How to access an external drive that's not recognized on a Mac

Most of the time, when you connect an external hard drive to your Mac’s USB port, you soon see it mount on the desktop. Apple likes to ensure these are easy to find, so they also appear in the Finder in the left-hand column under Devices, since Mac’s treat them the same way as another computer.

However, sometimes, an external drive doesn't show up. It’s annoying, especially when you need to transfer something right then. And besides, there can be a risk that data on the external USB pen, hard, or flash drive is corrupt, which means you can’t transfer what you need between devices at all.

Corrupt data can be one reason your Mac won't recognize an external drive, but there are other reasons too. Let’s take a look why this is happening and how you can get an external drive to appear on your Mac and get recover data to access to your documents.

How to fix an external disk drive that won't show up on a Mac

Reboot your MacWhy an external disk drive is not showing up? There could be a few reasons why an external hard or flash drive isn’t making an appearance.

Start with the basics:

  1. Check whether the drive is properly plugged in. It sounds obvious, but since this relies on a wire - either a USB cable or HDMI cable - if it’s not connected properly then it won’t appear on your desktop.
  2. Faulty cable. Assuming it’s plugged in correctly, not wobbly or loose, the cable could be at fault. Try connecting the same device with a different cable.
  3. Damaged USB or flash drive port. It could be a hardware issue with the Mac. If you’ve got another port, try connecting the device to that one.
  4. Reboot your Mac. Sometimes, if a disk won't boot, the cause is macOS issue. Hopefully, some data damage that can be fixed by restarting. Choose the Apple menu > Restart. Or press and hold the power button and, when a dialog box appears, click the Restart or press R.  Restarting your Mac essentially clears your macOS’s memory and starts it up fresh. 
  5. Incorrectly formatted drive. Not every drive is optimized for Macs. It could be that you are trying to connect something only fit to interact with Windows devices. If you’ve got a PC or laptop, it’s worth connecting and seeing if you can access the files through another device. The best way to look for an incorrectly formatted drive is to go to Apple (in the top toolbar menu) > About This Mac > Storage. See if the external drive shows up here. For more information, go to the same menu option, then select System Report.
  6. Mac not formatted to display external drives on the desktop. It could be that your Mac already recognizes the device, but just isn’t showing its icon on the desktop screen. Even if that is the case, the drive will still appear in the left-hand column of the Finder menu under Devices. You should be able to access your drive that way, and, in the Finder menu under Preferences > General, you can check External Drives to ensure that from now on it shows up on your desktop too.
  7. Reset NVRAM. To do this, shut down or restart your Mac, switch it back on and immediately press these four keys together for at least 20 seconds: Option, Command, P, and R. It should look as though your Mac has started again; if it has, release the keys when you hear the second startup chime. Hopefully, the hard drive has shown up now.
  8. Check Apple’s Disk Utility to see if an external drive is showing up. Disk Utility is within System Preferences, or you can find it using Spotlight. If it is visible, then click the option to Mount, which should make it visible on the desktop and in the External Drives option in the Finder menu.

recognize disk with Disk Utility

Unfortunately, if none of those options has worked and the external drive still isn’t visible, then it could have crashed, or be well and truly broken. But there might still be a way you can recover the data on the external drive

How to show connected devices in Finder

  1. Go to the Finder menu and select Preferences (Cmd+comma).
  2. From General tab tick External disks to ensure that from now on it shows on the desktop.

Recognize an external drive with Finder Preferences

In the Sidebar tab you can choose which folders and devices will be shown in the left-hand column of the Finder window.

Repair the failed external drives with First Aid

If your drive is having problems, you can try to fix them yourself with First Aid and therefore get access to your files. First Aid tool will check the disk for errors and then attempt a repair as needed. It helps to verify and repair a range of issues related to startup HD and external drive problems. If you are able to fix the hard drive or SSD in your Mac (or a external drive) using Disk Utility you will hopefully be able to recover your files.

To run Fist Aid on an external hard drive:

  1. Open Disk Utility. You can searching for it using Spotlight Search or via Finder > Application > Utility
  2. Check on your external hard drive, click the First Aid tab and select Run to start running diagnostics.

If First Aid successful in fixing errors, the external  drive should be available to mount. If the utility unable to repair issues, your drive truly broken or formatted using a file system that the Mac cannot read - in this way we suggest you follow the next steps to recover data from a damaged disk drive.

How to recover data from a crashed hard drive

Thankfully, there is an app for that. Disk Drill is the world’s premier data recovery software for Mac OS X. Powerful enough to retrieve long-lost, mistakenly deleted files from Macs, external hard drives and USB drives and camera cards.

An easy way to recover lost files on an external hard drive

Providing you already have Disk Drill Pro version, which you can get automatically by downloading from Setapp:

  1. Connect your drive to the Mac.
  2. Quit all other applications on the Mac, especially those that may be trying to access the external drive (e.g. iPhoto, Words)
  3. Launch Disk Drill.
  4. Click on the external drive that you are trying to recover files from. If it has partitions, you will see all of them. If, however, you still don’t see any volume to the external drive then you may need to try some of the steps above again or read the Disk Drill Scanning FAQs.
  5. To avoid the external drive being accessed during the recovery process, click Extras next to the drive or drive partition or file, then select Remount Volume As Read Only. A padlock will appear, protecting the drive during the process.
  6. Now click Rebuild (or Recover) next to the file(s) you are trying to recover. Once the scan is finished - it may take some time if the files are large - a list of files will appeal. Disk Drill data recovery
  7. Next, click Mount Found Items as Disk button on the bottom-left below the scan results.
  8. Disk Drill “strongly suggest saving the files to a different drive than the one you are trying to recover files from. Saving to the same drive substantially lowers your chances of recovery.”
  9. A drive icon will appear, which once you double click will give you the option to open the files as you would do before they were lost. Drag them to another location, such as your desktop or a folder on your Mac.
  10. Open the files to ensure they have been recovered properly and safely eject the external drive.

Disk Drill does have other ways to recover lost files but assuming there aren’t complications, this method is the most effective. Disk Drill Pro recovery app is available from Setapp, along with dozens of Mac apps that will make your life easier. Never have to worry about a crashed or corrupted external drive again.

A few more tips on getting your files back

  1. Macs and third-party apps that look after Macs, such as Disk Drill and iStat Menus come with a S.M.A.R.T. (also known as Self-Monitoring, Analysis and Reporting Technology) status monitor. If a SMART check reports errors, then it could mean the hard drive is at risk of failing completely. Within Disk Utility and Disk Drill, there are several solutions for this: Repair Disk Permissions and Repair Disk. If neither work, it’s recommended that you backup all of the data from the disk, erase, then run a SMART check again. The external hard drive should show up as Verified.
  2. Partitions can get lost within hard drives, temporarily hiding all of the information contained within. Disk Drill can help to identify and restore this information.
  3. Within Disk Drill, you can restore data when a hard drive is damaged or add formatting, which is also something Disk Utility can help with.
  4. CleanMyMac X, another useful app available from Setapp, can help you identify external hard drive errors and repair them. It is an essential tool worth trying when you’re having external hard drive difficulties.

Alternative ways to recover data from an external hard drive

Reset the System Management Controller (SMC) if your Mac shuts down when you plug in an external hard drive. Then use a different port to connect the external hard drive. If you’ve got a battery that you can’t remove:

  • Shut down and unplug the power adapter
  • Press Shift-Control-Option and the power button at the same time. Do this for 10 seconds
  • Release all keys
  • Plug the power adapter back in and switch your Mac back on

For Macs with removable batteries, you need to switch them off, remove the battery, then press and hold the power button for 5 seconds. After that, put the battery back in, plug in the power adapter and switch the power on again.

What’s your file format? One reason your Mac isn’t recognizing the hard drive is the file format. Windows uses NTFS file formats, while Macs, up until the introduction of Sierra, have used HFS+. Now, Apple has introduced the Apple File System (APFS) for newer operating systems. It is possible to format a hard drive so it can be read on Mac and Windows computers, providing you format using exFAT. However, if you’re having problems accessing the files and the issue is due to formatting, you will need to connect it to a device it can be read on, and then format the files correctly for the computer you are going to use it on next.

Employ the handy all-powerful Terminal, which always comes forward with solutions for difficult problems. Especially if System Information does recognize the USB or hard drive, but continues to hide it from you, disconnect the drive and try to find it using the Terminal, which you can find in Applications > Utilities.

  • Once in the Terminal, type in the command diskutil list
  • A list with information about volumes and drives should appear
  • Look for a section labelled /dev/disk_ (external, physical)
  • Make a note of the whole line after the word disk
  • Now put the following command into the Terminal diskutil info disk followed by the number or digits assigned to that disk
  • Now you should see detailed information about the drive, therefore confirming that your Mac can and does recognize it
  • Eject using the Terminal by entering the command diskutil eject disk followed by the number or digits assigned to that disk
  • Physically remove the disk from you Mac
  • Plug it back in and your Mac should recognize it

Console is also reliable when it comes to solving tricky problems, although it isn’t always that easy to use. You can find Console under Applications > Utilities > Console. Console shows if an external drive or any error is detected under the Errors and Faults tab. If no errors show up, then the problem is not caused by the device.

To sum up, there are lots of potential solutions for a Mac not reading an external hard drive. If we were to pick one, Disk Drill seems to be the most well-rounded, offering plenty of customizations and power in an easy-to-use interface. Disk Drill Pro recovery app is available via Setapp, along with 120+ Mac apps that strive to make your life much much easier. At the very least, you’ll never have to worry about a crashed or corrupted external drive ever again.

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