Freeing up space · Local snapshots and held space
Does reclaiming local snapshots affect my Time Machine backups?
Short answer: No. Local snapshots are short-term copies on your startup disk; Time Machine backups live on your backup drive. Storage Studio only thins local snapshots and prefers ones already backed up.
No. A local snapshot is a short-term copy macOS keeps on your startup disk so it can roll back recent changes; your Time Machine backup is the full history saved on your backup drive. Storage Studio only ever thins the local snapshots — your Time Machine history is left alone.
It also prefers deleting snapshots that are already saved to your Time Machine destination, so you don't give up a restore point that exists nowhere else. See the snapshot icons.