Every few months someone opens the Storage screen on a Mac and finds a category called System Data holding more space than their photos. There is no button next to it, which is what sends people looking for an app that promises to clean it. Most of that search is unnecessary, and some of it is risky.
Where the screen is
On macOS Ventura 13 and later, open System Settings from the Apple menu, click General in the sidebar, then click Storage. Apple documents this in its page on freeing up storage space on a Mac.
The bar at the top splits your drive by category and the list underneath gives recommendations. Read the bar first: if Documents or Photos is the big one, System Data is not your problem and the next sections do not apply.
What System Data holds
Apple is specific. The category covers files that do not fall into the others: files and data used by the system, including log files, caches, virtual memory files and other runtime system resources, plus temporary files, fonts, application support files and plug-ins.
And Apple says the part people most want to hear and least want to believe: you cannot manage the contents of this category. It is managed by macOS, and its size varies with the current state of the machine.
That is why there is no button. It is not hidden; it is not yours to empty.
What macOS clears by itself
When space is needed, Apple states that macOS clears caches and logs that are safe to delete, including temporary database files, interrupted downloads, staged macOS and app updates, and Safari website data.
The practical consequence is that a large System Data figure on a Mac with plenty of free space is not a problem waiting to happen. The system trims when it needs to, not when the number looks big to you.
What you can actually free
Apple's own Storage recommendations are the supported route: storing Desktop and Documents in iCloud Drive, storing photos and videos in iCloud Photos, keeping messages and attachments in iCloud, and optimising storage so only recently opened files stay on the Mac.
Two of the options there are worth singling out. Optimise Storage removes films and TV shows you have already watched. Empty Trash Automatically removes anything that has been in the Trash for more than thirty days, which matters because deleted files hold their space until the Trash empties.
Outside those, the genuinely recoverable items are the usual ones: downloads you forgot, disk images, old project folders, and virtual machines if you run any.
About the cleaner apps
The category exists because macOS needs those files. An app that empties it is deleting caches the system will rebuild, which frees space temporarily and costs performance while it rebuilds, or deleting something it should not. Apple's position is that the contents are managed by macOS, and that is the whole instruction.
If the screen looks different
Before Ventura the same information lived under the Apple menu, About This Mac, Storage, with a Manage button. The categories are the same; only the route changed.
If the Mac in question is old enough that storage is one of several complaints, the more useful question is how much longer it gets macOS at all. Which Macs the current macOS still supports answers that with Apple's own list.
Last updated October 4, 2026