Macintosh HD is the boot or startup disk of your Mac machine, containing millions of system files as well as the applications you install, which means the more applications installed on your Mac, the lesser drive space you have left on the startup disk. In such a situation, you might come across the error, “Your startup disk is almost full”. However, the same error sometimes prompts just like that when the startup disk contains a large amount of free space and still the Mac machine reports that the disk is almost full.

Read more about the error, likely causes, and resolution below:

The Error

Though Mac machines are termed as excellent computers whenever it comes to performance, they are not beyond the reach of problems and issues. Well, you actually realize the same when you come across a problem that was not supposed to be encountered on this ‘so-called’ excellent machine. A scenario highlighting a similar situation is shown below:

Your startup disk is almost fullBy looking at the error message, “Your startup disk is almost full”, you obviously realize and check if the startup disk is actually full. However, you wonder why the error prompted when you see the disk has more than half of the space free. You might ignore the error and click OK to close it. However, you might not be able to ignore this error when the same error prompts repeatedly and asks you to delete some files to create more free space.

The Step Generally Taken

This error can really get on your nerves over time and may cause you to make a bad decision by uninstalling multiple unwanted applications to free up some disk space. However, you should not take any steps to create free space on the startup disk before you check whether the startup disk is really full or not. In case the startup disk is full, you must free up the space equal to or at least 10 percent of the capacity of the disk.

In this regard, apart from uninstalling unwanted applications, you can put the following steps into practice:

  1. Empty the Trash
  2. Clear out downloads and desktop items
  3. In case your Mac has only one partition, check out your personal collection of movies and delete the unwanted ones or move some of them to an external drive. Likewise, check out the folders containing pictures, songs, and apps.
  4. Delete Big Caches.
  5. Scan hard drive for corrupted sectors and other hard drive disk errors.

Well, the error “Your startup disk is almost full” is quite common and prompts oftentimes even when the startup disk has enough free space available. Therefore, creating more free space is not the ultimate fix for the issue, as the cause of the error is not what is being reported.

Likely Causes of Error

Since the error points to the disk space, you must first check if the disk actually is almost full. However, if the startup disk has enough free space available, the issue is not what it is reported to be. In contrast, there might be some internal issues like a corrupted startup disk or other hardware issue. Do not perform fixes until you are sure about the causes.

Reset PRAM

PRAM stands for Parameter Random Access Memory that stores certain settings at a location that a Mac can access quickly. These settings include designated startup disk, speaker volume, display resolution, and more. When you reset PRAM, all these settings are refreshed automatically. See how you can reset PRAM on your Mac:

  1. Restart your Mac.
  2. Hold down the Command, Option, P, and R keys simultaneously before you see the gray screen.
  3. Once you hear the startup tone for the second time, release those keys immediately.

Since resetting PRAM refreshes some of your system settings, you will have to personalize them again. For this, Go to Apple icon and select System Preferences in the context menu.

Repair Startup Disk

Repairing the startup disk of your Mac securely requires you to have a secondary bootable media to boot from. For this, you can choose either the Recovery HD or the bootable DVD. Once you are into the boot menu, follow the steps mentioned below:

  1. In Mac OS X Utilities window, launch Disk Utility
  2. In the left pane of Disk Utility, highlight Macintosh HD
  3. In the First Aid tab at the right, click Repair Disk
  4. Wait for the disk repair to finish successfully, and then exit Disk Utility later
  5. If disk repair process fails to complete successfully, click Repair Disk again to retry repairing it
  6. Exit Disk Utility after the repair process is finished successfully
  7. Exit Mac OS X Utilities window and restart the Mac normally

This most likely fixes the problem, which means the same error should not prompt again. However, if the same error prompts again, then the issue is still there and you must try another fix. Well, whatever technique you implement to fix the issue at your end does not guarantee that the problem is not encountered again. You must have a recent backup of your Mac data since the issue might cause corruption in the entire hard drive leading to data loss. If nothing works for you, I suggest consulting an expert help.

Author Bio: Vishal is a technical writer who covers topic on Mac OS X. He keeps experimenting on his MacBook Pro and share useful information with Mac users. You can catch him on Facebook & Google + for more updates on OS X.