iCloud storage full and Mac storage full are different problems
The same message can mean two unrelated things. How to tell which one you have, and why fixing one does nothing for the other.
Two different messages, both saying storage is full, and the fixes have nothing in common. Buying iCloud space does not free your disk, and deleting files from your disk may not free iCloud space. Knowing which you have takes ten seconds.
Tell them apart
| Mac storage | iCloud storage | |
|---|---|---|
| Where to look | System Settings, General, Storage | System Settings, your name, iCloud |
| What it is | The physical drive in the Mac | The plan you pay Apple for |
| Fixed by | Deleting or moving files | Buying more, or deleting from iCloud |
| Typical size | 256 GB to 2 TB | 5 GB free, or a paid tier |
| Symptom | Apps fail to save, updates fail | Backups and syncing stop |
Why deleting files may not help iCloud
If a file is in iCloud Drive or Photos and you delete it on the Mac, it is deleted everywhere, which does free iCloud space, after the 30 day Recently Deleted period. If you instead remove the local download, the file stays in iCloud and only your Mac gets the space back. Those are two different actions and the menus sit next to each other.
Why buying iCloud storage may not help the Mac
More iCloud space lets syncing resume. It does not remove anything from your disk on its own, because files stay local until macOS evicts them or you remove the download. Turning on the optimise setting is what connects the two, and it is reactive rather than immediate.
The case where the answer is to buy
If your iPhone will not back up and your Mac has plenty of room, buy the storage. iCloud backups are the single most common reason the free 5 GB runs out, and no amount of cleaning your Mac changes that.
The case where the answer is to clean
If applications cannot save and updates fail, your disk is full and an iCloud plan will not touch it. The order to free 100 GB is the sequence, and how much free space a Mac needs sets the target.
What the money buys either way
Both are worth pricing honestly rather than reflexively, and iCloud storage against an external drive does exactly that, including the option of reclaiming what you already have, which is free.
Common questions
What is the difference between iCloud storage and Mac storage?
Mac storage is the physical drive in the machine. iCloud storage is the plan you pay Apple for. They are unrelated, and buying more of one does not free the other.
Will buying iCloud storage free up space on my Mac?
Not by itself. Files stay on the disk until macOS evicts them or you remove the download. Turning on Optimise Mac Storage connects the two, and it acts only when the disk is under pressure.
Why is my iCloud full when my Mac has space?
Usually device backups, which are the most common reason the free 5 GB runs out. That is an iCloud problem and cleaning the Mac does nothing for it.
Does deleting files from my Mac free iCloud space?
Only if the file is stored in iCloud and you delete it rather than removing the local download, and even then the space returns after the 30 day Recently Deleted period.