How to Clear System Data Storage on a Mac

If your Mac is running out of storage space, you have likely opened the Storage management settings only to discover a massive, grey bar labeled “System Data”. For many users, this mysterious category consumes hundreds of gigabytes of space, yet macOS provides no obvious button to delete it.

System Data is a catch-all category for files that do not fit into standard types like Apps, Documents, or Photos. In this guide, we will uncover what actually lives inside System Data and how to safely clear it to regain your valuable SSD space.

What is “System Data” on a Mac?

Contrary to the name, System Data does not consist solely of core macOS operating system files. Instead, it is mostly filled with temporary files, caches, and application data. The most common culprits include:

• Application caches: Web browsers, video editors, and design software save massive amounts of temporary data to speed up their performance.
• Time Machine local snapshots: If your backup drive is disconnected, macOS saves temporary backups to your internal drive until you reconnect it.
• iOS backups: Old iPhone and iPad backups stored via Finder (or iTunes on older macOS versions).
• Leftover application files: Dragging an app to the Trash does not delete its support files, which remain hidden in your user Library.

Method 1: Clear Local Time Machine Snapshots

Local snapshots are the most common cause of sudden, massive spikes in System Data. macOS is supposed to delete these automatically when you run low on space, but the automated process often fails.

1. Open the Terminal application (found in Applications > Utilities).
2. Type the following command to list all local snapshots on your drive:
   tmutil listlocalsnapshots /
3. If the command returns a list of dates, you have local snapshots consuming space.
4. You can delete them manually by typing:
   sudo tmutil deletelocalsnapshots 2023-10-27-142512 (replace the date string with the actual snapshot name from your list).
5. Alternatively, to instantly delete all of them without typing out every name, you can simply turn Time Machine off and on again. Open System Settings > General > Time Machine, remove your backup disk, and then re-add it.

Method 2: Safely Delete Cache Files

Your Mac stores temporary files in a hidden Library folder. Over months or years, these folders can bloat to an enormous size.

1. Open a Finder window.
2. Click Go in the top menu bar, hold down the Option (Alt) key, and click on Library when it appears in the list.
3. Locate and open the folder named Caches.
4. Inside, you will see dozens of folders named after your applications (e.g., com.apple.Safari or com.spotify.client).
5. Select the contents of the Caches folder (Command + A) and drag them to the Trash.
6. Warning: Only delete the contents of the Caches folder, not the Caches folder itself. Do not delete files from other folders in the Library unless you know exactly what you are doing.
7. Empty the Trash and restart your Mac.

Method 3: Delete Old iOS Backups

If you regularly back up your iPhone or iPad directly to your Mac rather than iCloud, those backups consume a massive portion of System Data.

1. Connect your iPhone or iPad to your Mac via USB.
2. Open Finder and select your device from the left sidebar.
3. Under the “Backups” section, click on the Manage Backups… button.
4. A window will appear listing all iOS backups stored on your Mac. Select any old or unnecessary backups and click Delete Backup.

Method 4: Optimise Storage via System Settings

macOS includes a built-in tool to help you find large files that might be miscategorised.

1. Open System Settings and navigate to General > Storage.
2. Review the Recommendations section at the top. Click Optimise next to “Optimise Storage” to automatically remove watched Apple TV movies and old email attachments.
3. Click the i (Info) icon next to the Documents category. Sort the list by “Size” to identify massive files hiding in your Downloads folder that macOS might have accidentally grouped into System Data calculations.

By regularly clearing local snapshots, emptying your cache folders, and managing your iOS backups, you can keep the mysterious System Data category from consuming your Mac’s storage.