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:

enter image description here

enter image description here

enter image description here

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, 2016 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, 2016 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, 2016 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, 2016 at 11:37
  • Not a duplicate. See the answer below. @Mark
    – CSstudent
    Feb 17, 2016 at 12:33

1 Answer 1


/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, 2017 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, 2017 at 3:14
  • What came into their mind? Things that are in /private actually belong in /usr/local, they don't? Well, I guess there is no turning back. Oct 6, 2022 at 18:33
  • There's nothing incorrect about this answer, but IMO it does not address the actual question. Traditional Unix/Linux/BSD systems have actual directories at /var, /etc, and /tmp -- but on macOS these are just symlinks to equivalent directories inside /private. Your answer nicely explains what's in there and why that data exists, but it does not explain what /private itself is for or why it exists. The reader is left wondering: What is the value of diverging from the norm?
    – JakeRobb
    Nov 2, 2023 at 17:06
  • I found the answer here -- in the NeXTSTEP days, it was a way to store those directories locally in a netboot scenario.
    – JakeRobb
    Nov 2, 2023 at 17:12

Not the answer you're looking for? Browse other questions tagged .