Why does System Data take so much disk space on Mac?

6 min read

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

But why does System take so much space, Mac users wonder? And what exactly is meant by "System Data," so you can reclaim this storage? 

Well, you're in the right place. Let's dive straight in and uncover the mysteries of System taking up disk Mac users often find puzzling. 

What is System Data on Mac

Although it sounds puzzling, System Data on Mac is no mystery at all. It includes all files that do not fall into the basic categories of Mac Storage. Basic categories are Applications, Music, Music Creation, Documents, Photos, Trash, iCloud Drive, Mail, and Other. So, whatever is not classified as these files is automatically labeled as System Data. We'll talk about it later in the article. 

The "System Data" 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 kinds of things. So, apart from macOS itself, what is System storage on Mac?

  • Old Time Machine backups
  • Old iOS backups
  • App cache (3-4 GB, can be quickly deleted with an app)
  • Temporary files
  • Unused disk images

Tip: Local snapshots 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 check your storage

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

For older macOS versions, select Apple Menu > About This Mac > Storage. 

For newer macOS versions, such as macOS Ventura, the steps are as follows: Apple Menu > About This Mac > More Info > Storage Settings. 

System Preferences - Storage

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

Here you get a nice little visual of your storage situation. You might be alarmed to discover that "System Data" is occupying a lot of disk space. But why is my system storage so high? Keep reading to find out why does system take up so much storage. 

How much System Data is normal on Mac?

The default size of the macOS system is 12 GB. It implies that having around 12GB of System Data is normal. 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 being the reason why "System Data" takes up so much storage. 

However, 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.

How to reduce System Data size on Mac

1. Reclaim "System Data" storage the easy way — automatically 

It is possible to reclaim some space manually, but there is a much easier way — using CleanMyMac X. It has a dedicated System Junk module that can remove cache and temporary files, resolve errors, and claw backspace in just a few clicks. Here's how: CleanMyMac X - System junk scan complete

  1. Open the app and select System Junk from the sidebar.
  2. Click Scan. Wait for the scan to complete and click Clean.

As you can see, I can delete around 16 GB of system caches (like outdated app data) and thus trim down the System Data size. It really is as simple as that — no digging around in system files or worrying that you might delete something important. It does it all safely and securely for you.

2. Remove "System Data" 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 Data" files:

System Data files

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

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

  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. 

3. Manage system storage on Mac using the built-in Optimize tool

One problem is that it's also tricky to manually identify all of the items categorized in "System Data" because when you go to Apple's Built-in Storage optimizing tool, you can't click on "System Data" to investigate further. Take a look for yourself.

For older macOS versions, go to Apple Menu > About This Mac > Storage > Manage.

For macOS Ventura, follow these steps: Apple menu > About This Mac > More Info > Storage. Under Recommendations, you may see the Optimize Storage tab.

If you don't see one, it may mean that the macOS thinks that there is nothing there for you to optimize thus far. 

Optimize storage

To reclaim some space, you can investigate and delete items in every category apart from "System Data" and "Other" in the left sidebar.

The first three options (Store in iCloud, Optimize Storage, and Empty Trash) won’t be a quick relief. But there is another option. If you review files by pressing the i icon on the list, 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 macOS System Data large problem. Luckily, there are workarounds.

4. 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:

Use Terminal

  • Open Finder > Application > Utilities and open Terminal.

  • Copy and paste in: tmutil listlocalsnapshotdates and press Return.

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 Return.

Repeat this for as many of the local backups as 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.

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

5. Empty the Trash

This one may seem obvious, but emptying the Trash/Bin can significantly thin out the System Data volume on your Mac. The thing is that Trash/Bin usually becomes a graveyard of unnecessary files and apps even if you turn on the option of emptying it automatically.

You have several alternatives here: 

  • Click the Trash icon from Dock and select Empty Trash/Bin.
  • Right-click the Trash icon and select Empty Trash/Bin. 
  • Use CleanMyMac X and its Trash Bins module — in addition to emptying Trash/Bin, it also clears out photo library and Mail trash, thus freeing up even more space.

Empty Trash

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

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

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