

Now that you know why we recommend you use third-party apps, let's explore the best Mac disk space analyzers to inspect and analyze disk space. If your startup disk consists of at least four separate volumes, you might notice a reduction in space available to Macintosh HD. In APFS, every disk is a container that can hold multiple volumes and shares the same pool of free space. As a result, it may show the System category taking a lot of space. But neither Finder or About This Mac shows the space taken by snapshots. When Time Machine creates local snapshots, the file system is aware of the changes. The APFS snapshot feature works differently.

Finder does not understand this mechanism and wrongly estimates free and used disk space. Instead of duplicating the data, it updates the metadata, and the on-disk data gets shared.
