It can be frustrating when you get a message on your Mac saying that the disk is full. This often happens even when it seems like there should be plenty of storage space left. There are a few common reasons why Macs display the disk full message even when space is available.
Your Mac’s Storage is Actually Full
The most straightforward reason your Mac says the disk is full is that the storage really is completely used up. Here are some things that can gradually eat up your spare disk space over time:
- Photos and video files from your iPhone, digital cameras, etc.
- Documents and spreadsheets for work and school
- Downloaded movies, TV shows, and other media
- App installers and software updates
- Cached files from web browsers and other apps
- Backups from Time Machine or other backup software
Media files like photos, videos, music, and downloads can easily accumulate to fill up hundreds of gigabytes without you realizing it. Documents and other work files can also take up a considerable amount of space.
Check the Storage section under About This Mac to see a detailed breakdown of what types of files are taking up space on your Mac. This can help identify where large chunks of disk space are being used.
The File System is Cluttered
Even with free space available, MacOS can sometimes struggle to save new files if the file system itself is cluttered with too many small files. This file system fragmentation can make it appear that the disk is full even when there is still free space.
Creating new files requires finding open blocks of storage space on the disk. If the disk has become fragmented with tons of small files scattered around, MacOS has a hard time locating open contiguous blocks large enough to accommodate new data.
This is a common problem for Macs that are several years old and have saved/deleted/overwritten many files over time. Defragmenting or reformatting the drive may help consolidate free space and reduce this file system clutter.
Old Files Haven’t Been Removed from Trash
When you delete files on your Mac, they get moved to the Trash folder but are not automatically removed from the disk itself. If you don’t periodically empty the Trash, those deleted files will continue taking up disk space.
Large individual files or many smaller deleted files over time can linger in the Trash and make storage appear full. Simply emptying the Trash should immediately free up the space those files are using.
Your Hard Drive is Nearly Full
MacOS requires a certain amount of free space on the startup drive specifically to operate properly. This disk space acts as a buffer for creating temporary files, saving system updates, etc.
If your startup drive has less than about 10-15% free storage, MacOS may generate the disk full warning even if the true free space is slightly more than 0 bytes. Try freeing up storage to get at least 10-15% available space.
Large System Files or Apps are Taking Up Space
Certain Mac system files and default apps can consume sizable chunks of your startup disk’s storage over time:
- System cache files – Cache files speed up performance by temporarily storing data from apps and web browsers. But they can grow large, sometimes over 100GB.
- Language translator data – The translation dictionaries for Mac’s built-in multi-language support can take up 20-30GB.
- Xcode files – Apple’s development tools are over 10GB.
- GarageBand loops and sounds – GarageBand’s default content can take up to 6GB.
Checking for these sprawling system apps and clearing out their cache/temporary files can potentially recover significant storage space.
iTunes Media Folder is Using Space
The iTunes Media folder, commonly located in your user account’s Music folder, contains all copies of imported songs, videos, app installers and other media. Even if you delete the original source files, the copies in the iTunes Media folder remain.
This folder can easily grow to tens or hundreds of gigabytes without you realizing it. Deleting the unused media files in this folder can clear up space.
Time Machine Snapshots are Not Deleted
If you use Time Machine to back up your Mac, each time a backup runs, it creates a “local snapshot” of your Mac’s data at that point in time. These snapshots allow Time Machine to incrementally backup only what changed since the prior snapshot.
But over time, these snapshots can really add up and take over significant storage space even though you don’t directly access them. Deleting old snapshots can therefore free up capacity.
External Drives are Also Full
One other possible reason your Mac may complain about being out of storage – external drives connected to your Mac could be completely full. This includes USB flash drives, Thunderbolt drives, SD cards, etc.
MacOS sees all connected drives as part of the same storage system. So if any external drive is completely out of space, the Mac may warn that the disk is full even if its own internal drive has free capacity.
Eject and remove any completely full external drives to isolate the issue to your Mac’s internal drive.
How to Free Up Disk Space on a Mac
Once you know why your Mac says its disk is full, what can you actually do to recover more available space? Here are some suggestions:
Empty the Trash
As mentioned previously, manually emptying your Trash will remove files that have accumulated there from deletions over time. In most cases, Trash files are safe to remove permanently.
Delete Cached and Temporary Files
Many apps create temporary working files and cached data to enhance performance. But these files often aren’t critical and can be safely deleted to regain storage capacity. The easiest way is to use a dedicated cache cleaner app for Mac.
Remove Unneeded Language Files
If you don’t use certain languages that MacOS supports, deleting their dictionary files under System Preferences > Keyboard > Input Sources can recover up to 20-30GB.
Uninstall Unneeded Apps
Take an inventory of any apps you no longer need or use infrequently. Completely uninstalling them will remove all their associated files and free up space.
Store Files in iCloud
Use the Optimize Storage option under Apple ID settings to offload infrequently used files to iCloud and keep them off your Mac’s drive until needed again.
Manually Delete Unneeded Files
Sort through your personal documents, media, downloads folders and trash anything you know you don’t need anymore. Also clear out duplicate files.
Reduce Photos/Video Library Size
Use the storage management options in Photos app to shrink the size of your library by removing duplicate/similar images, storing originals only in iCloud, or using compression.
Delete iOS Device Backups
If you back up multiple old iPhones/iPads to your Mac, delete their backups from iTunes or Finder to potentially recover huge amounts of storage capacity.
Reformat Drive and Reinstall macOS
Finally, as a last resort if your Mac’s disk is extremely cluttered, formatting/reinstalling can wipe the slate clean. Be sure to backup all your important files first!
Tips to Avoid Disk Full Problems
Here are some tips to avoid constantly seeing that irritating disk full message on your Mac:
- Regularly empty the Trash – don’t let deleted files pile up
- Manually clear out cached files once a month
- Delete unneeded apps you never use
- Use cloud storage for infrequently accessed documents and media
- Occasionally sort through and remove duplicates/unneeded files
- Monitor your storage usage under About This Mac > Storage
- Expand storage capacity if needed by upgrading internal SSD or adding external drive
Conclusion
A Mac warning about disk space being full is usually easily solvable by deleting unused files and clearing caches. But it can also indicate it’s time to upgrade your storage capacity if your needs have outgrown your available disk space. With a little disk cleaning and organizing of files, you can get back to a Mac with plenty of headroom before hitting any storage limits.