Bytesweep How to free up space on a Mac
Twelve places the space actually goes, ordered by how many gigabytes you get back. Every one has the real path, so you can check it yourself before deleting anything.
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Start here: the four that are usually 80% of it
On most Macs that are "full", four things account for the bulk of it, and none of them are your documents. Time Machine's local snapshots, Xcode's build folder, Docker's disk image, and old iPhone backups. Check those four before you start deleting photos.
Why the Finder is not much help
Apple's own storage screen groups most of the answer into a grey bar labelled "System Data" and gives you no way in. It also counts online-only iCloud files as though they were on the disk, and does not show you purgeable space separately, so the numbers rarely add up to what you see.
You will be doing this again in three months
Almost nothing on this page stays fixed. DerivedData is back after the next build. Local snapshots return within the hour. Docker regrows with every image you pull, and the model you delete today is one you re-download in February. Working through the list by hand takes an afternoon and buys you a few months — which is fine once, and tiring on the fourth repeat.
Before you delete anything
Deleting inside ~/Library is where people lose work. That folder holds application caches you can throw away and, right next to them, mail, keys, licences and databases you cannot. Nothing below tells you to delete a whole folder blind — every item names what it is and what regenerates.
The twelve, biggest first
Typical recovery on a three-year-old developer Mac. Yours will differ, but the order rarely does.
1. Time Machine local snapshots — often 10 to 80 GB
Even with Time Machine "off", macOS keeps hourly snapshots on your internal drive. They show as purgeable, macOS frees them only under pressure, and they are the single most common answer to "my disk is full and I cannot find why". List them:
tmutil listlocalsnapshots /Thin them to reclaim roughly 20 GB, keeping the newest:
tmutil thinlocalsnapshots / 21474836480 4Do not delete every snapshot out of habit if Time Machine is your only backup — the most recent one is the local copy of changes not yet written to the backup drive.
2. Xcode DerivedData and device support — 20 to 60 GB
Build intermediates that never shrink, plus symbol caches for every iPhone you have ever plugged in.
~/Library/Developer/Xcode/DerivedData
~/Library/Developer/Xcode/iOS DeviceSupport
~/Library/Developer/Xcode/ArchivesDerivedData rebuilds itself on the next build — safe. Archives are your shipped builds and their dSYMs; deleting those loses your ability to symbolicate crash reports from released versions. Full Xcode cleanup guide →
3. Docker's disk image — 15 to 60 GB
Docker Desktop keeps everything inside one file that grows and does not shrink when you delete images.
~/Library/Containers/com.docker.docker/Data/vms/0/data/Docker.rawNever delete that file directly — it is every image, container and volume you have. Reclaim from inside Docker instead. How to shrink Docker.raw →
4. Local AI models — 20 to 200 GB
The fastest-growing item on a developer's disk, and invisible to every mainstream cleaner. Ollama, LM Studio, Hugging Face and PyTorch each keep their own store.
~/.ollama/models
~/.cache/huggingface/hubA 40 GB model is a re-download; one you fine-tuned yourself is gone for good. Where every AI tool keeps its models →
Four down, eight to go — or ten seconds
Every folder on this page is one Bytesweep already knows by name. It measures the whole disk in about ten seconds, shows all twelve at once with real sizes rather than estimates, and tells you which ones are safe before you touch them. And every sweep goes to a restore point you can undo for seven days — the one thing the manual route cannot offer, because rm has no undo.
5. iPhone and iPad backups — 10 to 60 GB
Local device backups, often several generations of the same phone.
~/Library/Application Support/MobileSync/BackupEach subfolder is one backup, dated. Keep the newest for each device you still own; delete the rest. Manage them from Finder → your device → Manage Backups rather than deleting folders by hand.
6. iOS simulators — 5 to 30 GB
Runtimes for iOS versions you no longer target, plus simulator devices Xcode can no longer use. The supported way to clear the dead ones:
xcrun simctl delete unavailable7. node_modules across old projects — 5 to 50 GB
Not one big folder: a hundred small ones. A project you have not opened in a year is still holding its full dependency tree, and npm install brings it back in seconds. The same goes for target in Rust projects, .venv in Python ones and build everywhere.
8. Package manager caches — 3 to 20 GB
Downloaded archives kept in case you install the same version again.
brew cleanup -s
~/Library/Caches/pip
~/.npm/_cacache
~/.cargo/registry/cacheAll rebuild themselves. This is the safest category on the list.
9. Mail attachments — 2 to 20 GB
Years of downloaded attachments cached locally.
~/Library/Containers/com.apple.mail/Data/Library/Mail DownloadsSafe for IMAP accounts, where the server still has the message. If you have POP accounts, the local copy may be the only copy.
10. Leftovers from apps you deleted years ago
Dragging an app to the Trash leaves its support files, preferences, caches and launch agents behind, in four different folders, for as long as the Mac lives.
~/Library/Application Support
~/Library/Caches
~/Library/Preferences
~/Library/LaunchAgents11. Duplicate files and near-identical photos
Exact copies are the easy half. Burst shots, re-saved exports and HEIC/JPEG pairs of the same picture waste far more, and no checksum will ever match them. Finding near-duplicates →
12. Downloads, old installers and big videos
The obvious one, listed last because it is almost never the answer. Sort Downloads by size, not by date — a single forgotten disk image outweighs a year of PDFs.
Three things that do not work
Emptying the Trash and restarting
Worth doing, but on a genuinely full Mac it returns a few hundred megabytes. It is not the reason you are out of space.
"Optimise Storage" alone
macOS offloads files to iCloud, which helps, but nothing in the System Data bucket is touched by it — and the offloaded files still count in the Finder's numbers until you look closely.
Deleting caches to make the Mac faster
Freeing disk space is not a performance fix. A Mac with 40 GB free runs exactly as fast as one with 400 GB free. Anything promising speed in exchange for deleted caches is selling you a feeling.
Or let something find all twelve for you
Bytesweep scans the whole disk in about ten seconds, sorts what it finds into safe, worth a look and do not delete, and puts everything you sweep into a restore point so undo is one click for seven days.
No card, no account. macOS 11 Big Sur or later, Apple silicon and Intel.
Questions
How much space should I keep free on a Mac?
Around 10% of the drive, or 20 GB, whichever is larger. Below that macOS starts struggling to write swap and snapshots, and apps begin failing in confusing ways. Above it, more free space buys you nothing.
What is purgeable space, and why can I not get at it?
Purgeable is space macOS believes it can reclaim on demand: local snapshots, cached iCloud files, and some app caches. It is counted as used in some places and free in others, which is why the numbers disagree. macOS releases it only when something actually needs the room, so it can sit there while you stare at a full disk.
Is it safe to delete files in ~/Library?
Some of it, and not by the folderful. ~/Library/Caches mostly regenerates. ~/Library/Application Support holds real application data — licences, local databases, mail. Delete by item, knowing what each one is, never the whole folder.
Will freeing up space speed up my Mac?
Only if you were nearly full. Below about 10% free, macOS runs short of room for swap and temporary files and does slow down. Above that, going from 100 GB free to 400 GB free changes nothing.
Do I need an app to do this?
Not to find the folders — this page gives you every path, and the Finder and Terminal can do the rest. The three things hand-work cannot do are measuring the whole disk in one pass instead of guessing folder by folder, being warned that the folder you selected holds an SSH key or unpushed git history before it goes, and undoing it afterwards. That last one is the real gap: rm is final, and Bytesweep moves things to a restore point you can reverse in one click for seven days. If you enjoy the afternoon, keep the paths and skip the app.