator password if the operation requires authorization.
After the volume mounts, it should become available in Finder. Open Finder and look under Locations in the sidebar. You may also see the volume on the desktop if Finder is configured to show external disks there.
5. Confirm that the volume is available
Open the mounted volume in Finder and check that its folders and files are visible. If Disk Utility reports an error, do not repeatedly disconnect and reconnect the disk while it is busy. Review the troubleshooting steps below.
How to Unmount a Disk in Disk Utility
Unmount a volume when you want to temporarily make it unavailable without disconnecting the physical device.
Warning: Unmounting can interrupt file transfers and make open files inaccessible. Save your work and close apps that use the volume first.
1. Close files and applications using the disk
Close Finder windows displaying the volume and quit apps that have files stored on it. If a copy, backup, export, or download is in progress, wait until it finishes.
Some background processes may continue using a disk even when no obvious window is open. If Disk Utility cannot unmount the volume, see the troubleshooting section.
2. Open Disk Utility
Open Finder > Applications > Utilities > Disk Utility, or search for Disk Utility with Command-Space.
If the device is not shown in the expected way, choose View > Show All Devices.
3. Select the volume
Click the volume you want to unmount in the sidebar. Select the volume rather than the physical disk when possible.
4. Click Unmount
Click Unmount in the toolbar. You can also choose File > Unmount.
The volume should disappear from Finder and become unavailable to applications. The physical disk may remain listed in Disk Utility because it is still connected.
To use the volume again, select it and click Mount.
Unmounting Versus Ejecting an External Disk
The terms unmount and eject are related but not identical in everyday Mac use.
- Unmount: Makes a volume unavailable to macOS while the physical disk remains connected.
- Eject: Unmounts the volume and signals that an external device can be disconnected.
For a disk you plan to remove from your Mac, use Eject in Finder or Disk Utility rather than only unmounting the volume. In Finder, click the Eject button next to the disk in the sidebar. You can also Control-click the disk and choose Eject.
When the disk disappears from Finder and stops showing activity, disconnect the cable or remove the device. Never pull out a USB drive, external SSD, or memory card while macOS is writing data.
If an external device contains multiple mounted volumes, ejecting the device may require ejecting each volume first.
What to Do If Mount Is Unavailable
The Mount button may be unavailable for several reasons:
- The volume is already mounted.
- You selected the physical disk instead of an unmounted volume.
- The disk is not connected properly.
- macOS cannot read the file system.
- The volume is damaged.
- The disk requires a password or special software.
- The storage device has a hardware problem.
First, confirm the device appears in Disk Utility under View > Show All Devices. Check whether the volume is listed beneath the physical disk.
If the volume is listed but will not mount, select it and review the information shown in the main window. Do not click Erase as a quick fix. Erasing removes the volume’s data.
You can also run First Aid to check the volume’s directory structure. First Aid is not a replacement for a backup, and repairs can sometimes fail if the disk has a hardware problem. For a separate walkthrough, see How to Repair a Mac Disk with First Aid.
What to Do If a Disk Will Not Unmount
If Disk Utility reports that a volume cannot be unmounted:
- Close all files stored on the volume.
- Quit apps that may be using those files.
- Close Finder windows for the disk.
- Wait for file transfers, backups, indexing, or synchronization to finish.
- Try Unmount again.
If the problem continues, restart the Mac and try again after logging in. For an external disk, check the cable, adapter, hub, and power connection. A directly connected device may work more reliably than one connected through a hub.
Do not disconnect the disk by force if the Mac may still be writing data. Forced removal can damage the file system or cause unsaved data to be lost.
If the Disk Does Not Appear in Disk Utility
When no disk or volume appears in Disk Utility:
- Disconnect and reconnect the external device, if it is safe to do so.
- Try another USB or Thunderbolt port.
- Check the cable and power adapter.
- Connect the device directly to the Mac instead of through a hub.
- Test the device with another compatible Mac, if available.
- In Disk Utility, choose View > Show All Devices.
- Restart the Mac and check Disk Utility again.
If an internal startup disk is missing, the issue may require macOS Recovery or additional hardware troubleshooting. See How to Fix a Startup Disk Not Showing on Mac for more focused steps.
A disk that does not appear even after checking its connection may have a failed enclosure, cable, power source, or storage device.
Can You Mount a Disk from Finder?
Finder does not provide a general Mount command for every unmounted volume. If the device is connected but its volume is unavailable, Disk Utility is the appropriate built-in tool.
Finder is useful for ejecting a mounted external disk. It can also show a disk that has already been mounted by Disk Utility. If the volume is missing from Finder, first check whether it is mounted and visible in Disk Utility.
Frequently Asked Questions
Does mounting a disk delete its files?
No. Mounting only makes the volume available to macOS. It does not erase, format, or reorganize the files.
Does unmounting a disk erase data?
No. Unmounting removes the volume from active use. The files remain on the disk, and you can mount the volume again later.
Should I unmount or eject an external hard drive?
Use Eject when you plan to disconnect the external drive. Use Unmount when you want to make the volume temporarily unavailable while leaving the device connected.
Why is my disk visible in Disk Utility but not Finder?
The volume may be unmounted, hidden by Finder settings, unsupported, encrypted, or damaged. Select the volume in Disk Utility and click Mount if that option is available.
Can I mount a disk while another app is using it?
You may be able to mount it, but applications may not recognize it immediately. Close related apps first, especially if the disk is used for backups, media libraries, virtual machines, or file transfers.
What happens if I unplug a disk without ejecting it?
macOS may still be writing cached data or file-system information. Removing the disk without ejecting it can cause data loss or file-system corruption. Eject the disk and wait until macOS confirms that it can be removed.
Is mounting the same as connecting a disk?
No. Connecting refers to the physical device being attached to the Mac. Mounting refers to macOS making a volume on that device available for use.
Final Thoughts
Disk Utility provides a safe way to make an unavailable volume accessible or temporarily remove it from use. Use Mount when a connected volume is not available in Finder, and use Unmount when you need to stop using it without disconnecting the device. Before removing an external disk, eject it properly and wait until it disappears from Finder.