Excluding folders from Time Machine means they are not restored if your disk fails. Never exclude Documents, Desktop, or project folders unless you back them up elsewhere.
What you will achieve
Exclude specific folders from Time Machine backups so regenerable data — caches, virtual machines, developer dependencies — does not bloat backup size or slow hourly snapshots.
1) What to exclude (and what not to)
Good candidates:
- Virtual machine bundles (
.pvm, Parallels, UTM images) if you snapshot VMs separately. node_modules, Docker image layers, or build output folders you can rebuild.- Large media scratch disks copied from external sources.
- Cloud-sync folders already in iCloud/Dropbox (optional — avoids duplicate backup of synced data).
Bad candidates: tax records, photos with no other copy, mail archives, anything you cannot recreate.
2) Add exclusions in System Settings
- Open System Settings → General → Time Machine.
- Click Options… (or Options button next to your backup disk).
- Click + and navigate to the folder to exclude.
- Confirm — excluded items appear in the list with a minus button to remove later.
Exclusions apply to future backups; already-backed-up data may remain on the Time Machine disk until old snapshots age out.
3) Exclude via Time Machine plist (advanced)
System Settings is preferred. Legacy tmutil addexclusion still works in Terminal:
sudo tmutil addexclusion -p /path/to/folderThe -p flag persists across reboots. Verify with tmutil isexcluded /path/to/folder.
4) Apple Silicon vs Intel
Behaviour is identical. Apple Silicon developers often exclude large arm64 VM images; Intel Macs may exclude x86 Linux VM disks — same process. Local snapshots on the internal SSD still skip excluded paths, freeing space during heavy development work.
5) Impact on backup size and speed
Excluding a 100 GB Parallels VM can shrink the next backup dramatically. First backup after adding exclusions still contains old snapshots until Time Machine prunes them — allow time or manually thin backups only if you understand snapshot deletion risks.
6) Re-include if needed
Remove the folder from Options → exclusions list, or:
sudo tmutil removeexclusion -p /path/to/folderThe next backup includes the folder incrementally.
7) Network and encrypted backups
Exclusions apply equally to APFS local disks and network Time Machine destinations. Encrypted backups still honour exclusions — excluded data is simply not encrypted on the backup disk because it is not copied.
Verify
tmutil isexcluded returns true for excluded paths; Time Machine backup size growth slows for excluded heavy folders; critical personal data remains unlisted in exclusions.