Disk Almost Full
Apple macOS
Severity: ModerateWhat Does This Error Mean?
When macOS shows a 'Your disk is almost full' warning, your Mac's internal storage is running dangerously low. macOS needs free disk space not just for files, but for system operations, virtual memory, software updates, and temporary files. When the disk fills up, your Mac slows down significantly, apps start crashing, and eventually macOS may refuse to start. You need to delete or move files to free space.
Affected Models
- MacBook Air
- MacBook Pro
- iMac
- Mac Mini
- Mac Pro
- Mac Studio
Common Causes
- Photos and videos have accumulated over the years and are filling the internal drive
- Time Machine local snapshots are taking up large amounts of space
- App cache files, log files, and system temp files have built up
- Large downloads or installer files are sitting in the Downloads folder unused
- iOS device backups created by Finder or iTunes are stored on the Mac's internal drive
How to Fix It
-
Use macOS built-in storage management. Go to Apple menu > About This Mac > More Info > Storage > Manage. Review recommendations like 'Optimise Storage,' 'Empty Trash Automatically,' and 'Reduce Clutter.'
The Optimise Storage option automatically moves older photos to iCloud and keeps only recent files on the Mac, which can free up gigabytes quickly.
-
Delete large files you no longer need. In the Storage Management window, click 'Documents' on the left, then sort by size to see the largest files. Delete any you no longer need.
Downloads folders often contain large installer files and downloads that were never cleaned up. Check ~/Downloads first.
-
Remove old iPhone and iPad backups. Open Finder, click your iPhone or iPad in the sidebar under Locations, then click Manage Backups. Delete old backups you no longer need.
A single iPhone backup can be 10–50 GB. Old backups from previous devices are safe to delete.
-
Clear app caches. Open Finder, press Command + Shift + G, type ~/Library/Caches/ and press Enter. Select all folders inside and delete them. Empty the Trash.
App caches rebuild automatically. Clearing them can recover several gigabytes. Some apps like browsers accumulate large caches over time.
-
Move photos and videos to an external drive or iCloud Photos. If your photo library is large, consider enabling iCloud Photos (Settings > your name > iCloud > Photos) and choosing 'Optimize Mac Storage.'
A large photo library is often the single biggest user of storage. Moving it to iCloud or an external drive solves the space problem long-term.
When to Call a Professional
If you have deleted everything you can and still cannot free enough space, a technician can help identify hidden large files and system caches. For MacBooks where the internal storage cannot be upgraded, an external drive for files and photos is the long-term solution.
Frequently Asked Questions
How much free space does my Mac need to run well?
Apple recommends keeping at least 10–15% of your drive free. For practical purposes, aim for at least 20–30 GB free on a modern Mac. macOS uses free space for virtual memory (swap), temporary files, and update downloads. Belowe 10 GB free, performance noticeably degrades. Below 5 GB, the Mac can become unstable.
What are Time Machine local snapshots and can I delete them?
When your Time Machine backup drive is not connected, macOS stores temporary backups called local snapshots on your internal drive. They are automatically deleted when you need the space, but you can manually delete them by opening Terminal and typing: tmutil deletelocalsnapshots / — this frees space immediately.
My Mac says I have 5 GB free but I cannot find what is using the space.
Hidden system files and caches can consume significant space without appearing in normal file searches. Download DaisyDisk or GrandPerspective (both free) — they visualize exactly what is using your disk space, including hidden files. This usually reveals the culprit quickly, whether it is a huge cache, a log file, or a virtual machine disk image.