Freeing Up Space on The Hard Drive
2. You can remove data from your Home folder except for the /Home/Library/ folder.
3. Visit The XLab FAQs and read the FAQ on freeing up space on your hard drive.
4. Also see Freeing space on your Mac OS X startup disk.
5. See Where did my Disk Space go?.
6. See The Storage Display.
You must Empty the Trash in order to recover the space they occupied on the hard drive.
You should consider replacing the drive with a larger one. Check out OWC for drives, tutorials, and toolkits.
The SSD of the Air and macbook Pro Retina SSD are "working platform" computers.
Your best practical option is buying a 1TB external HD for $65 and offload BIG FILES
regardless of internal HD or SSD, need an external backup for time machine and same for important file storage.
The "low" capacity of the SSD on the Air and entry level Retina are meant to be working platforms for these computers.
*Meaning ALL your programs and your working data (stuff you use at least every week).
To try to use either the Air or Retina as a massive storage platform of any kind (lots of pics, music, movies etc.) is both not indicated or practical.
external storage, quality too, is absurdly cheap right now.
superslim external HD perfect for the Air, its even thinner than the Air itself.
see this: only 7mm thick
Or better still this HUGE HD, which is very small, very reliable and very cheap:
2 Terabytes, 2.5" and only $119
"Other" is everything that is not in one of the categories listed, including:
rar & tar
virtual machine & OS
and a ton of "other" stuff
For those really interested in knowing what and where data is being stored on their drive:
WhatSize - my personal recommendation
DiskInventoryX - the free alternative
Turn off Time Machine. Remove snapshots.
Time Machine Snapshots
Open the Terminal in the Utilities folder and enter or paste the appropriate command line. Press RETURN and enter your admin password when prompted. It will not be echoed. Press RETURN again.
To turn them ON: sudo tmutil enablelocal
To turn them OFF: sudo tmutil disablelocal
Note that turning them OFF will also delete all existing snapshots.
For more about snapshots see: OS X Mountain Lion- About local snapshots.