The Mac “Startup Disk Almost Full” Message and How to Fix It

Feb 6, 2016 - 31 Comments

Mac Startup disk is almost full error message, here is how to fix it

Many Mac users will inevitably see the “Your startup disk almost full” error message show up in OS X, with a vague note to delete some files in order to make more space available on the Mac. While you can disregard the message for a little while, it will usually come back again shortly, and often soon after the startup disk will actually fill up and start causing problems in Mac OS X. Thus, if you see the “Your startup disk is almost full” error message in Mac OS X, you should address the issue before it becomes a problem.

We’ll cover some easy tips on how to quickly figure out what’s taking up the disk space on the Mac, as well as how to clear out storage capacity in order to resolve an almost full Mac.


It’s good practice to start a manual backup of the Mac with Time Machine before removing anything, this insures that if you accidentally delete the wrong thing you can get it back. As always, don’t delete files if you do not know what they are used for!

1: Get an Overview of What’s Eating Up Mac Startup Disk Space

Mac users can quickly see what’s taking up disk space through the system Storage summary, this can help lead you on the right path and give you an idea of what’s going on and where to look.

  1. Open the  Apple menu and go to “About This Mac”
  2. Choose the “Storage” tab (older versions of OS X need to click on ‘More Info’ before the Storage tab appears)
  3. Review the storage usage to see what is eating up space and where you can focus your initial efforts on reclaiming some storage capacity

See what is using Disk Storage on a Mac startup disk

You’ll often see things that are immediately actionable in this list. Perhaps the “Backups” section is taking up many GB of space from locally stored iDevice backup files going back to the year 1400 BCE, you can delete old iPhone and iPad backups from iTunes easily and safely, just be sure you keep recent backups of devices, or use iCloud.

Sometimes you’ll discover your disk space has vanished to files you want to keep, however. A common example is discovering that “Photos” or “Movies” takes up many GB of local disk space but you don’t want to delete those files for obvious reasons. In those cases, you may want to offload them to an external hard drive for backups, a 5TB external drive on Amazon is affordable and will offer an abundant of disk space for such purposes.

Finally, many users discover that Other is taking up a fair amount of storage, this is usually stuff like downloads, caches, and whatever else doesn’t fall into the obvious media classifications. You can learn more about the “Other” storage space in Mac OS X and how to clear it out here.

2: Use Finder Search to Track Down Large Files

Did you know OS X can help you locate files with large sizes? Yes indeed, and using the Mac Search feature to find large files makes quick work of locating and deleting junk that is no longer needed but takes up space anyway. This is easy to use and quite helpful for remedying the “startup disk almost full” error message, here’s what you’ll want to do:

  1. Go to any folder within the Mac Finder if you haven’t done so already, then hit Command+F to bring up the Finder Search feature
  2. Change the search parameters to “This Mac”, then choose “File Size” as the primary search operator
  3. Choose “is greater than” as the secondary search operator, then pick a file size to narrow large files by (for example, 1 GB, or 500 MB)

Finding large file size files in Mac OS X search can help clear out startup disk that is full

You can trash items directly from this search window by dragging them into the Trash or by hitting Command+Delete.

You’ll need to use your own discretion to determine whether or not you can delete some of the large files and items that turn up in the file size search, but don’t be surprised to come across large applications in OS X (you can delete most large apps if you don’t use them or need them), large .ipa files from iOS app backups, large disk image .dmg files, zip archives, and other items.

3: Investigate & Clear the Downloads Folder

The user Downloads folder can quickly accumulate all sorts of stuff you already used, no longer need, or is just outright unnecessary. This is often a primary location where the aforementioned large files accumulate over time as things are downloaded, installed, used, and then not removed. Sorting the directory in List view by File Size is often quite helpful in narrowing down the bloat:

Find large files in the downloads folder to delete

Again, user discretion is going to be necessary to determine if you can or can’t delete stuff in the Downloads folder, so if something is important or gets a lot of use you won’t want to remove it, whereas old combo updates or disk images and zip archives that have been used or extracted already are often save to get rid of.

4: Empty the Trash to Actually Delete the Files

Empty the Trash if you haven’t done so already. This may sound obvious to some users, but it’s an often overlooked step. Just moving something to the trash doesn’t actually delete it, you have to empty the Trash, and the Trash can easily become a receptacle to the large files you trashed but haven’t actually removed yet.

Empty the Trash on a Mac

Right-clicking (or a control+click) on the Trash icon and choosing “Empty Trash” is all that’s needed here.

5: Restart the Mac, then Check Storage Again

After you’ve cleared out some files and emptied the Trash, you should reboot the Mac. This is particularly true if it has been a while since the Mac has been restarted, as simply rebooting can often free up quite a bit of disk space by clearing out temporary items and the /private/var/ cache folders that can slowly accumulate to clutter up a drive. Rebooting also has the benefit of clearing out virtual memory, which takes up disk space, and sleep image files.

Restart a Mac

Go to the  Apple menu and choose “Restart”, when the Mac boots back up you can return back to the  Apple menu and choose “About This Mac” and the Storage tab to again review what your disk situation is like, chances are good at this point you will have tackled the space hogs and storage waste to do away with the “full disk” alert message on the Mac.

Still out of startup disk space? Start the process over again, you’ll need to remove more files, or you can try some of the other tips mentioned below.

More Tips for Freeing Up Storage Space on a Full Mac Disk

Something else to keep in mind that once you get that “startup disk almost full” error message on a Mac, the computer is going to be struggling to perform simple tasks like using virtual memory, downloading app updates, handling Photos and iCloud data, and much more, once it’s at that point the Mac will actually start running slower than it should be since OS X becomes occupied with trying to maintain itself given the storage constraints.

If you followed the above tips, you should be good to go at this point, but ultimately if you’re continuously running out of disk space you may need to upgrade the hard drive on the Mac in question, or at least get a large external drive to offload large files onto.

Have any other tips for tackling a full or almost full Mac startup disk? Let us know in the comments.

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Posted by: Paul Horowitz in Mac OS X, Tips & Tricks, Troubleshooting

31 Comments

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  1. Carl Mobic says:

    When buying a new Mac or iPhone, I highly recommend buying a LARGER storage capacity then you initially think you will need. You will thank yourself later as you avoid this issue, at least early in the shelf life of the hardware. For Mac, get at least a 256GB drive, if not 512GB or 1TB. Apple should default all Macs to 512GB and above for internal storage, this is 2016 not 2001.

    Apple is notoriously stingy with storage capacity and charges a fortune for each upgrade, but again, think of the future. How long will you have your Mac? 4 years? Longer? Pay the extra $200-$500 for the greater disk space, you will be glad you did. Same thing with iPhone, the 16GB model should be gone for good, it’s a farce that Apple still sells it and basically forces everyone into the larger model. They should be 64GB, 128GB, and 256 GB iPhones from here on out.

    Remember: Always get the bigger model than you think you’ll need!

    • Zelda says:

      I agree with always buying the capacity size larger than you think you’ll need, since Macs (and iPhones) can’t be upgraded later it’s the best way to future proof your device. Go for the SSD if it’s optional, and max out the RAM too on a Mac when possible. Costs a bit more but for Macs in particular you’ll be glad you did over time. And many Macs still cruise great for many years, I think a 5+ year lifespan and often longer is not unusual, depending on usage. For web and word processing, no problem. For professionals it may be shorter, but that’s always the way things are.

      • Teachermanret says:

        Couldn’t agree more. Back in mid 2014 our need for a bigger screen for genealogy (eyes aren’t what they were), we decided a 27″ iMac would be the thing. So off to the store and had a play with ancestry.co.uk. Wow! What a difference that made. So we finally specked the iMac with 16gb ram, 3tb fusion drive and 4gb video. Paradise! It wasn’t long before we added an extra 16gb to max out at 32gb ram. Note – this extra ram did make a real difference, not just imaginary.

        So yes, go for the biggest drive, the most video ram etc that you can. It really will make a big difference.

        A few weeks later we upgraded our tiny Netgear NAS to a much heftier model 314 with 4 X 4 gig WD red drives. So no trouble with backups. Bliss.

  2. yyz guy says:

    No mention of the open source Disk Inventory X ?

    http://www.derlien.com/index.html

    I’d use that before anything mentioned in this article.

  3. Teachermanret says:

    Re last message about WD red drives. I meant 4 X 4 Tb drives. 16 Tb in all configured as Raid 5

  4. Di Keller says:

    Well I just did that trashed around 200gb of movies and they just moved to other ???

  5. Michael Rosenthal says:

    There’s a sweet little utility that I’ve run on every new Mac and whenever upgrading the OS, Monolingual. It’s free and it frees up about 1.5 GB of storage with its first run by removing the localization languages hidden in OS X and many apps. If you never plan to use your machine in more than your native language, you might as well remove Russian, Chinese, Thai, Korean, etc. You can always reinstall them if needed later with a reinstall of the OS. If you install apps very often you should run it every month or two to remove newly introduced localization languages.

  6. Dr.No says:

    When RAM and hard disk sizes first became a percentage average of predicting use,the computer was all but revealed.The boot lid speed boasts are those which act to use hi class gaming graphics where Gpu number crunching is by no means a passable imaginary thing as you do have to build the database and prime the data too programme the said info as those streams that become many protocols for video programming metadata into the simple single sets you could class as professional,or even economically commercial,as cycle remains to be with this thing that a Pentium four long ago proved of no worth to line Syncro follow words for info as intellect gatherers of knowing acting as agents of use!where you have sync he’d into family personal computers and zoom includes ray dot enforcement scandals of approach you for what is known not a be or do? That cat club sale?

  7. archangel says:

    there is no ‘storage’ tab on Mavericks under ‘more info”

    Now what?

  8. Valtteri says:

    ”GrandPerspective” is a cool app to check what things are using the most storage!

  9. Darwufche says:

    What constitutes “Other”? It is the largest segment on my 500gb drive.
    Also, I backup to external drive, so why is there a significant amount of “Backups” on the startup?

    • Don Nguyen says:

      If you read the article, the Other storage space is mentioned, and a link to details about the Other storage is provided.

      • Darwufche says:

        Thanks Don.
        I did read but not very carefully, obviously. Links show there isn’t much to be done with it but something is better than nothing!

  10. Omni Disksweeper is what I use to help my customers track down what’s eating up storage space. I make it available via Self Service using Casper. It’s a small app, so it will usually be able to install on a full hard drive without using up too much additional space. It’s funny that when a lot of people see this warning, they’re clueless about what it means. They ask how to fix it, and I tell them that there’s only one solution to the problem. They must delete data. It’s that simple. For me the bare minimum storage is at least 500GB. That’s how I protect myself against running out of local storage. Some people opt for smaller storage because of price, but then they neglect to understand that all those photos, videos, downloads, etc. use up storage.

  11. OddBall says:

    Besides pompous actor inns of what you do with loads of data is catabolic ally NOT this and where you have no idea but too conceded that it’s trash throw it away is the space saver,universe,mine,germ hunts diseases next week dog tars come back as man can also get ill,reals? Wake up you muppet!

  12. vdiv says:

    How do you all feel about CCleaner for Mac? I find it indispensable for Windows and Android, but development for MacOS on it has been slow.

  13. Sherwood says:

    I’m getting this message with 60+ GB of free space. /Users is a symlink to another disk on the systems. What’s up?

  14. Mothana says:

    my problem in other and i dont know how to remove it it take more than 70 GB i don’t have a lot of data please help me how move it.???
    Mothana

  15. Jim Murphy says:

    I have been pulling my hair out, because I have 500 GB on my iMac and was down to 3 GB. After a lot of false starts, I tried omni disk sweeper. It showed me 397 GB was taken up with cores files. Tonight, I figured out what they were: files that began the day I installed Smart PSS, an exterior security camera tied to my computer. It has been taking 1.4 GB chunks away from me every day for over a year. Now I just have to find out if I can delete them without any problem. But I thought this was interesting news. Hope it helps someone else.

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