The iPhone backups quietly filling your Mac
Every iPhone and iPad you have plugged into this Mac may still have a full backup on it. Here is where they live and which are safe to remove.
A phone backup made on a Mac is a full copy of the phone. Not a summary, not a difference against last time: a complete set of the photos, messages and app data that were on the device the day it was plugged in. On a phone that has been in use for a few years, one backup is comfortably 30 to 60 GB.
The problem is that they accumulate. Backing up a new phone does not remove the old phone's backup, and neither does selling the old phone. Macs that have seen three or four devices routinely carry a hundred gigabytes of backups for hardware nobody owns any more.
Where they actually live
One folder, and it is inside the hidden Library folder, which is why almost nobody finds it by browsing:
~/Library/Application Support/MobileSync/Backup/Each subfolder is one backup, named with a long device identifier rather than anything readable. That naming is the whole difficulty: you can see that you have four backups and roughly how big each is, and still have no idea which phone is which.
To check the total quickly, in Terminal:
du -sh ~/Library/Application\ Support/MobileSync/Backup/*Reading them by device and date instead
macOS will tell you which backup belongs to which device, in two places. Either is better than guessing from the folder names.
- Open Finder, connect the device, select it in the sidebar, then General, then Manage Backups. Every backup is listed with its device name and the date it was made.
- Or open System Settings, General, Storage, and look for iOS Files. The same backups are listed with sizes, and no device needs to be connected.
The second route is the useful one, because the backups you most want to remove belong to devices you cannot connect any more.
Which are safe to remove
- A backup of a device you no longer own. Safe, once you are sure nothing was left only on that phone.
- A backup older than the one beside it for the same device. The newer one is a full copy, so the older is redundant.
- Any backup of a device that now backs up to iCloud. Check on the device itself first, in Settings, your name, iCloud, iCloud Backup.
The safe way to remove one
Use the Manage Backups list, or drag the folder to the Trash. Do not delete the Backup folder itself, only the device folders inside it, and do not edit anything inside a backup: they are internally indexed, and a half removed backup is a backup that will not restore.
If the space does not come back after emptying the Trash, that is a separate and very common effect. See purgeable space, which explains why a Mac can report the same free space after you have removed fifty gigabytes.
The related folder worth knowing about
Developers get a second copy of this problem. Every iOS version ever attached to a Mac leaves a support bundle behind, and those are several gigabytes each. They sit apart from backups, and are covered along with the other build caches in what fills a developer's Mac.
Common questions
Where are iPhone backups stored on a Mac?
In ~/Library/Application Support/MobileSync/Backup/, with one folder per backup named after a device identifier. The Library folder is hidden, so the quickest way to see the list with real device names and dates is System Settings, General, Storage, iOS Files.
Is it safe to delete old iPhone backups?
Yes, provided the data exists somewhere else. A backup for a device you no longer own, or an older backup of a device that has a newer one, is redundant. Each backup is a complete copy rather than an increment, so removing the older one loses nothing from the newer.
How much space does an iPhone backup use?
Roughly as much as the used space on the phone, commonly 30 to 60 GB for a phone that has been in use a few years. Several devices backed up over several years is the usual reason a Mac has lost a hundred gigabytes to a folder nobody has opened.