macOS · Disk Full
“Your startup disk
is almost full.”
This arrives while you are mid-task, and every guide answers it with an essay. Here is the short version: a few categories account for almost all recoverable space on almost every Mac, and doing them in the right order gets you working again in about ten minutes.
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Where the time goes when you are in a hurry
You do not know what is big, so you delete what is visible
Downloads gets emptied, the Trash gets emptied, and 4 GB comes back from a disk that needs 40. The large things are somewhere you were not looking, and hunting for them by hand is the expensive part.
Deleting a large file frees nothing, apparently
Because a local snapshot still references it, or the app that made it is still holding it open. macOS reclaims on its own schedule, so the feedback you get while triaging is unreliable.
The Mac needs headroom, not just a bit of space
Below roughly 10% free, macOS starts struggling — swap, snapshot thinning, and app saves all compete. Recovering exactly enough to continue means being back here tomorrow.
The advice assumes you are a developer
Half of it is about Xcode. Useful for the people it is about, and an evening wasted for everyone else who follows it to the end.
The order that works
One: the large files, ranked
Start here every time. Disk images, video exports, virtual machines, installers you kept "just in case". This is the highest gigabytes-per-minute step on almost every Mac, and it is usually a dozen files rather than a thousand.
Two: caches, by category
Browser caches, developer tooling — Xcode derived data and archives, npm, yarn, pip, Cargo, CocoaPods, Homebrew — plus Slack, Discord, Zoom, Spotify and user logs. Sized before anything is removed, so you can see whether it is worth the rebuild cost before you pay it.
Three: duplicates, matched by content
The same file under four names is invisible to anything comparing filenames. Nothing is deleted by default — duplicates move to a folder you nominate, which is the right trade when you are working quickly.
Four: the storage breakdown, for what is left
Size by folder, sorted, for the part you still cannot account for. This is where an old iOS backup or a forgotten VM turns up. Slower than the first three steps, and the one that ends the mystery.
Everything is measured before it is removed
Every step reports what it found and what it would recover before you agree to anything. Triaging is not the moment to be surprised.
Aim past what you need
Recover enough to get headroom, not just enough to save the file you were working on. Below about 10% free, macOS gets slow in ways that are hard to attribute and easy to blame on the hardware.
What it does not do yet
- — System-level cleanup needs the privileged helper installed. Without it, everything at the user level still works — and that is where most of the recoverable space is.
- — Deletion is gated by a generated allow-list, so the scanner can occasionally offer a path the cleaner then declines. Safe direction for the error, and the refusal is reported rather than hidden.
- — Local snapshots are not thinned for you. VaultSort shows what they cost; Time Machine decides when they go, and overriding that behind your back is how backups go missing.
- — Space can take a moment to appear. macOS reclaims lazily, especially on a disk that was already under pressure.
Questions people ask
I need 20 GB in the next ten minutes. What do I do?
Large files first, then caches. Between them they cover it on most Macs. Skip the duplicate scan while you are in a hurry — it is the highest-value step over a week and not the fastest one right now.
Why is my disk still full after emptying the Trash?
Local snapshots most often, or a file still held open by a running app. Quit the app, and give macOS a minute — snapshot thinning happens on its own schedule rather than yours.
Is it safe to delete cache files?
Mostly — a cache is rebuildable by definition. The cost is the rebuild: slower first page loads, a slower next build. Categories with real consequences are reported rather than cleared for you, so you decide whether the space is worth it.
How do I stop this happening again?
The mess is usually three folders — Downloads, the Desktop, and one project directory. Organizing them is reversible and takes a minute, and it turns the next clean-up into a ten-minute job instead of an evening.
Try it on your own files
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