Why does System take so much disk space on Mac

5 min read

For any Mac owner who is running low on space, the first thing we do is check our storage availability.

But have you ever wondered why is "System" using so much disk space? And what exactly is meant by "System" so can reclaim the space? 

Well, you're in the right place. Let's dive straight in and uncover the system storage mysteries. 

How to Check your storage

Just in case you need a quick reminder, here's how you can check your storage.

  1. Select Apple Menu > About This Mac > Storage. 

How to check System storage on Mac

Tip: Give your Mac about a minute to calculate the real System size. The categories’ size may drastically change.

Here you get a nice little visual of your storage situation. You might be alarmed to discover "System" is occupying a lot of disk space. But what exactly is it? Keep reading. 

My system occupies 11.24 GB on disk, and what have you got?

The default size of the macOS system is 12 GB. If your “System” data shows something around 14-20 GB, you have pretty good chances to slim it down to that original size. This is good news, but you’ll have to delete some unimportant files.

Why does "System" take up so much Mac storage?

As you can see, "System" is taking up 11.24GB of space on my drive. So what's going on here?

What is "System" in Mac storage

The "System" in Mac storage is a bit of a gray area (literally). It's a bit of a category dumping ground as well as being home to your system and macOS folders; it holds all kind of things like: 

Apart from macOS itself, what’s inside?

  • Old Time Machine backups

  • Old iOS backups

  • App cache (3-4 GB, can be quickly deleted with an app)

  • Temporary files

  • Unused disk images

Your operating system should automatically maintain and clear this category, but this doesn't always happen, resulting in a loss of precious disk space, and often the reason why "System" takes up so much storage.

Tip: Local snaphots are temporary Time Machine backups that are stored on your Mac for 24 hours. If you’ve been moving a lot of files around, this category may quickly inflate. But don’t worry, these files will be gone if you come back tomorrow.

How to manage system storage on Mac

The next problem is, it's also tricky to manually identify all of the items categorized in "System" because when you go to Apple's Built-in Storage optimizing tool, you can't click on "System" to investigate further. 

Take a look for yourself: Apple Menu > About This Mac > Storage > Manage.

How to manage storage on Mac

You can investigate and delete items in every category apart from "System" and "Other" in the left sidebar.

The first three options (Store in iCloud, Optimise Storage, Empty Bin) won’t be a quick relief. But the last option, Reduce Clutter, can be helpful. If you click on Review Files you’ll be able to scan through large files all across your drive.

But have you noticed? Apple suggests that you clean up only those files and documents that are created by you. This doesn’t address the problem of the System itself being too large. Luckily, there are workarounds.

Why is Mac “System” so big?

I find it frustrating that Apple doesn't just let you see what is stored in "System" so, I use the Space Lens tool from CleanMyMac X. This cool little tool builds a pleasing on the eye, virtual map of your storage and shows precisely what folders and files are cluttering your Mac's System. Extra brownie points as the app is notarized by Apple. 

Here's how you can get a beautiful overview in seconds:

Scan completed in Space lens module in CleanMyMacX

  1. Launch the app — download the free version here.  

  2. In the left sidebar, select Space Lens and press Scan.

  3. Browse through your files, select any files you no longer need, and press Remove.

Enjoy browsing through the aesthetically pleasing bubbles of information. The bigger the bubble, the more space it occupies. It's fun to see your storage displayed in this way and gives you a clear indication of what is actually eating away space on your Mac. 

So how can you free up “System” storage?

1. Remove "System" files manually

I'm not going to lie; doing this manually is a bit of a long-winded process. And I hate to sound like a nagging mum, but I must say with caution, double-check all files and folders carefully before you delete something that could affect your system.

Here's how to check and delete storage "System" files:

Mac caches folder

  1. Open a Finder window, and press  Go > Go To Folder.

  2. Paste in the following command box ~/Library/Caches and press Go.

  3. Scroll through your subfolders, press Command-I to see information on each folder, and send to the Trash bin what you no longer need.

You can also repeat this process for ~Library/Logs to remove old system logs. 

2. Remove old Time Machine backups

Believe it or not, your macOS keeps a local copy of your Time Machine backups, these should get automatically deleted when space is low, but sometimes they don't. 

You can reclaim storage by manually deleting these; here's how:

How to remove old Time Machine backups

  • Open Finder > Application>Utilities and launch Terminal.

  • Copy and paste in: tmutil listlocalsnapshotdates then press Enter.

If you have any,you'll see a list of backups sorted by date. To delete them:

  • Type in: tmutil deletelocalsnapshots xxxxxxx where you see 'xxxxxxx' this should be the name of one of your listed backups — press Enter.

Repeat this for as many of the local backups you want to remove. What I like to do, is after I delete one, check back in the Storage tab to see how much space you've reclaimed.

This can take a while, so hang in there, or move to my next tip.

Tip: Don't delete your local copies if you think you might need them in the future. 

3. Reclaim "System" storage the easy way

If you're not a fan of poking around in your system library files or using Terminal, there is a much easier way using the app I mentioned earlier, CleanMyMac X

It has a dedicated System Junk module that can remove cache, temporary files, resolve errors and claw backspace in just a few clicks, here's how:

CleanMyMac X - System junk scan complete

  1. Launch the app and select System Junk from the sidebar.

  2. Press Scan. Wait for the scan to complete and press Clean.

As you can see, I can delete around 6 GB of system caches (like outdated app data) and thus trim down the System size.

It really is as simple as that, no digging around in system files, worrying that you might delete something important. It does it all safely and securely for you.

Hopefully, you're no longer wondering why "System" takes so much disk space on my Mac. 

Following these tips will help you get to the bottom of the "System" storage conundrum and simultaneously recover some space.

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