Tips to safely erase free space on your Mac

6 min read

It's estimated that every year globally, we generate 40 million tons of electronic waste. That's like throwing away 800 laptops every second. Unless you securely clean your free space or wipe your hard drive, there's potentially a lot of recoverable personal data floating around.

Are you looking to erase the free space on your Mac? You've come to the right place. Data privacy has never been more important, but surprisingly, not everyone realizes that your Mac is not entirely erasing that data when you delete a file. 

Did you know? Deleted files are identified as free space, available to be written over with new data. Meaning, they can be fully or partially reconstructed if your Mac ends up in the wrong hands. Unless, of course, you erase your Mac's free space.

What do we mean by erase

On macOS, secure erase means your data is replaced with a random set of zeroes and ones. In this way files are “shredded” digitally. Which app should you use? There is a free Shredder tool that is a part of CleanMyMac X — you may use this simple eraser to do the job.

Let’s take a look at how to erase free space and securely erase the hard drive on your Mac.

Why erase free space on your Mac hard drive?

Here’s a quick look at some top reasons to erase your Mac’s free space:

  • You’re selling an old Mac or a used hard drive.

  • You work with top-secret non-disclosure agreements.

  • Your Mac has become too expensive to repair, and it’s time to recycle.

  • You want to be sure your deleted data is really gone.  

Sometimes emptying your trash just isn’t enough; We need to remove files securely.

If your Mac has an SSD, Apple claims that erasing free space on your Mac’s hard drive is unnecessary because a standard erase makes the recovery of data difficult. 

Not everyone wants to take Apple’s word for it. Standard erase doesn’t make me entirely comfortable that my data can’t be recovered.  Luckily there are some options if you’d prefer to take your Mac’s deleted data fate into your own hands. 

You can both easily and safely wipe the free space on your Mac to prevent future recovery of deleted files and data.

How to find out if you have an HDD or SSD disk:

  1. Press and hold the Option key on your Mac.
  2. Click the Apple icon top left and select System Information.

  3. Click Storage in the left sidebar.
  4. Now, select the drive from the list at the top and look for Medium Type

  5. Here you'll discover if you have an HDD or SSD. 

No matter which drive your Mac has, let’s look at how to erase your Mac’s free space. 

Erase your free space

One way to securely erase free space on your Mac hard drive is to use the CleanMyMac X Shredder module. Though the main app is paid, this particular tool is 100% free to use.

As we’ve said this feature can be used free of charge and it erases files along with their digital footprints, making them irretrievable. Removal of this nature takes a little longer than a quick empty of your trash, but it does ensure that all data gets rewritten, leaving no chance of recovery at a later date.

Tip: Be sure to select files carefully for secure removal. This action is irreversible.

How to erase free space on your Mac with CleanMyMac X:

Shredder module of CleanMyMacX

  1. Download the free version of CleanMyMac X - It’s also notarized by Apple.

  2. Launch the app, and select Shredder from the sidebar.

  3. Click on the Select Files button.

  4. Now, browse which files you want to remove and press Open.

Or you can just drag and drop the file to feed it into the Shredder.

I found it helpful that once the process finishes, you get an update on remaining free space, and you can also view a log of the removed items. I also love the fact this is really simple to use, for quick peace of mind.

Erase a drive using Disk Utility

If you’re planning on transferring ownership or your Mac, Apple recommends erasing the entire disk; this protects you from any standard erased files or data being rebuilt or recovered.

Disk Utility can feel like a scary place to be clicking around. This powerful and notoriously tricky to locate feature can securely erase your Mac hard drive, ultimately preparing your Mac for new ownership.

Tip: Don’t forget to backup any important files you want to keep before erasing a disk. 

If you’re trying to erase your Mac’s startup disk, you will need to start up from macOS Recovery first. On your computer, the Startup disk is the main hard drive, and your Mac is using it to run macOS, so it would be unlikely you would be able to erase it without following the next steps.

Startup from macOS Recovery on a Mac with Apple silicon

    • Mac with Apple silicon: Turn on your Mac and press and hold the power button until you the startup options appear. Click the icon labeled Options and then Continue.
    • Intel-based Mac: Turn on your Mac and press and hold Command (⌘) + R. Release when the Apple logo or other image appears.
    • If prompted to enter a password, this will be the primary admin account password. The macOS utilities screen will appear, select Disk Utility.
    • Once open, select View in the top menu and choose Show All Devices. The disk your Mac started up from will be top of the list. 
    • Select the disk that you want to erase, and click Erase at the top.
    • Give your device a new name, select a format. (Disk Utility shows a compatible format by default.) and finally, choose GUID Partition Map and click Erase.
    • When it's finished, quit Disk Utility.

If you're not erasing your Mac's main hard drive, then follow these steps: 

  • Select the Finder icon from the Dock on your Mac and select Applications.
  • Now, scroll down to Utilities and then select Disk Utility. You can now follow the same steps as above from point 5.


Final option: If you only need to free up space

There is a difference between “erase” and “free up” when we talk about disk space. If you only need to free up a few gigabytes removing the junk on your drive, that’s much easier to do.

You have 2 options:

1) Use the Optimized Storage feature (a default macOS feature)

This feature is found under Apple menu > System Settings > General > Storage.

2) Use a dedicated junk “destroyer”

The one we’ve told you about is CleanMyMac X. But the same app has another cool feature, called System Junk, that removes clutter in almost astronomical amounts.

It looks like shown below; note how many categories of junk it identifies:

CleanMyMac X - User cache files in System Junk module
It's up to you to select which option suits your needs. Whether you want to erase free space on your Mac, by selecting which files to remove with a handy tool like CleanMyMac X or opt for the complete drive erasure treatment, it's always good to know your options. 

Thanks for reading. Come back soon for more useful Mac tips.

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