The short answer
Usually, after a check. Might hold something you care about. Look inside before removing it.
What is it?
Full local backups of iPhone and iPad made by Finder (or iTunes on older macOS), one folder per backup in ~/Library/Application Support/MobileSync/Backup. Each holds messages, app data, settings and, unless iCloud Photos is on, photos: typically from a few GB to over 100 GB.
Full device backups, one folder per device. Keep the latest of each device or offload; deleted backups cannot be restored.
What happens if you delete it?
A deleted backup cannot be recovered. The next backup of that device starts from scratch and takes longer.
How to remove it properly
Connect a device, select it in the Finder sidebar, click Manage Backups in the General tab, choose an old backup and click Delete Backup. Keep the most recent backup of each device you still use, or copy older ones to an external drive first.
Better moved to an external drive than deleted.
Before you delete it
Archived backups and encrypted backups (which also contain saved passwords and Health data) may be the only copy of that state: do not delete one you might need to restore from.
How MoreRoom helps
MoreRoom recognises this item and labels it “Review first”: it shows what’s inside, its size and last use, so you can decide. Nothing is removed without your say, and everything goes to the Trash first, with Undo.
Frequently asked questions
Is it safe to delete old iPhone backups on Mac?
Usually, after a check. Might hold something you care about. Look inside before removing it. A deleted backup cannot be recovered. The next backup of that device starts from scratch and takes longer.
Will iPhone and iPad backups come back after I delete it?
No. A deleted backup cannot be recovered. The next backup of that device starts from scratch and takes longer.
How do I remove iPhone and iPad backups properly?
Connect a device, select it in the Finder sidebar, click Manage Backups in the General tab, choose an old backup and click Delete Backup. Keep the most recent backup of each device you still use, or copy older ones to an external drive first.