System Data

A menu bar app that shows what is really inside macOS "System Data" and lets you delete it, item by item.

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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.