what lives inside 'system data'
the category includes several distinct types of data with very different recoverability. caches are the largest and safest: ~/library/caches holds browser caches (safari and chrome each grow to several gigabytes), app caches from creative tools, and various system caches. these are all safe to delete — every app that needs them will rebuild them. /library/caches is the system-wide equivalent.
local time machine snapshots are often the most surprising contributor. when you use time machine with an external drive, macos also keeps local snapshots on your ssd as a safety net for when the drive isn't connected. these can run to 20–40 gb on a machine that time machines regularly. they're managed automatically but you can force-clear them: `tmutil deletelocalsnapshots /` in terminal removes all local snapshots.
xcode simulator runtimes sit inside ~/library/developer/xcode/ios devicesupport and ~/library/developer/coresimulatior/profiles. each ios version you've ever tested against adds a 2–8 gb runtime. if you haven't tested on ios 15 for a year, that runtime is recoverable — remove old runtimes via xcode → settings → platforms.
ios device backups live at ~/library/application support/mobilesync/backup. a backup for a large iphone can reach 10–20 gb per device, and old backups from previous phones often remain after you switch devices. check what's there in finder and remove backups for devices you no longer own.
using a treemap to find the real culprits
the 'system data' category in about this mac aggregates all of the above plus more, but it doesn't let you drill in. grove scans the actual directories and shows you which ones are large. the directories worth checking first: ~/library/caches, ~/library/application support, ~/library/developer, ~/library/containers (holds sandboxed app data), and /private/var/folders (system temp and caches).
grove's reveal-in-finder button opens any directory you click on directly, so you can inspect its contents before deciding. this is the important discipline: see first, act second. a folder labelled 'application support' could hold settings you'd regret losing, or it could be a 15 gb video rendering cache from an app you uninstalled two years ago. the treemap tells you the size; finder tells you what's inside.
frequently asked
is system data the same as 'other' in older mac storage views?
yes. apple renamed 'other' to 'system data' in macOS Monterey. the contents are essentially the same: caches, logs, temp files, app support data, local time machine snapshots, and anything that doesn't fit into apps, documents, photos, or system (the macOS installation itself).
can i safely delete files in ~/library/caches?
generally yes. the caches directory holds temporary data that apps rebuild when they need it. clearing the whole folder won't break anything, though apps may run slightly slower on their first launch while they rebuild their caches. if you want to be conservative, clear specific app subdirectories rather than the whole folder.
how do i delete local time machine snapshots?
open terminal and run `sudo tmutil deletelocalsnapshots /`. this removes all local snapshots from your boot volume. your actual time machine backup history on the external drive is unaffected. to check how much space snapshots are using before deleting, run `tmutil listlocalsnapshots /`.
why does system data grow back after i clear it?
because most of what lives there is generated automatically: macos creates new snapshots every hour when your time machine drive isn't connected, browsers rebuild caches as you browse, and apps write new log files as they run. system data isn't a one-time cleanup; it's a category to revisit every few months, particularly the time machine snapshots and the largest app caches.
Last updated June 22, 2026