Over the last few days my hard drive has gone from a few GB of free space, to zero KB, absolutely full. I then deleted about 1GB of files, and now the free space has gone down to 640MB, and then went up to 690MB. This is without doing anything major. Over the past few days, almost all of what I've done is on the internet.

Is this some type of malware (though I thought malware usually deleted stuff), and how can I see why this is happening, and what recently has been taking up so much room. (I've just switched my PC to ubuntu and it has something called Disk Examiner which shows you what is taking up the most room, is there something like that for Mac?)

  • How much RAM do you have? You will want to keep at least 4X the total RAM free on the hard drive to handle the system needs. It needs to make a sleep image as large as RAM and virtual memory will take space on disk as swap if you open more programs than can fit in RAM. Look in /private/var/vm to see how much space is used now and reboot to clean out the swap files so you have room to delete things that are needed less urgently than a working system. – bmike Jun 23 '11 at 18:07

To find out what takes up space, you can use Disk Inventory X, http://www.derlien.com/, which is free, or DaisyDisk, http://www.daisydiskapp.com/, also in the Mac App Store.


Checking the space

You can use OmniDiskSweeper to check what is occupied your space. It's free.

Or, if you like command-line, run Terminal.app and enter this:

du -kx /some/directory | sort -nr > $HOME/DiskUsage.txt
less $HOME/DiskUsage.txt

you will get sorted size-list (in kB) for all directories under the /some/directory.

Swap files

Another check - swap file. If your apps take more memory as you have, the OS do "swap" parts of memory into HDD. (In the linux or FreeBSD there are usually dedicated HDD partitions (slices) but on OS X these are files.

You can check their size with:

ls -l /private/var/vm

you will get something like the next:

total 12582912
-rw------T  1 root  wheel  4294967296 23 jún 14:30 sleepimage
-rw-------  1 root  wheel    67108864 15 jún 09:03 swapfile0
-rw-------  1 root  wheel    67108864 23 jún 14:54 swapfile1
-rw-------  1 root  wheel   134217728 23 jún 14:54 swapfile2
-rw-------  1 root  wheel   268435456 23 jún 14:54 swapfile3
-rw-------  1 root  wheel   536870912 23 jún 14:54 swapfile4
-rw-------  1 root  wheel  1073741824 23 jún 14:54 swapfile5

As you can see, in my HDD are now 5 swapfiles with total size 2GB. When start too much programs (or have 50 browser windows or soo) sometimes the swap increases up 5 GB or more. Simply close applications and the swap will be freed.

The another 4GB file (sleepimage) is the space, where OS X store its memory content when going to sleep (SafeSleep - storing memory content in the file). While it is possible turn of the SafeSleep and get 4GB HDD space (or less, if you have less memory) via pmset command, i do not recommend this.


When you browsing a lot, Safari storing some content into his cache/files. You can partially clear from the menu: Safari -> Empty Cache

Or simply check your cache files in the $HOME/Library/Caches with the OmniDiskSweeper or the du -kx $HOME/Library/Caches | sort -nr command from the Terminal.

You can Trash everything from the $HOME/Library/Caches without problems, but (for the safe) is better relog or reboot after the delete.


Another space-waste can be the Logfiles. You can check them with your Console.app (Utilities). (in the bottom left corner it showing the current size) - You can trash a big ones from the application directly.


I agree with all of the above and I've had great luck with Disk Inventory to identify how many large files were quietly sitting there including many duplicates.

I can only add a number of suggestions of other small things that might collectively help you recover HD space.

I'm not sure what OS you're running but Snow leopard used 4 Gb less HD space that Leopard on my iMac.

iDVD and GarageBand are very large applications and you could uninstall them if you don't use them. If you do use them, they have large folders with templates so possibly you could delete some of these templates.

Check activity monitor for memory pages outs. This is similar to Windows pagefile and if this number is high, it means you're consuming HD space when there isn't enough ram to manage everything that is running on your machine. Add more ram, page outs goes down and frees up HD space.

Check to see if the Login Items that start automatically are really apps that you need to run automatically. Go to system preferences, accounts, login items and delete any that aren't required by highlighting the app and clicking on the minus sign. This can free up ram and reduce page outs.

Reduce the number of widgets in dashboard. Collectively they may have grown and can consume ram and in turn generate extra page outs. On my laptop, I had 12 and now get by with 2.

Spotlight automatically indexes almost your entire drive. Open system preferences, spotlight and de-select the items that you can exclude from indexing. I reduced my indexing from 14 categories to just 7.

In addition to the main Trash bin, mail and iPhoto have dedicated trash bins to be emptied. I never knew iPhoto had its own trash and recovered almost 1gb when I emptied the iPhoto trash.


The one thing to remember is that MacOS is a Unix variant, and these kinds of systems use considerable amounts of disk space as system cache. In fact, even if you run out of physical ram, your system doesn't see this and immediately starts using available disk space to handle active tasks. It can be that just by running, you're using up that space.

Typically for a Mac, you should always keep at least 5-7GB free, to handle memory requests, caching, swapping in and out, etc. 1GB is asking for trouble...you might also notice that the machine starts going slower and slower, especially now that it needs to search for available blocks of open space, randomly scattered across your disk.

I would suggest a few things:

• Back everything up now. I bought a 2GB external drive for €70, partitioned it for Time machine and File backup, and backed-up the disk (in one partition) and the files via Time Machine in the other.

• Use an application like Snow Leopard Cache Cleaner to run through the system and flush caches and delete extra languages and old PPC-based code in apps. That will free up some space.

• Try to clean off your disk so there's at least 10Gb free on the boot disk. Back up any large files to an external disk...OS X will automatically run in the background and defrag any files under 20MB on the fly, but you can use Snow Leopard Cache Cleaner to Optimize files afterwards. Move old, large files off (like an iTunes library) clean up the drive, and then migrate the important files back.

You shouldn't need to reinstall anything - just don't let the drive fill-up!

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