OmniDiskSweeper run from the Applications folder. It shows that the user’s Documents folder is the largest folder on the drive. Note also the size of the Spotlight Database as 0 bytes.
When run normally, as above, Joe noted that OmniDiskSweeper only shows files that are visible to the user that ran it. Since few people ever run as a fully priviledged “root” user, this means you’re almost always going to miss something, including system-level files or files and folders belonging to other user accounts on that Mac.
To give OmniDiskSweeper full access to all files on your drive, you must run the application from the Terminal using the sudo command, which stands for “Super User Do” and gives access to all files on a user’s drive. As with all sudo commands, triple-check the syntax before executing it (or simply copy/paste from here) as it is possible to cause irreversible damage to the OS and file system if the wrong command is entered. Assuming you have OmniDiskSweeper installed in your main Applications folder, that command is:
sudo /Applications/OmniDiskSweeper.app/Contents/MacOS/OmniDiskSweeper
Once an administrative password is entered, the application will launch and allow you to scan the drive for all files. Note below that the .Spotlight-V100 folder now shows over 800MB of content where before it appeared empty.
OmniDiskSweeper run as root using Terminal. Compare the Spotlight Database size to the previous screenshot. When run as root, the application can access and size this and other locations on the drive.
Thanks for the excellent tip, Joe!