macOS Tahoe Storage settings never finishes calculating System Data (September 6, 2026)

What Storage settings does on macOS Tahoe

Storage settings is the pane a Mac user opens when the disk is full and they want to know why. On macOS Tahoe it often fails to answer. The System Data category calculates and keeps calculating, and the Photos section behaves the same way, so the screen stays busy indefinitely instead of resolving to a figure.

The reader report is the clearest statement of the symptom: "Several hours later it's still calculating. The same for the Photo section." The reader went on to wonder whether either section would ever complete. The author's own hedge in the same piece tells you how routine this is: he discusses the System Data category as it behaves "when it's able to complete calculating successfully".

This is not a crash and it is not data loss. It is a diagnostic tool that does not produce a diagnosis, at exactly the moment you need one.

Why System Data is unreadable even when it completes

Suppose the calculation does finish. You are then shown a single number for a category Apple defines as "the storage space used by all Apple and third-party files that don't belong to any more specific category". That is a definition by exclusion, and it tells you nothing about what to delete.

The author is blunt about where that leaves even an expert: "I still haven't a clue to the scope of what System Data includes, other than Apple's unforthcoming definition." On the documentation, his line is "Look for those answers in Apple's documentation and you'll be disappointed."

So the problem has two halves, and the second half is the more serious one. A pane that never finishes is a defect. A category that means nothing when it does finish is a documentation failure, and no software update will fix that on its own.

What is actually consuming the space

The same September 6, 2026 piece names the areas worth suspecting: QuickLook thumbnail caching, APFS snapshots and Finder Gallery view performance. Snapshots are singled out because of what they capture: "because they include almost every file in a volume, it's all too common for them to capture huge and ever-changing data such as virtual machines."

The mechanism behind that was documented four days earlier, in the September 2, 2026 explanation of caches and purging. The deleted service, subsystem com.apple.cache_delete, manages purgeable space by querying the caching services listed in /System/Library/CacheDelete. Purgeable space includes application disk caches such as Safari and Mail, QuickLook preview caches and Time Machine local snapshots.

Two details from that piece are worth carrying. Purging active QuickLook previews makes the Finder slower until the previews rebuild, so free space is bought with responsiveness. And purging happens harder than you might expect: "There are some occasions when, even though there's ample free space, multiple rounds of purging may be undertaken. One of the most obvious is when installing a macOS update."

What was published elsewhere that Sunday

Almost nothing, and that is worth stating rather than hiding. September 6, 2026 was a Sunday, and 9to5Mac published only two items that day, on Netflix games and on App Store revenue changes. Neither touches macOS, Mac bugs, updates or security.

So there is no competing macOS defect story for this date and no release to install. This storage piece is the only macOS defect reporting dated September 6, 2026, which is why it gets the whole post.

What you can do today

1. If Storage settings has been calculating System Data or Photos for hours, stop waiting and close it. On macOS Tahoe it may never finish, and leaving it open tells you nothing.

2. Use a third-party browsable storage analyser instead. The point is browsability: you want a tree you can walk down to the folder that is actually holding the space, not one number for a category defined as everything else. Expect to pay for a good one, and that cost is the workaround.

3. If you run virtual machines, move them onto a separate volume and exclude that volume from snapshots. Snapshots capture almost every file in a volume, and a virtual machine is a huge file that changes constantly, so it is the worst possible thing for a snapshot to hold.

4. Back up any inactive virtual machines separately, because excluding the volume from snapshots means excluding it from that safety net. This is a manual layout, and the manual part is the price.

5. Expect the Finder to feel slower for a while after a big space recovery. QuickLook previews get purged under pressure and have to be rebuilt, so sluggish previews after clearing space are expected rather than a new fault.

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