System Data
A menu bar app that shows what is really inside macOS "System Data" and lets you delete it, item by item.
Open System Settings > General > Storage on a developer Mac and "System
Data" is often the largest line, with no way to see inside it. Finder puts
everything it cannot attribute to an app, photos or documents in that bucket:
simulator runtimes, Xcode symbol caches, package-manager stores, virtual
machine disks, the unified log, per-app data folders.
This app opens the bucket. It is not a cache cleaner: ~/Library/Caches is
one small line among fifty, and the app never deletes anything you did not
click.
Every release is listed in CHANGELOG.md, including the two
that shipped a broken updater and what to do if you are on one of them.
Install
brew install --cask Jarvis322/tap/sysdata
Or download SysDataMenu-<version>.dmg from the
latest release,
open it and drag the app onto Applications. A .zip of the same app is
attached to every release for anyone scripting the download.
Releases from 0.3.2 on are signed with a Developer ID and notarized by
Apple, so the app opens without a Gatekeeper prompt. From 0.3.7 the binary
is universal; 0.3.2 to 0.3.6 were Apple Silicon only and will not launch on
an Intel Mac.
Build from source (Xcode 16 or later):
git clone https://github.com/Jarvis322/macos-sysdata.git
cd macos-sysdata
scripts/build-app.sh
open build/SysDataMenu.app
The app has a Launch at login switch in its footer.
Updates
The app can check GitHub once a day for a newer release and offer to install
it. It is off by default, and it is the only network request the app
makes: with the switch off, nothing leaves the Mac.
Installing replaces the app in place. Before anything is moved, the download
must have come from github.com over HTTPS, pass the same Gatekeeper
assessment a fresh download gets, and be signed by the same team as the copy
asking for the update. Anything else is discarded with a message, and the
installed app is left alone.
Uninstall
brew uninstall --zap --cask sysdata
--zap is the part that matters: without it the app goes and its files stay.
If it was installed by dragging the disk image, drag the app to the Trash and
remove the four things it leaves behind:
rm -rf ~/Library/Application\ Support/SysDataMenu \
~/Library/Caches/local.sysdata.menu \
~/Library/HTTPStorages/local.sysdata.menu \
~/Library/Preferences/local.sysdata.menu.plist
The first of those is the scan history, which records the path of everything
the app measured and everything you deleted. It never leaves the machine, but
it is the file worth being deliberate about. Remember what changed in the
settings menu deletes it at any time without uninstalling anything.
Two grants outlive the app, because macOS keeps them rather than the app:
- Full Disk Access, in System Settings > Privacy & Security. Remove the
entry with the − button.
- Notifications, if you turned the low-space warning on.
If Launch at login was on, switch it off before uninstalling, or remove
the entry from System Settings > General > Login Items afterwards.
Nothing else is left. The app installs no privileged helper, no launch daemon
and no kernel extension: every root action runs as a one-off osascript
prompt, which is why it asks each time and shows you the command first.
What it does
- Menu bar total. The icon shows the size of everything the scan found,
the number Storage settings calls System Data. The window header says how
much of it is safe to free right now. It scans on launch and once a day.
Results appear as each place is measured, with a count in the header, so a
slow first scan on a full disk cannot be mistaken for a stuck one.
- Every item has a real size, measured on disk, plus a badge:
Safe regenerates automatically, Review costs you something (a
simulator, a login, a re-download), Manual cannot be removed by the app
and the info button shows the command or settings path.
- Trash first. Review items go to the Trash, so a wrong click can be
undone for 30 days. Safe items are deleted outright because they come back
on their own.
- Quiet rows. Reveal, hide and the breakdown chevron appear on hover, the
way Finder and Mail do it; delete stays visible, because it is the reason
the window is open. Right-click reaches all of them without a pointer.
- Idle time. Rows past a fortnight say how long they have sat untouched,
and the sort control orders by it. Size cannot tell a build folder for
today's work apart from one for a project abandoned two years ago; those
are the same number of bytes and opposite decisions. Simulator runtimes
take their date from
simctl, which knows when one was last booted.
- What changed. Each scan and deletion is written to a local file, so the
list can show growth beside each size, and a history view can answer three
things a single scan cannot: what came back, what grew most, and what you
deleted. A cache cleared on Monday that is 12 GB again by Friday is the
most useful thing this app can tell you. Switch it off and the file is
deleted; nothing leaves the machine either way.
- Breakdown. Click a row to see its five largest entries before deciding.
- Filter. A scan finds around 180 items across eighteen groups, so the
field under the header narrows the list by name, description or group. The
selection survives it, because ticking Select safe and then filtering
to untick two of them is how the two controls are meant to be used
together. Folding a category keeps it too. Neither one quietly edits the
batch: the footer says how many selected rows are not on screen, next to
the button that would take them.
- Batch delete. Tick rows and use Delete N selected. Select safe
ticks everything regenerable that is on screen, and unticks it on a second
press. Root actions are folded into one script where they can be, and the
confirmation says so — including when they cannot, because a delete of
something you do not own is run on its own and asks again.
- Read the command first. The confirmation shows every operation
verbatim before anything runs —
As administrator: rm -rf /Library/Logs/DiagnosticReports/*, not a count of items. The source is
published so you can see what this does to your machine; this is the same
promise at the moment it matters. Copy puts the whole plan on the
pasteboard, since a list that scrolls inside 120pt often has to be read
somewhere else.
- Low space warning. Optional, off until you switch it on. The daily scan
knows the disk is nearly full a day before you do. It only ever tells you:
nothing this app could delete unattended is worth the one time it gets it
wrong. Fires on the way down and stays quiet until free space has been back
above the line.
- Hide. The eye button removes an item from future scans (Ollama models
you want to keep, say). A footer link brings hidden items back.
- Purgeable space is shown in the header, with a tooltip saying what it
is and what it is not. It is macOS's estimate of what it could give back,
not space you can plan around: writing 6.44 GB on the test machine cost
6.44 GB of real free space and took nothing from the 3.55 GB pool, which
then refilled itself. The measurement is in
docs/purgeable-measurement.md, along with
why forcing macOS to evict is not a feature here.
- Faster shutdown. A booted iOS simulator ignores the quit request and
makes macOS wait 33 seconds before killing it (
launchd: "Service did not
exit 33 seconds after SIGTERM"). Because the app is running at power off,
it shuts every simulator down the moment the shutdown starts and only
quits once that is done. Switch in the footer, on by default. Measured on
a MacBook Air with three simulators booted: userspace teardown went from
33,074 ms to 5,842 ms, the remaining 5 s being macOS's own service timeout.
Check your own numbers after a restart with
grep "Userspace teardown took" /var/log/com.apple.xpc.launchd/launchd.log.2.
- Four languages, following the system: English, Turkish, Simplified
Chinese and Japanese. Every interface string is translated in all of them.
SysDataMenu --json prints the whole inventory for scripts.
What it finds
| Category |
Items |
Badge |
| Time Machine snapshots |
local APFS snapshots (tmutil) |
Safe |
| Simulator devices |
per-device caches, unavailable devices, erase a device; the system dyld cache is reported (macOS blocks deleting it, even as root) |
Safe / Review / Manual |
| Simulator runtimes |
each installed runtime disk image |
Review |
| Xcode |
DerivedData, DeviceSupport, preview devices, caches, Archives, inactive Xcode.app copies |
Safe / Review |
| Package managers |
brew, npm, pnpm, yarn, pip, uv, CocoaPods, Gradle, Cargo, SwiftPM, Go, Cypress, Playwright; the whole Homebrew prefix. A pnpm store left behind by an uninstalled pnpm is found by its default path, since pnpm store path is exactly what is missing then |
Safe / Review / Manual |
| Developer tool data |
Ollama and Hugging Face models, nvm/rustup/pyenv/rbenv/SDKMAN toolchains, conda, Maven, CocoaPods specs, Gradle distributions, Go modules, Bun, Deno, VS Code and Cursor extensions, Docker CLI, OrbStack, Lima, Colima; the AI coding tools (Claude Code, Codex, Grok, Copilot, Kilo, Gemini, Antigravity); any other hidden home folder over 100 MB |
Safe / Review |
| Logs & diagnostics |
unified log store (log erase), crash reports, ASL, ~/Library/Logs |
Safe |
| Temporary files |
/private/var/folders user cache and temp, files older than 3 days |
Safe |
| Docker |
docker system prune reclaimable space |
Review |
| Virtual machines |
Parallels, UTM, VMware Fusion, VirtualBox, Tart |
Review |
| Trash |
~/.Trash |
Safe |
| iOS device backups |
each MobileSync backup with device name and date |
Review |
| Shared & other users |
/Users/Shared app data (BlueStacks and friends), other accounts |
Review / Manual |
| Android |
AVD emulators, SDK system images, platforms, build tools, NDK, emulator, Android Studio caches |
Review / Safe |
| App data & caches |
Slack, Discord, Teams, Zoom, Spotify, Safari, Adobe, Steam, Epic, Photos, Quick Look and Final Cut render caches; Claude VM bundles; Chrome on-device model; any Application Support / Containers / Group Containers folder over 200 MB, caches over 100 MB |
Safe / Review |
| Project build folders |
node_modules, .build, Pods, DerivedData, and the web frameworks' output (.next, .nuxt, .svelte-kit, .astro, .angular, .turbo, .parcel-cache, .expo) under Desktop, Documents, Developer, Projects |
Review |
| System |
macOS installers, device firmware, Mail downloads, /Library/Caches, /Library/Application Support, Command Line Tools, cryptexes, Spotlight index, swap, iCloud local copies |
Safe / Review / Manual |
| Other large folders |
catch-all: every folder over 500 MB under ~, /Library, /private/var, /opt, /usr/local and /Users/Shared that no category above explains, shown with its full path |
Review |
The catch-all pass runs last and takes the longest (it walks the home folder
once, skipping everything another probe already explains). The header shows
which phase the scan is in.
Folders Finder attributes to Photos, Music, Movies, Messages, Mail, iCloud
Drive and Applications are left out, because they are not System Data.
Desktop, Documents and Downloads are left out too, for a second reason:
Storage settings counts them as Documents, and what is in them is your own
work, which no delete regenerates. The things under them that are
reclaimable — build folders, virtual machines, render files — still each get
their own row, named for what they are.
What it writes down
Two files it writes, and two macOS makes for it. All four on the machine:
| Path |
What is in it |
~/Library/Preferences/local.sysdata.menu.plist |
the switches, the sort order, hidden item ids |
~/Library/Application Support/SysDataMenu/history.json |
each scan's item sizes, and each deletion with its paths |
~/Library/Caches/local.sysdata.menu |
macOS's own cache folder for the app |
~/Library/HTTPStorages/local.sysdata.menu |
what URLSession keeps for the update check |
The history file exists so the list can show what changed; it holds no more
than the window already shows, it is capped at six months, and turning
Remember what changed off deletes it. Nothing is sent anywhere. The one
network request the app can make is the daily update check, which is off
unless you switch it on — and the last two rows above are what making it
costs.
Uninstalling removes all four.
Permissions, once
Two things can prompt, and both can be settled one time:
- Folder access. One grant, Full Disk Access, in System Settings >
Privacy & Security. Until it exists the app leaves every protected place
alone — app containers, Desktop, Documents, Downloads, Music, Pictures,
Movies — rather than asking about them one at a time, so a first launch is
a single banner instead of a queue of dialogs naming each app whose
container it touched. The scan still runs and still finds plenty; the
banner says it is incomplete. Without the grant, Mail, Safari and Time
Machine data stay hidden too. macOS quits the app when the grant is
toggled, so reopen it afterwards. The grant
is remembered by code-signing identity, which is why
scripts/build-app.sh
signs with your Developer ID or Apple Development certificate when one is
in the keychain. An ad-hoc signature changes on every build and macOS would
forget the grant each time. Override with CODESIGN_IDENTITY="...".
- Administrator password. Needed for root actions. Batching folds them
into one script, so one password covers all of them — except a delete of
something you do not own, which is run on its own and asks again; the
confirmation says which case you are in rather than promising a single
prompt. Avoiding the prompt entirely would require a privileged helper
daemon, which is deliberately out of scope for a small tool.
Scripting
/Applications/SysDataMenu.app/Contents/MacOS/SysDataMenu --json > inventory.json
jq '.items[] | select(.safety == "safe") | [.name, .sizeBytes]' inventory.json
The output has freeBytes, purgeableBytes, totalBytes and one record per
item with id, category, name, detail, sizeBytes, safety,
manual, path, lastModified and idleDays. The last two are absent when
the item is not a folder this app measured — a docker system prune estimate
or an APFS snapshot has no age.
# everything safe that nothing has touched in six months
jq '.items[] | select(.safety == "safe" and .idleDays > 180) | [.name, .sizeBytes]' inventory.json
sysdata is a bash script covering the Safe categories only, for machines
where you would rather not run an app:
./sysdata # scan
./sysdata clean # dry run
./sysdata clean --yes # apply
How it works
Sources/SysDataMenu/Probes holds one StorageProbe per category. Each
probe measures its locations with a single filesystem enumeration
(allocated blocks, no symlink traversal, the same numbers Finder uses) and
returns StorageItems with a name, a size, a safety level and a
ReclaimAction: remove paths, empty directories, prune by age, run a tool's
own clean command, or run a script as root through the system authorization
dialog. Probes never mutate anything; Reclaimer is the only place that
deletes.
The catch-all probe receives every path the other probes claimed and reports
whatever large folder is left, so the inventory stays complete on machines
with software the app has never heard of. Adding a category means adding one
probe and registering it in ProbeRegistry.
Interface strings live in Resources/Localizable.xcstrings;
scripts/compile-strings.sh turns the catalog into the .lproj tables
SwiftPM ships (en, tr, zh-Hans, ja), and a test checks that every key has a
Turkish translation. ci.sh fails if a hand-edited .lproj drifts from what
the catalog would generate, so the catalog stays the single source of truth.
Checks
scripts/ci.sh # build, tests, lint, bundle, strings
SYSDATA_SCAN_TESTS=1 scripts/ci.sh # and the tests that walk the whole disk
Run before pushing; the release script runs it too. 92 tests. The
disk-walking set is gated because it measures this machine rather than a
fixture: it scans the real disk, and it downloads the published release and
puts it to Gatekeeper, which is the only way the updater's redirect handling
can be exercised at all.
Releasing
Write the version's section in CHANGELOG.md first — the
release script refuses without one, and uses it as the release notes. A list
of commit subjects says what was touched, not what changed for anyone using
the app.
One command bumps VERSION, runs the tests, builds a signed and notarized
app, commits, tags, pushes, publishes the GitHub release with the changelog
section as its notes, and updates the Homebrew cask:
scripts/release.sh # patch
scripts/release.sh minor
It expects gh to be logged in and a notarytool keychain profile (once:
xcrun notarytool store-credentials sysdata --key AuthKey.p8 --key-id ID --issuer ISSUER).
Requirements
macOS 14 or later. Xcode 16 or later to build. Xcode command line tools for
the simulator and Xcode categories; other tools are optional and skipped when
absent.
License
Proprietary; see LICENSE. The source is here to be read, not
reused: you can build and run it yourself, but copying, redistributing or
forking it for distribution needs written permission. Versions up to v0.3.7
were MIT and stay MIT.
Made by @yigitech.
它是一款免费的 macOS 菜单栏应用，可以打开存储设置中含义模糊的「系统数据」分类，准确显示到底是什么在占用空间（模拟器运行时、Xcode 缓存、包管理器存储、虚拟机磁盘、日志、各应用数据），让你逐项删除而不用靠猜。