Cleaning up Disk Space on your Mac

Posted by Derek Wyatt on December 25, 2016
How to use the terminal to find out where your disk space is going and how to clean it up

My nephew asked me (again) how to clean up disk space on his mac. He tells me that he deletes files and empties the trash but nothing happens. Clearly he's either:

  1. Drunk
  2. Speaking through one of many different personalities that he posesses, none of which know what the other is doing
  3. Lying

There are a number of pages out there that will tell you how to reclaim disk space but the best tools to do this are good ol' unix tools that have been around for decades. Incidentally, Disk Inventory X is also a great tool for visualizing what your disk usage looks like so you should download it, run it, and see what you've got. But here, I'm going to show you what I do.

First, you'll need a command line shell, so go to the Finder and launch Applications -> Utilities -> Terminal. From there you'll want to do this:

# Change to your home directory
> cd ~

# Find out how much disk you have available
> df .
Filesystem     1K-blocks      Used Available Use% Mounted on
/dev/disk1     487350400 458293832  28800568  95% /

# You can see that I have, essentially, a 500GB disk on my mac and I'm using nearly all of it.
# If I want to know where it's going, I would first find out how much is being used in my
# home directory.

# This might take a while to run so be patient
> du -sh
354G    .

# 354 GB.  Well, that's a lot.  Now let's break that down:
> du -sk * | sort -n
0   Public
4   molex.parts.txt
8   Desktop
8   song.txt
20  bin
240 scratch
1228    Applications
6292    Pictures
1385960 Macheist
1561260 code
2864748 Dropbox
2955184 Documents
11738324    Downloads
12477984    Library
19843364    Movies
29010916    Videos - March 22nd 2009
43003148    Music
48296516    AudioData
195036888   Guitar

That's the most important command. You run du in in summary mode, where all of the numbers are in kilobytes and then you sort them numerically, where the larger numbers go to the bottom. I do a lot of work with my guitar and I have a lot of data associated with it so it's the biggest by far. Let's take the Music directory and see what's in there:

# Head into the Music diredtory and rerun the du command there
> cd Music
> du -sk * | sort -n
716 Audio Music Apps
42968676    iTunes

# Not much of value in that, so let's look in the iTunes directory
> cd iTunes
> du -sk * | sort -n
4   sentinel
16  iTunes Library Extras.itdb
32  iTunes Library Genius.itdb
940 iTunes Library.itl
1944    Previous iTunes Libraries
212240  Album Artwork
42753492    iTunes Media

# Keep going
> cd iTunes\ Media
> du -sk * | sort -n
0   Automatically Add to iTunes.localized
0   Downloads
7256    Voice Memos
3331504 Audiobooks
39414720    Music

# Let's look in Music.  But I'm only going to be interested in the top 2
> cd Music
> du -sk * | sort -n | tail -2
1728208 Pat Metheny
1844824 Dave Matthews Band

Dave an Pat! I love Dave and Pat's just ridiculously good... Well, I'm not going to delete them but it was fun to look. If I wanted to wipe out Dave then I could go to iTunes and delete him, but there's no way I doing that.

There you go. That's how to see what you've got per folder, but don't forget about Disk Inventory X because it does, essentially, the same thing but graphically and more fun, if you're afraid of the command line.