System Data is a broad macOS storage label, not one folder you can safely erase. It can include caches, logs, temporary data, local snapshots, and other system-managed material.
Investigate without breaking macOS
Do not delete folders solely because they appear under Library or have an unfamiliar name. First identify the app or service that owns the data, check its own settings, and keep a backup before any cleanup.
Why the number can change
Storage reporting can change after updates, indexing, backup activity, or cache rebuilding. Give macOS time to settle before assuming the number is wrong. DiskClue can explain inspectable storage in a selected location, but does not claim to decode every system-managed byte.
A careful next step
Use this guide to understand the storage you see, then make changes only after reviewing their purpose. DiskClue can help make the evidence easier to inspect in the current MVP.
Understand your storage with DiskClue →