Why does macOS and System Data storage keep fluctuating in Tahoe?

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Level 1

8 points

Why does macOS and System Data storage keep fluctuating in Tahoe?

On my MacBook Pro M3 Max, I’ve noticed that the reported sizes of macOS and System Data in System Settings > Storage keep changing significantly.

macOS size has ranged from ~25 GB to 26+ GB without visible updates.
System Data swings between ~30 GB and 60+ GB.
Is this normal background cleanup/indexing after the upgrade, or could something else be causing such large fluctuations?

MacBook Pro 16″, macOS 26.0

Posted on Sep 25, 2025 9:28 AM

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Answer 1

Sep 25, 2025 9:36 AM in response to _TaMee_

Those changes are all within the normal range. In particular, System Data is a catch-all category for files that macOS doesn't put in other categories (System Data used to be called 'Other').

Also, the information in System Settings > General > Storage is unfortunately not terribly reliable (for some users, System Data just shows 'Calculating...' without every settling on a value).

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Answer 2

_TaMee_ Author

Level 1

8 points

Sep 25, 2025 9:45 AM in response to neuroanatomist

For me too, it keeps on changing with every closing and reopening settings --> Storage. It shows Calculating for a while and then shows different numbers and those are all high...

It never happened until September 15th just before upgrade to Tahoe :(

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