Mac or MacBook can't detect my external drive.

Mac or MacBook Doesn't recognize External Drives. Troubleshooting tips

Macs like most other computers are well working hardware which includes all the newest technologies, unfortunately sometimes hardware and software miscommunicate and causes issues in proper work. There is a lot of cases when you can fix their communication by your own just following some easy tips. For example external drives are widely used invention which nowadays helps a lot of people save money while trying to expand their drives or data storage without a high-priced upgrades. Also it helps to share large size files in a much easier way. Unfortunately in some cases Macs encounter problems while trying to detect some recently plugged in devices. You may face this issue any time you try to connect your external device, even if it worked well several times before.

There are plenty of reasons why this may happen. Probably the most frequent is that we disconnect them straight from the port without ejecting in our operating system first, this results in our drives being still in the run mode while they are out of use. Also the connector or wires might be broken, frayed or worn. Sometimes it's a power or connection problems, sometimes errors in the system preferences. There are cases, when you had well working plugged in device, but once your computer went to sleep with connected external drive, after waking up drive is no longer available. Here we describe the most popular issues and tips how to solve them. Before we start the troubleshooting work, first try to reconnect you external device several times, quite often it helps to solve this problem.


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Connections rules

Its really quick and convenient just to plug in and out your devices, usually this task for your mac is to easy, but there are cases when it couldn't recognize your device or drive. Even manufacturers declare it is an plug-and-play. However this work most cases but not all. The best way is to follow recommendations how to connect devices to Mac.

The most reliable path to connect external drives is following these steps.

  • Turn on your mac device
  • Connect usb cable into computer then to device
  • Turn on your external drive.

The super slow plug in

A lot of people declares that their usb flash drives works only when they connect them to computer very slow. If they try plug it in a usual way devices can't detect the drives. Only a slow connections allows to detect them and this case appears in any manufacturer computer, doesn't matter its an apple or windows operating system.

Eject in a safe way

As it was mentioned wrong unplugging could be a reason for your issue with external drive. Your friend might tell that he never ejects his drive, but there always are a chance that this time will be lucky one and after unplugging your drive will be no more detectable. Always perform a safe remove, which you can do in a very easy way. Just right click on your external drive and select Eject device or if u prefer you can just drag your device to Trash which is going to replace to eject symbol while you drag on. This will turn down your device from any tasks and will ensure that it will be available next time you connect it.


If you can put it on it doesn't matter it fits

Just like in most cases, this rule is valid there. If your connection is dirty or loose it may cause a problems to detect and mount your drive. For that reason you should ensure is your hub clean and connection is tight. Check your cable's condition, if it's damaged, frayed or worn may also be a problem while your mac trying to detect or mount your device. Also these reason may cause an disconnection issues. What is more additional hubs can help you to connect but also there is a possibility it cause an connection issue, so you should try connect directly without any additional hubs.

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Power issues

Some cases when you face and issue with your external drive, is caused by lacking of power. Some devices often have their own power source, and while receiving enough power they mounts on its own. If your external drive doesn't have own power supply try plug it in a different usb port if it still not working try use and self-powered USB hub. Quite often case when macs doesn't provide enough power into built-in USB hubs, so additional self-powered hubs helps to solve this issue. Alternatively you can try plug in your power cable into computer and reconnect your drive.

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Check your settings

If none of those check works mentioned above could help, begin a bit more complicated solutions. Before starting a troubleshooting steps, check the base mac system preferences. Open your Finder then locate for Preferences. Under both General and Sidebar tabs search for the section Show these item on the desktop (or sidebar). Ensure that External Disks and Hard Drives have a check mark in the box. If you found them disabled, click on the white box to enable icons on desktop.


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Run Disk Utility

Launch Disk Utility and look up if your external drive is visible here. To open up your Disk Utility go to Applications then open Utilities and there look for Disk Utility. If your drive appears here but shows its not mounted, select the mount option in top-middle, which should mount that drive. To ensure click on the Apple logo in your screen's top left corner and select About This Mac. Inside select the Storage tab and search for your drive. If you can't find it there, come back to Disk Utility and select your external drive from sidebar. Then click on First Aid or verify(repair) disk. This option should find and solve your drives issues.


Check your external drive format

If disk utility tools couldn't solve your problems you should check format of your drive. Ensure that it isn't listed as NTFS format, otherwise perform a reformat using the erase function in Disk Utility, the new format you should choose is exFAT, Fat or Mac OS Extended.


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Use terminal to solve your issue

First you should check if you mac detects your drive is plugged in. To do this open About this Mac and storage tab. For more detailed information choose System Report in Overview tab. In sidebar select USB from hardware section. There you will find all devices connected via usb which your mac detects. If you found your external drive connected in system report but you can't reach it, try disconnect it and remount using Terminal. To open terminal in applications window select Utilities then Terminal. Write down command diskutil list in the terminal. Terminal should display you basic information about all available drives and volumes connected to your mac. In the list search for section labeled /dev/disk_ (external/physical). The disk_ part is the physical disk identifier in a operating system, and the underscore is a number or digit assigned to this drive. Write down whole line including the number or digits which goes after word disk. If your drive has several partitions an letter s follows the disk identifier. The number after letter s is a count of the partition.


Once you got your external drive name in terminal you can use another command diskutil info disk_, ensure you entered your drive symbol instead of underscore. This command opens up detailed information about the drive, including its manufacturer name, its size and is it removable, and more facts.
Furthermore you're sure your disk is viable in system, use Terminal to eject it by using command diskutil eject disk_. Don't forget to replace underscore with your disk identifier symbol. After executing ejection command, check is it really removed by typing diskutil list command again. When you're sure your drive is ejected, disconnect it physically from your computer. This should fix your issues.


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NVRAM (non-volatile random-access memory) is small part of your Macs memory that stores certain settings in a location where macOS can access. In this memory is stored information like your computer’s speaker volume, screen resolution, startup disk selection, and any recent kernel panic reports. To reset the NVRAM shutdown your Mac. Turn it on and after loading chime hold down together Option, Command, P and R buttons. Keep holding this combination at least 20 seconds. This should make a view like your computer is restarting and if you hear start up chime again release the buttons.

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Does your MacBook shuts down when you plug in your external drive?

You might face this issue when your drive draws too much power from an usb port. Your Mac's SMC shuts down the computer to protect itself. If it happens frequently, try connect your external drive to its own power source if its supplied. In case it's impossible for drives like thumb drives, connect it to another usb port or change the cable you're using. If none of those options available, try reset your Macs SMC.

Resetting SMC

If the battery is integrated:

Shut down your mac and unplug the power adapter. Hold down Shift, Control and Option buttons together with power button for 10 seconds. Then release all buttons and reconnect your power adapter. Turn on your mac in usual way.

If the battery is removable:

Shut down your mac, unplug power adapter and remove battery. Press and hold power button for 5 seconds. Replace the battery and and reconnect your power adapter. Turn on your mac in usual way.

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Inspect your external drive via Console

In times of trouble, Console might be really useful app which displays list of log and error information that helps you or the service provider to troubleshoot problems of your Mac. However Console can't fix your issues, but information displayed in it might help find a solution. Let's check your what's going when you plug in your device via Console. First open up a Console, which can be done by accessing Applications then selecting Utilities and finally a Console. In opened window select Error and Faults tab. Then connect your external device and look for a changes in console. If it detects your device or if displays an error about it. In case no changes in console appear the problem is not your usb device.


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Video Showing how to troubleshoot external HDD detection problems:

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About the author:

Tomas Meskauskas

I am passionate about computer security and technology. I have an experience of 10 years working in various companies related to computer technical issue solving and Internet security. I have been working as an editor for since 2010. Follow me on Twitter to stay informed about the latest tech news or online security threats. Contact Tomas Meskauskas.

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