If an M4 Mac mini says the disk is almost full, open the Apple menu, About This Mac, Storage and look at what is taking the space. The internal drive cannot be upgraded later, so use Optimize Storage, empty the Trash, delete old downloads and local Time Machine snapshots, and move large folders to an external Thunderbolt or USB-C drive, which a Mac mini's ports suit well.
Differential
Likely causes of “Apple Mac mini M4 storage is full or nearly full”, and how to tell them apart
- 1
Large folders of media and downloads
What separates it Storage lists Documents, Movies or Downloads as the biggest items
How to confirm Move them to an external drive or iCloud
- 2
System Data that keeps growing
What separates it System Data is tens of gigabytes or stuck on Calculating
How to confirm Delete local Time Machine snapshots and restart; install the latest macOS
- 3
Apps and caches
What separates it Applications or caches are large
How to confirm Remove apps you do not use and clear caches with the app's own settings
- 4
A small internal drive
What separates it A 256 GB drive fills after macOS updates and a few apps
How to confirm Add an external SSD for files
- 5
Failed updates leaving snapshots
What separates it Updates fail for lack of space
How to confirm Free space first, then retry the update
Before you touch a setting
Record this first — changing settings destroys the evidence
- What the storage bar lists as biggest
- Whether System Data is large or calculating
- The drive size
- Whether Time Machine runs
Try in this order
0 of 5 completedSee what uses space
ReversibleOpen Apple menu, About This Mac, Storage, then Storage Settings.
Turn on Optimize Storage
ReversibleIn Storage Settings turn on the recommendations: store in iCloud, empty Trash automatically and reduce clutter.
Delete old downloads and installers
ReversibleOpen Downloads in Finder and remove old installers and disk images.
Clear local Time Machine snapshots
ReversibleUse Terminal's tmutil to list and remove local snapshots if System Data is large.
Add external storage
ReversibleUse an external SSD on a Thunderbolt port for projects and media.
Model-specific
What is true of this model and not of its siblings
- Internal storage
- The standard M4 Mac mini starts at 256 GB, and Apple sells larger configurations; the drive cannot be added to later.
- Other desktops
- The iMac and Mac Studio have the same Storage settings; the Mac Studio's internal storage is also fixed.
- A desk machine suits external storage
- A Mac mini stays plugged in, so a fast external SSD on a Thunderbolt port is an easy way to add space for media and projects.
- Other models this page answers
- These steps also fit the iMac 24-inch (M4).
Stop boundary
When this stops being a self-service repair
- !If space will not free up, back up and contact Apple Support
- !If updates keep failing, free 30 GB first
- !If the disk shows errors, run Disk Utility First Aid
Evidence ledger
Sources behind this answer
Checking storage, moving and deleting files, System Data, iCloud optimization and temporary space.
Free disk space as a cause of slowness.
Four Thunderbolt 4 ports, up to two external displays, camera, speakers, Ethernet and weight.
M4 and M4 Pro ports, HDMI, Ethernet, display support, speaker, Wi-Fi 6E and weight.
M2 Max and M2 Ultra ports, SDXC slot, HDMI, 10Gb Ethernet, display support, speaker and weight.
AppleCare+ service fees for Mac models: $49 to $99 for damaged screens or external enclosures and $149 to $299 for other accidental damage.
Exact questions
Common questions
Can I upgrade the SSD in an M4 Mac mini?+
No. Apple's Mac mini uses storage on the board, so choose the size when you buy or use an external drive.
Why does my Mac mini say System Data is calculating?+
Owners report this on macOS Tahoe. Restart, free a few gigabytes and let it finish; clearing snapshots helps.
Is an external SSD fast enough for a Mac mini?+
A Thunderbolt 4 or USB-C 10 Gb/s SSD is fast enough for most files and works well on a Mac mini.
What does Optimize Storage do on a Mac?+
It stores files in iCloud, removes watched Apple TV shows and old email attachments and empties the Trash on a schedule, which frees space without deleting your own documents.
Should I delete caches by hand to free space?+
No. Clear caches from inside the apps, and leave the Library folders alone; deleting the wrong files can break apps and macOS.