You're right that macOS has per-user temp (and cache) dirs under /private/var/folders/ (since 10.5), but it still has traditional shared /tmp (via the /private/

You're right that macOS has per-user temp (and cache) dirs under /private/var/folders/ (since 10.5), but it still has traditional shared /tmp (via the /private/tmp symlink) since not everything respects the per-user temp dir. https://magnusviri.com/what-is-var-folders.html https://magnusviri.com/what-is-var-folders.html That's not the reason for /private though. Rather, /private is a holdover from NeXTSTEP days which could mount the OS via NFS (NetBoot), and where /private was local to the machine: "Each NetBoot client will share the server's root file system, but there are several administrative files (such as the NetInfo database, log files, and the swapfile) that must be unique to each client. The server must have a separate directory tree for each client, which the client mounts on its own /private directory during startup. This lets a client keep its own files separate from those of other clients." https://www.nextcomputers.org/files/manuals/nsa/13_NetBoot.htmld/index.html#13ep https://www.nextcomputers.org/files/manuals/nsa/13_NetBoot.h...