Mac Startup Disk is Full?

Calm down, there is a way to solve this problem following all the instructions given in this article.

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15 Tips on How to Fix “Startup Disk is Almost Full” Error

Although the latest models of Apple computers are equipped with terabyte hard drives, sooner or later, users find that their Startup Disk is almost full. Even a little iTunes or iPhoto library can take up almost 64 or 128 gigabytes of disk space. Over time, after the gradual filling of the disk, the message “Your startup disk is almost full” starts to pop up on your Mac screen. This means that your Mac storage space is already occupied and you need to clean up your Mac.  

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Unfortunately, the unwelcome message about low free disk space may appear at the most inopportune moment, for example, when you urgently need to record a movie before a trip or create a backup copy of your iPhone. Moreover, if you have a lack of free storage space, most likely your Mac will start running slow. You should have at least 15% of a free space on the startup disk to run your Mac properly. That’s why you should speed up your Mac, or at least avoid getting the annoying message that Mac Startup Disk is full.

In this article, we will cover some easy tips on how to clean up your Mac as well as figure out what is the Startup disk, when does the message appear and how can you discover what’s taking up your disk space.


What is a Startup Disk on macOS?

The startup disk is the partition of the volume, where the macOS is installed and where the users’ files and apps are usually stored.

By default, the Startup Disk is the disk named “Macintosh HD” when the computer is turned on for the first time. The name of the disk can be changed, but it would still be the Startup Disk.

startup drive

What to do when “Startup Disk Full” message appears?

The message saying your startup disk is almost full is likely to appear when you have too many files on your Mac and there is a lack of free disk space.

When your Startup Disk is almost full, your Mac’s performance slows down.  In order to complete operations, the macOS requires space to store temporary system files and, when there is poor free space, the Mac runs too slow or crashes.

So the first thing you should do is to analyze your disk usage and start to free up space on Mac.

If the message “Startup Disk Full” appears in the most inappropriate moment and you do not have much time to explore your disk usage, we recommend that you use a Free app Startup Disk Full Fixer. Startup Disk Full Fixer will help you to quickly clean up your disk from junk files and stop the annoying message to disturb you. It will take less than a minute to find and remove such junk files as application caches, logs, remains, mail downloads, Xcode junk, iTunes temporary files.

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How to find what is taking up space on my Startup Disk?

You can view your storage usage by selecting “About This Mac” in the  Apple menu and switching to the Storage section.

mac startup disk full

There are six general categories of data stored on your Startup Disk. The larger the bar, the larger the space taken up by those types of files.

storage space

  • Photos
  • Apps
  • Movies
  • Audios
  • Backups
  • Documents
  • Other

As the “Startup Disk Full” message appears on your screen due to lack of free disk space, the first thing recommended is to clean up your Macintosh HD of unneeded files.

As soon as you know what’s taking up your disk space, you can review your folders and find out the unneeded files for removal.

Movies, Pictures or Backups usually take up the most space. But it often happens that the biggest space eaters are the “Other” files, including caches, logs, cookies, archives, disk images, plugins, extensions and so on. You can find and remove unneeded files manually or use special software tools for a quick and easy cleanup.

How to Clean up Mac Startup Disk

  1. Check Your Trash

It may sound elementary, but we frequently delete files and forget to empty the Trash. The files in the Trash still occupy your disk space, so it is recommended that you empty the Trash folder at least once a week.

To delete files from the Trash folder permanently, make a right click on the Trash in the dock panel and select Empty Trash. Another way to complete this task is to open the Trash and click the Empty button in the top right corner.

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  • how to free up space on mac

  1. Delete Downloads

How many times have you downloaded files from web browsers, messengers, torrents, mail? When you download files from the Internet, by default, they are saved in the Downloads folder, which can easily be found at this location:

Macintosh HD → Users → Current User → Downloads

startup disk is full

According to statistic, the average user accumulates 0.5 GB per week in the Downloads folder.

All of the files in the Downloads folder usually stay unorganized and may take up several Gigabytes of free space. Also, you probably have needed these files only once, for example, the installation files (disk images). Thus, more than half the files in the Downloads are not needed and should be deleted.

Sorting the list of files by size, kind or date will help you to quickly find out what unneeded files you have and remove them.

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  1. Clear Cache

A cache file is a temporary data file created by apps, browsers and many other programs to help your Mac run faster.  Note, when you remove cache files, they will be recreated the next time you run the application. Nevertheless, you may no longer be using some applications, while their leftovers still remain in the Cache folder and occupy tens of gigabytes of your disk memory. So, it’s a good idea to clear the cache from time to time.

Cache files are stored in the Library folders, which you can find in the following locations:

  • /Library/Caches
  • ~/Library/Caches

In /Library/Caches you will find temporary files created by the system. Usually, these files don’t occupy too much space. However, in the ~/Library/Caches folder, you will see a huge number of junk files, which are created when you run applications. As a result, this folder may increase substantially in size.

 other storage on mac

By default, the Library folder is hidden on macOS, as Apple. To open it, follow these steps:

  1. Open the Finder window.
  2. From Menu click Go → Go to Folder.
  3. In the dialog box type ~/Library/Cache and click Go.

mac disk cleanup

  1. Remove Logs

While the Library folder is open, you can also find another type of temporary file – Log files. They are stored in the Logs folder. Please make sure, before you remove the logs of the system, apps and mobile devices, that you no longer need them.

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  1. Remove Language Resources

Language Resources is the data stored by apps for different language localizations. Your system has 26 pre-installed dictionaries of 818 Mb. Apart from English, there are German, Chinese, French, Portuguese, Italian, Korean, Russian, Hindi, Thai and other languages. Localizations are the most misjudged space eaters. If you don’t  need iTunes translations for Vietnamese, you should delete these dictionaries, which are stored in the following directory:

Macintosh HD → Users → Your User → Library → Dictionaries

You can easily find out which files should be deleted by their name.

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All previous steps can be easily done by the ClearDisk application. Simply press the Scan button, and the ClearDisk app will do all the work instead of you. It will find all junk files in just a few seconds:

  1. Delete Old iPhone Backups

If you often sync your iPhone with iTunes, then the application creates dozens of backup copies on your device, and they often eat off a significant amount of gigabytes of disk space, as they include movies, music, and other large files. To find old backups, launch iTunes → Go to Menu Bar → iTunes → Preferences.

Here you will see a list of all the backups iTunes managed to make while working with your gadget. If you are sure that you do not need them, safely remove them. But make sure they are in iCloud!

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Another way to find and remove iOS backups is to go to the following location:

Library → Application Support→ MobileSync → Backup folder

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  1. Delete Mail Downloads

If you use the standard macOS Mail application, when you view email attachments, the system saves them to a separate folder on your hard drive. In several months of working with the mail client, the folder’s size can grow up to several GB.

The easiest way to find this folder is to search via Spotlight. Just type “Mail Downloads” in the search field.

mac storage

If this method didn’t work, then open the Finder → press Shift+Cmd+G key shortcut and in a search field enter:


how to delete temporary files on mac

Preview the files and save those which you need, or delete all the files at once.

  1. Uninstall Unused Apps

Check your Applications folder. The number of all the installed applications may sometimes exceed 100; in fact, some may not be used regularly or not used anymore. These apps take up a lot of space on your Mac’s hard drive. So it’s time to uninstall such unused programs. But please note, moving an app to Trash just by dragging and dropping it to Trash is not enough. You need to remove the app’s cache and other service files, which are stored in the Library folder.  We recommend that you read the instruction how to uninstall apps completely or use a free program App Cleaner & Uninstaller to remove apps correctly and completely.

  • Instead of manual searching for apps’ service files and wasting your time, App Cleaner & Uninstaller will automatically find all the service files of the apps and even the leftovers of already removed apps.

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  1. Remove Remains

Remains are the broken service files left after deleting the apps. Such broken service files are unnecessary and they just take up your disk memory, so you should find and remove them.

The apps’ leftovers are usually stored in the Library folder; however, they sometimes can be scattered in different locations all over your drive, littering your Mac. Searching for them manually seems to be an impracticable task. Fortunately, with the help of App Cleaner & Uninstaller, you can find and remove them with ease. The application finds and shows these files in the Remains section.

remove leftovers

  1. Move Big and Infrequently Used Files to External Drive

If you need to free up gigabytes of data, the best way to do it as quickly as possible is to check out your Movies folder. Video content is the biggest space eater as well as audio and photo files in the Music and Pictures folders.

Check also your disk for other files with large sizes. For this, go to Finder → click File in the Menu Bar → select New Smart Folder.

your startup disk is full

In the top right corner click the ‘Plus” button and, in the parameter fields, select “File Size” … “is greater than,” and set the needed file size, for example, 1GB or 500MB. Preview the biggest files and remove/move unused ones.

disk full mac

Even if you removed the biggest files, like videos or music, you may still have lots of other huge files you don’t suspect. We recommend that you analyze your disk space usage deeper and find out what’s taking up the most space on your disk. For this, you can use the Disk Expert app, which shows you the disk space usage in a sunburst diagram and allows you to easily operate the biggest files and folders.

  • Disk Expert is capable of scanning custom folders, identifying the biggest files and collecting files from various folders into unified “drop lists” for further movement to external hard drives.

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  1. Use Cloud-Based Data Storage Services

If you use the Dropbox service, you know that, even in a free version, the service provides 2 gigabytes of space. This means that you can move big files and folders from your hard drive to the cloud storage. Use the “Selective synchronization” option, which allows you to delete content sent to the cloud from the hard drive. To do this, go to the Preferences → Sync section and specify the desired folders to sync.

startup disk is full mac

Except for Dropbox, there are dozens of other similar services you can use, such as Google Drive, iDrive, Microsoft SkyDrive and so on.

  1. Delete Unnecessary Desktop Pictures and ScreenSavers

Most Mac users like good screensavers and do not limit themselves to the default collection.  If you are a screensaver fan and have a big collection of them, don’t forget that they may eat up a sizeable memory on your disk. It is recommended that you remove unneeded screensavers. For this purpose, you can again use App Cleaner & Uninstaller Pro which finds all the screen savers and shows them in the Extensions section.

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To find the desktop wallpapers, go to the following directory:

Macintosh HD → Library → Desktop Pictures

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It contains 52 images of 432.52 Mb. You are free to delete all redundant pictures.

  1. Find and Remove Duplicate Files

You may have created copies of documents or downloaded some files twice, and then forgotten about it. Duplicate files take up useless disk space on your Mac. Searching for duplicates manually seems to be a long and hard process. The only thing you can do quite quickly is to find the duplicate media files (music and video) in the iTunes Library.

To find duplicate music and video files, follow these steps:

  • Open iTunes.
  • Click the View in the Menu.
  • Select Show Duplicate Items.

iTunes will show you a list of duplicates. Examine the list and remove the duplicates.

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Unfortunately, for all other types of duplicate files, you will have to look through each folder individually. This could take hours. But don’t panic; there is a solution. We will now discuss another way to find duplicates. We are sure you will find this useful.

For other types of duplicate files, use a special application Duplicate File Finder, which will help you to find and remove duplicate files in less than 5 minutes.

  • Duplicate File Finder allows you to scan any folders and drives and find all duplicate files, including videos, music, pictures, documents, archives and other duplicate files. The application finds even Similar folders and can merge them so that you can easily organize your files and folders.

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  1. Restart Your Mac

Once you’ve cleaned up your hard drive, you should restart your Mac. A simply rebooting of the system can help to free up the disk space cluttered by temporary items and cache folders. It will also clean the virtual memory and sleep image files.

how to clean startup disk

  1. Clear Ram Memory on Your Mac

And, finally, it’s time to think about your RAM memory as well. This will not just create more space on your Mac but will help speed it up. This is especially important when your startup disk is almost full and your Mac’s speed is starting to lag. Memory Cleaner can work in the background and clear inactive RAM when the memory is filled up. The application is absolutely free and you can download it from the App Store.

memory usage - 100%


Well, that seems to be all. So, using these tips you can delete up to 20 GB of data not really needed on the computer. Hope these tips help you to free up disk space on your Mac and fix the “Startup Disk is Full” error message. Just note that you can clean up your Mac manually, but this may take too much time. Also, you can use professional tools, which will help you to save time and do a quick efficient cleanup of your hard drive.

Professional Mac Cleaner Tools