Two buckets, one confusion: iCloud storage vs. the disk in your Mac
Your Mac says the disk is full. Your iPhone says iCloud is full. You delete files from iCloud, but your Mac still has no space. You upgrade iCloud storage, but your Mac's disk doesn't budge. Sound familiar?
The confusion is understandable: iCloud storage and Mac storage are two separate things that overlap just enough to be misleading. Here's how they actually work.
The short version
| Mac storage | iCloud storage | |
|---|---|---|
| What it is | The physical disk inside your Mac (SSD) | Cloud storage on Apple's servers |
| Capacity | Fixed — whatever your Mac shipped with | Starts at 5 GB free; expandable with a paid plan |
| What lives there | macOS, apps, local files, caches | iCloud Drive files, Photos, backups, Messages, Mail |
| When it's full | Mac slows down, apps crash, updates fail | Devices stop backing up, syncing pauses |
Where they overlap — and where they don't
The overlap happens with iCloud-synced content: iCloud Drive files, Photos, Messages, and Safari data. When these are synced, a copy exists both in iCloud and on your Mac's disk. That's why the same file can count against both storage pools at once.
Things that are only on your Mac and never touch iCloud:
- Apps you installed
- App caches and temporary files
- System Data (caches, logs, snapshots)
- Local-only files outside iCloud Drive folders
Things that are only in iCloud and don't take Mac space (when Optimize Mac Storage is on):
- Photos and videos offloaded from your library
- iCloud Drive files with the cloud download icon
- Device backups from your iPhone/iPad
Why freeing iCloud doesn't free your Mac
If you delete old iPhone backups from iCloud, that frees iCloud storage — but those backups were never stored on your Mac's disk, so your local disk doesn't change.
Conversely, if you clear app caches and system data from your Mac, that frees local disk space — but those files were never in iCloud, so your iCloud storage stays the same.
The only actions that free both simultaneously are deleting iCloud-synced content: removing photos from your iCloud-connected library, deleting files from iCloud Drive, or clearing Messages with Messages in iCloud enabled.
What "Optimize Mac Storage" does in this context
When Optimize Mac Storage is enabled (in iCloud settings or in Photos settings), macOS offloads full-resolution files to iCloud and keeps only lightweight placeholders on your disk. This frees Mac storage without freeing iCloud storage — the originals stay in the cloud.
Think of it as shifting the weight from your Mac's bucket to iCloud's bucket. If your iCloud is already full, Optimize Mac Storage can't offload anything new until you free cloud space first.
Common scenarios, decoded
"My Mac disk is full but iCloud has plenty of room"
Your disk is full of local-only content: app caches, System Data, apps themselves, or files stored outside iCloud Drive. Turn on Optimize Mac Storage for iCloud Drive and Photos to push synced content to the cloud. Then clean caches and System Data to free the rest.
"iCloud is full but my Mac has free space"
Your iCloud is packed with device backups, photos, or iCloud Drive files. Check System Settings → Apple ID → iCloud → Manage to see the breakdown. iPhone backups and photos are usually the biggest iCloud consumers.
"Both are full"
Start with the Mac side — clear caches and system junk to make room, then turn on Optimize Mac Storage so the Mac can offload synced files. For iCloud, review device backups and large iCloud Drive files.
Free up your Mac side of the equation
Gigatidy cleans the local-only junk — caches, logs, app leftovers — that iCloud can't help with. Your photos and documents stay untouched.
Meet Gigatidy →FAQ
Does upgrading iCloud storage free space on my Mac?
Not directly. A larger iCloud plan gives you more cloud room, which lets Optimize Mac Storage offload more files — but only if the feature is turned on. Without it, upgrading iCloud has no effect on your Mac's disk.
If I delete a file from iCloud Drive, is it also deleted from my Mac?
Yes — iCloud Drive syncs both ways. Deleting a file from iCloud.com or another device removes it from your Mac too (it goes to the iCloud Recently Deleted folder for 30 days). Be careful with deletions.
Do app caches count against iCloud storage?
No. App caches, System Data, and temporary files are entirely local to your Mac. They never sync to iCloud and only consume disk space on the machine itself.