"Your disk is almost full": what to do in the next ten minutes

On this page

1. Minute one: save your work
2. Check the real number
3. Empty the Trash
4. Remove one big thing you recognise
5. Restart if swap has grown
6. If you need room for one task, safe mode
7. What not to do in a hurry
8. Tonight: the longer fix

When macOS says "Your startup disk is almost full.", save what you're working on, empty the Trash, and delete one or two big files you recognise. That's usually enough to get through the day. The proper clean-up can wait until tonight, and it goes better when you're not doing it in a hurry.

I'm writing this on a Mac that's in exactly that state. On 12 October 2026 my MacBook Air had 4.6 GB free out of 455.3 GB, so everything below is what I'd actually do on it, in the order I'd do it.

Minute one: save your work

When a disk is nearly full, the first thing to fail is usually saving. An app that needs to write a large file can't, and macOS has its own messages for that, along the lines of "Additional … of disk space is required to copy this file." Save open documents now, and don't start an export, a big download or a software update until you have some room back.

Check the real number

Finder, System Settings and Terminal can show three different figures for free space, because they count purgeable space and units differently. This is the one I trust, because it comes straight from the APFS container:

diskutil info / | grep "Container Free Space"

On my Mac it printed 4.6 GB. df -h / said 4.3Gi for the same space, because it counts in binary units (a gibibyte is about 1.07 GB). If Finder shows much more than either of these, the difference is purgeable space, which macOS hands back by itself when something needs it. The purgeable space post explains how that works.

Empty the Trash

Files in the Trash still take up space. In Finder, choose Finder → Empty Trash. It's the only step on this page that gives space back straight away, and it's the one people forget, especially after a clean-up that moved a lot of things there.

If the free space barely moves afterwards, local snapshots may still hold the deleted files. This lists them, and doesn't change anything:

tmutil listlocalsnapshots /

Snapshots named com.apple.TimeMachine… are Time Machine's and expire on their own, usually within a day. Mine showed only three named com.apple.os.update…, which belong to macOS updates, and I leave those alone.

Remove one big thing you recognise

Don't go hunting through dozens of small folders now. Look for one or two large files you know you don't need: a screen recording, a disk image you've already installed from, an exported video, an "Install macOS" app. This lists every file over 1 GB in your home folder, without changing anything:

find ~ -xdev -type f -size +1G 2>/dev/null

The first time you run it, macOS may ask whether Terminal can access your Desktop, Documents and Downloads. If you'd rather not use Terminal, Finder can do the same search: press Command-F in your home folder, choose Other… from the first pop-up, tick File Size and set it to greater than 1 GB.

Two other quick wins, if they apply to you:

• iPhone or iPad backups you no longer need. A backup made on a Mac holds almost all of a device's data and settings, so each one can be large. Where they are and how to delete them.
• Old iOS simulator runtimes, if you have Xcode. xcrun simctl runtime list shows them with a total at the end; mine came to 18.7G for three runtimes. The Xcode post has the delete command and what to keep.

Move what you pick to the Trash, then empty it again.

Restart if swap has grown

When apps use more memory than the Mac has, macOS writes the overflow to swap files on disk. They can grow over a long session, and a restart starts them again from nothing. This shows how much swap there is right now:

sysctl vm.swapusage

Mine said total = 7168.00M used = 5489.00M: 7 GB of swap files on a Mac with 4.6 GB free. That space comes back after a restart, which makes restarting one of the quickest things you can do here. Close your apps first, so the swap doesn't build straight back up.

If you need room for one task, safe mode

Apple documents one more trick for when you need space only for a while, for example to get a macOS update installed. Starting up in safe mode clears some system caches, including font caches and the kernel cache, which "can temporarily make more storage space available" (Apple Support: Start up your Mac in safe mode). The caches come back after a normal restart, so it's for finishing a job, not for keeping the space.

What not to do in a hurry

• Don't delete things you can't name. A folder you don't recognise in ~/Library is usually an app's settings or data, not junk.
• Don't run sudo rm on anything a forum post suggests. The system volume is sealed and read-only anyway, and the folders you can delete from with sudo are the ones macOS needs.
• Don't start with caches. My ~/Library/Caches folder is 2.9 GB, and apps rebuild it as you use them. It's the last place I'd look, not the first.
• Don't install a cleaner from a pop-up that says your Mac is infected or slow. A full disk is a storage problem, nothing more.

Tonight: the longer fix

Once you're out of the red, take half an hour to find out where the space actually went. System Settings → General → Storage shows it by category. I wrote up the order I work through on my own Mac, with the big, boring things first.

Spaceback, which I make, can help with that part. Its scanners, the Storage Map and cleaning Downloads, large files and core junk are free. Everything you pick moves to the Trash, so the space comes back when you empty it, the same as the steps above.

Vlada Misici builds Spaceback, a storage cleaner for Mac and iPhone. Every number in these posts was measured on a real Mac, and every command was run before it went on the page. Found a mistake? Email vlada@queazy.app and it gets fixed.