System Data over 300GB: safe Mac storage diagnosis checklist

A practical first-pass checklist for System Data over 300GB. The goal is to recover space without deleting the folder that proves expensive to rebuild.

Avoid random Library deletion

System Data and full-disk reports are labels, not a cleanup plan. The same number can hide caches, developer tools, local snapshots, downloads, or app support data.

First read-only checks

Use read-only size checks first, classify the largest folders, and move uncertain items to Trash only after you know what generated them.

du -sh ~/Library/* 2>/dev/null | sort -h | tail
tmutil listlocalsnapshots /

Usually safer cleanup candidates

• Old installers or archives already backed up
• Regenerable app caches after the app is closed
• Developer caches with a clear rebuild path

Review before deleting

• Unknown Library folders
• Photo, mail, or message stores
• Project folders and app support data without an owner review