Gigabytes of disk space shown as hidden space in DaisyDisk

Solution 1:

Starting up from the recovery partition and repairing the disk fixed the issue. (Disk Utility showed an error about an invalid free block count.) Thanks @cksum.

Solution 2:

DaisyDisk's hidden space (if scanned as administrator) should be within 4-8GB limit for most Macs. If the numbers are larger, try repairing the volume as this may serve an indicator for file system errors.

Taras Brizitsky, DaisyDisk's designer.

Solution 3:

Another possibility—and one that ended up being the culprit in my particular case—is that your machine is making local backups when it's unable to connect to your external backup source. In this case, you can just disable the backups by entering the following command in the Terminal:

sudo tmutil disablelocal

Later, if and when you decide to re-enable the backup, you can reverse it with the following Terminal command:

sudo tmutil enablelocal

Update for MacOS Sierra and Later

It seems like the disablelocal and enablelocal commands are no longer available. As an alternative you can delete local snapshots by doing the following:

1. Get a list of the local snapshots by running:

   tmutil listlocalsnapshots

   You should get some output like

   com.apple.TimeMachine.2018-10-03-145245.

2. Delete a snapshot by running:

   tmutil deletelocalsnapshots <date of snapshot>

   So, for example, using the output from step 1, you would run:

   tmutil deletelocalsnapshots 2018-10-03-145245

   And you should get some output like

   Deleted local snapshot '2018-10-03-145245'

Solution 4:

According to DaisyDisk manual:

Sometimes the amount of "used" space on a disk may appear greater than the total size of all scanned files and folders on that disk. This is normal. The difference is usually taken by the file system overhead and system stuff like Spotlight index, but in certain cases a significant amount of disk space may be hiding in other users' accounts or folders that are normally not visible to you. In order to reveal those folders you should scan the disk as administrator.

(Hidden space) is a virtual disk map item that only appears when the total size of restricted files is significant, so you can see whether it's worth rescanning the disk as administrator or not.

Large amounts of hidden disk space may also indicate to file system errors. Follow our troubleshooting guide for details.

In case you have a lot of hidden disk space when running it as administrator, it's possible that you have file system errors or broken file permissions.