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The temp folder macOS never mentions, and why it is 2 GB

Every app writes to a per user temp folder with an unreadable name. What is in it, when macOS clears it, and why deleting it by hand is a bad idea.

5 min read

If you have ever run a size tool as an administrator and seen a path like /private/var/folders/8x/qk_9m... near the top of the list, this is what it is. It is not malware and it is not a bug. It is where your Mac puts temporary files, and the unreadable name is deliberate.

What is actually in it

Each user gets a private temp area, split into two parts:

  • A T folder. This is what $TMPDIR points at. Apps write scratch files here and are supposed to clean up after themselves. Many do not.
  • A C folder. Per user caches, including the compiled shader and dynamic linker caches macOS builds for speed.
echo $TMPDIR
du -sh $TMPDIR ${TMPDIR%/T/}/C 2>/dev/null

That prints your own two folders rather than every user's. If the C side is the large one, that is macOS's own caching and it will rebuild whatever you remove. If the T side is large, some application is leaving scratch files behind, and the folder names inside usually say which.

When macOS clears it, and when it does not

Temporary items are cleaned on a schedule and on restart, and a Mac that has been awake for two months has had far fewer of those opportunities than one that reboots weekly. If this folder is large and you cannot remember your last restart, the restart is the fix and it costs nothing.

The other case is a specific application writing gigabytes and never cleaning up: video exports, virtual machines and package builds are the usual sources. Those are worth chasing to the app rather than deleting in place, because the same files will be back next week.

Why not to delete it by hand

Running apps hold open files in there right now. Removing the folder underneath a running app is how you get a spinning beachball, a lost document, or an app that will not launch until the next reboot. macOS recreates the structure, but the app that was using it does not find out gracefully.

The safe sequence is: restart the Mac, then measure again. If it is still large after a restart, look at what is inside and deal with the application responsible.

Where this fits

On most Macs this folder is a footnote next to the real consumers. It is worth knowing about mainly so that you can recognise it and move on: it is one of the things counted in the System Data bucket, along with caches and snapshots, and it is rarely where a full disk is hiding.

Common questions

What is /private/var/folders on a Mac?

It is the per user temporary and cache area macOS creates, with a randomly named folder per user. The T folder inside it is what $TMPDIR points at, and the C folder holds system caches such as compiled shader and linker caches.

Is it safe to delete /private/var/folders?

Not while apps are running, because they hold open files in there. Restarting the Mac clears temporary items safely, which is the correct way to do it. If it is still large after a restart, an application is leaving files behind and that is what to investigate.

How big should the temp folder be on a Mac?

There is no fixed size. It depends on what has run since the last restart. On a working Mac measured in September 2026 it was 1.9 GB, which is unremarkable. Several tens of gigabytes usually means one application is not cleaning up.

Does restarting a Mac clear temporary files?

Yes, that is part of what a restart does, and it is why a Mac that has not been restarted in months accumulates more in this folder. It is the safest way to clear it and needs no third party tool.

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