If you need to look up how much of your Mac’s disk space is being used, you can simply choose About This Mac from the Apple menu, and then click the More Info button to bring up the system information summary. In here, you can click the Storage section, to see all attached hard drives and a colorized breakdown of the file types and sizes stored on each. While this feature is convenient, sometimes it may not show an accurate breakdown of the space used.
In some instances, you may see the calculated amount of free disk space differ from that when you select your hard drive in the Finder and press Command-i to get information on it, and at other times while the total disk space calculation might be correct, the breakdown does not seem correct. For instance, you may see the “Other” file type category taking up a large portion (if not all) of the calculated space used.
These errors occur simply because the sizes calculated in the About This Mac window are done from file metadata information that is collected into the Spotlight index, and not from any monitoring of the physical size on disk (as is done in the Finder information window). Therefore, if you are seeing incorrect storage calculations then it is likely your Spotlight index is damaged and needs to be rebuilt, which can be done with the following steps:
- Open the Spotlight system preferences.
- Go to the Privacy tab.
- Drag your hard drive to the list to add it.
- Select your drive, and then click the minus button to remove it.
Perform these steps for any hard drive that shows an improper storage calculation in the About This Mac window.
When you complete these steps, if you check the storage calculations before indexing is complete, then you will see the About This Mac window progressively update and change as more files are added to Spotlight’s index. Therefore, wait for the Spotlight index to fully rebuild (the progress of which can be seen by opening the Spotlight menu) before you check the storage use in the About This Mac window again.