Where did my Mac storage go?

macOS tells you "System Data: 148 GB" and stops there. Bytesweep shows you the actual folders and files, then clears the ones that are safe to remove, with one-click undo.

Free to try for 3 days. Cleaning needs a licence: $29.99 once per computer. No subscription. Runs offline.

Storage: treemap of a 297.8 GB home folder by category

What "System Data" and "Other" actually contain

On current macOS, System Data holds caches, logs, swap files, Time Machine local snapshots, app support data and developer files such as Xcode DerivedData, device support files, iOS simulators, Docker.raw and the Homebrew and pip caches. iPhone backups and Mail have rows of their own in Storage settings, so they are not part of it. Bytesweep names each item, tells you how large it is, and lets you thin local snapshots with a single click.

One scan, nine views

Treemap, Folders, Sunburst, Flame, Bubbles, Mind Map, Top Sizes, Age Map and Categories. A treemap makes big files obvious. The Age Map exposes the ten-year-old downloads you forgot. Every view drills down to the file and opens it in Finder.

Cleaning that you can undo

Safe Sweep collects only provably safe items: caches, logs, build outputs, trash, installers older than 30 days. Everything moves to a restore point on the same disk, so Undo puts it back in one click for seven days.

Bytesweep vs CleanMyMac, DaisyDisk and the rest

	Bytesweep	CleanMyMac	DaisyDisk	GrandPerspective	Finder Storage
Price	$29.99 once	from $3.33/month	$9.99 once	Free	Built in
Payment model	One-time	Subscription	One-time	Open source	—
App updater	Yes	Yes	No	No	No
Malware scanning	No (local adware check)	Yes	No	No	No
Visual views	9	1 (Space Lens)	1 sunburst	1 treemap	0
Cleans junk automatically	Yes	Yes	No	No	Partly
Time Machine snapshot thinning	Yes	Yes	No	No	Partly
App leftovers & uninstaller	Yes	Yes	No	No	No
Duplicate + similar photo finder	Yes	Yes	No	No	No
One-click undo	Yes	No	No	No	No
Linux too	Yes	No	No	No	No

Questions

Is it safe to delete System Data on a Mac?

Not as a whole, no. Parts of it are caches and snapshots that regenerate, and parts are files your apps need. Bytesweep separates the two, only sweeps the safe categories, and keeps a restore point so you can undo.

Does it work on Apple silicon?

Yes. Bytesweep is a universal app for Apple silicon and Intel Macs running macOS 14 Sonoma or later. On macOS 13 or older, use Bytesweep 1.x.

Will it delete my iCloud files?

No. Bytesweep flags files inside iCloud Drive, OneDrive, Dropbox and Google Drive, shows which are online-only versus really on disk, and can evict a local copy back to the cloud instead of deleting it.