What Is Taking Up Space on My Mac?

Why guessing does not work

Disk usage is not evenly distributed, and it is not where you expect. The folders people check first — Desktop, Documents — are usually small. The space is in media libraries, application data, caches, disk images and backups.

That is why the category view matters. It replaces the question “which folder should I open” with a measurement.

The categories, and what they mean

• Applications. The application bundles themselves. Usually smaller than people assume, because most of an application’s footprint is its data.
• Documents. Files you created, including many file types that do not have their own category.
• Photos, Music, Video. Media libraries, which are directories presented as single items in Finder.
• Mail and Messages. Local copies of mail and message attachments, which grow steadily and are rarely reviewed.
• System Data. The catch-all: caches, logs, temporary files, support data, snapshots and file system overhead.
• Purgeable. Space macOS can reclaim when it needs to, counted separately from free space.

Why the numbers do not add up

Several things make the visible categories sum to less than the drive capacity:

• System reservations. macOS keeps space aside for the system and for updates.
• File system overhead. Metadata, journaling and indexing data occupy space without belonging to any category.
• Local snapshots. Time Machine keeps snapshots on the startup disk between backups. They do not appear in Finder.
• Purgeable space. Counted separately from free space, and reclaimed only when something needs it.

So a drive can report itself as nearly full while the categories look unremarkable. That gap is usually snapshots, reservations and purgeable space.

Checking it with Finder

Finder can sort a folder by size: switch to list view and click the Size column. That is enough for a folder you already suspect. It is not enough to find the suspect, because Finder has no view of the whole disk ordered by size, and you have to choose the folder before you can sort it.

Checking it with Neatwise

The Storage Analyzer reports usage both by category and by folder, which is the two-step drill-down this task needs. Once you know which folder is responsible, the Large File Finder lists the files inside it by size.

For the catch-all category specifically, the Junk Cleaner reports which parts of it are clearable and how much each part occupies.

What to do with the answer

Knowing where the space went does not commit you to deleting it. The useful outcomes are:

• Files you had forgotten. Decide whether they are needed. If they are, move them to external storage.
• Duplicates. Keep one copy.
• Applications you no longer use. Remove them with their support files.
• Caches and temporary data. Clear them if the size justifies it.
• Media you want to keep. Move it off the startup disk rather than deleting it.

If the answer turns out to be that space is disappearing steadily rather than sitting in one place, that is a different problem — see Why Is My Mac Storage Full?.