Connect an External Hard Drive to Mac, 12 Things to Know

By Simon Irons / July 23, 2019
Connect External Hard Drive to Mac

No matter what the reason is;

Whether it is pictures you took on that special holiday or your mega music collection in iTunes

you need an external hard drive for your Mac now … Because you need a backup of that important stuff or need to take some files elsewhere and an external drive is the best way to do it.

Perhaps you are reading this article because the drive hasn’t arrived yet and you want to get ahead of the game or

it has and you’re not sure what to do with it.

It is for all those reasons,

for you that I wrote this article. ‘Connect External Hard Drive to Mac,12 things to know.

This article is written for those who have a Macbook, Macbook Pro, Macbook Air or iMac running Mac OS Sierra. I cover the connection options from Macbook late 2010, through to the 2015, 2016 and 2017 versions.

I answer the questions, How to connect an external hard drive to a Mac, How to find the external hard drive on a Mac, What if the external hard drive is not showing up in Mac Disk Utility and other questions you may have. I hope you enjoy my article and find it useful.

It’s arrived. The Box is here

First of all. Go on, remove the packaging. And what you should find inside the box is;

The hard drive enclosure itself, a USB cable and perhaps a power adaptor if your drive is powered from the mains.

Open up and sign into your Mac.

1. Understanding which USB cable Connects to your Mac

The USB (Universal Serial Bus) cable provides the physical connection between your Mac and the external drive. It allows your Mac to transfer files to and from the external drive.

And can also provide power to the drive if your drive is one that is bus powered as many of the portables are now.

The thing to know is that the USB cable is a standard cable but there are a few ‘standards’ of USB connections available to your Mac depending on when your Mac was manufactured.

The difference between the types of USB and standards being the physical connections, file transfer speed and power draw supported.

The great thing about the USB standard is that there is backwards compatibility.

For example

USB 3.0 is backwards compatible with USB 2.0.

USB 3.0 is the faster protocol (5 Gbit/s minus the protocol’s overhead) so drives that conform to USB 3.0 send data back and forth at USB 3.0 speed, if they are connected to a Mac with a USB 3.0 port.

Slower if connected to a Mac with a USB 2.0 port (480 Mbit/s minus overheads). In this instance the physical USB cable connections are interchangeable between a Mac with USB 3.0 and a Mac with USB 2.0 ports.

The USB cable connection in this case is called a type A connector.

Actually Macs with USB 3.1 gen 1 and 2, USB 3.0 and USB 2.0 all have type A ports.

USB Type A Ports on the Mac

USB Type A Ports on the Mac

The compatible USB cable connector will look like this at the end that connects to your Mac.

USB Type A Cable at the Mac End

USB Type A Cable at the Mac End

And may have a colored blue strip in the connector.

2. Remember that I mentioned earlier about power?

This has implications if the USB cable supplied with your drive is too short and you want to purchase a longer replacement USB cable.

The faster the protocol the more power it takes to power the external drive. The USB cables are slightly thicker as you go up the generations, as there is extra wiring inside the cable to accommodate the greater power drawn by the faster drives.

This means that if you are replacing a shorter USB 3.1 cable for a Mac with a USB 3.1 port that is connecting to an external drive that supports USB 3.1. If you want to see the maximum speed the external drive is capable of, purchase a USB 3.1 type A replacement cable.

Alternatively if you’re connecting this same drive to a Mac with USB 3.0 or USB 2.0 ports then your Mac wouldn’t be able to send files to the drive at USB 3.1 speed.

In this case purchasing a longer USB 3.0 cable wouldn’t matter so much because with backwards compatibility the drive would work, just slower that’s all.

3. Macs with Thunderbolt 1 or 2

Your Mac may have a Thunderbolt port as well as USB type A ports.

Apple introduced these with the 2011 generation of Macbook Pro

Thunderbolt Port Alongside USB type A Port on Mac

Thunderbolt Port Alongside USB type A Port on Mac

These ports have the tell tale lightening bolt symbol beside them.

The ports are faster and were designed to allow connections to a Thunderbolt screen, or FireWire or gigabit Ethernet as well as external storage.

It looks very similar to a mini display port but it is different hence the symbol right by the port.

The Thunderbolt port allows multiple devices to be connected at the same time and for that you will need a Thunderbolt adaptor supporting the devices you would like to connect.

The Thunderbolt cable connection for these Macs looks like this


Thunderbolt Cable Connection

Thunderbolt Cable Connection

These ports are physically different to USB type A ports that support USB 3.1, 3.0 and 2.0 but they are backwards compatible.

You will just need to get yourself an adaptor cable to plug USB 3.1, 3.0 or 2.0 hard drives into.

This document on the Apple sites discusses the different kinds of adapter cables you can get for your Mac

4. Macs with USB C and Thunderbolt 3 Connectivity

USB C type connections were introduced first on the Macbook 2015 edition. This Macbook has a single USB C port, which supports the speed and protocols of USB 3.1 gen 1.

You charge the Macbook using this port and the good news is that with an adaptor cable you can also use an external hard drive.

This port does not support Thunderbolt devices or displays, so there is no point purchasing a Thunderbolt external drive to connect to this Macbook.

5. Newer iMac (2017) and Macbook Pro (2016 and later) come with USB C ports.

USB C Thunderbolt 3 Ports

USB C Thunderbolt 3 Ports

All these ports support Thunderbolt devices and are Thunderbolt 3 compatible.

And because of backwards compatibility you can put USB 3.1, 3.0 and earlier hard drives on with the appropriate adaptor cable.

Ok, now you understand the different type of USB ports and cables it is time to plug in your external drive.

Further information on Mac ports can be found in this Apple article

Mac Basics: Ports on your Mac

If you are not sure how to find out what type of USB protocols your Mac supports take a look at the Frequently Asked Questions below.

6. Does your external hard drive need a power cable?


Typical External Hard Drive Power Cable

Typical External Hard Drive Power Cable

Desktop external hard drives typically need a separate power adaptor.

A portable external hard drive is likely to be bus powered via the USB cable.

The thing to know is that if you have an external power adaptor do not turn on the power to the external drive yet. Make sure your external drive is where you want it and it is on a firm surface before you power it up.

Spinning, powered up drives, do not appreciate knocks and shakes. You may shorten the life of the hard drive and make your files inaccessible if your drive gets a knock while the drive is working.

Solid State drives (SSD) do not have moving mechanical components and you’ll not have to be so concerned if your are connecting one of those external drives.

External drive on a firm surface? Good. Power it up.

You may hear the fan or see a light come on the front of the drive to tell you it’s powered and working

7. Now Connect the External Hard drive to your Mac

Via its USB cable or adaptor cable if you are using one and the USB cable into the adaptor.

If the drive is USB bus powered it will power up when you connect the USB cable to your Mac.

8. How to Find an External Hard Drive on a Mac

There are several ways to find your external hard drive on a Mac.

First Look at your Mac’s screen and within a few seconds you should see a new icon on the desktop letting you know your external hard drive is connected and seen by the Mac.

External Drive Icon On Desktop

External Drive Icon On Desktop


You can also check in a finder window on your Mac. The drive will be listed under devices.

External Drive In Finder Window

External Drive In Finder Window

If your external drive is not appearing either as an icon or in the finder window check my frequently asked questions below.

Double click on the icon on your desktop to open up the external drive for use or

click on the external drive under devices in your finder window to open up the external drive.

Double click to open up a window to the drive so you can see your nice empty drive.

So what if I don’t see an Icon?

You may need to format the external drive for your Mac. Take a look at my frequently asked questions below for other options otherwise skip ahead to where I tell you how to format your external hard drive to use on your Mac


9. How to use an External Hard Drive on a Mac

Using an external hard drive on a Mac is just as easy as using files in any other folder on your Mac. The normal copy and paste commands you are used to using on your Mac are all available for you to use.

You can drag and drop from the finder window or folder on your internal hard drive to the finder window on your external hard drive.

The Mac treats the external hard drive as it does your internal hard drive.

10. Format Your External Hard Drive to use on your Mac

To do this you will need to make use of a piece of software that’s standard on Mac OS called Disk Utility. This is what you will use to format the external hard drive.

Formatting Your Drive Using Disk Utility

Your Mac is able to read and write files on disks formatted in something called Mac OS Extended (Journaled) file system (also known as HFS+). Formatting changes the file system that is set up on the external drive and writes a new file structure onto it.

The whole process only takes minutes. And

Once done you can use the drive as you would your internal drives.

Note that: reformatting means that you will lose any files or pre-installed windows software programs on the external drive.

If you know the external drive comes with PC software. And you want make use of this software when you share the drive between a Mac and a PC. Copy those programs off onto your Windows machine temporarily before you reformat. Then you can copy them back later onto a PC readable partition on the external drive if you want to use them.

Do you have an external hard drive with your Windows PC documents already on there? So you can’t just go ahead and reformat. Read my article “External Hard Drive Compatible with Mac & PC without Reformatting” to find out how.
If you don’t care about the PC programs or files.

And you’re only ever planning on using the external drive on a Mac then go ahead and reformat.

Disk Utility is found by clicking on the Applications Folder on your Mac’s Dock.

Then select the Utilities folder (within the Application folder)

Inside that you will find the Disk Utility command.


You can use spotlight search

Spotlight Search Symbol

Spotlight Search Symbol

Click on the symbol and type in Disk Utility

Disk Utility In Spotlight Search

Disk Utility In Spotlight Search


Select Disk Utility to start up the software.

The first disk listed on the right hand side of the Disk Utility screen will be your internal disk.

Internal External Drive List

Internal External Drive List Circled in Yellow

Do not touch that as it has your operating system on it and all your files. Odds are the Mac won’t allow you to touch it anyway.

Select the new external drive in the list

Take care to select the drive at the right level in the hierarchy listed.

Select Drive at the Right Level

Select drive at the Right Level

Selecting the external drive at a lower level will cause errors when you format.

Then you will have options across the top of the Disk Utility screen that you can use.

What if the external hard drive is not showing up in the Mac disk Utility? Take a look at my Frequently Asked Questions below to find out what may be happening.

Select the erase option.

Select Erase

Select Erase

This is the option to use to format the external drive. It essentially erases the current file structure and writes a new one onto the disk.

If there are any existing files on the external drive they will be erased. Copy them off first.

The next screen allows you to enter the detail for the formatting you want.

Format Window Popup

Format Window Popup

Give your drive a Name.

Give the external drive a name that represents what you plan to use the hard drive for. Then

Choose Mac OS Extended (Journaled) File system as the format option from the list of options. (the up and down arrows allow you to select the correct one)

If you are thinking of formatting the external drive in the new Apple File System (AFS) of High Sierra take a look at my Frequently Asked Questions below.

Make sure the scheme is set at GUID Partition Map

Now select the erase button. The process only takes a few minutes and once done your external drive is ready for you to use.

You can then dismiss the disk utility screen.

YouTube Video External Hard Drive Setup on a Mac

For anyone feeling technically challenged I suggest watching this YouTube video by Acguevara. He uses a

Seagate external hard drive in his example but this video is valid for all the makes and models of drives out there on the market. The process is the same for setting up on a Mac.

Seagate External Hard Drive How to Set Up On Mac – MacOS Sierra

Video Credit: Acguevara

Acquevara explains the process in this video really well and shows you how easy it is to do.

11. The Drive is formatted

Hooray, once formatted you can use the external drive as you would a USB stick, obviously your external drive is way bigger.

Step 9 covers how to open up the external drive and use, congratulations, your job is done.

If you want to use your shiny new disk as a backup drive for Time Machine read my article on the site here.

In a few more steps you’ll have that all set up too.

Do you want to know how to set up your external hard drive so that you can share your new external drive between a Mac and a PC? You can read all about it in “External drive for Mac and PC with files interchangeable“.

12. To Disconnect the External Hard Drive from Your Mac

The last important thing to know is to make sure that you are not accidentally corrupting the information on your external hard drive.

It pays to disconnect the drive properly.

This is done by ejecting your external hard drive from your Mac computer.

Hover over the icon for the external drive on the desktop. Right click and select the Eject option.

Right Click to Eject External Drive

Right Click to Eject External Drive

Go to the finder window and click on the arrow to the right of the drive name to eject the hard drive.

External Drive In Finder Window

External Drive In Finder Window

Wait a few seconds for the icon to disappear.

This enables the Mac to write whatever it finally needs to down to the disk and leaves everything in a consistent state.

You may hear the fan wind down or the light on the hard drive flicker and go out.

Now you can remove the USB cable from your computer and the power cable if you have one for the external hard drive you are using.

You can now safely pick up, move the disk and put the disk away if you want. Somewhere it won’t get knocked or banged around or store in a protective case.

Frequently Asked Questions

1. How do I find out what ports and what USB protocols my Mac supports?

If you are not sure from looking at the pictures in this article on the physical connections you have on your Mac. For example you may have a USB type A port but not know if your Mac supports USB 3.1, 3.0 or 2.0 then you can …

Head to the top left of your desktop. Click on the Apple symbol and select about this Mac.

About This Mac Screen

About This Mac

the next popup window allows you to choose the different options to tell you what is on your Mac and what your Mac is capable of.

Choose System Report

Choose System Report

Select System Report

The following popup window shows you the hardware interfaces you have on your Mac.

Find Out What You have on Your Mac

Find Out What You have on Your Mac

Click on the options for USB, you will see whether you have USB 2.0 or USB 3.0 or 3.1 by the information you are given there. Click on each arrow to expand the USB section so that you can see what you have.

You can also check the Thunderbolt and FireWire options too.

This page on the Apple site is useful for more information as well.

Using USB devices with your Mac

2. External Hard Drive Not Showing up Mac Disk Utility?

One thing to know is that occasionally something can happen to the software at the USB port on the Mac. For example if you have had something else plugged into the port and your Mac hasn’t recognized that you have disconnected it.

A power down and a restart of your Mac should reset all the external ports and sort out the software on the port itself.

If you don’t want to shutdown and restart right now and you have multiple USB ports you can always try another port.

Another thing to try is to go into Disk Utility and see if the drive appears on the external drives list there.

If you have an older Mac 2010 or earlier and you are trying to use a new USB 3.0 portable drive it could be the power drawn by the drive is more than the USB 2.0 protocol supports. Check the power draw of the drive, if it is too much you may need a drive powered by a power cable

3. Mac doesn’t recognize External hard drive?

Can’t Copy or Paste to the External Drive?

Can’t put files on the drive? And the drive seems some how write protected then the odds are the drive is not formatted in a format the Mac is able to use.

A thing to know is that a number of drives out on the market are NTFS formatted.

You may already be aware the external drive is in a PC format.

It means that they are set up by the manufacturer to work on a PC by default. NTFS is a file system a PC recognizes and uses straightaway.

You’ll need just a little more effort for the drive to work on a Mac. Don’t worry. Know that in a few minutes you’ll have the drive up and running.

What you’ll need to do is format the external drive on your Mac, once done you’ll be happily playing, copying, pasting and backing up all you want onto the drive. Take a look at point 10 above.

4. I click On Erase and Get an Error

Erase Process Failed

Erase Process Failed

Don’t worry, this little quirk is something that seems to happen fairly often in Mac OS Sierra. Just retry and you should be fine.

5. What if I want to format my External Drive as AFS (Apple File System)?

Or indeed your external drive is AFS formatted.

AFS is a new file system introduced by Apple with High Sierra. It is faster and more efficient, particularly designed for solid state disks (SSD’s). But AFS does not support Time Machine. If you want to use Time Machine to backup you Mac you will need to format your external drive as Mac OS Extended (Journaled) file system.

If you plan to use the external drive for copying and pasting files from and to then you can select the Apple File System from the available formatting options in the Erase screen of Disk Utility with Mac OS High Sierra.

Last Words

And there you have it the 12 things to know when you connect external hard drive to Mac. Works for any Mac, iMac, Macbook Air, or Macbook Pro. You can now take advantage of using less expensive external drives. Drives that are not Mac specific drives, as we all know – Mac specific drives can be a little pricey.

Now you’re in the know, are you ready to choose an external hard drive for your Mac? Take a look at some of the best.

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