What a treemap shows
Each rectangle represents a file or directory, with area proportional to its storage use. One huge rectangle deserves attention before a long tail of tiny files. Nesting expresses directory hierarchy, while color commonly separates video, images, archives, apps, and other types.
The point is decision speed. Start with the largest block, identify its parent, and drill into the next level. A few steps often reveal the true source of growth.
Logical size is not physical usage
Sparse files, hard links, APFS clones, and cloud placeholders can make a file's stated size differ from what it occupies locally. An iCloud item may advertise many gigabytes while only a small placeholder exists on the Mac.
A useful analyzer should focus on the space deletion can actually reclaim. Diskly measures the local footprint of cloud placeholders and deduplicates hard links by inode to reduce inflated totals.
Drill down from the whole-disk view
After a scan, resist the urge to clean everything. Inspect the three to five largest blocks first. Are they personal media, app support, virtual machines, or reproducible cache? Enter the largest folder and repeat.
For an unfamiliar path, inspect its full location, file type, and modification date. The path often reveals the owning app; time helps establish whether it is still active. Size becomes actionable only when paired with context.
When to scan again
Rescan after moving or deleting a large batch to confirm the space actually returned. You can also scan before and after installing a large game, finishing a video project, or upgrading developer tools. The difference between snapshots can be more informative than either snapshot alone.
If the macOS Storage panel and analyzer disagree, check whether both include the same volumes, purgeable data, and cloud placeholders before comparing totals.
Understand first, clean second
Diskly scans locally on your Mac, maps real usage in a treemap, and keeps every cleanup suggestion reviewable.
Download free trial