An external drive that does not appear on your Mac may have a loose connection, insufficient power, an unsupported format, a damaged file system, or a hardware failure. Start with simple checks—reconnect the drive, try another port or cable, and confirm that macOS can see it in Disk Utility. If the drive appears there, you may be able to mount or repair it without erasing your files.
Quick Answer
- Disconnect and reconnect the drive securely.
- Try another USB port, cable, adapter, or Mac.
- Open Disk Utility and choose View > Show All Devices.
- If the drive is listed but gray, select its volume and click Mount.
- If it is mounted but missing from Finder, check Finder > Settings > General and Sidebar.
- Run First Aid in Disk Utility.
- Do not erase or format the drive unless you have confirmed that its data is backed up or no longer needed.
If Disk Utility does not detect the drive at all after you test the connection, the cable, enclosure, or drive itself may have failed.
Check the Connection and Power
Before changing settings or repairing the disk, rule out a physical connection problem.
- Disconnect the external drive from your Mac.
- Inspect the cable and connectors for visible damage.
- Reconnect the cable firmly at both ends.
- Try a different port on your Mac.
- If you are using a USB hub, dock, or adapter, connect the drive directly to the Mac.
- If the drive has a separate power adapter, confirm that it is connected and switched on.
- Wait several seconds for the drive to spin up or its indicator light to turn on.
Bus-powered drives receive power through the USB connection. Some Macs or hubs may not provide enough power for certain portable hard drives, especially when multiple devices share the same hub. A powered hub or the drive’s original power adapter may help.
If the drive makes repeated clicking sounds, fails to spin up, becomes unusually hot, or repeatedly disconnects, stop using it. Continued use can make a failing mechanical drive harder to recover.
Try a Different Cable, Adapter, or Mac
A damaged cable can provide enough power for a light to turn on without providing a stable data connection. Test with a known-good cable that supports data transfer, not only charging.
Also test the drive with:
- Another USB or Thunderbolt port
- A different adapter or dock
- Another Mac, if available
- A Windows PC, if the drive uses a Windows-compatible format
If the drive works with another cable or computer, the original connection is the likely cause. If it fails everywhere, the drive, enclosure, or power supply may be defective.
Do not repeatedly unplug a drive while it is actively copying files. If the drive is intermittently detected, wait for it to finish any activity before disconnecting it.
Make Sure Finder Is Showing External Drives
The drive may be mounted but hidden in Finder.
- Open Finder.
- In the menu bar, choose Finder > Settings.
- Select General.
- Under “Show these items on the desktop,” select External disks.
- Select Sidebar.
- Under “Locations,” select External disks.
Close Finder Settings and check the desktop and Finder sidebar. If the drive appears, macOS had mounted it; it was simply hidden from view.
You can also open Finder and choose Go > Computer. Mounted volumes normally appear in this window.
Use Disk Utility to Find and Mount the Drive
Disk Utility can show storage devices that do not appear in Finder.
- Open Disk Utility. You can find it in Applications > Utilities or by searching with Spotlight.
- In the menu bar, choose View > Show All Devices.
- Look in the sidebar for the external drive.
Disk Utility generally displays a physical device at the top level, with one or more volumes underneath it. A volume is the usable storage area that normally appears in Finder.
If the drive is listed but grayed out
A gray volume may be recognized but not currently mounted.
- Select the gray volume in the sidebar.
- Click Mount in the toolbar.
- Wait for the volume to appear in Finder.
If Mount fails, note the error message. It may indicate file-system damage, an unsupported format, encryption, or a hardware problem.
If the physical drive is listed but its volume is missing, the partition information or file system may be damaged. Do not immediately click Erase if you need the files. Erasing creates a new file system and normally destroys the existing directory structure.
Run First Aid in Disk Utility
Disk Utility’s First Aid checks a volume for certain file-system problems and attempts repairs.
Warning: First Aid can modify the drive’s file-system structures. It is generally intended to preserve files, but no repair operation is risk-free. If the drive is failing, make a backup or create a copy of important data first when possible. Do not run repairs on a drive that is making severe mechanical noises or disconnecting repeatedly.
- Open Disk Utility and choose View > Show All Devices.
- Select the volume associated with the external drive.
- Click First Aid.
- Read the prompt, then click Run.
- Wait for the process to finish.
- If the volume is part of a device with multiple levels, repeat First Aid for the other relevant volume or container, then the physical device.
If First Aid reports that the volume appears to be OK, try mounting it again. If it reports that repairs cannot be completed, copy any accessible files immediately and consider professional data recovery before attempting more changes.
Check Whether the Drive Uses an Unsupported Format
macOS can recognize a drive without being able to write to it, and some file systems may not be fully supported for normal use. Common formats include:
- APFS: Common on modern Mac storage
- Mac OS Extended: An older Mac format
- exFAT: Useful for sharing files between Mac and Windows
- MS-DOS (FAT): Common on smaller removable devices, with file-size limitations
- NTFS: Common on Windows; macOS may read it but typically cannot write to it without additional software
In Disk Utility, select the volume and check the information shown in the window. If the format is unfamiliar or the drive was created for another operating system, avoid reformatting until you have confirmed that you do not need its existing data.
If the drive is empty or backed up and you need to change its format, see How to Format an External Drive on a Mac. Formatting erases the selected volume.
Unlock an Encrypted Drive
An encrypted external drive may not mount until it is unlocked.
Look for a password prompt after connecting the drive. If no prompt appears:
- Open Disk Utility.
- Select the external volume.
- Click Mount or Unlock, if available.
- Enter the drive’s password when asked.
You need the correct password or recovery key to access an encrypted volume. Do not erase the drive to bypass the password. That removes the existing data rather than recovering access.
Restart the Mac and Check for macOS Problems
A restart can clear a temporary USB, Finder, or storage-service problem.
- Save your work and close open apps.
- Choose Apple menu > Restart.
- After the Mac restarts, reconnect the drive directly to the Mac.
- Check Finder and Disk Utility again.
If other USB devices also fail, the issue may involve the Mac’s port, hub, adapter, or system hardware rather than the external drive.
Check the Drive in System Information
System Information can show whether the Mac detects a USB or Thunderbolt device even when Disk Utility does not show a usable volume.
- Hold the Option key and choose Apple menu > System Information.
- In the sidebar, select USB or the relevant Thunderbolt section.
- Look for the drive, enclosure, or adapter.
If the device appears in System Information but not Disk Utility, macOS may detect the hardware while failing to recognize its storage structure. That can point to a damaged file system, an incompatible enclosure, or a problem with the drive’s partition table.
If it does not appear in System Information, focus on the cable, power, adapter, port, enclosure, or drive hardware.
When Not to Erase the Drive
Do not use Erase, Partition, or Format as a first troubleshooting step if the drive contains important files. These actions can destroy the information needed to recover the data.
You should consider erasing only when:
- You have a verified backup
- The drive contains no important data
- You are intentionally repurposing the drive
- A data-recovery professional has advised you to do so
If you need to create multiple volumes for separate uses, review How to Partition an External Drive on a Mac. If you need stronger protection for a working drive, see How to Encrypt an External Drive on a Mac.
Troubleshooting
Disk Utility shows the drive, but First Aid fails
Stop making changes if the drive contains valuable data. Try copying files if the volume becomes accessible, or use a professional data-recovery service. Repeated repair attempts can worsen a physically failing drive.
The drive mounts and then disappears
This often indicates an unstable cable, insufficient power, a failing enclosure, overheating, or a failing drive. Try a direct connection, another cable, and another computer. Avoid using a questionable drive for important files.
The drive is visible but cannot be opened
Check whether it is locked or encrypted. If it is mounted but access is denied, the issue may involve permissions or a file-system format. Do not change permissions randomly, particularly on a drive used for backups or another Mac’s system files.
The drive works on Windows but not on the Mac
Check the drive’s format and encryption. Windows-specific software or an NTFS volume may require compatible Mac software for full access. If you need the drive to work with both systems and can erase it, exFAT is often used for cross-platform storage, but confirm your backup first.
The drive is not detected anywhere
If it does not appear in Finder, Disk Utility, or System Information—and another cable, port, power source, and computer make no difference—the hardware may have failed. For important files, disconnect it and seek data-recovery advice rather than continuing to test it.
You disconnected the drive without ejecting it
An unsafe disconnection can interrupt writing and damage the file system. If the drive mounts again, copy important files and run First Aid. For future use, eject it in Finder before unplugging it. You can also review How to Safely Eject an External Drive on a Mac.
Frequently Asked Questions
Why does my external drive not appear on my Mac?
The most common causes are a loose or faulty connection, insufficient power, a hidden Finder setting, an unsupported or damaged file system, or hardware failure. Disk Utility can help distinguish between these causes.
Can I repair an external drive without erasing it?
Often, yes. Try mounting the volume and running First Aid in Disk Utility. However, repair is not guaranteed, and you should protect important data before making changes.
Will mounting an external drive erase it?
No. Mounting makes an existing volume available to macOS. Do not choose Erase, Partition, or Format unless you intend to remove the existing data.
Why does Disk Utility see the drive but Finder does not?
The volume may be unmounted, encrypted, damaged, or hidden by Finder settings. Select it in Disk Utility and try Mount, then check Finder’s external-disk settings.
Should I keep using a clicking external hard drive?
No. Repeated clicking, grinding, or spin-up failure can indicate mechanical damage. Disconnect it and consider professional data recovery if the files matter.
Final Thoughts
Start with the connection, power, cable, and Finder settings. Then use Disk Utility to determine whether the drive is recognized, mount it, and run First Aid when appropriate. Avoid erasing a drive until you have confirmed that its files are backed up or no longer needed. If the drive is missing from both Disk Utility and System Information, or shows signs of physical failure, professional recovery may be the safest next step.