How to fix the “Startup Disk Almost Full” error on Mac OS X [Troubleshooting Guide]

Basically the error message “Startup Disk Almost Full” on your Mac OS X is pretty accurate because that’s what exactly is happening to your computer. The startup disk is a partition where the operating system is installed and when it reaches 85% and above, performance may start to deteriorate and you may notice your Mac is slowing down by the day.

In this post, I will tackle this error message but instead of dwelling on the technical side of this issue like explaining why and how it happens, I will be dwelling more on how to get rid of fit and bring your Mac back to its optimum performance. I will show you how to free up some space on your computer so this error won’t be showing up every minute or so. Go through the steps below to know what to do.

But before we jump right into our troubleshooting, if you have other concerns with your Mac OS X, I suggest you visit our Mac OS X troubleshooting page for we will be supporting it. We will be publishing troubleshooting guides to help you fix issues with your computer so, take time browsing the page as we may already have published articles that are related to your concerns. If you need further assistance, however, you can always contact us by completing our computer issues questionnaire.

Ways to free up some space on Mac OS X with “Startup Disk Almost Full” error

The only remedy to a full hard disk is to delete some file to free up some space and that’s what we need to do to basically get rid of the “Startup Disk Almost Full” error on your Mac OS X. Again, instead of dwelling on the technical side of this issue, we will give you ways on how to remedy it. So, try to go through each step below.

Step 1: Visit the Download, Music and Movies folders and delete some files

Just like any other operating system, the OS X accumulates files and data over time but those files are actually not that huge compared to ones you intentionally download like movies and music tracks. This is the reason why you have to visit the Download, Music and Movies folders as they often harbor files that take up so much resources.

  • Download – this folder is the default destination of everything you downloaded from the Internet unless you change the destination manually. You may have downloaded files and programs before and have left them in that folder without being used anymore. Therefore, find those files and then delete them if you don’t need them anymore.
  • Music – as the name implies, it houses all your music tracks and depending on the music app you’re using, you may already have music tracks that have duplicates. I suggest you delete those you don’t play anymore and look for duplicates and get rid of them.
  • Movies – movie files nowadays, at least, use up 1GB of storage space not to mention those drama series in which one episode almost equals to a movie. I understand there are movies you want to watch over and over and there are those you cannot stand to watch the second time. Delete ones you don’t want to watch anymore and probably compress or archive ones that are left. Here’s how you archive your files:
  1. Press Ctrl + click the file you want to compress (recommended for movie files).
  2. Select, “Compress .”

This step alone can free up several gigs of storage depending on the number of files you have and those you deleted.

Step 2: It’s time to clean up the Photos library

Aside from your downloads, movies and music, files that take up so much space are photos. I understand many of them may hold a memory but there are, of course, shots you can live without. So, my advice to you is make a backup of photos you cannot afford to lose and I know it may be a pain to manually select them one by one but it all depends on you. I suggest you upload them in the cloud or make a backup to a flash drive and other external storage devices. Once you made a backup, delete everything that doesn’t matter to you anymore.

If you are into a more critical thing, then you should try deleting Photos cache which is created by the system. There is also the Faces cache which is created whenever you use Faces. These maybe just caches but they actually take up some space and if you can remove them safely, I suggest you do:

  1. Open Finder and navigate to your Photos library (normally, it’s in the Pictures folder).
  2. Ctrl+click your Photos library, and select “Show Package Contents.”
  3. Open resources, and then modelresource.

Step 3: Delete or remove applications you don’t use anymore

There are apps that are important to you, there are also those that you don’t need anymore. More often, large apps accumulate huge data so if you’re not using them anymore, they only take up storage space but are useless. It’s better to remove them and you can do so by clicking the Launchpad icon in the Dock and then holding down an app’s icon until all the icons begin to jiggle, then click an app’s delete button (X).

Dragging the app’s icon to the trash only deletes the icon but there could still be tons of leftovers and installation files left on the hard drive. That’s why you need to properly remove the app from your Mac OS X to make sure everything that needs to be deleted, gets deleted.

Step 4: Delete cache files on your Mac

Caches get generated when your Mac is running and the longer you use it, the more caches are created. After months of use, there may already be a few gigs of storage used by the caches themselves. These files are being used by the system to make its performance even smoother. When deleted, they will be replaced with new ones and that, actually, is a good thing. In fact, it’s better that you delete the caches from time to time so old ones will be dleted and only new ones will remain. Here’s how you do it:

  1. Open a Finder window and select Go in the menu bar.
  2. Click on “Go to Folder…”
  3. Type in ~/Library/Caches
  4. Delete the files/folders that are taking up the most space.
  5. Now click on “Go to Folder…”
  6. Type in /Library/Caches (simply lose the ~ symbol) and delete the folders that take up the most space.

Step 5: Delete language packs of your apps

Almost every app has language packs, which often consists of more than ten languages. Now imagine if you have 50 apps with language packs.

Deleting those files won’t do any harm to your Mac, so we suggest you delete them to try and save up some space. Those files often have the extension name .lproj and to find them, follow these steps:

  1. Open a Finder window.
  2. Go to Applications.
  3. Ctrl+click on an application.
  4. Select “Show Package Contents.”
  5. Go to Contents, then Resources.
  6. Drag files you don’t use to the trash.

Step 6: Delete iOS updates and backups

If you have other Apple devices, which are most probably connected to your Mac, their backups and updates may also take up some space on your computer. To delete firmware updates for your iOS devices, follow these steps:

  1. Open Finder.
  2. Select “Go” in the menu bar.
  3. Click on “Go to Folder…”
  4. For iPad enter ~/Library/iTunes/iPad Software Updates
  5. or enter for iPhone ~/Library/iTunes/iPhone Software Updates

To delete iOS backups, follow these:

  1. Launch a Finder window.
  2. Click “Go” in the menu bar.
  3. Select “Go to Folder…”
  4. Then, type in ~/Library/Application Support/MobileSync/Backup/

Step 7: Empty out the Trash

After deleting all those files, it’s time to empty out the Trash as many of them may have ended up in it while others may have been deleted immediately depending on how large those files were. After you did this, you should see a bump on your Mac’s current storage space, so it’s very important and this is how you do it:

  1. Press Ctrl + click your Trash in the the Dock.
  2. Select “Empty Trash.”
  3. And click “Empty Trash.”

Hopefully all these steps will be able to help you.

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