The 15 inch MacBook Air with the M4 chip starts with a modest base drive, and since the storage is built in and cannot be changed later, a message that the disk is almost full is solved by clearing, moving or archiving. Open the Apple menu, System Settings, General, Storage and let it calculate. The bar shows Applications, Documents, Photos, Messages, iCloud Drive and System Data. The Air is a lighter machine than the Pro and is often used for photos,
The checks in more detail
school work and light editing, so Photos, Messages attachments, Downloads and the Trash are the first places to look. Click the information button beside a category to see the biggest items, and the Recommendations at the top offer to store files in iCloud, optimize Apple TV downloads and empty the Trash automatically. Start with Messages, where years of photos and videos accumulate; use the Manage button to delete the largest attachments. Go through Downloads, where installers, disk images and zip files collect, and delete them.
In Photos, check whether the library is stored on the Mac in full and whether iCloud Photos with Optimize Mac Storage is on, which keeps small versions on the Mac and the originals in iCloud. Remove apps you no longer use by using Launchpad or the Applications folder. Delete old iOS backups, listed under General, Storage, iOS Files. For documents and projects, move large folders to an external SSD or a cloud service, and keep an archive. System Data can look large because of caches and local Time Machine snapshots, and a restart usually shrinks it.
Because the Air has no fan and a smaller drive, keep at least ten percent free so that macOS can swap memory and install updates. If you are always short, a fast external drive is cheaper than a repair, and buying more storage in a new Mac is the permanent answer. Check iCloud's own storage if you use it, since a full iCloud account stops Photos from syncing. Empty the Trash at the end, since deleted items still count until it is emptied. If the numbers still look wrong, contact Apple Support.
Differential
Likely causes of “Apple MacBook Air 15-inch (M4) storage is full or nearly full”, and how to tell them apart
- 1
Messages and Photos media
What separates it These categories are large
How to confirm Delete big attachments and use Optimize Mac Storage
- 2
Downloads and installers
What separates it Old files pile up
How to confirm Delete them
- 3
Old device backups
What separates it iOS Files is large
How to confirm Remove old backups
- 4
An unemptied Trash
What separates it Space does not return
How to confirm Empty the Trash
- 5
A small base drive
What separates it The drive is always nearly full
How to confirm Use an external SSD or the cloud
Before you touch a setting
Record this first — changing settings destroys the evidence
- The storage breakdown
- The largest category
- Whether iCloud Photos is on
- How much is free
Try in this order
0 of 6 completedOpen the storage view
ReversibleIn System Settings.
Clear Messages attachments
ReversibleThe largest ones.
Empty Downloads and the Trash
ReversibleBoth.
Turn on Optimize Mac Storage
ReversibleFor Photos.
Remove old backups
ReversibleAnd unused apps.
Restart
ReversibleTo refresh the figure.
Model-specific
What is true of this model and not of its siblings
- Fixed storage
- It cannot be changed.
- Messages
- Attachments add up.
Stop boundary
When this stops being a self-service repair
- !If the figures stay wrong after a restart, contact Apple Support
- !If you are always short, use an external drive or a larger Mac next time
- !Back up first
Evidence ledger
Sources behind this answer
Exact questions
Common questions
Can I upgrade the Air's storage later?+
No.
What does Optimize Mac Storage do?+
Keeps small versions of photos on the Mac.
How much space should I keep free?+
About ten percent.
Does the Trash count?+
Yes, until emptied.