What do I do if I see Low Disk Space ("Startup disk is almost full")?

What to do when you get the warning that "Your startup disk is almost full."

What is a startup disk?

A startup disk is a volume or partition of a drive that contains a usable operating system. Simply put, it's your computer's hard drive.

Why is your startup disk full?

The typical amount of free space that should usually be on a hard drive should not get below 15% of the hard drive's capacity. Anything less than that and you will experience slowness and errors the further you get below that mark.

If your startup disk is full and you get a message of warning from your Mac, this is an indication that you need to free up space.

What to do when your startup disk is full?

To make more space on your startup disk you will need to:

Delete files from your Mac.
Or move files to an external hard drive or some other form of external storage.

What is taking up all of my startup disk space?

Using "About This Mac"

Click the Apple Icon in the menu at the top-left corner of your screen.
Choose “About This Mac.”
Click Storage.

Note: If you are running an older version of OS X you may have to first click “More Info…” and then “Storage”.

Using a tool to scan your hard drive

For Mac users, we recommend using JDiskReport
Download the program and double-click to open it
Select "Scan file tree..." and choose your hard drive that should be marked with a "/"
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