A Mac app, in a window or in the menu bar, that shows what is really inside macOS "System Data" and lets you delete it, item by item.
macos-sysdata.yigitech.dev

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. There is a short tour at macos-sysdata.yigitech.dev, and contributions are described in CONTRIBUTING.md.

Up to 1.0.4 the app was called SysDataMenu. The bundle identifier, the Homebrew cask and the command-line binary kept their names, so Full Disk Access, your settings and any scripts carry over without reinstalling.

brew install --cask Jarvis322/tap/sysdata

Or download the disk image, open it and drag the app onto Applications. Every release carries the same image as SysDataMenu-<version>.dmg. A .zip of the same app is attached to every release for anyone scripting the download.

If the app is already in Applications from the disk image, brew install stops with "It seems there is already an App". Hand the existing copy to Homebrew instead:

brew install --cask --adopt Jarvis322/tap/sysdata

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/System Data Unpacked.app"

The app has a Launch at login switch in its footer.

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.

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.

• 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. Fires on the way down and stays quiet until free space has been back above the line. While you are under the line, the window offers to free the safe items in one press.
• Weekly summary. Optional. Once a week, if System Data has grown by more than 2 GB, a notification says by how much and what grew most.
• Unusual growth. Optional. After the daily scan, a notification when a category is at least 50% and 2 GB above its median over its last 14 scans. It waits for another 2 GB before the same category speaks again.
• Trends. Each row carries a small line showing where its size has been heading over recent scans.
• A map of the disk. Categories start folded and are listed largest first, so the folded list reads as a map. Each header carries a bar: the category's size next to the largest one, split into what is Safe, what needs Review and what is Manual. A category that has grown well past its recent size is marked in amber. One line above the list sums it up: System Data, free space, and the change over the past week.
• Automatic clean, opt-in. Once a week, delete the items marked Safe and say what was freed. The only thing the app ever does on its own, and drawn as narrowly as possible: nothing marked Review, nothing that needs a password, and never on a scan you are watching.
• Safe items to the Trash, if you want an undo window for the items that are normally deleted outright. They free nothing until the Trash is emptied.
• A window or the menu bar. On the first launch after 1.2.0 the app asks which you want, once. The same panel opens as a real window — from Applications, from the Dock, or from Settings > Open in a window — and the menu bar icon can be switched off entirely. With the icon on, it shows System Data's size, free space, or just the icon.
• 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.
• Nine languages, following the system: English, Turkish, Simplified Chinese, Japanese, German, French, Spanish, Korean and Russian. Every interface string is translated in all of them; the last five are machine-assisted, and native-speaker corrections are welcome (see CONTRIBUTING.md).
• Who made it. Folders nothing else explains are traced to their owner from their path: "Belongs to Google Chrome", or — the useful one — "Left by com.example.app, which is no longer installed on this Mac". The 13 GB ~/Library/Metadata is named for what it is, Spotlight's index.
• Idle projects. Build folders are dated by the project's own files, not by the last npm install, and one link selects every project nobody has changed in 60 days.
• Projects. One row per project with everything it costs, wherever it lies: its node_modules and .next, its folder in DerivedData, the Docker images only its Compose containers use. It shows how much that grew this week, warns when it was built this week (an archive then lasts only until the next build), marks DerivedData whose project is gone, and archives the lot in one click, never touching source files or Docker volumes. "Copy card" puts the totals on an image for a post, naming no project.
• Unused simulator runtimes. A runtime no installed SDK builds against and no simulator sits on is marked unused — every Xcode update leaves one.
• Docker, piece by piece. Build cache, unused images, stopped containers and unused volumes each get a row, a size and the prune command that frees exactly that. Volumes carry a warning: databases keep their data there.
• When the disk does not give the space back, because local snapshots still hold it, the notice now has a button that deletes them — through the same confirmation as every other row.
• Widget. System Data, free space and what is safe to free, on the desktop or in Notification Center, as of the last scan.
• Shortcuts. Free Safe Items and Get System Data Size, for a weekly automation or anything else Shortcuts can run.
• SysDataMenu --json prints the whole inventory for scripts.

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.

Two files it writes, and two macOS makes for it. All four on the machine:

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.

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.

"/Applications/System Data Unpacked.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

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, de, fr, es, ko, ru), and a test checks that every key in the catalog is used by the interface. ci.sh fails if a hand-edited .lproj drifts from what the catalog would generate, so the catalog stays the single source of truth.

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.

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).

The app is free, and the source is open to read. If it cleared some room on your Mac and you want to say thanks, you can sponsor the work on GitHub.

It helps cover the Apple Developer Program membership and notarization every release goes through, and the time that goes into new probes, the four languages, and reviewing the community pull requests that keep landing. None of it is required: every feature is in the free app, nothing is gated behind a sponsorship, and the app stays exactly as capable whether you sponsor or not.

There is a Sponsor button at the top of this repository too, next to the Star button.

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.

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.