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How to free up space on a MacBook Air

The MacBook Air is a wonderful machine with one recurring frustration: the base SSD. A 128 GB or 256 GB drive fills faster than anyone expects, and because the storage is soldered to the logic board there is no upgrade path. The fix is a disciplined cleanup plus a couple of habits. This guide covers both, in the order that returns the most space soonest.

Updated 2026-08-02 · Written by the CleanerMac team · macOS 13–15 tested

Why the Air fills up so quickly

Three things conspire. macOS itself, with its recovery volume and system data, takes a meaningful bite before you install anything. Time Machine keeps hourly local snapshots on the internal disk whenever your backup drive is not connected. And iCloud Drive, Photos and Messages sync everything down locally by default unless you explicitly tell them not to.

On top of that, macOS wants roughly 10–15% of the volume free to work comfortably — for swap, temporary files and updates. On a 256 GB Air that is 25–38 GB you cannot really use. The practical capacity is smaller than the label suggests, which is why the Air needs more active management than a 1 TB Pro.

Start with an honest measurement

Open Terminal and run df -h /. The Avail column is the real number; Finder and the Storage pane both include purgeable space and will flatter you.

Then run du -sh ~/* | sort -h followed by du -sh ~/Library/* | sort -h. Two commands, two minutes, and you will almost certainly have found your culprit. Also open Apple menu → System Settings → General → Storage for the category view and Apple's four built-in recommendations, which are worth enabling regardless.

Step 1 — Thin Time Machine local snapshots

This is consistently the biggest and least-known win on a MacBook Air, precisely because Airs travel and their backup drives sit at home.

Check what you have with tmutil listlocalsnapshots /, then reclaim with sudo tmutil thinlocalsnapshots / 999999999999 4. The long number is a byte target meaning “as much as possible”, and 4 is the highest urgency level. Backups on your external drive are not affected. Re-run df -h / to see the difference. Background on why this works is in our purgeable space guide.

Step 2 — Turn on Optimise Mac Storage properly

On a small SSD, iCloud offloading is the difference between comfortable and constantly full — but only if you configure it and then verify it.

• Photos → Settings → iCloud → Optimise Mac Storage. Full-resolution originals stay in iCloud; local thumbnails are tiny.
• Messages → Settings → iMessage → Enable Messages in iCloud. Attachments are the hidden weight here.
• Desktop & Documents → System Settings → Apple ID → iCloud Drive → Options. Convenient, but be aware that files you open regularly stay local.
• Optimise Mac Storage in the Storage pane, which lets macOS evict watched TV purchases and old email attachments.

Important caveat: enabling these does not free space instantly. macOS evicts local copies gradually and under pressure. Check df -h / a day later, not a minute later.

Step 3 — Delete old iOS backups

An iPhone backup on a 256 GB Air is a serious proportion of the disk. Look in ~/Library/Application Support/MobileSync/Backup, check modification dates, and remove anything for a device you no longer own or a backup you have already restored. Going forward, back your iPhone up to iCloud rather than to a MacBook Air — the Air is the wrong machine for that job.

Step 4 — Caches, Downloads and the Trash

1. Empty Downloads. Sort by size and delete every .dmg, .pkg and extracted archive.
2. Quit apps, then empty the contents of their folders in ~/Library/Caches. Browsers are usually the largest — each has a built-in Clear Browsing Data option that is safer than deleting by hand. Full details in how to clear cache on Mac.
3. Empty the Trash, plus Photos' Recently Deleted and Mail's Trash mailbox.

Step 5 — Find the large and the duplicated

Use Command-F in Finder with a File Size greater than 1 GB criterion, or find ~ -type f -size +1G 2>/dev/null in Terminal. Video, virtual machine images and old project archives dominate. Our find large files on Mac guide covers the methods in detail, and removing duplicate files handles the copies of the same file scattered across folders — a common find on a machine that has been through several migrations.

Step 6 — Uninstall properly, not by dragging

On a small disk, app leftovers matter. Dragging an app to the Trash leaves its caches, containers, preferences and Application Support data behind. Follow how to completely uninstall apps on Mac, and be particularly thorough with Adobe apps, Docker, Xcode and anything installed via a custom installer.

What to move off the machine entirely

A fast external SSD over USB-C or Thunderbolt is inexpensive and turns the storage problem into a non-issue for archival content. Keep the internal drive for what you are working on this month.

Keeping a small SSD healthy long term

Set a target of 15% free and check it monthly with df -h /. Turn on Empty Trash Automatically in the Storage settings. Connect your Time Machine drive on a regular rhythm so snapshots flush rather than accumulate. Clear Downloads by habit. Uninstall properly. And if the Air has also started feeling slow, remember that a nearly full disk is one of the main causes — see how to speed up a slow Mac.

If you would rather not repeat this by hand, CleanerMac runs the same pass in one scan: snapshots, caches, backups, large files, duplicates and app leftovers, each labelled in plain language, with your own files routed through the Trash so those removals stay recoverable. It is a small native menu-bar app, works on Apple silicon and Intel, and everything happens on your Mac. For the general version of this guide across all Mac models, see how to free up space on Mac.

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