[micdaflip]

Over the past few months of using my MacBook Pro I've noticed that the available free space on my hard drive is slowly getting less and less. In Windows I have no problem recovering that space via third party software, but on my Mac I'm clueless.

Where does the free space go and why? Are there any Mactel products that will recover this space?

[Chuckit]

The space isn't disappearing. It's being used by something. A few possibilities:

• Virtual memory
• Caches
• Actual program files (e.g. e-mail)

The first is "recovered" every time the computer starts up, and you don't want to recover it before then. It will generally only grow up to a certain point and then stop. The second can be reclaimed with some third-party tools like Cocktail. The third can be reclaimed by deleting unwanted files. OmniDiskSweeper is useful for this — I freed up about 5 GB of files I'd forgotten about with DiskSweeper's help.

[Big Mac]

Yup.

[steve626]

I have noticed that sometimes my various Macintosh's (I have an iMacG3, iMacG5, and PowerBook G4, running 10.2.8, 10.4.6, and 10.3.9) have more space available after rebooting. This might be due to some housekeeping like the kind mentioned by Chuckit which is performed when the Mac starts up. I suspect the process is a bit different with different versions of OS X.

There is another possibility, although probably somewhat unlikely. If your disk's file system needs maintenance, running fsck or Disk Utility or Disk Warrior will sometimes result in more free space being "available."

Probably the most likely is just adding files over time. At work, I get scores of emails every day with attachments, the attachments really eat up space (powerpoint files, for instance). Other disk space eaters include iTunes and iPhoto, as each picture or music file takes up several megabytes. Be aware also that web browsers have caches that fill up and are emptied according to some sort of defined process within the browsers.