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Mac storage full? How to free up space, and what System Data is

By the AI Repair team · Updated

When your Mac says “Your disk is almost full”, it’s worth acting: a nearly full disk can slow your Mac down and stop updates from installing. Most of the space usually goes to a few things you can find in minutes, and macOS has the tools built in. Here’s how to see what is using space, what is safe to remove, and what “System Data” really is.

In short

Choose Apple menu › System Settings › General › Storage to see what is using space. Turn on the recommendations that suit you, then review the biggest categories: large files and downloads, old iPhone backups, Messages attachments and photos. Empty the Trash. System Data is managed by macOS and can’t be deleted directly, but a restart, and if needed safe mode, often shrinks it.

1. See what’s using space

  • macOS Ventura or later: choose Apple menu › System Settings, click General in the sidebar (you may need to scroll), then Storage.
  • macOS Monterey: choose Apple menu › About This Mac, click Storage, then Manage.

Give it a minute: the colored bar and the list fill in as your Mac adds everything up. Each category with an info button (ⓘ), such as Applications, Documents, iOS Files, Messages, Photos and Trash, opens a list of what is inside. Select an item and click Delete, or Show in Finder to look first. Files deleted here are erased at once, not moved to the Trash, so check each one before you click. A few categories, like macOS and System Data, only show their size.

2. Turn on Apple’s recommendations

At the top of Storage, macOS suggests ways to save space. Each one explains itself, and you can choose any of them:

  • Store in iCloud keeps your Desktop and Documents, photos and messages in iCloud, and keeps only recently opened files on your Mac when space runs low. It needs enough iCloud storage, which is a paid plan beyond the free 5 GB.
  • Optimize Storage removes Apple TV movies and shows you’ve already watched, and keeps only recent email attachments on your Mac.
  • Empty Trash Automatically erases items that have been in the Trash for more than 30 days.

Apple adds that when space is needed, macOS also clears caches and logs that are safe to delete, such as interrupted downloads and staged updates, by itself (Apple’s guide).

3. Empty the Trash and clear out Downloads

Files you delete keep using space until you empty the Trash: Control-click the Trash in the Dock and choose Empty Trash. Emptying it can’t be undone, so have a quick look inside first.

Then open your Downloads folder (it’s in the Finder sidebar, or choose Go › Downloads in Finder). It quietly collects everything you’ve ever downloaded. Installer files ending in .dmg or .pkg are safe to delete once the app is installed. A full macOS installer, called something like “Install macOS…”, may also be sitting in your Applications folder; you can delete it after the update.

4. Find large files

In Storage, click the info button next to Documents. It can list your largest files and your downloads, biggest first, so you can delete what you no longer need or move it to an external drive.

You can also search for big files in Finder: start a search, click the add button (+) under the search field, choose Other from the first menu, pick File size, and set it to “is greater than”, for example, 1 GB.

5. Remove old iPhone and iPad backups

If you’ve ever backed up an iPhone or iPad to your Mac, each backup can take many gigabytes, and old ones stay until you delete them. In Storage, click the info button next to iOS Files to see and delete them. Or connect the device, select it in the Finder sidebar, click General, then Manage Backups, and Control-click a backup to delete it. Keep at least your most recent backup unless the device is backed up to iCloud.

6. Photos, Messages and Mail

  • Photos: if you use iCloud Photos, open Photos, choose Photos › Settings, click iCloud and select Optimize Mac Storage. Full-size originals stay in iCloud, and smaller versions stay on your Mac.
  • Messages: years of photos and videos in chats add up. In Storage, the info button next to Messages lists large attachments. In Messages, Settings › General › Keep messages can be set to One Year or 30 Days instead of Forever. Older conversations and their attachments are then deleted, and if you use Messages in iCloud, from your iPhone and iPad too. Save any photos you want to keep first.
  • Mail: choose Mailbox › Erase Deleted Items and Mailbox › Erase Junk Mail. Both delete for good, so look through Junk first. In Mail › Settings › General, Remove unedited downloads can remove attachments you opened but didn’t change, for example once their message is deleted.

On macOS Monterey, these apps’ Settings menus are called Preferences.

7. Remove apps you don’t use

In Storage, click the info button next to Applications to see your apps by size, and when each was last used. Select one you don’t need and click Delete. Apps such as GarageBand can bring several gigabytes of sound libraries with them. If your Mac has more than one user account, accounts that are no longer used also take space.

8. What is System Data, and can you shrink it?

System Data is everything that doesn’t fit the other categories. Apple says it “primarily includes files and data used by the system, such as log files, caches, VM files, and other runtime system resources”, plus temporary files, fonts and app support files (Apple’s explanation). In older versions of macOS it was called “Other”.

You can’t open it and delete things from it, and Apple says you shouldn’t need to: macOS manages it, and its size changes with what your Mac is doing. It often grows while a macOS update is downloaded and waiting to be installed, or when an app keeps a large cache. A few safe things often bring it down:

  1. Restart your Mac. Some temporary files are cleared when it starts up again.
  2. Install a waiting macOS update from System Settings › General › Software Update (System Preferences › Software Update on Monterey). The files staged for it are then cleared.
  3. Start up in safe mode once. Apple says safe mode clears some system caches, which “can temporarily make more storage space available” (Apple’s steps). On a Mac with Apple silicon, shut down, press and hold the power button until the startup options appear, select your startup disk, then hold Shift and click Continue in Safe Mode. On an Intel Mac, hold Shift as it starts up and let go at the login window. Restart normally afterwards.

Don’t delete files by hand from the system folders or your Library folder, or with commands you find online. It’s easy to remove something macOS or an app needs, and there’s no undo.

9. Is it safe to delete caches?

Apple never asks you to delete cache files by hand. macOS already clears the caches that are safe to delete when it needs space, and caches you remove are created again as apps need them. Clearing them gives you space back for a while, which helps when you need room now, for an update say, and apps can be slower until they’ve rebuilt them. Don’t do it by deleting folders yourself: it’s easy to take something an app needs, with no way back. If one app keeps a huge cache, such as a video or photo editor, clear it from that app’s own settings, which knows what it can safely let go.

10. Not enough space for a macOS update?

Apple doesn’t publish a fixed figure for recent versions, but you don’t need to guess: when there isn’t enough room, Software Update tells you how much space the update needs. Compare that with the free space in Storage settings, and free up the difference, plus some to spare, using the steps above. Install updates from System Settings › General › Software Update (System Preferences › Software Update on Monterey) rather than a full installer, because Apple says Software Update can use less space. If you’re only a little short, safe mode (section 8) can free a little room for a while: install the update straight after.

Apple Intelligence also needs room for its models: Apple says up to 14 GB on Macs with an M3 chip or later and at least 12 GB of memory, and up to 8 GB on other Macs.

Advice to skip

  • Pasting Terminal commands such as sudo rm -rf to delete system files or Time Machine snapshots. Storage settings, Finder and macOS itself do each of these jobs safely.
  • Turning off System Integrity Protection to delete protected files. It protects macOS from harmful software.
  • Erasing your Mac to get space back. It deletes everything on it, and the steps above free space without losing anything you want to keep.
  • “Deep cleaning” System Data with a cleaner app. macOS manages it; see our guide Do you need a Mac cleaner app?

Common questions

Why is my Mac storage full when I hardly have any files?

The space is usually going somewhere you don’t see every day: old iPhone backups, years of Messages attachments, a photo library, a downloaded macOS update, or a large System Data figure. Open Storage settings and look at the biggest categories first.

How much free space should a Mac have?

Apple doesn’t give a number. Keep enough room for macOS to work and to install updates, which tell you exactly what they need, and act when your Mac warns you that the disk is almost full. If your Mac feels slow and the disk is nearly full, making room is a good first step.

What does “purgeable” mean in Mac storage?

It is space taken up by things macOS can remove by itself when it needs room, such as some caches and local Time Machine snapshots. That’s why “available” space can be larger than truly free space: macOS counts purgeable space as available.

Why didn’t emptying the Trash free up space?

Storage settings can take a while to recalculate. If you use Time Machine, a local snapshot may still hold the deleted files for a time; macOS counts that space as available and removes the snapshot by itself when the space is needed.

Can I delete System Data on a Mac?

Not directly, and you shouldn’t try: it holds files macOS and your apps need. Restarting, installing a waiting update and starting once in safe mode are the safe ways to shrink it, and macOS clears much of it by itself when space runs low.