I was running OmniDiskSweeper today, and I came across something called "Private" using 3.9GB. It is listed directly under the root directory along with Users, Library, System, and Applications, so I am assuming it is something included with OS X itself. I'm just curious about what this actually is, because I don't remember seeing this before. Here are some screenshots:

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Mid 2012 15 inch MacBook Pro running OS X 10.11.3 El Capitan

  • Have you tried googling some of the file names? the more unique the more chance of finding the cause.
    – MrU
    Feb 17 '16 at 9:34
  • @Mark I believe your proposed duplicate is more of a /private/tmp-related question, but ComputerScienceStudent's question here asks more of "what is /private for". Feb 17 '16 at 11:32
  • @Mark, "What's the “Private” directory in OS X for?" and "Why is /tmp a symlink to /private/tmp?" are not duplicate questions, not even possible duplicates IMPO. Feb 17 '16 at 11:35
  • The answer in the duplicate is an answer here - it could be expanded a bit but it is still the same answer
    – mmmmmm
    Feb 17 '16 at 11:37
  • Not a duplicate. See the answer below. @Mark
    – CSstudent
    Feb 17 '16 at 12:33

/private has been around for a loooooong time. Every Mac has it.

It is part of your Mac: the directory stores essential system files and caches, along with other databases that your system requires to operate.

I'll give a quick explanation contents of the folders /private/etc, /private/tmp, and /private/var, usually found in /private:


Data files for system use, configurations for various command line tools etc


System logs, mostly


More logs, databases for daemons, virtual memory swap file(s), sleep image etc.

In essence, deleting anything in this directory is probably not a good idea, save for a few files. If you do delete them however, some required essential files will get regenerated on startup.

It's probably a good idea to Google the exact full directory path of any system folders you intend to tinker with before actually beginning to experiment with stuff inside.

I hope this helps.

  • My app needs to store a file not accessible/readable by a regular user. Would /private/etc/myfile be a good place to store it?
    – OrangePot
    Dec 4 '17 at 20:31
  • @OrangePot I believe that /private is generally reserved for system use and probably shouldn't be used for concealing files from the user. You'd also need root access to write to /private. I'd recommend storing your files in /tmp, with root being the owner and permissions as 700 or rwx------ (only root can r/w/x) Dec 5 '17 at 3:14

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