Clearing caches is the standard advice when a Mac runs out of space, and mostly it is good advice. Cache files exist to be regenerated. Deleting them costs you one slightly slower app launch and nothing else.
But “clear your caches” gets repeated without the two exceptions, and both of them destroy something you cannot get back.
1. /System/Library/Caches
This holds kernel and system caches. Deleting its contents can leave a Mac that will not boot.
The trap is the name. There are three folders on macOS with “Caches” in the path, and they are not interchangeable:
• ~/Library/Caches — your user application cache. Safe, and designed to refill.
• /Library/Caches — system-wide cache. Usually safe to thin selectively, may need an admin password, and you should only remove folders you recognise.
• /System/Library/Caches — protected system cache. Never a cleanup target.
A guide that says “go to Library/Caches and delete everything” is ambiguous about which of the three it means. Assume it means the first, and read the full path before you delete anything.
2. ~/Library/Containers
Despite the name, this is not cache at all. It holds the live working data of every sandboxed app on the Mac, including your Notes database. Deleting a container destroys real user data, not regenerable files.
This one catches people because it sits directly alongside ~/Library/Caches in the same folder, and it is usually large. Size is not a signal that something is junk.
Three more worth leaving alone
Swap files, sleep images and app language packs. Cleaning tools sometimes remove these because they inflate the headline number of gigabytes “freed”. What you actually get is slow wake-from-sleep, or apps that crash on launch, in exchange for a couple of gigabytes.
What is safe, and how to do it
The contents of ~/Library/Caches. The contents, not the folders themselves, since some apps expect their folder to exist.
1 Quit every app you can. A running app holds its cache files open and will rewrite them immediately.
2 In Finder choose Go > Go to Folder (Shift-Cmd-G).
3 Type ~/Library/Caches and press Return.
4 Sort by size. A handful of folders account for almost everything, so there is no reason to work through hundreds of small ones.
5 Delete what is inside the large ones.
6 Empty the Trash. Nothing is freed until you do.
On one reference Mac, application caches held 28.5 GB, with Chrome’s cache alone accounting for 13.5 GB of that. That is the cache only, not the browser profile holding your bookmarks and logins, which should never be deleted.
Browser caches are frequently the single largest item. Clear them from inside the browser rather than from Finder: Chrome uses Command-Shift-Delete, Firefox uses Settings > Privacy & Security > Clear Data, and Safari keeps its cache in a sandboxed container, so it is emptied from the Develop menu.
If you would rather see the sizes first
The reason people delete the wrong folder is that Finder shows names, not sizes, and gives no indication which are safe. If you want to clear cache on a Mac with the numbers in front of you, Broomkit groups application caches as a single reclaimable category and shows the gigabyte total per source before anything moves, and it will not offer you either of the two folders above.
Whatever you use, the rule holds: read the full path before deleting, and prefer moving files to the Trash over an outright delete, so a mistake stays reversible for a few days.
Disclosure: the author develops Broomkit, one of the tools mentioned.
