How do I reduce system capacity on Mac?

 Having spent some years coding applications for macOS we’ve created a tool that everybody can use. The all-round problem fixer for Mac.

Solid-state drive (SSD) is fantastically fast, but its high cost means that Macs with built-in SSD startup drives have a much lower capacity than their hard disk-based counterparts. This can be a problem if you have a large collection of photos or music files, or if you use your Mac to edit video. And so, if you have an SSD, you probably spend a lot of time checking the Storage tab in About this Mac. One thing you’ll have noticed is that colored bar labeled ‘System Data’. What is it and how do you clear it? Read on and find out.

What is System Data on Mac?

Apple has made some changes in the storage categories with the recent macOS update. The Other storage has disappeared, but instead, a new System Data tab appeared. There is also a macOS storage tab, which contains all macOS-related files and data. So, what does System Data include?

Part of this storage includes application leftovers, temporary files, and old cache. It also contains other items like disk images, archives, plugins, extensions, and everything else that doesn’t fit into the macOS category.

What to do when Mac System Data grows too large

Some of the temporary files generated by your apps and macOS usually get deleted automatically. But sometimes they don't, and when they accumulate, Mac System Data may grow bigger.

macOS System Data is mainly stored in both the System and Library folders. If System Data is taking up too much disk space on your Mac, explore those two folders and see what's stored in them.

If you're having a lot of your space allocated for System Data, you may have Time Machine snapshots stored on your Mac. Later in this article, we're going to explain how to remove Time Machine backups.

How to reduce System Data on Mac

1. Check for unnecessary files

Much of the storage space used by the OS for system-related tasks is cleared when macOS deletes the files automatically, but sometimes that doesn’t happen, which is why the System Data category can grow very large. Apple doesn’t explain what comprises this category of storage, but it’s likely that the following are part of it:

• Time Machine backups
• Old iOS backups
• App cache files
• Unused disk images

Not knowing what files are included in System Data storage makes finding them tricky. However, it’s far from impossible. My favourite tool for clearing unnecessary system junk from my Mac is CleanMyMac X. It has lots of tools for clearing out junk files, but for our purposes, there’s one that really helps: System Junk. This handy utility scans your Mac and identifies things like temporary files, translation files in apps, broken preferences files, old updates, and system cache files that are no longer needed. You can then remove them with one click. Or you can choose which ones you want to get rid of and remove just those. If you want to give it a go, you can download a free version of CleanMyMac X here.

Once you’ve downloaded and installed it, do this:

1. Launch CleanMyMac X.
2. Choose System Junk in the sidebar.
3. Press Scan.
4. Once it’s finished, if you’re happy to remove the files CleanMyMac X recommends, press Clean.
5. If not, choose Review Details and go through the list of results.
6. Uncheck the box next to any items you don’t want to delete.

That will help you to clear System Data storage on Mac.

As you can see from the screenshot, the app offers to remove my Unused Disk Images (the remains of DMG installers), broken downloads, old app updates. If you use Photoshop or other media editor you’ll see the option to delete Document Versions — intermediate edits of your files. In other words, you have many options for freeing up space at your disposal.

2. Manually remove Time Machine backups

Aside from using CleanMyMac X, one of the most straightforward ways to clear System Data on a Mac is to get rid of Time Machine backups. Wait, what? You thought Time Machine backups were stored on an external or network drive? They are! But macOS also keeps a copy of your backup on your startup drive in case the external drive isn’t available when you need to restore files. That way, you can restore data on a MacBook even when you’re on the move.

macOS should delete Time Machine backups when your Mac runs low on storage, but it doesn’t always work out that way. And besides, you might not want to wait until your Mac is short of space before you delete them. So, here’s how to delete System Data on a Mac by removing Time Machine backups. Remember that will remove local copies of your backups, so if you think you might need them, don’t do it.

1. Go to Applications > Utilities and launch Terminal.
2. When a Terminal window opens, type: tmutil listlocalsnapshotdates
3. Press Return.

You will now see a list of stored Time Machine backups, listed by date.

1. Type: tmutil deletelocalsnapshots xxxxxxx where ‘xxxxxxx’ is the name of one of the backups listed . This will take the form of a date followed by a text string.
2. Press Return.
3. Repeat steps 1 and 2 for as many backups as you want to remove, checking the Storage tab in About this Mac each time to see how much space you’ve cleared.

3. Optimize your storage

If you’ve faced a cluttered storage situation, there’s another way to fix it. Apple has anticipated such an issue and equipped the macOS with some features to optimize your space.

Go to the Apple menu and select About This Mac. Select the Storage tab and press Manage. In the window that appears, you can see some of the useful suggestions. "Store in iCloud" lets you transfer all your data to cloud storage and reclaim some GBs on your Mac. The second option allows you to delete the heaviest files, like movies and programs.

Turning on "Empty Bin Automatically" can be a useful option if you forget to do it regularly.

By pressing Review Files, you will jump into the Documents section. Review the files that are stored on your Mac and pay attention to the Unsupported Apps category. It can contain some programs that can no longer run on your macOS version.

4. Clear application logs and support files

Apps and programs generate lots of files. They help improve your experience within the app, but when you remove the application, those leftover files may still be stored on your Mac.

Here’s how to check if you still have them:

1. Open Finder.
2. Click Go menu > Go to Folder.
3. Type ~/Library/Application Support and press Enter.

Each app’s folder has a corresponding name: you can remove the folders that belong to apps you’ve already deleted.

You can also search for app-related data in these locations:

~/Library/Caches

~/Library/Logs

~/Library/Containers

~/Library/Cookies

Make sure you only delete leftover files: it’s better to keep files of the apps you still use.

5. Clean up your Downloads folder

The Downloads folder is a place we all rarely clean up. Eventually, it gets filled with all sorts of items — photos, movies, PDFs, installers and dusty files you downloaded a long time ago. They can add to your System Data storage. Here’s how to clear them up:

1. Go to Finder > Downloads.
2. Right-click and select Sort By > Size.

The largest files will appear on the top of your list — move the ones you don’t need to the Trash.

Downloads is probably one of the largest folders that falls into the System Data category. But what are other files that take place? To find out that, you’ll need to browse your storage. The easiest way to do it is to use CleanMyMac X. This app has a Space Lens module that builds a virtual map of your storage and shows what’s inside every folder. It then lets you delete unneeded files and free up space on your Mac.

1. Download CleanMyMac X here — a link to the free version.
2. Install and launch the app.
3. Go to Space Lens.
4. Click Scan.

Those bubbles show your largest folders and you can zoom in and out and delete junk files right from there.

Bonus tip: remove duplicate files

Aside from the bizarre system files, another thing that nibbles on your storage is duplicates. Remember that track you’ve accidentally added twice? Or a mail attachment you’ve opened several times? All these files just sit on your Mac and take up precious space.

Here’s how you can quickly delete them in a few clicks.

1. Download and open Gemini 2
2. Choose a folder and click Scan for Duplicates.
3. Wait for the scan to finish.

Now you can click Smart Cleanup to get rid of detected duplicates and remove System Data on Mac. Or click Review Results if you want to double-check what’s being deleted.

What else can you do to clear System Data on Mac?

Believe it or not, one thing you can do is wait. When you first choose the Storage tab in About this Mac, macOS seems to allocate quite a lot to System Data that it then reallocates elsewhere. For example, some users have reported that after waiting for a few minutes, much of the storage labelled ‘System Data’ is moved to the iCloud label. So if you wait, you might find that the System Data isn't taking up disk space in the huge quantities that it seemed to be at first.

The other thing you can do is investigate what files are designated as ‘System Data’. We’ve already talked about Time Machine backups, but everything stored in your Mac’s System or Library folders comes under the ‘System Data’ heading in About this Mac. That is:

/Library

/System

~/Library

~/System

Click on the Go menu in Finder and select Go to Folder, then paste in each of the paths above in turn.

Go through the subfolders in each and press Command-I to Get Info and check how much data is in each. You’ll quickly discover where your precious storage has gone.

It’s likely that much of it is accounted for by cache files for apps like Photos and Safari. macOS caches as much data as it can to avoid having to re-download it, which boosts performance. And it’s smart enough to know that it must delete cache files when you run low on storage.

If you decide that you don’t want to leave it up to the operating system to free up storage, don’t just start trashing cache files or folders randomly, you might delete something you shouldn’t. So be careful.

System Data storage can occupy tens of gigabytes of space on your Mac for Time Machine backups and cache files. It should be managed by macOS so you’re never short of space. But if you want to do a System Data cleanup, or just free up more space on your Mac, give CleanMyMac X a go. You might be surprised by how much space you get back.