Can T Access External Hard Drive Mac

  1. Can't Access External Hard Drive Mac Compatible
  2. Can't Access Files On External Hard Drive Mac

Mac or MacBook Doesn't Detect External Drive? 7 Ways You Can Fix It!

I'm trying to access a macbook hard drive that won't boot. The user said that it failed to complete an OS update and now it won't boot at all. They've asked me to pull all the data off the hard drive and see if the drive can be initialized and the OS installed. Choose one of these to open the Disk Utility. In the window that opens, you will then see your Mac HDD listed, along with the hard drive you want to use as your Time Machine. You will see the name of the your external hard drive listed twice. Single click on the lower one. To the right, you will then see three tabs - 'First Aid', 'Erase'.

An external hard drive is a lifesaver when you need a lot of storage to store your files. What's great is that you can carry the drive with you wherever you go and efficiently move large files from one Mac to another. Due to large storage capacities, you can use your external hard drive as a storage backup for your Mac.

Unfortunately, sometimes Macs and MacBooks can't recognize the external drive. That can happen when you eject the external drive the wrong way by unplugging it from your Mac without ejecting it. Then when you plug it back in suddenly, your Mac can't recognize the drive.

There are more reasons why your Mac might not recognize your external drive. Follow the troubleshooting steps in this article to find out the problem and fix it.

Video on Mac or MacBook Doesn't Detect My External Drive. 7 Ways You Can Fix It!

Table of Contents:

  • Method 1.Check Your Settings
  • Method 2.Run Disk Utility
  • Method 3.Reformat External Drive
  • Method 4.Remount External Drive Using Terminal
  • Method 5.Reset NVRAM
  • Method 6.Reset SMC
  • Method 7.Inspect The External Drive via Console

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Check Your Settings

Before proceeding to more complex troubleshooting steps, check your settings if hard and external disks are set to be shown on the desktop.

1. Go to the upper menu and click on the 'Finder' menu.
2. Go to 'Preferences.'

3. In the 'General' tab under 'Show these items on the desktop', check the boxes next to 'Hard disk' and 'External disk.'

If the boxes are checked and you don't see the external drive on your desktop, proceed to the next step.

Run Disk Utility

Go to Disk Utility and look up if your external drive is visible there. Run First Aid to find the issue with your drive.

1. In the upper menu, click on the 'Go' menu and select 'Utility.'

2. In the Utility window, find and click on 'Disk utility.'
3. If you see your external drive in the Disk Utility window, but it shows that it's not mounted, select the drive and click on the 'Mount' button.

4. Then, go to the upper menu and click on the Apple logo.
5. Click on 'About This Mac.'

6. Go to the 'Storage' tab. If you can't see your external drive there, go back to the 'Disk Utility' window.

7. Select the drive and click on 'First Aid.'
8. Then click on 'Run' and wait for the process to finish.

The First Aid option will check the disk for errors and then repair the disk if necessary. Click on 'Repair Disk' if you see this option pop up.

Reformat External Drive

If you see your drive in the Disk Utility window but could not mount it to your Mac, you might have a disk format issue. In this case, you need to reformat the drive. PCs with Windows operating systems use the New Technology File System (NTFS). In contrast, Macs with macOS operating systems use the Hierarchical File System (HFS+). By default, USB flash drives and other external drives are formatted with the NTFS file system - this works great on PCs, while Macs can read data in the format but struggle to write it. Fortunately, you can format your external drive with the File Allocation Table (FAT32) or Extended File Allocation Table (ExFAT) file system.


Format FAT32 [on a Mac, known as MS-DOS (FAT)] is fully compatible with all versions of Windows and Mac operating systems. Therefore, even the oldest operating system versions, Windows XP SP1 and OS x 10.5 Leopard are compatible. The FAT32 file system is also supported by Xbox 360, PlayStation 3, and most cameras. Unfortunately, this particular file system does have file size restrictions. The maximum size of supported files is 4GB which means you can't write files larger than 4GB. Also, you can't create a startup drive for Macs within storage media that uses the FAT32 file system. Suppose you are not planning to use external storage to transfer large files or create executable partitions (such as a Mac startup drive). In that case, the FAT32 format can be a great option.

ExFAT is a file system format that has an advantage over the FAT32 file system. It has no restrictions on file or partition sizes. Therefore, you can write a 1TB size file and create partitions of 5TB within the device. Despite the improved data size, some older versions of operating systems are no longer compatible with this file system format. The oldest versions of operating systems compatible with ExFAT are Mac OS X Snow Leopard 10.6.5 or later, OS X Lion, Windows XP SP2, or later (with an additional update for exFAT support, Windows Vista SP1 or later and Windows 7.

Unfortunately, the ExFAT file system format is not supported by various cameras, video game consoles, and other devices that can read and/or write to external storage. If you will be using a USB flash drive or external storage device with any of these devices, the required format is FAT32. If the drive is to be used only with computers with modern versions of operating systems, the recommended format is ExFAT.

Format external drive:

1. In the upper menu, click on the 'Go' menu and select 'Utility.'
2. In the Utility window, find and click on 'Disk utility.' In the Disk Utility window, select your drive.
3. Click on the 'Erase' option.

4. Choose the disk format as ExFAT, MS-DOS (FAT), or Mac OS Extended (Journaled).

5. Click on 'Erase.'
6. Then, go to the upper menu and click on the Apple logo.
7. Click on 'About This Mac.'
8. Go to the 'Storage' tab to see if your external drive is visible.

Remount External Drive Using Terminal

First, check if the system recognizes your drive. If it does see that the external drive is plugged into your Mac, but it doesn't show up, try to remount the drive using Terminal.

1. Then, go to the upper menu and click on the Apple logo.
2. Click on 'About This Mac.'
3. Go to the 'Storage' tab to see if your external drive is visible.
4. Open Spotlight by pressing Command + Space keys on your keyboard.
5. In the Spotlight, enter 'Terminal' to open it.
6. In the Terminal window, enter: diskutil list

The 'diskutil list' command will display the essential information about all available drives and volumes attached.
7. Then search for /dev/disk_ (external, physical). Make sure to remember the number following after the word 'disk.'
8. In the same Terminal window, enter another command line: diskutil info disk(digit)

9. After that, eject your disk by entering the command: diskutil eject disk(digit)
10. After executing the eject command, check if it was removed by entering the command line: diskutil list

If you don't see your drive in the list, that means you removed it successfully. Then remove the drive physically from your Mac.


Nonvolatile Random Access Memory (NVRAM) stores hard drive information. If NVRAM has encountered bugs, your external drive not showing up can be the cause of it. In this case, it's best to reset NVRAM.

1. Restart your Mac.
2. When you hear the startup sound, simultaneously hold down Command + Option + P + R keys on your keyboard for 20 seconds.
3. When you hear the startup sound for the second time, you can let go of the keys.

If you have a newer Mac, you don't need to restart your Mac to reset NVRAM. Just hold down the keys for 20-30 seconds, and the NVRAM will be reset.

Reset SMC

If your Mac or MacBook shuts down after connecting your external drive, that means the drive consumes too much power from the USB port. If your drive can't connect to an additional power source and the issue keeps on repeating, try resetting SMC (System Management Controller).

If the battery is integrated:

1. Shut down your Mac.
2. Unplug all peripherals.
3. Simultaneously hold down Shift + Control + Option keys on your keyboard together with the Power button for 10 seconds. If you have a MacBook Pro, the Touch ID button is also the power button.
4. Then reconnect your power cable and other devices.
5. Turn on your Mac.

If the battery is removable:

1. Shut down your Mac.
2. Unplug all peripherals and remove the battery.
3. Press and hold the Power button for 5 seconds.
4. Insert the battery and connect your Mac to the power source.
5. Turn on your Mac.

Inspect The External Drive via Console

The Console app can be handy in times of trouble. It displays log information that helps to troubleshoot problems on your Mac. It won't fix the problem but will provide information to diagnose the problem.

1. In the upper menu, click on the 'Go' menu and select 'Utility.'

2. In the Utility window, find and click on 'Console.'
3. Select the 'Error and Faults' tab.

Can't Access External Hard Drive Mac Compatible

4. Plug in your external drive to your Mac.
5. Then look to see if it detects your drive or if there's an error. If no errors pop up and nothing happens, then your problem is not with the external drive.

Let us know in the comments which solution helped you fix the problem!

Compatibility issues between Microsoft’s Windows and Apple’s MacOS have diminished sharply over the years, but that doesn’t mean those issues have completely disappeared. Today, if you buy a new external hard drive, you may notice that working between the two is an often demoralizing task.

Fortunately, there is a solution. You can “partition” your hard drive, or divide it into different sections with different rules and functions. In this case, you can partition your drive so that part of it works properly with MacOS and part of it works properly with Windows. Both computers have the necessary tools to help you partition a new drive once you have it connected.

It’s a split, niche scenario

A quick Google search may lead you to believe you’re on the right path by formatting the entire drive with Extensible File Allocation Table, or exFAT. It’s a simpler, universal method if every file you store is less than 4GB in size. However, this format doesn’t support larger files, which can be problematic for transferring 4K videos and so on between Macs and Windows 10 PCs.

Meanwhile, the NTFS system used by Windows 10 supports large files, but this format can’t be read natively by MacOS. That puts you in a peculiar pickle, limiting any shared file between the two platforms at 4GB or smaller. If you want to save larger files, you’ll need to create a second, dedicated space using a format optimized for MacOS (Extended) or Windows 10 (NTFS).

That said, our guide splits the external drive in half: One primary section capable of storing files larger than 4GB, and a secondary section capable of sharing files between MacOS and Windows 10. It’s not the ideal solution — we get it — but it works nonetheless.

Before digging in, select a primary format you’ll use the most: MacOS Extended if you primarily use Mac with a secondary exFAT partition, or NTFS if you mainly use Windows 10 with a secondary exFAT partition.

Finally, formatting deletes all data stored on the drive. Make sure you back up anything important before beginning the formatting process. We have guides for Windows and MacOS in case you need a helping hand.

Partition the drive on Windows 10

We have a full guide on how to complete the process from Windows 10 here. But let’s go through the important steps you need to know to quickly partition the drive while working on Windows. The process is less straightforward in Windows than what you see on a Mac, but it’s now easier than ever.

Can't Access Files On External Hard Drive Mac

Step 1: Right-click on the Start button and select Disk Management on the Power User menu.

Your PC’s primary boot drive (C:) hosting Windows and other programs appears as Disk 1. If your PC has a secondary “data” drive (D:), Disk Management assigns it as Disk 0. Windows 10 typically lists an external drive as Disk 2 along with the next successive alphabetic label if you don’t have any other internal disk-based storage. Windows 10 lists optical drives differently.

Typically, external drives are formatted out of the box. However, you may encounter a “Not Initialized” error when connecting the device to your PC. That means it’s not formatted correctly to work with Windows. Even more, it won’t have an assigned drive letter in File Explorer (This PC), and may not even have allocated space for saving data.

If you see an Initialize Disk pop-up window, it provides two formats: Master Boot Record (MBR) and GUID Partition Table (GPT). The former is older and only supports capacities up to 2TB, but is compatible with older versions of Windows. GPT is a newer format supporting larger capacities but isn’t compatible with older versions of Windows.

Select the partition style and click the OK button to continue. If you accidentally closed the pop-up, right-click on the listed disk and select “Initialize Disk” on the pop-up.

If you didn’t get the pop-up warning, move on to Step 2.

Step 2: Right-click on the unallocated space, and select the New Simple Volume option on the pop-up menu, as shown above.

Step 3: The New Simple Volume Wizard begins. Click the Next button.

Step 4: Since we’re creating two partitions, divide the listed physical number in half. Type that number into the field next to Simple Volume Size in MB and click the Next button to continue. In our scenario, we’re dividing a 1TB SanDisk Ultra solid-state drive.

Step 5: Allow the Wizard to assign a drive letter, or manually assign the letter using the drop-down menu. Click the Next button to proceed.

Step 6: Select a file system. Since your primary PC is Windows 10, use NTFS. Enter a volume label (drive name) too — we used “Windows 10,” though you can label this partition with anything. Click the Next button to proceed.

Step 7: Click the Finish button to complete.

In Disk Management, the external disk should list one new volume — “Windows 10” in our example — and a second portion with unallocated space.

Right-click on that unallocated space and repeat step 1 to step 6. This time, however, choose exFAT as the file system during step 6, which you’ll use to share files with MacOS. Note that you don’t need to specify a volume size.

The result should look something like this:

Partition the drive in MacOS Big Sur


Partitioning an external drive in MacOS isn’t quite as troublesome. Assuming that your external drive has no partitions, you will need to create two. If the drive already has a Mac-friendly partition, you can skip ahead to step 5.

You may first see an “initialize” error because the drive’s file system isn’t “readable.” Click on the Initialize button on the small pop-up screen to create your first compatible partition and begin at step 5. If the error does not appear, start with step 1.

Here, we used the same SanDisk SSD, although MacOS pulled the Seagate USB adapter’s name rather than the drive’s actual name (the adapter came from an external Seagate drive). Note that the following instructions also apply to Catalina — the only real differences are the visual changes to the UI and how internal volumes are listed.

Step 1: With Finder highlighted, click Go on the menu bar followed by Utilities on the drop-down menu.

Step 2: Double-click the Disk Utility icon in the following window.

Step 3: With Disk Utility open, your drive appears under External located on the left. Click Erase, located on the app’s top toolbar, as shown below.

Step 4: In the following pop-up window, enter a name. Select MacOS Extended (Journalist) as the format and GUID Partition Map as the scheme.

Step 5: Click the Erase button to make these changes.

Step 6: Once complete, your drive should have a single partition. Highlight the drive again in Disk Utility and then click Partition listed at the top instead.

Step 7: On the following pop-up (it won’t move), click the small Plus button located under the blue pie chart to add a second partition.

Step 8: A second portion appears, slicing the pie graph down the middle. Enter a volume name (we chose Windows) and select the exFAT format.

Step 9: Click the Apply button to add the new partition.

Step 10: Click the Partition button in an additional pop-up window to complete the process.

Step 11: Click the Done button to finish.

The result should look something like this:

Note that two icons representing each drive should appear on your desktop, as shown above.

It’s good to mention that the exFAT file system isn’t 100% reliable, so you might want to hook your hard drive up to a Windows computer and create a secondary Windows partition to NTFS. The Windows section contains our in-depth explanation of this.

Final notes

As you can see, partitioning a hard drive isn’t a complicated process, whether you’re using Windows or a Mac. You can also choose to install a paid application like Paragon’s Microsoft NTFS software or the free and open-source Tuxera on your Mac to enable NTFS to read/write support.

Keep in mind that even with third-party software, some features like Time Machine won’t work correctly with an NTFS file system.

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