# What is inside System Data on Mac: a Terminal audit

_Updated 2026-10-21_

> **Quick answer:** System Data is not one folder. Run a handful of read-only `du` commands and add up the results. The big ones are almost always `~/Library/Caches`, `~/Library/Application Support`, `~/Library/Developer` and `~/.cache`.


## Before you start

- Everything below only reads sizes. Nothing is deleted.
- System locations ask for your administrator password because of `sudo`.
- `Operation not permitted` on some folders is normal: macOS protects them.
- Sizes here use `du`, which counts the space really used on disk.


## Step 1: your user Library

```
du -sh ~/Library/Caches ~/Library/Application\ Support ~/Library/Developer ~/Library/Containers ~/Library/Logs 2>/dev/null
```


## Step 2: tool folders in your home directory

```
du -sh ~/.cache ~/.npm ~/.gradle ~/.cargo ~/.docker 2>/dev/null
```


## Step 3: system-wide locations

```
sudo du -sh /Library/Caches /private/var/log /private/var/vm 2>/dev/null
```


## Step 4: the whole data volume, folder by folder

```
sudo du -xhd 1 /System/Volumes/Data 2>/dev/null | sort -h | tail -15
```

The `-x` flag stays on one volume so nothing is counted twice.


## Step 5: snapshots

```
tmutil listlocalsnapshots /
diskutil apfs listSnapshots /
```


## A real example

These are the results from one developer's Mac:

| Location | Size |
|---|---|
| ~/Library/Caches | 31 GB |
| ~/Library/Developer | 9.8 GB |
| ~/Library/Application Support | 7.8 GB at the time |
| ~/.cache | 4.5 GB |
| ~/Library/Containers | 2.0 GB |
| /private/var/vm (swap) | 2.0 GB |
| ~/.npm | 1.4 GB |
| /Library/Caches | 120 MB |
| /private/var/log | 85 MB |
| ~/Library/Logs | 15 MB |

And the data volume by top-level folder: Users 135 GB, Applications 46 GB, System 28 GB, Library 13 GB, private 7 GB, opt 4.5 GB, usr 1 GB and a 210 MB hidden `.fseventsd`, about 234 GB in total. Storage settings on the same Mac said roughly 340 GB used. The gap is the part files alone do not explain: other volumes in the same APFS container (the sealed system volume alone was 13.7 GB), snapshots and metadata.


## Turn the numbers into actions

| If this is big | Read |
|---|---|
| ~/Library/Caches | [Is it safe to delete ~/Library/Caches](/guides/is-it-safe-to-delete-library-caches-mac/) |
| ~/Library/Developer | [Clearing Xcode DerivedData](/guides/clear-xcode-derived-data-mac/) |
| ~/Library/Application Support | [Application Support too big](/guides/application-support-too-big-mac/) |
| Docker data in Containers | [Docker.raw looks huge](/guides/docker-raw-too-big-mac/) |
| Snapshots | [Deleting local snapshots](/guides/delete-time-machine-local-snapshots-mac/) |
| Swap and system logs | Leave them alone. macOS manages them |

If you would rather see all of this at a glance, [See Your Disk](/) runs the same measurement and draws it as a map, with whatever no folder explains shown as its own System Data block. The full cleanup order is in [how to clear System Data safely](/guides/how-to-clear-system-data-on-mac/).

Get See Your Disk: [Mac App Store](https://apps.apple.com/us/app/clean-systemdata-seeyourdisk/id6817565741) · [GitHub](https://github.com/bikmeev/see-your-disk)

## Frequently asked questions

**Why do the numbers not add up to what Storage settings says?**
Files you can measure are only part of used space. The rest is other volumes in the same APFS container, snapshots, purgeable space and metadata. On the Mac below, the files on the data volume added up to about 234 GB while Storage settings reported roughly 340 GB used.

**Do I need sudo for these commands?**
Only for system locations such as /Library and /private. Commands on folders in your own home folder do not need it.

**Are these commands safe?**
Yes. du, ls, tmutil list and diskutil list only read sizes and names. Nothing in this guide deletes anything.

**What is /private/var/folders?**
A set of per-user temporary and cache folders that macOS manages. Do not delete things there by hand.

## Related guides

- [What is System Data on Mac, and why is it so big?](https://seeyourdisk.com/guides/what-is-system-data-on-mac/)
- [How to clear System Data on Mac safely](https://seeyourdisk.com/guides/how-to-clear-system-data-on-mac/)
- [Application Support is too big on Mac: what you can delete](https://seeyourdisk.com/guides/application-support-too-big-mac/)
- [How to see what is taking up space on your Mac](https://seeyourdisk.com/guides/see-what-is-taking-up-space-on-mac/)