Tidy MacIf your Mac is full but you can’t see big files, the space is hidden in one of four places: the Trash (deleted files still count until you empty it), Time Machine local snapshots (old copies of files you deleted), purgeable space that macOS hasn’t freed yet, or System Data such as caches and device backups. Empty the Trash, thin snapshots, then check System Data.
- Empty the Trash; deleted files still use space until you do.
- Thin Time Machine local snapshots, which keep copies of files you deleted.
- Restart so macOS can release purgeable space and swap files.
- Check System Data for device backups, caches and developer files.
1. The Trash
Deleted files stay on the disk until you empty the Trash. Some apps also have their own trash (Photos’ Recently Deleted keeps photos for 30 days, Mail has Deleted Messages).
2. Time Machine local snapshots
If Time Machine is on, macOS keeps hourly snapshots on your internal drive. A file you deleted today can still exist in a snapshot, so the space doesn’t come back. Thin them:
sudo tmutil thinlocalsnapshots / 999999999999 43. Purgeable space
macOS marks some space as purgeable (snapshots, iCloud files with local copies, caches) and frees it only when it needs to. Finder and System Settings may count it differently, which is why the numbers disagree. Purgeable space explained
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4. System Data
Everything that isn’t Apps, Documents or Photos: device backups, caches, developer files, AI models. What is System Data?
Still stuck?
Restart once more; then use the System Data explainer or Tidy Mac. Its Home screen shows purgeable space and local snapshots, and splits System Data into named parts with a plain-English line for each, free, before anything is removed.