External Hard Drive Not Recognized on Mac: How to Fix It
Before we start
Fixing a problem with an external hard drive can be really hard for non tech-savvy users. But there’s no need to panic! Just ask for help from a real pro, and they are easy to find!
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However, if you're eager to fix this bug yourself, keep reading. We outline a range of straightforward solutions to an external hard drive not showing up on Mac in the following sections.
Your external drive not showing up on Mac? Here’s what to do
When you plug in a hard drive into your Mac, you expect it to pop up in Locations in Finder—next to your remote disk and the computer itself. But what if it’s not there? There can be many reasons for a Mac not reading a hard drive—poor connection, faulty cable or, in the worst-case scenario, corrupt hard drive data. Whatever happens, there are always ways to deal with it.
1. Edit your preferences
If this is not the first time you’re using an external hard drive and experiencing such a problem, it is not likely to be an issue for you. However, you could still check your preferences—just in case.
Your settings might not be set to display external hard drives on your desktop. To fix that, go to Finder and click on the Finder button in the menu bar at the top of the screen. Follow Preferences → General → Show these items on the desktop. Make sure you tick the boxes next to External disks and Hard disks. Then go to Sidebar and check Hard disks and External disks there as well.
2. Ensure your cable has sufficient power
Some hard drives require more power supply than others, different types and brands of cables provide more or less energy. Normally, a device requires up to 500 mA, which can be provided by a standard USB 1.0 or 2.0.
However, if your hard drive needs a stronger power output, it may work slower than expected or not connect at all. Check that your USB cable is delivering enough power to the hard drive and, if need be, swap to a more powerful connector or to a different USB port on your Mac.
You could also use an external power source or even a self-powered USB hub—adding its power to the power of your Mac might resolve the issue. Don’t forget to have your Mac connected to the charger.
3. Try Other Devices for Power Supply
If you find that no matter what type of cable you use, the hard drive is still not showing up, the problem might be in your Mac’s hardware. Try using another Mac or Windows device—if it only works on a PC, it’s likely that your hardware is not formatted to be launched on a MacOS device.
4. Use Terminal
For average users, the Terminal app is a last-resort solution because they tend to find it complicated. However, it’s almost always effective and isn’t actually that bad if you carefully follow the steps:
- Open Terminal by following Applications → Utilities → Terminal
- Type in diskutil list - a command that extracts information from the system to analyse any volumes and drives attached to your Mac
- A list of your disks will appear—search for a line with /dev/disk_ (external, physical)—the underscore signifies a digit assigned to your disk’s identifier
- Type in another command—diskutil info disk_, with the digit of the external disk that you’re interested in in place of the underscore
- If your system recognises the drive, this action should reveal the information about your drive. Then you can eject it by typing in diskutil eject disk_, with your drive’s assigned digit in place of the underscore
- You can now type in the diskutil list command again—if the drive is gone from the list, you can remove it from the USB port and reconnect it. It should now be able to mount normally
If you’re running MacOS Mojave or Catalina, you might come across the “Operation not permitted” error when entering a Terminal command. This is not a software bug—it occurs due to additional System Integrity Protection security measures that Apple introduced in the newer versions of the operating system. It locks down certain areas of the system and only relieves the lockdown during updates.
To fix this error, you need to grant Terminal full disk access:
- Quit Terminal and go to the Apple Menu → System Preferences → Security and Privacy → Privacy
- Scroll down the menu on the left until you see Full Disk Access
- To make changes to the list of apps that have the permission, click on the lock symbol in the bottom left corner of the window and enter your password when prompted;
- Click on the Plus button to add a new utility to the list. Look for Terminal in Applications → Utilities
- Once you’ve added Terminal, click on the padlock again to disable access to editing.
5. Engage Disk Utility
Disk Utility often becomes the ultimate fix for a lot of Mac problems, including those related to external drives. It can help to access and repair some disk issues by checking partition Macs and performing additional checks across the system.
To use Disk Utility, follow these steps:
- Go to Applications → Utilities → Disk Utility → View → Show All Devices
- The sidebar on the left will display any external drives—you should be able to view your hard drive there
- Click on the volume for a menu to appear. If the drive has been mounted, there will be an option to unmount the device. If you can’t see a volume list, your Mac can’t access the drive at all and you won’t be able to mount it
6. Change the format of your HD
Macs use HFS+ or APFS format, whereas Windows computers employ NTFS. FAT32 and exFAT are recognised by both Mac and Windows devices. You can check the formatting by going to the Apple menu at the top of the screen and following About This Mac → Storage.
If you see that your device’s format is not Mac friendly, you can change it through the following steps:
- Plug in the connector of your device slowly into the port of your Mac—this ensures proper initiation
- Go to Applications → Utilities → Disk Utility
- You should be able to see the external hard drive under the External heading in the sidebar on the left. Click on it to open the drive’s information
- In the menu bar at the top of the window, click on Erase and choose the format compatible with your Mac device
- Initiate reformatting. Bear in mind—all of your hard drive’s contents will be erased during the process
If you can’t sacrifice the data on the disk, you can reformat it using a Windows device:
- Connect your drive to a Windows PC
- Locate the drive in the sidebar in the File Explorer
- Copy all of the drive’s contents into a separate folder on the PC
- Right-click on the drive’s icon and choose Format from the drop-down menu
- Choose a format that’s compatible with both Mac and Windows devices—exFAT is the most modern and preferred one
- Name your hard drive in the Volume label window
- Click Start to initiate formatting. It should only take a few seconds until it’s done, and then you can use your hard drive on a Mac device
- Make sure to transfer the data back to the disk from the folder you’d created
7. Run First Aid
Regardless, you can always run the First Aid program. It checks the disk for any errors that could potentially cause the external hard drive not mounting on your Mac. It will then attempt to repair them. If you right-click on the device’s icon, the First Aid bar will show up in a drop-down menu. You will also see the options Restore and Erase—they act to clear any data from your hard drive, so if you store important documents there you should refrain from choosing those.
Launch First Aid by сlicking Run and then Continue. As a result of the screening, you will be advised on any errors that your Mac finds on the disk. If the program discovers an “Overlapped extent allocation” error, it’s likely that some of your files are corrupted. The list of affected files will be displayed in the DamagedFiles folder in your drive—you should delete them. If, by chance, they contain important information, make sure they’re not corrupted.
If the First Aid process fails, you have two options: run the program again and repair the disk, or to back up all the data you possibly can, change the format of the disk and reinstall your current operating system. After that you can recover the data you’d backed up.
8. Reset NVRAM
Nonvolatile random-access memory (NVRAM) stores local settings such as volume, screen resolution, and hard drive information. Mac’s firmware can primarily access this information, such as before it starts booting when you restart it. It ensures such small details as keeping your time zone consistent or keeping the volume muted when restarting your Mac.
NVRAM bugs are the source of many glitches, including a USB flash drive not showing up. Resetting it is easy and generally harmless, although it might mean that you’ll have to reset any basic custom settings you have on your laptop.
- Restart your computer
- When you hear the startup sound, hold command + option + P + R
- This causes your Mac to restart again—when you hear the startup sound for the second time, you can let go of the keys
On newer Macs, there’s no need to even restart the computer—just press down the combination for 20-30 seconds and your NVRAM will be reset.
9. Try Plugging It In Slowly
A strange feature regarding all USB cables—sometimes it may connect and function better if you plug it in more slowly. This is due to a design flaw in the power-up sequence of some of the USB drives. The power contacts in your USB connector are designed to make contact with the USB port first. Plugging in slowly applies power to the USB device and it gives the device extra time to initialise. This assists the proper order of events and hence mounting of your hard drive.
10. Try a Different Drive
If you’ve tried all the methods described above, isolate the problem by plugging in a different external hard drive. If another disk is recognised, the problem might be in the drive itself. Have you recently dropped it or subjected it to water damage? Check for any hardware issues. In the worst-case scenario you’ll have to replace the drive.
Here are a few reliable hard drives and SSDs that you could use with a Mac device:
- WD My Passport HD. 4TB capacity, USB 3.0 Interface—$120
- Portable Samsung T5 SSD. 200GB - 2TB capacity, USB 3.1 (2 generation) interface—$220. USB-C/USB-A
- G-Technology G-RAID With Thunderbolt 3 HD. 8TB—24TB capacity, USB 3.1, Thunderbolt 3 interface—$690. Also has a USB-C port
- Adata SD700 External SSD. Up to 1TB capacity, USB 3.0 interface—$90
How to avoid external hard drive not mounting on Mac
You now have a clear idea of how to access an external hard drive on Mac and what to do if it won’t mount. To make sure that you don’t face the same problem in the future, always check that the disk is in the right format for your operating system, that it has a strong enough power supply, and that the connector of your USB cable is not damaged. However, there are several additional things that you can do to avoid future complications.
1. Make sure the USB port is clean and properly connected
Dirty or loosely connected USB ports can create short currents, external hard drive's not showing up on Mac and struggling to read data. It’s common for a connector to get a bit wonky if you’ve used it for a while—the power contacts won’t align correctly.
In this case, your only option would be to get a new cable or, if you’re very persistent, get it fixed. If the connector or the USB port is dusty, you can clean it by blowing compressed air into the port and gently swabbing it with a cotton bud dipped in alcohol solution.
2. Always properly eject the device
Removing the drive without safe ejection can corrupt data on the device, which in the future can make your Mac unable to recognise it. Any operating system employs write caching—files are not immediately written on your hard drive when you transfer it or back it up, but are cached until all the side writing and reading operations are finished.
If the USB device is not safely ejected while the cache is in use, data can become damaged. Contrastingly, removing it safely clears the cache and stops background operations in the device, therefore protecting it.
3. Keep your operating system up to date
An out-of-date operating system causes problems for all areas of your computer’s functioning. Updates improve stability and performance, as well as ensuring your Mac’s security and minimising the risk of your files getting corrupted.
To install the latest version of your operating system, go to the Apple menu at the top of the screen and select System Preferences → Software Update. If an Update button is available, make sure all of your important work is saved before you click it as it restarts your computer.
4. Try a data recovery app
If you’ve tried launching First Aid and reformatting your drive and it’s still not detected on your Mac, the device itself is most likely broken and needs to be repaired or replaced. But even if the drive is broken, it still stores some, if not all of the information that you’ve backed up on it. Check out some of the apps here.
You might have some related questions that this article hasn’t answered. Here are some popular enquiries that you might be interested in.
How do you connect an external hard drive to a Mac?
Connect the hard drive with a clean USB port on your Mac via a suitable cable (preferably the one that came in a package with it). If your Mac has a different port, such as Thunderbolt or Firewire, make sure you get an adaptor for it. The drive’s icon should appear on your desktop or under the Devices heading in Finder. You can then open the disk and use it for backup or view its contents.
How do I revive a dead hard drive?
If you find your hard drive breaking down while it’s connected to your computer, it’s best to stop using it as soon as possible. To check if the problem is in the device itself, try connecting it to a different port or even a different computer. Try a different cable as well.
If these simple operations don’t work, you’ll have to open and examine the disk. Pay attention to the sounds that it makes when activated. For instance, a clicking noise indicates a malfunctioning head assembly—the part of the hard drive that reads data off its platters. Most of the time, the recommendation is to have it fixed by a professional. You shouldn’t attempt to repair the drive at home as there is a low chance of success and you’re likely to damage the data stored on the disk.
How do I back up my hard drive?
You can back up all your valuable data on Mac by using Time Machine. It’s a handy tool that comes with each Mac device by default for data maintenance, recovery, and backup. It will be useful if you need to bring back the files you lost after emptying the Trash or to be more efficient with your storage space.
To launch Time Machine backup, connect your hard drive disk to your MaBook and go to the Apple menu at the top of the screen. Go to System Preferences and find the Time Machine icon. Click on Select Backup Disk. A window will appear where you can select your external hard drive for backup.
Why does my Mac shut down when I connect a hard drive?
Just as some hard drives are not recognised because they don’t get enough power, some of them drain too much from your Mac. In this case, the system management controller will automatically shut the laptop down to protect it. If you think that that’s the case, try connecting the disk to an external power source such as a USB hub and reset your SMC.
If your Mac has a removable battery, use these steps to recent the SMC:
- Shut down your Mac and disconnect it from all sources of power, including the battery
- Hold the power button for 5 seconds
- Reconnect your Mac to the power source and put the battery back in
- Turn the Mac back on
If your battery is unremovable:
- Shut down your Mac and disconnect it from the charger
- Hold Shift + Control + Option + Power button for 10 seconds
- Release the keys and reconnect the Mac with the power source
- Turn the Mac back on