Your instruction on how to format Mac hard drive

The transition from hard drives to solid state storage on both portable and desktop Macs has meant a significant reduction in storage space for most of us. That in turn has meant that many of us now have at least one external hard drive, SSD, or USB stick on which to store files. But those drives too quickly fill up and so it’s useful to know how to clean up an external hard drive. 

How you go about cleaning up depends on what you use the external drive for, so here’s our guide on how to format an external hard drive on Mac.

How to format an external hard drive on Mac 

Let's figure out how to format the following types of volumes:

  • USB drive or flash stick
  • External hard drive
  • Internal hard drive

How to format a hard drive for Mac using Disk Utility

If your Mac runs a newer operating system, like macOS Mojave or macOS Catalina, you need to launch the built-in Disk Utility tool. But before that, you'll have to decide: are you erasing just a volume on your drive or your main startup drive? The latter contains your macOS and if you erase it without a prior backup, you'll be in trouble.

Okay. Suppose, you'd like to format a hard drive that is your startup drive. Then, you'll need to start your Mac in a Recovery Mode.

  • Shut down your Mac and turn it back on.
  • Upon the startup, press and hold Command (⌘) and R keys.
  • Release the keys when Apple logo appears.
Format external hard drive on MacBook

You are now in macOS Utilities. To format a hard drive for Mac, choose Disk Utility in the list and click Continue.

But if you only need to format a volume (or a partition), you can access Disk Utility without entering a Recovery Mode. 

Open the Launchpad in the Dock.
Type in "Disk Utility" in the search field.

Here it is, Disk Utility where you can easily format external hard drive for Mac or any connected drive.

Select the drive you would like to format and click "Erase" at the top of the pane. The same works for any type of drive be it a USB stick or external storage. Please, be extra careful and pay attention to what is actually selected.

Clear unused Time Machine space

How to clear space on a Time Machine hard drive

If you use an external hard drive for Time Machine and find that it’s running out of space, you may need to delete older backups. Time Machine will normally warn you when free space is low and offer to delete backups automatically.

If it doesn’t, you can do it yourself from within Time Machine, using Terminal, or by again using an app like CleanMyMac X which has a module designed specifically for slimming down old Time Machine backups. Follow our guide on how to thin Time Machine snapshots.

How to clean unused space taken by Time Machine

Tip:
To slim down your Time Machine backups, click on the Maintenance tab in CleanMyMac X.


How to reformat an external hard drive safely

If you're looking to format or reformat an external hard drive on your Mac, there are a couple of safety precautions.

1. Make sure you've got a backup option

Your Mac's hard drive may contain a number of partitions, including a separate partition for the macOS itself. If you accidentally format a part that contains your operating system, you'll have problems. But if that's what you aimed to do, proceed with cautionTo prepare the backup, plug in an external drive with enough free space on it. Then, run Time Machine from your Launchpad.

2. Pick an appropriate file format

Disk Utility will make you choose between APFS and Mac OS Extended. Here are a few more considerations:

  • APFS is a preferred format for newer macOS versions.
  • If you like to roll back to High Sierra, then choose Mac OS Extended (Journaled)
  • If your external drive will be used with older Mac that runs High Sierra or older system, again, choose Mac OS Extended.

If you want to securely erase the volume, select Security Options and choose them. If your Mac is a new one with an SSD drive, the Security Options may not be available.

3. What if you can't reformat an external hard drive on your Mac?

In some cases Disk Utility will not show your external drive. You can try one of the following:

  • Use a different cable
  • Shut down your Mac and unplug all peripherals.
  • Try to format Mac external hard drive again.
    Format Mac hard drive

    Free up space on all your drives at once

    Dragging files to the Trash is a very slow way to free up space on a hard drive. However, you can speed it up by identifying those files that will free up the most space the fastest — in other words, the files taking up the most space. By deleting them, perhaps after archiving them on another drive you don’t use on a day-to-day basis — you’ll quickly free up lots of space. 

    You can identify the largest files on a drive manually by setting the Finder to list view and sorting files by size (click on the top of the Size column). However, you need to do that for every folder on the drive. Old files are another good candidate for deleting, or at least moving somewhere else. If you haven’t opened a file in six months or more, the chances are you won’t need it very often. You can use the same method to identify old files by sorting on Date Modified. Again, you’ll have to do it for every folder, so it could be time consuming. A much quicker way to identify and delete large and old files from your external hard drive or USB flash drive is to use a dedicated app like CleanMyMac X

    Below are two ways of removing files from your drives: the easy way and the manual one. Choose the one you like!

    Remove files with CleanMyMac X

    CleanMyMac has a utility designed specifically to identify files that are occupying lots of space and those that haven’t been opened for a while. 

    1. Download CleanMyMac X and launch the app.
    2. Choose Large & Old files tab.
    3. Choose the disk and press Scan.
    4. You can go through files one at a time or click on the categories to the left of the list to filter them.
    5. When you find a file you want to delete, check the circle next to it.
    6. Click Remove.

    There are lots of options for freeing up space on an external hard drive, depending on what you use it for. If it’s a Time Machine backup or iTunes Library, you should do it from within those applications. Otherwise, one of the quickest ways to do it is to use CleanMyMac X to remove large and old files. That way you can reclaim the maximum amount of space for the minimum effort.

    Thanks for reading and stay tuned!


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